Association of Chemotherapy with Survival in Elderly Patients with Multiple Comorbidities and Estrogen Receptor-Positive, Node-Positive Breast Cancer

Importance: Breast cancer risk and comorbidities increase with age. Data are lacking on the association of adjuvant chemotherapy with survival in elderly patients with multiple comorbidities and node-positive breast cancer. Objective: To examine the association of chemotherapy with survival in elderly patients with multiple comorbidities and estrogen receptor-positive, node-positive breast cancer. Design, Setting, and Participants: This retrospective cohort study included patients in the US National Cancer Database who were 70 years or older; had a Charlson/Deyo comorbidity score of 2 or 3; had estrogen receptor-positive, ERBB2 (formerly HER2 or HER2/neu)-negative breast cancer; and underwent surgery for pathologic node-positive breast cancer from January 1, 2010, to December 31, 2014. Propensity scores were used to match patients receiving adjuvant chemotherapy with those not receiving adjuvant chemotherapy based on age, comorbidity score, facility type, facility location, pathologic T and N stage, and receipt of adjuvant endocrine and radiation therapy. Data analysis was performed from December 13, 2018, to April 28, 2020. Exposures: Chemotherapy. Main Outcomes and Measures: The association of adjuvant chemotherapy with overall survival was estimated using a double robust Cox proportional hazards regression model. Results: Of a total of 2445870 patients in the data set, 1592 patients (mean [SD] age, 77.5 [5.5] years; 1543 [96.9%] female) met the inclusion criteria and were included in the initial nonmatched analysis. Of these patients, 350 (22.0%) received chemotherapy and 1242 (78.0%) did not. Compared with patients who did not receive chemotherapy, patients who received chemotherapy were younger (mean age, 74 vs 78 years; P <.001), had larger primary tumors (pT3/T4 tumors: 72 [20.6%] vs 182 [14.7%]; P =.005), and had higher pathologic nodal burden (75 [21.4%] vs 81 [6.5%] with stage pN3 disease and 182 [52.0%] vs 936 [75.4%] with stage pN1 disease; P <.001). More patients who received chemotherapy also received other adjuvant treatments, including endocrine therapy (309 [88.3%] vs 1025 [82.5%]; P =.01) and radiation therapy (236 [67.4%] vs 540 [43.5%]; P <.001). In the matched cohort, with a median follow-up of 43.1 months (95% CI, 39.6-46.5 months), no statistically significant difference was found in median overall survival between the chemotherapy and no chemotherapy groups (78.9 months [95% CI, 78.9 months to not reached] vs 62.7 months [95% CI, 56.2 months to not reached]; P =.13). After adjustment for potential confounding factors, receipt of chemotherapy was associated with improved survival (hazard ratio, 0.67; 95% CI, 0.48-0.93; P =.02). Conclusions and Relevance: This cohort study found that in node-positive, estrogen receptor-positive elderly patients with breast cancer and multiple comorbidities, receipt of chemotherapy was associated with improved overall survival. Despite attempts to adjust for selection bias, these findings suggest that physicians carefully selected patients likely to derive treatment benefit from adjuvant chemotherapy based on certain unmeasured variables. A standardized, multidisciplinary approach to care may be associated with long-term treatment outcomes in this subset of the population.