De-escalating adjuvant therapies in older patients with lower risk estrogen receptor-positive breast cancer treated with breast-conserving surgery: A systematic review and meta-analysis.

Purpose: Radiation therapy (RT) and endocrine therapy (ET) are standard treatments for hormone receptor-positive (HR+) breast cancer after breast-conserving surgery (BCS). However, many older patients are at greater risk of treatment-related toxicities and non-cancer related death, and less likely to benefit from these standard treatments. A systematic review was performed evaluating outcomes of omitting RT or ET in older patients aged ≥50 treated with BCS for lower-risk breast cancer.

Methods: Medline, Embase, and the Cochrane Register of Controlled Trials were queried from 1980 to April 30th, 2020 for randomized controlled studies (RCTs) and prospective cohort studies (PCSs) evaluating omission of RT and/or ET compared to RT plus ET in patients. Meta-analysis was performed using random-effects models with findings reported as risk ratios (RR) with 95% confidence intervals (CI).

Results: From 3860 citations, 10 prospective studies met eligibility criteria. Omission of RT alone was evaluated in 7 RCTs (n = 4604) and one PCS (n = 667); omission of ET alone was assessed in 1 PCS (n = 271); and omission of either ET or RT was compared to ET plus RT in 1 RCT (n = 495). Adjuvant RT compared to no RT reduced 5- and 10-year in-breast tumor recurrence [5-year: RR 0.16, 95 %CI 0.09-0.27 l 10-year: 0.28, 95 %CI 0.16-0.5], but had no effect on survival [5-year: RR 0.94, 95 %CI 0.77-1.15; 10-year: 1.01, 95 %CI 0.9-1.12].

Conclusion: The current body of evidence suggests that RT can be omitted in older patients with lower-risk disease. However, more trials on the omission of ET are required to better inform treatment decisions.