Treatment outcomes and survival of patients with breast cancer aged 75 and older: A comparative study using propensity score-adjusted analysis.

e13763 Background: With an aging society, the incidence of breast cancer among elderly patients is expected to rise. We aimed to explore treatment outcomes in breast cancer patients aged 75 and older at our institution. The lack of consensus on whether adjuvant therapy for elderly breast cancer patients should mimic that for younger patients prompted our investigation. Methods: We conducted a comparative study using data from 1553 breast cancer surgery cases (stage 0-3) treated between April 2007 and August 2021. Patients were divided into two groups: those aged 75 and older (n=184) and those aged 74 and younger (n=1369). Variables investigated included mean age, tumor size, stage, and subtype; surgical procedures and adjuvant therapies; overall survival (OS); and OS in the 75 and older group, considering the presence or absence of hormone therapy, and propensity score-adjusted OS. Results: Comparing the group aged 74 and younger with the group aged 75 and older revealed: Mean age: (55.5 years vs. 79.6 years), tumor size: (2.4 cm vs. 2.3 cm), stage (0/1/2/3) (%): (7.3/43.1/44.1/4/6 vs. 7.6/43.4/43.4/5.7), subtype (Luminal A/Luminal B/TN/HER2) (%): (60.0/16.7/11.3/7.9 vs. 63.5/10.7/15.7/5.7). Except for age, no significant differences were observed. Mastectomy (%): 45.9 vs. 50.8, axillary lymph node dissection (%): 33 vs. 22.3, adjuvant therapy (%): 93.2 vs. 65.7, adjuvant hormone therapy (%): 90 vs. 68, adjuvant chemotherapy (%): 68 vs. 14. The group aged 75 and older received significantly less adjuvant hormone therapy and chemotherapy. Kaplan-Meier 10-year OS rates: 90.3% vs. 77.5%, showing a trend toward lower survival in the group aged 75 and older, albeit not statistically significant. No significant differences were found in overall survival rates by subtype. In the group aged 75 and older, hormone therapy was omitted in 44.6% and administered in 55.4%, resulting in a significant difference in 10-year OS rates (63.5% vs. 84.7%). Following propensity score adjustment for age, stage, and subtype, the hormone therapy-free group exhibited a higher 10-year OS rate of 100%, in contrast to 84.7% in the hormone therapy group. Conclusions: Breast cancer cases in patients aged 75 and older show similar biological characteristics to those aged 74 and younger. The absence of adjuvant therapy does not impact OS, even though elderly patients aged 75 and older are less likely to receive adjuvant hormone therapy and chemotherapy.