Abstract P1-09-04: Use of adjuvant chemotherapy and outcomes in women 70 years and older with HER-2 positive or triple negative breast cancer
Authors: Hsu T , Speers C , Tyldesley S , Mcgahan C , Chia SK 
Published: August 2014

Background: Chemotherapy use decreases with increasing age. There is a stronger rationale for adjuvant chemotherapy in HER-2 positive (HER2+) and triple negative (TN) breast cancer (BC) due to a higher risk of recurrence, known benefit of trastuzumab with chemotherapy and lack of other systemic options.

Aims: 1) Compare outcomes of resected HER2+ and TN BC in older women (age ≥70) (OW) vs. younger women (age 50-69) (YW) 2) Determine chemotherapy use in OW vs. YW 3) Explore factors associated with chemotherapy use in women with HER2+ and TN BC and determine how these factors differ by age group (OW vs. YW)

Methods: Women ≥50 years old with newly diagnosed resected HER2+ or TN stage I-III BC in British Columbia from 2003-2006 were included. Data on comorbidity, performance status, and reason for no chemotherapy was gathered via chart review of OW. Kaplan-Meier curves for relapse-free survival (RFS), breast cancer-specific survival (BCSS) and overall survival (OS) were calculated. Logistic regression was used to model the likelihood of receiving chemotherapy and Cox proportional hazards was used to model BCSS and OS.

Results: OW (n = 292) had larger tumors (p = 0.002), more often had mastectomy and less often had adjuvant radiation (p&lt;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&lt;0.001); odds decreased with increasing age (OR 15.9 and 7.4 for women age 50-59 and 60-69 vs. ≥70, p&lt;0.001). Odds of receiving chemotherapy were higher in women with HER2+, ER/PR negative tumours than those with HER2+, ER/PR positive (OR 2.2) and TN tumours (OR 1.7) (p = 0.004). Some factors associated with chemotherapy use differed between YW and OW: tumour size (T2 vs. T1, OR 2.6, p = 0.059) and grade (high grade vs. low grade, OR 6.5, p = 0.02) were only associated with chemotherapy use in YW. OW with more comorbid conditions (CCI≥2) were less likely to receive chemotherapy than those with zero or one comorbid condition (OR 5.0 and 2.7 respectively, p = 0.009).

In OW, reasons cited for not administering chemotherapy included: patient refusal (45.2%), patient age (38.1%), perceived minimal benefit (36.7%), patient comorbidity (28.6%), and concern about chemotherapy toxicity (28.6%). Chemotherapy was not mentioned in almost 1 in 5 cases (17.6%).

OW had worse 5-year RFS (75.4 vs. 83.2%, p = 0.002), BCSS (79.5 vs. 88.1%, p&lt;0.001) and OS (63.7 vs. 85.8%, p&lt;0.001). After adjusting for known prognostic factors and treatment differences, increasing age was still significantly associated with poorer 5-year OS (HR 1.2, p = 0.003), but not with BCSS after adjusting for the competing risk of non-BC deaths. 5-year OS, but not BC-specific outcomes (RFS, BCSS), was significantly better in those who received chemotherapy compared to those who did not.

Conclusion: OW with HER2+/TN BC are less likely to receive adjuvant chemotherapy than YW. Factors associated with chemotherapy receipt differ in OW, with tumor size and grade only being influential in YW. Age was only independently associated with OS and not BCSS, suggesting inferior BCSS rates in OW may be due to the presence of larger tumors or differences in treatments received by OW.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-09-04.