Use of adjuvant chemotherapy and outcomes in women age 70 and older with HER2-positive (HER2+) or triple-negative (TN) breast cancer (BC).

Abstract

1044 Background: Chemotherapy use decreases with increasing age. There is a stronger rationale for adjuvant chemotherapy in HER2+ and TN BC due to a higher risk of recurrence, known benefit of trastuzumab with chemotherapy and lack of other systemic options. Aims: 1) Characterize and compare outcomes of resected HER2+/TN BC in older women (age ≥70) (OW) vs. younger women (age 50-69) (YW) 2) Determine chemotherapy use in OW vs. YW 3) Compare outcomes in OW based on receipt of chemotherapy. Methods: Women ≥ 50 years old with newly diagnosed resected HER2+ or TN stage I-III BC in British Columbia between 2003 and 2006 were included. Demographic, prognostic and treatment characteristics were compared in OW vs. YW using Chi-Square and t-tests. Kaplan-Meier curves for relapse-free survival (RFS), breast cancer-specific survival (BCSS) and overall survival (OS) were calculated in the various cohorts. Results: OW (n=292) had larger tumors (p=0.002), more often had mastectomy and less often had adjuvant radiation (p<0.001) than YW (n=946). There were no differences in nodal or receptor status. OW vs. YW were less likely to receive chemotherapy (28.1 vs. 81.3%, p<0.001); odds decreased with increasing age (OR 15.9 and 7.4 for women age 50-59 and 60-69 vs. ≥70, p<0.001). OW had worse 5-year RFS (75.4 vs. 83.2%, p=0.002), local RFS (93.2 vs. 95.5%, p=0.05) and distant RFS (77.5 vs. 85.5%, p=0.001). Both 5-year BCSS (79.5 vs. 88.1%, p<0.001) and OS (63.7 vs. 85.8%, p<0.001) were worse in OW vs. YW. OS, but not BC-specific outcomes (RFS, BCSS), was significantly better in those who received chemotherapy compared to those who did not (Table). Conclusions: OW with HER2+ and TN BC are less likely to receive adjuvant chemotherapy than YW. No difference in BCSS was noted in OW based on receipt of chemotherapy, possibly due to a small sample size. Differences in OS based on receipt of adjuvant chemotherapy suggest that oncologists in British Columbia are accurately identifying women with limited life expectancy less likely to benefit from chemotherapy. [Table: see text]