IJC

International Journal of Cancer

Dose-dense adjuvant chemotherapy in HER2-positive early

breast cancer patients before and after the introduction of
trastuzumab: Exploratory analysis of the GIM2 trial
Matteo Lambertini 1,2, Francesca Poggio3, Marco Bruzzone4, Benedetta Conte3, Claudia Bighin3, Evandro de Azambuja5,
Mario Giuliano6, Michele De Laurentiis7, Francesco Cognetti8,9, Alessandra Fabi8,9, Giancarlo Bisagni10, Antonio Durando11,
Anna Turletti12, Ylenia Urracci13, Ornella Garrone14, Fabio Puglisi15,16, Filippo Montemurro17, Marcello Ceppi4, and
Lucia Del Mastro2,3, on behalf of the GIM2 investigators
1
Department of Medical Oncology, U.O.C. Clinica di Oncologia Medica, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
2
Department of Internal Medicine and Medical Specialties (DiMI), School of Medicine, University of Genova, Genoa, Italy
3
Department of Medical Oncology, Breast Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
4
Clinical Epidemiology Unit, IRCCS Ospedale Policlinico San Martino, Genoa, Italy
5
Department of Medical Oncology, Institut Jules Bordet and l’Université Libre de Bruxelles (U.L.B), Brussels, Belgium
6
Department of Clinical Medicine and Surgery, University of Naples “Federico II”, Naples, Italy
7
Medical Oncology, Istituto Nazionale Tumori-IRCCS Fondazione Pascale, Naples, Italy
8
La Sapienza University, Rome, Italy
9
Department of Medical Oncology 1, Istituto Nazionale Tumori Regina Elena, Rome, Italy
10
Department of Medical Oncology, Azienda Unità Sanitaria Locale – IRCCS di Reggio Emilia, Reggio Emilia, Italy
11
Breast Unit, Azienda Ospedaliera Universitaria Città della Salute e delle Scienze, Torino, Italy
12
Medical Oncology, Martini Hospital, ASL Città’ di Torino, Italy
13
Department of Medical Oncology, Hospital Businco, Cagliari, Italy
14
Breast Unit, Medical Oncology, Azienda Ospedaliera S. Croce e Carle, Ospedale di Insegnamento, Cuneo, Italy
15
Unit of Medical Oncology and Cancer Prevention, IRCCS Centro di Riferimento Oncologico Aviano-National Cancer Institute, Aviano (Udine), Italy
16
Medical Oncology, Department of Medicine, University of Udine, Udine, Italy
17
Day Hospital Oncologico Multidisciplinare, Istituto di Candiolo, FPO-IRCCS, Candiolo, Torino, Italy
Cancer Therapy and Prevention

Additional Supporting Information may be found in the online version of this article.
Key words: breast cancer, adjuvant chemotherapy, dose-dense, HER2, trastuzumab
Abbreviations: CI: confidence intervals; DFS: disease-free survival; EBCTCG: Early Breast Cancer Trialists’ Collaborative Group; EC: epi-
rubicin and cyclophosphamide; FEC: fluorouracil, epirubicin and cyclophosphamide; GIM: Gruppo Italiano Mammella; HRs: hazard ratios; OS:
overall survival; P: paclitaxel; T-DM1: trastuzumab-emtansine
Conflict of interest: Dr Lambertini served as a consultant for Teva, and received honoraria from Theramex, Takeda and Roche outside the
present work. Dr Bighin served as a consultant for Novartis and Roche, honoraria from Novartis, Roche, Ipsen, Astrazeneca, Pfizer and
research funding from Roche outside the present work. Dr de Azambuja received honoraria and advisory role from Roche/GNE, Novartis,
SeaGen, travel grants from Roche/GNE and GSK Novartis, research grants from Roche/GNE, AstraZeneca, GSK Novartis and Servier (to the
Institution) outside the present work. Dr Giuliano received honoraria from Roche, Pfizer, AstraZeneca, Novartis, Celgene, Eli Lilly, Amgen and
Eisai outside the present work. Dr Alessandra Fabi received honoraria and advisory role from Amgen, Celgene, Eli Lilly, Eisai, MSD, Novartis,
Pfizer, Roche, Takeda outside the present work. Dr Anna Turletti received honoraria from Ipsen, EISAI, Novartis, AstraZeneca, Celgene and
Pierre Fabre, and travel grants from Roche, Lilly, EISAI and Pierre Fabre outside the present work. Dr Garrone served as a consultant for
Celgene, Eisai, Pfizer, Amgen, honoraria from Celgene, Novartis, Eisai, Pfizer, research funding from Eisai, and travel grants from Celgene and
Roche/GNE outside the present work. Prof. Puglisi received honoraria and advisory role from Celgene, Eli Lilly, Ipsen, MSD, Novartis, Roche
and Takeda, travel grants from Celgene, Roche and Servier and research grants from AstraZeneca, EISAI and Roche outside the present work.
Dr Montemurro served as a consultant for Roche and Lilly, and received honoraria from Roche, Novartis, Pfizer and AstraZeneca outside the
present work. Dr Del Mastro received honoraria from Takeda and personal fees from Ipsen and Takeda outside the present work. The other
authors declare no conflict of interests.
DOI: 10.1002/ijc.32789
History: Received 13 Jun 2019; Accepted 4 Nov 2019; Online 4 Dec 2019
Correspondence to: Matteo Lambertini, E-mail: matteo.lambertini@unige.it

Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC

Lambertini et al. 161

Dose-dense adjuvant chemotherapy is standard of care in high-risk early breast cancer patients. However, its role in HER2-positive
patients is still uncertain. In this exploratory analysis of the GIM2 trial, we investigated the efficacy of dose-dense chemotherapy in
HER2-positive breast cancer patients with or without exposure to trastuzumab. In the GIM2 trial, node-positive early breast cancer
patients were randomized to receive four cycles of (fluorouracil)epirubicin/cyclophosphamide followed by four cycles of paclitaxel
administered every 2 (dose-dense) or 3 (standard-interval) weeks. After approval of adjuvant trastuzumab, protocol was amended in
April 2006 to allow use of trastuzumab for 1 year after chemotherapy completion in HER2-positive patients. The efficacy of dose-
dense chemotherapy in terms of disease-free survival (DFS) and overall survival (OS) was assessed according to HER2 status and
trastuzumab use. Out of 2,003 breast cancer patients, HER2 status was negative/unknown in 1,551 patients; among the
452 patients with HER2-positive breast cancer, chemotherapy alone or followed by trastuzumab was given to 320 and 132 patients,
respectively. Median follow-up was 8.1 years. No significant interaction between HER2 status, trastuzumab use and chemotherapy
treatment was observed for both DFS (p = 0.698) and OS (p = 0.708). Nevertheless, there was no apparent benefit in the
HER2-positive group treated with trastuzumab (DFS: HR, 0.99; 95% CI 0.52–1.89; OS: HR, 0.95; 95% CI 0.37–2.41). Although dose-
dense chemotherapy was associated with a significant survival improvement in high-risk breast cancer patients, its benefit
appeared to be smaller (if any) in patients with HER2-positive disease who received adjuvant trastuzumab.

What’s new?
Dose-dense chemotherapy is standard of care in high-risk early breast cancer; however, its role in HER2-positive
patients is still uncertain. In this exploratory analysis of the GIM2 trial, we showed that the benefit of dose-dense
chemotherapy appeared to be small (if any) in HER2-positive patients who received trastuzumab raising concerns on the
need of chemotherapy escalation approaches in this setting. These findings may guide the choice of adjuvant
chemotherapy in HER2-positive early breast cancer patients.

Introduction investigated the efficacy of dose-dense chemotherapy as adjuvant

Cancer Therapy and Prevention

Polychemotherapy following surgical resection remains a mainstay treatment of high-risk early breast cancer patients.12 The trial
adjuvant treatment for many patients with early breast cancer.1,2 was conducted at the turn of the years in which adjuvant
Although the combination of docetaxel and cyclophosphamide trastuzumab became standard of care in HER2-positive breast
can be considered a valid alternative in some cases,3 the sequential cancer. Therefore, some of the patients included in the trial
use of a taxane with anthracycline- and cyclophosphamide-based received adjuvant trastuzumab while others did not undergo
chemotherapy represents the preferred approach in high-risk anti-HER2 targeted therapy. This represented a unique opportu-
patients.4 In breast cancer patients at higher risk of disease recur- nity to explore the efficacy of dose-dense adjuvant chemotherapy
rence, dose-dense chemotherapy obtained by shortening the inter- in HER2-positive early breast cancer patients before and after
val between treatment cycles is associated with a significant the introduction of adjuvant trastuzumab.
improvement in survival outcomes.5
Before the introduction of adjuvant anti-HER2 targeted ther-
apy, the efficacy of dose-dense chemotherapy was demonstrated Materials and Methods
also in patients with HER2-positive early breast cancer.5,6 However, Study design and participants
chemotherapy plus anti-HER2 targeted therapy is the current stan- Details of the GIM2 study design were previously reported.12,13
dard of care in this setting.7 Three studies showed the feasibility Briefly, GIM2 was a multicenter, open-label, randomized phase
(in terms of no increased likelihood of developing cardiac events) III study including patients aged 18–70 years who had under-
of administering dose-dense anthracycline- and taxane-based che- gone radical surgery for a histologically confirmed invasive breast
motherapy in combination with adjuvant trastuzumab in patients cancer with metastasis in at least one axillary lymph node.
with HER2-positive early breast cancer.8–10 However, none of these According to the criteria in force at the time of study con-
studies was designed to investigate the superiority of the dose- duction, HER2 status was defined as positive in the presence
dense schedule over standard-interval chemotherapy. Therefore, of at least 10% of cells with HER2 expression assessed by
the need for prescribing dose-dense chemotherapy in patients with immunohistochemistry or in the presence of gene amplifica-
HER2-positive early breast cancer undergoing adjuvant anti-HER2 tion documented by in situ hybridization assay. The presence
targeted therapy remains unknown.11 of at least 10% of positive cells by immunohistochemical anal-
The Gruppo Italiano Mammella (GIM) 2 trial (ClinicalTrials. ysis was the criteria to define the tumor positive for estrogen
gov Identifier: NCT00433420) is one of the largest studies that and/or progesterone receptors.

Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC

 162 Dose-dense chemotherapy in HER2+

The trial was conducted at 81 Italian centers. The Institu- Objectives and endpoints
tional Review Boards of all participating centers approved the This exploratory analysis aimed at investigating a potential
GIM2 protocol and all enrolled patients provided written interaction between HER2 status, trastuzumab use and chemo-
informed consent before study entry. The present analysis was therapy by evaluating the efficacy of dose-dense chemotherapy
approved by the members of the GIM2 Steering Committee. in the subgroup of patients with HER2-positive breast cancer
with or without subsequent exposure to adjuvant trastuzumab
and in those with HER2-negative/unknown disease.
Study procedures Outcomes were compared between three groups of patients:
In the GIM2 trial, eligible patients were randomized in a HER2-positive group not exposed to adjuvant trastuzumab
1:1:1:1 ratio to one of the following four arms: standard- (HER2-positive no trastuzumab group), HER2-positive group
interval fluorouracil, epirubicin and cyclophosphamide (FEC) exposed to adjuvant trastuzumab (HER2-positive trastuzumab
followed (−) by paclitaxel (P), standard-interval EC-P, dose- group) and HER2-negative/unknown group.
dense FEC-P and dose-dense EC-P. The number of cycles As in the main GIM2 trial,12 disease-free survival (DFS)
(4 of anthracycline-based chemotherapy and 4 of single-agent was the primary endpoint; overall survival (OS) and adverse
taxane) and the dose of chemotherapy agents (fluorouracil at events were secondary endpoints.
600 mg/m2, epirubicin at 90 mg/m2, cyclophosphamide at
600 mg/m2 and paclitaxel at 175 mg/m2) were the same in all Statistical analyses
treatment arms. In the dose-dense arms, administration of Sample size calculation and statistical assumptions of the GIM2
subcutaneous pegfilgrastim (6 mg) was mandatory 24–72 hr primary objective were previously described.12 The present
after chemotherapy.14 analysis focusing on the efficacy of dose-dense chemotherapy
After approval of adjuvant trastuzumab by the Italian regu- according to HER2 status and trastuzumab use was not
latory authorities, an amendment in April 2006 allowed the preplanned in the trial protocol, and the power of the statistical
administration of the anti-HER2 monoclonal antibody for analyses was not prespecified. For the purpose of the present
1 year after chemotherapy in patients with HER2-positive dis- analysis, the two dose-dense arms were considered together as
ease. Patients with hormone receptor-positive disease received well as the two standard-interval arms. The 88 patients
adjuvant endocrine therapy following completion of chemo- included in the five centers that refused randomization to the
therapy according to local guidelines. dose-dense arms were excluded from this analysis (Fig. 1).
Cancer Therapy and Prevention

2,091 patients randomly assigned

88 excluded from current analysis

(not randomized to dose-dense arms)

2,003 includedin the currentanalysis

1,002 assigned to dose-dense chemotherapy 1,001 assigned to standard interval chemotherapy

(500 to FEC-P and 502 to EC-P) (500 to FEC-P and 501 to EC-P)
166 HER2-positive no trastuzumab 154 HER2-positive no trastuzumab
60 HER2-positive trastuzumab 72 HER2-positive trastuzumab
617 HER2-negative 626 HER2-negative
159 HER2-unknown 149 HER2-unknown

320 HER2-positive/no trastuzumab 132 HER2-positive/trastuzumab 1,551 HER2-negative/unknown

108 developed DFS events 37 developed DFS events 434 developed DFS events
57 developed OS events 18 developed OS events 220 developed OS events

Figure 1. The consolidated standards of reporting trials (CONSORT) flow diagram for the GIM2 study. Abbreviations: DFS, disease-free
survival; EC, epirubicin, cyclophosphamide; FEC, fluorouracil, epirubicin, cyclophosphamide; P, paclitaxel; OS, overall survival.

Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC

Lambertini et al. 163

Table 1. Baseline patient and tumor characteristics

HER2-positive no HER2-positive HER2-negative/
trastuzumab trastuzumab unknown
(n = 320) n (%) (n = 132) n (%) (n = 1,551) n (%) p value
Median age at study entry 52 50 52 0.421
Age at study entry 0.004
≤40 years 62 (19.4) 25 (18.9) 208 (13.4)
41–64 years 214 (66.9) 98 (74.2) 1,176 (75.8)
≥65 years 44 (13.7) 9 (6.8) 167 (10.8)
Menopausal status 0.692
Premenopausal 157 (49.1) 70 (53.0) 762 (49.1)
Postmenopausal 163 (50.9) 62 (47.0) 789 (50.9)
Type of surgery 0.034
Mastectomy 141 (44.1) 62 (47.0) 575 (37.1)
Lumpectomy 179 (55.9) 70 (53.0) 974 (62.8)
Unknown 0 (0.0) 0 (0.0) 2 (0.1)
Tumor size 0.266
pT1 152 (47.5) 65 (49.2) 806 (52.0)
pT2 135 (42.2) 55 (41.7) 634 (40.9)
pT3–T4 31 (9.7) 12 (9.1) 104 (6.7)
Unknown 2 (0.6) 0 (0.0) 7 (0.4)
Nodal status <0.001
pN1 (1–3) 162 (50.6) 70 (53.0) 969 (62.5)
pN2 (4–9)–N3 (≥10) 158 (49.4) 62 (47.0) 582 (37.5)
Tumor grade <0.001
G1 12 (3.7) 2 (1.5) 106 (6.8)
G2 105 (32.8) 44 (33.3) 759 (48.9)
G3 191 (59.7) 86 (65.1) 618 (39.8)

Cancer Therapy and Prevention

Unknown 12 (3.7) 0 (0.0) 68 (4.4)
Hormone receptor status <0.001
ER and/or PR positive 239 (74.7) 74 (56.1) 1,198 (77.2)
ER and PR negative 79 (24.7) 58 (43.9) 198 (12.8)
Unknown 2 (0.6) 0 (0.0) 155 (10.0)
Ki67 value (%) <0.001
0–14 42 (13.1) 11 (8.3) 433 (27.9)
15–20 44 (13.7) 16 (12.1) 241 (15.5)
>20 176 (55.0) 93 (70.4) 533 (34.4)
Unknown 58 (18.1) 12 (9.1) 344 (22.2)
CT treatment 0.327
FEC 172 (53.7) 65 (49.2) 763 (49.2)
EC 148 (46.3) 67 (50.8) 788 (50.8)
Treatment arm 0.471
DD 166 (51.9) 60 (45.5) 776 (50.0)
SI 154 (48.1) 72 (54.5) 775 (50.0)
Endocrine therapy1 <0.001
Tamoxifen ( GnRHa) 98 (41.0) 20 (27.0) 532 (44.4)
Tamoxifen ( GnRHa)àAI 54 (22.6) 18 (24.3) 347 (29.0)
AI 65 (27.2) 32 (43.2) 233 (19.4)
None 11 (4.6) 3 (4.1) 30 (2.5)
Unknown 11 (4.6) 1 (1.4) 56 (4.7)

Bold values indicate significance levels < 0.05.

1
The percentages were calculated on the total number of patients with hormone receptor-positive breast cancer.
Abbreviations: pT, pathologic tumor stage; pN, pathologic nodal stage; G, tumor grade; ER, estrogen receptor; PR, progesterone receptor; CT, chemother-
apy; FEC, fluorouracil, epirubicin, and cyclophosphamide; EC, epirubicin and cyclophosphamide; DD, dose-dense; SI, standard interval; GnRHa,
gonadotropin-releasing hormone agonist; AI, aromatase inhibitor.

Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC

 164 Dose-dense chemotherapy in HER2+

Table 2. Disease-free survival and overall survival events in the intention-to-treat population
HER2-positive no HER2-positive HER2-negative/
trastuzumab trastuzumab unknown
(n = 320) n (%) (n = 132) n (%) (n = 1,551) n (%) p value
Follow-up, median (IQR) years 8.0 (6.0–9.0) 7.3 (6.1–8.8) 7.9 (6.4–9.2) 0.032
No events 212 (66.3) 95 (72.0) 1,117 (72.0) 0.116
Loco-regional recurrence only 31 (9.7) 10 (7.6) 89 (5.7) 0.032
Distant recurrence 61 (19.1) 25 (18.9) 245 (15.8) 0.251
Second primary malignancy 7 (2.2) 0 (−) 41 (2.6) 0.136
Second primary breast cancer 5 (1.6) 1 (0.8) 33 (2.1) 0.632
Death without any disease-free survival event 4 (1.3) 1 (0.8) 26 (1.7) 0.841
Death with some disease-free survival event 53 (16.6) 17 (12.9) 194 (12.5) 0.153
Abbreviations: IQR, interquartile range.

(a) HER2-positive no trastuzumab (b) HER2-positive trastuzumab

100 100

80 80
Disease free survival (%)

Disease free survival (%)

60 60

40 40
HR, 0.78; 95% CI 0.53–1.13 HR, 0.99; 95% CI 0.52–1.89
aHR, 0.79; 95% CI 0.53–1.17 aHR, 0.71; 95% CI 0.35–1.42
20 20
Standard Standard
Cancer Therapy and Prevention

Dose-dense Dose-dense
0 0
0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10
Time since random assignment (years) Time since random assignment (years)
Number at risk Number at risk
Standard 154 138 125 115 105 100 91 80 60 30 13 Standard 72 66 55 52 51 49 48 35 22 13 9
Dose-dense 166 156 139 130 123 115 108 99 65 35 11 Dose-dense 60 59 52 44 44 43 41 29 21 13 5

(c) HER2-negative/unknown
100

80
Disease free survival (%)

60

40
HR, 0.74; 95% CI 0.61–0.89
aHR, 0.72; 95% CI 0.59–0.87
20
Standard
Dose-dense
0
0 1 2 3 4 5 6 7 8 9 10
Time since random assignment (years)

Number at risk
Standard 775 725 662 606 578 548 520 430 300 170 80
Dose-dense 776 742 692 659 622 590 558 488 344 189 82

Figure 2. Disease-free survival for the comparison between dose-dense and standard-interval chemotherapy: HER2-positive no trastuzumab
group (a); HER2-positive trastuzumab group (b); HER2-negative/unknown group (c). Abbreviations: aHR, adjusted hazard ratio; CI, confidence
intervals; HR, hazard ratio. [Color figure can be viewed at wileyonlinelibrary.com]

Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC

Lambertini et al. 165

DFS and OS were defined as previously described.12 The het- proportional hazards model. The variables included in the mul-
erogeneity of treatment effect (dose-dense vs. standard-interval) tivariate Cox regression models were age, type of surgery,
according to HER2 status and trastuzumab use was investigated tumor size, number of lymph nodes, tumor grade, Ki67, hor-
by including in each final model (for DFS and OS) an interaction mone receptor status and endocrine therapy. Likelihood ratio
term representing the modification of the effect of dose-dense test was applied to test the contribution of each variable to the
chemotherapy in patients with HER2-positive disease treated with final model.
or without trastuzumab. For descriptive purposes, DFS and OS in As previously described,12 adverse events were assessed clini-
patients assigned to dose-dense or standard-interval chemother- cally as well as by hematological and biochemical measurements
apy were also compared separately within each of the three throughout chemotherapy and were graded according to the
groups of interest (HER2-positive no trastuzumab, HER2-positive National Cancer Institute common toxicity criteria version 2.0.
trastuzumab and HER2-negative/unknown). All reported statistical analyses were based on the
DFS and OS probabilities were computed according to the intention-to-treat population. All statistical tests were 2-sided,
Kaplan–Meier method and the log–log method was used to cal- and p values <0.05 were considered statistically significant.
culate confidence intervals (CI) of survival time probabilities. STATA 13.1 (StataCorp. 2013. Stata Statistical Software:
To estimate treatment effect, unadjusted and adjusted hazard Release 13. College Station, TX: StataCorp LP) was used to
ratios (HRs) with 95% CI were calculated with the Cox perform all statistical analyses.

(a) HER2-positive no trastuzumab (b) HER2-positive trastuzumab

100 100

80 80
Overall survival (%)
Overall survival (%)

60 60

40 40
HR, 0.63; 95% CI 0.37–1.07 HR, 0.95; 95% CI 0.37–2.41

Cancer Therapy and Prevention

aHR, 0.59; 95% CI 0.34–1.03 aHR, 0.91; 95% CI 0.31–2.68
20 20
Standard Standard
Dose-dense Dose-dense
0 0
0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10
Time since random assignment (years) Time since random assignment (years)

Number at risk Number at risk

Standard 154 147 140 131 122 120 110 98 76 40 17 Standard 72 72 68 62 61 55 54 43 26 15 10
Dose-dense 166 162 158 152 148 143 129 116 82 43 13 Dose-dense 60 60 56 52 50 49 46 33 21 13 5

(c) HER2-negative/unknown

100

80
Overall survival (%)

60

40
HR, 0.66; 95% CI 0.50–0.86
aHR, 0.64; 95% CI 0.49–0.84
20
Standard
Dose-dense
0
0 1 2 3 4 5 6 7 8 9 10
Time since random assignment (years)
Number at risk
Standard 775 745 718 678 649 623 590 500 345 200 101
Dose-dense 776 754 727 706 682 662 634 553 389 225 100

Figure 3. Overall survival for the comparison between dose-dense and standard-interval chemotherapy: HER2-positive no trastuzumab group
(a); HER2-positive trastuzumab group (b); HER2-negative/unknown group (c). Abbreviations: aHR, adjusted hazard ratio; CI, confidence
intervals; HR, hazard ratio. [Color figure can be viewed at wileyonlinelibrary.com]

Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC

 166 Dose-dense chemotherapy in HER2+

Data availability Almost 90% of the patients in all treatment groups com-
Data can be made available upon reasonable request to the pleted the planned number of chemotherapy cycles
corresponding author. (Supporting Information Table S1). Supporting Information
Table S2 reports the rate and grade of the adverse events
occurring in at least 5% of the patients in the dose-dense
Results and standard-interval arms of the three groups. In terms of
Between April 24, 2003 and July 3, 2006, 2,003 breast cancer grade 3–4 adverse events, neutropenia was more common
patients were randomized to receive dose-dense (n = 1,002) or among patients treated with standard-interval chemother-
standard-interval (n = 1,001) chemotherapy (Fig. 1). apy (ranging between 38.9 and 53.3%) while those in the
Among these patients, HER2 status was negative in 1,243 dose-dense arms tended to developed more often anemia
(62.0%), unknown in 308 (15.4%) and positive in 452 (22.6%) (ranging between 1.2 and 1.7%), myalgia (ranging between
cases. Out of 452 patients with HER2-positive breast cancer, 1.7 and 3.3%) and ALT elevation (ranging between 1.2 and
320 (70.8%) received chemotherapy alone without trastuzumab 3.4%). The highest rate of grade 3–4 asthenia (10.2%) was
while 132 (29.2%) received trastuzumab at the completion of observed in the dose-dense arms of the HER2-positive
chemotherapy. Table 1 reports baseline patient and tumor trastuzumab group. There were no cases of treatment-
characteristics in the three groups of interest. related deaths.

(a) Standard-Interval (b) Standard-Interval

100

80 80
Disease free survival (%)

Overall survival (%)

60 60
HER2– / Unk: Reference group HER2– / Unk: Reference group
HER2+ / No T: HR, 1.27; 95% CI 0.95–1.70 / aHR, 0.96; 95% CI 0.71–1.30 HER2+ / No T: HR, 1.32; 95% CI 0.90–1.94 / aHR, 0.95; 95% CI 0.63–1.43
HER2+ / T: HR, 0.93; 95% CI 0.59–1.47 / aHR, 0.81; 95% CI 0.50–1.31 HER2+ / T: HR, 0.84; 95% CI 0.44–1.61 / aHR, 0.67; 95% CI 0.34–1.30
40 40

20 HER2+ / No T 20 HER2+ / No T
Cancer Therapy and Prevention

HER2+ / T HER2+ / T
HER2– / Unk HER2– / Unk
0 0

0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10
Time since random assignment (years) Time since random assignment (years)
Number at risk Number at risk
HER2+ / No T 154 138 125 115 105 100 91 80 60 30 13 HER2+ / No T 154 147 140 131 122 120 110 98 76 40 17
HER2+ / T 72 66 55 52 51 49 48 35 22 13 9 HER2+ / T 72 72 68 62 61 55 54 43 26 15 10
HER2– / Unk 775 725 662 606 578 548 520 430 300 170 80 HER2– / Unk 775 745 718 678 649 623 590 500 345 200 101

(c) Dose-Dense (d) Dose-Dense

100 100

80 80
Disease free survival (%)

Overall survival (%)

60 60
HER2– / Unk: Reference group HER2– /Unk: Reference group
HER2+ / No T: HR, 1.35; 95% CI 0.99–1.84 / aHR, 1.20; 95% CI 0.87–1.66 HER2+ / No T: HR, 1.27; 95% CI 0.81–2.00 / aHR, 1.09; 95% CI 0.68–1.74
HER2+ / T: HR, 1.25; 95% CI 0.76–2.05 / aHR, 0.92; 95% CI 0.55–1.56 HER2+ / T: HR, 1.28; 95% CI 0.62–2.63 / aHR, 0.93; 95% CI 0.43–2.00
40 40

20 HER2+ / No T 20 HER2+ / No T
HER2+ / T HER2+ / T
HER2– / Unk HER2– / Unk
0 0

0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10

Time since random assignment (years) Time since random assignment (years)

Number at risk Number at risk

HER2+ / No T 166 156 139 130 123 115 108 99 65 35 11 HER2+ / No T 166 162 158 152 148 143 129 116 82 43 13
HER2+ / T 60 59 52 44 44 43 41 29 21 13 5 HER2+ / T 60 60 56 52 50 49 46 33 21 13 5
HER2– / Unk 776 742 692 659 622 590 558 488 344 189 82 HER2– / Unk 776 754 727 706 682 662 634 553 389 225 100

Figure 4. Disease-free survival in the standard interval cohort (a); Overall survival in the standard interval cohort (b); Disease-free survival in the
dose-dense cohort (c); Overall survival in the dose-dense cohort (d). Abbreviations: aHR, adjusted hazard ratio; CI, confidence intervals; HER2+/No T,
HER2-positive no trastuzumab group; HER2+/T, HER2-positive trastuzumab group; HER2−/Unk, HER2-negative/unknown group; HR, hazard ratio.
[Color figure can be viewed at wileyonlinelibrary.com]

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Lambertini et al. 167

Median follow-up was 8.1 years (IQR, 7.0–9.3). Number Discussion

and type of survival events in the three cohorts are reported in To the best of our knowledge, this is the first analysis explor-
Table 2. No significant interaction between HER2 status, ing the efficacy of dose-dense adjuvant chemotherapy in
trastuzumab use and chemotherapy treatment was observed for patients with HER2-positive disease receiving adjuvant
both DFS (univariate p = 0.698 and multivariate p = 0.705) and trastuzumab. At a median follow-up of 8.1 years, we showed
OS (univariate p = 0.708 and multivariate p = 0.826). Neverthe- that dose-dense chemotherapy significantly improved both
less, the benefit of dose-dense chemotherapy appeared to be DFS and OS of patients with HER2-negative/unknown breast
smaller in the HER2-positive trastuzumab group. cancer. Although no significant interaction between HER2 sta-
In the HER2-positive no trastuzumab group, DFS at tus, trastuzumab use and chemotherapy were observed, the
7 years was 72.1 and 64.4% in the dose-dense and standard- benefit of dose-dense chemotherapy appeared to be smaller
interval arms, respectively (HR, 0.78; 95% CI 0.53–1.13; (if any) in the subgroup of patients with HER2-positive dis-
adjusted HR, 0.79; 95% CI 0.53–1.17; Fig. 2a). OS at 7 years ease who received adjuvant trastuzumab.
was 85.2 and 78.6% in the dose-dense and standard-interval At a longer follow-up than previously reported in other dose-
arms, respectively (HR, 0.63; 95% CI 0.37–1.07; adjusted HR, dense adjuvant chemotherapy trials, our analysis confirms the
0.59; 95% CI 0.34–1.03; Fig. 3a). benefit of shortening the interval between treatment cycles in
In the HER2-positive trastuzumab group, DFS at 7 years high-risk early breast cancer patients (with a 6.6 and 5.6% abso-
was 68.7 and 72.3% in the dose-dense and standard-interval lute improvement in DFS and OS at 7 years, respectively, in the
arms, respectively (HR, 0.99; 95% CI 0.52–1.89; adjusted HR, HER2-negative/unknown population). This is in line with the
0.71; 95% CI 0.35–1.42; Fig. 2b). OS at 7 years was 84.9 and findings from the recent Early Breast Cancer Trialists’ Collabora-
86.1% in the dose-dense and standard-interval arms, respec- tive Group (EBCTCG) meta-analysis5 supporting the use of
tively (HR, 0.95; 95% CI 0.37–2.41; adjusted HR, 0.91; 95% dose-dense chemotherapy as the preferred adjuvant chemother-
CI, 0.31–2.68; Fig. 3b). apy approach in patients deemed at higher risk of disease recur-
In the HER2-negative/unknown group, DFS at 7 years was rence. In terms of adverse events, as also confirmed in our
78.7 and 72.1% in the dose-dense and standard-interval arms, analysis, the rate of grade 3–4 neutropenia is lower with the use
respectively (HR, 0.74; 95% CI 0.61–0.89; adjusted HR, 0.72; 95% of dose-dense chemotherapy considering that primary prophy-
CI 0.59–0.87; Fig. 2c). OS at 7 years was 90.9 and 85.3% in the laxis with granulocyte colony-stimulating factor is mandatory in
dose-dense and standard-interval arms, respectively (HR, 0.66; this setting.5 On the other hand, a higher rate of grade 3–4 ane-
95% CI 0.50–0.86; adjusted HR, 0.64; 95% CI 0.49–0.84; Fig. 3c). mia is expected when shortening the interval between cycles but

Cancer Therapy and Prevention

Comparing DFS of the HER2-positive groups with that of with no difference in cardiotoxicity or other nonhematological
the HER2-negative/unknown group among patients that toxicities and neither in treatment compliance.5 Nevertheless,
received standard-interval chemotherapy, univariate HRs were despite the positive risk–benefit ratio in the overall high-risk
1.27 (95% CI 0.95–1.70) in the HER2-positive no trastuzumab breast cancer population, in the era of treatment personalization
group (adjusted HR, 0.96; 95% CI 0.71–1.30) and 0.93 (95% CI and de-escalation, it remains crucial to better define the popula-
0.59–1.47) in the HER2-positive trastuzumab group (adjusted tion of patients that really benefit from this approach.
HR, 0.81; 95% CI 0.50–1.31; Fig. 4a). For OS, univariate HRs Before the introduction of targeted therapies, a retrospective
were 1.32 (95% CI 0.90–1.94) in the HER2-positive no analysis conducted within the phase III MIG1 trial in patients
trastuzumab group (adjusted HR, 0.95; 95% CI 0.63–1.43) and with HER2-positive disease demonstrated that anthracycline-
0.84 (95% CI 0.44–1.61) in the HER2-positive trastuzumab based dose-dense chemotherapy is highly effective in this set-
group (adjusted HR, 0.67; 95% CI 0.34–1.30; Fig. 4b). ting.6 Similarly, the EBCTCG meta-analysis, in which the major-
Comparing DFS of the HER2-positive groups with that of ity of patients with HER2-positive disease were not exposed to
the HER2-negative/unknown group among patients that targeted therapy, showed that dose-dense chemotherapy was
received dose-dense chemotherapy, univariate HRs were 1.35 effective irrespectively of HER2 status.5 Consistently with previ-
(95% CI 0.99–1.84) in the HER2-positive no trastuzumab group ous findings, our analysis showed apparent similar absolute and
(adjusted HR, 1.20; 95% CI 0.87–1.66) and 1.25 (95% CI relative DFS and OS benefits of administering anthracycline-
0.76–2.05) in the HER2-positive trastuzumab group (adjusted and taxane-based chemotherapy with a dose-dense schedule in
HR, 0.92; 95% CI 0.55–1.56; Fig. 4c). For OS, univariate HRs patients with HER2-positive tumors not treated with adjuvant
were 1.27 (95% CI 0.81–2.00) in the HER2-positive no trastuzumab and those with HER2-negative/unknown disease.
trastuzumab group (adjusted HR, 1.09; 95% CI 0.68–1.74), and The high proliferative capability and their sensitivity to
1.28 (95% CI 0.62–2.63) in the HER2-positive trastuzumab anthracycline-based chemotherapy15 may explain the potential
group (adjusted HR, 0.93; 95% CI 0.43–2.00; Fig. 4d). predictive value of HER2-positivity in the absence of targeted
Results of the Cox regression model for all the variables therapy for the efficacy of dose-dense regimens. Nevertheless, it
evaluated in the study are reported as Supporting Information should be highlighted that trastuzumab has radically changed
Table S3 for disease-free survival and Supporting Information the prognosis of patients with HER2-positive early breast cancer
Table S4 for overall survival. converting this tumor from an aggressive subtype to one with

Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC

 168 Dose-dense chemotherapy in HER2+

good outcomes; thus, anti-HER2 targeted therapy remains the Our findings should be considered with caution because of
cornerstone in the treatment of this disease.16 In our analysis, we some important limitations. This is an exploratory analysis
also explored the benefit of introducing adjuvant trastuzumab in that was not preplanned in the original protocol. No strong
patients with HER2-positive disease. Considering that patients conclusions can be derived considering both the wide 95% CI
receiving anti-HER2 targeted therapy had to survive long enough and that the observed differences within the cohort of patients
to be offered trastuzumab, a potential lead-time bias cannot be with HER2-positive disease failed to achieve statistical signifi-
excluded in this analysis. However, despite this potential bias, our cance. This may be due also to lack of power based on the
data do not exhibit a severe violation of the proportional hazards small number of patients with HER2-positive disease particu-
assumption to seriously affect our findings when the effect of the larly in the cohort treated with adjuvant trastuzumab. For this
treatments within the HER2/trastuzumab strata is compared same reason, despite our original intent considering the differ-
(data not shown). As expected, we observed that patients with ent behavior of HER2-positive tumors according to hormone
HER2-positive tumors treated with dose-dense or standard- receptor status,23 it was not possible to explore potential dif-
interval chemotherapy without adjuvant trastuzumab have ferences in treatment effect between patients with hormone
generally experienced worse DFS and OS than those exposed to receptor-positive or negative disease. In addition, HER2 test-
adjuvant trastuzumab or patients with HER2-negative/unknown ing was performed locally in an era in which there was no
disease. Therefore, chemotherapy escalation approaches should be specific recommendation on the type of test to be used.
considered with particular cautious in this setting where anti- Finally, in terms of safety, cardiotoxicity was not systemati-
HER2 blockade is the mainstay therapy.16,17 cally collected in the trial. Despite these limitations, impor-
In the current anti-HER2 targeted therapy era, the benefit of tantly, our analysis was conducted within a large multicenter
dose-dense chemotherapy remains unknown when trastuzumab randomized trial with a median follow-up exceeding 8 years
is administered.11 Differently from previous studies in which all and it allowed for the first time to have some insights on the
patients received dose-dense chemotherapy,8–10 we could specifi- effect of dose-dense chemotherapy in the anti-HER2 targeted
cally explore whether dose intensification may benefit patients therapy era. Notably, it will be difficult to replicate these find-
treated with adjuvant trastuzumab. Despite no significant inter- ings within other dose-dense studies considering that in the
action was observed between HER2 status, trastuzumab treat- older trials most of the patients with HER2-positive disease
ment and the effect of dose-dense chemotherapy, no apparent did not receive anti-HER2 therapy5 while in the more recent
absolute and relative differences in DFS and OS could be ones all of them received trastuzumab.18,24 Therefore, this
Cancer Therapy and Prevention

observed between the dose-dense and standard-interval sched- analysis retains a unique value with important clinical impli-
ules among patients with HER2-positive patients who received cations for the choice of the best adjuvant chemotherapy
trastuzumab. Similar conclusions were reached in a recently regimen.
presented secondary analysis of the PANTHER trial showing no In conclusion, our exploratory analysis of the GIM2 trial
apparent significant benefit of dose-dense chemotherapy in showed that dose-dense chemotherapy remains associated
patients with HER2-positive early breast cancer who underwent with a significant survival improvement in high-risk early
adjuvant trastuzumab.18 These data are of particular relevance in breast cancer patients with HER2-negative/unknown disease.
the current chemotherapy de-escalation era thanks to the avail- Although no significant interaction between HER2 status,
ability of effective anti-HER2 targeted agents.19 Based on recent trastuzumab use and chemotherapy was observed, the benefit
findings, patients with stage I HER2-positive breast cancer are of dose-dense chemotherapy appeared to be smaller (if any)
candidates to receive adjuvant weekly paclitaxel and in patients with HER2-positive who received adjuvant
trastuzumab.17 On the contrary, patients with stage II-III disease trastuzumab. Results of the FeDeriCa trial (NCT03493854)
may benefit from a neoadjuvant approach with taxane-based are awaited to better assess the need for chemotherapy escala-
chemotherapy (with or without anthracyclines) plus dual anti- tion approaches in this setting.
HER2 blockade with trastuzumab and pertuzumab,20,21 and the
possibility to switch to trastuzumab-emtansine (T-DM1) in the
case of residual disease at surgery.22 In such scenario of increased
Acknowledgements
optimization of anti-HER2 blockade, we may speculate that Dr Lambertini acknowledges the European Society for Medical Oncology
increasing the dose intensity of chemotherapy in the early setting (ESMO) for an ESMO Merit Award to present these results during the
might not be considered a needed treatment strategy. 2019 ESMO Breast Cancer Congress in Berlin (Germany) on May 4, 2019.

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Cancer Therapy and Prevention

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Int. J. Cancer: 147, 160–169 (2020) © 2019 UICC