Abstract 143P
Background
Adjuvant systemic therapy in women with early ER+/HER2+ breast cancer includes chemotherapy (ChT), one year of anti-HER2 therapy and at least five years of hormonal therapy (HT). Here, we explore the impact of de-escalation of adjuvant therapy on the outcome in women with early ER+/HER2+ breast cancer.
Methods
All women with ER+ (IHC ≥ 1%) and HER2+ (IHC3+ and/or FISH ratio ≥ 2.0) early breast cancer who received adjuvant systemic therapy at the Institute of Oncology Ljubljana between year 2006 and 2016 were retrospectively included in this study. For various reasons ChT, anti-HER2 therapy (trastuzumab) or HT were omitted or administered for shorter duration (i.e. de-escalated) in some women. The relationship between de-escalated therapy and distant disease-free survival (DDFS) was analysed using a multivariate Cox proportional-hazards model (Table).
Results
A total of 292 women with ER+/HER2+ early breast cancer and median age of 53.9 years (range 24-85 years) were included. Patients were followed up to 10 years (median time 6.6 years) and death or distant recurrence occurred in 58 (19.9%) women. The estimated DDFS at 5 and 10 years was 86% and 74%, respectively. A total of 84 (28.9%), 92 (31.5%) and 45 (15.4%) women did not receive adjuvant ChT, received no or < 1yr of trastuzumab and discontinued HT prematurely. De-escalation of HT (HR 4.44; p<0.001) and trastuzumab (HR 3.42; p=0.02) had a significant detrimental effect on the DDFS. In contrast, there was a non-significant effect of de-escalated ChT on DDFS (HR 1.15; p=0.78) (Table). Table: 143P
| Covariate | N | HR | 95% CI | P |
| Age | 292 | 1.01 | 0.99-1.04 | 0.29 |
| Stage Stage I (ref.) | 107 | |||
| Stage II | 118 | 3.65 | 1.64-8.12 | < 0.01 |
| Stage III | 67 | 10.04 | 4.22-23.85 | < 0.001 |
| Trastuzumab 1yr of therapy (ref.) | 200 | |||
| No or <1 yr. | 92 | 3.42 | 1.26-9.27 | 0.02 |
| HT Yes (ref.) | 247 | |||
| No or discontinued HT | 45 | 4.44 | 2.39-8.25 | < 0.001 |
| ChT Yes (ref.) | 208 | |||
| No | 84 | 1.15 | 0.44-3.01 | 0.78 |
| Treatment period 2006-2010 (ref.) | 133 | |||
| 2011-2016 | 159 | 0.58 | 0.32-1.04 | 0.07 |
Conclusions
Women with early ER+/HER2+ breast cancer should be strongly encouraged not to omit or discontinue HT and anti-HER2 therapy prematurely. De-escalation of adjuvant ChT therapy might not be detrimental for some women with this subtype of breast cancer.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Institute of Oncology Ljubljana.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.