A Single-Institutional Prospective Study Comparing Clinical Outcome and Toxicities of 1-Week Versus 3-Week Adjuvant Radiotherapy in Post-Mastectomy Breast Carcinoma: 3-Year Follow-Up

Abstract

Objective: Recent data showed 1-week schedule as non-inferior to the 3-week schedule of adjuvant radiotherapy in breast carcinoma in terms of local control and normal tissue toxicity. In governmental set-ups for mostly poor patients, it is highly desirable to validate this data and apply in practice. This study was done to compare recurrence-free survival, and acute and late toxicities of these two schedules.

Methods: In this prospective, observational, single-institutional study, post-mastectomy breast carcinoma patients (pT3N0M0; or early disease with positive margin) were 1:1 divided in two groups: Arm A received adjuvant chest wall radiation 26Gy in 5 fractions over 1 week, and Arm B received 40Gy in 15 fractions over 3 weeks. Patients with both arms completed adjuvant therapy, and they were followed up 3-monthly for 1 year, then 6-monthly. Acute and late toxicities were assessed using Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Statistical analysis was done using SPSS v30.0.

Results: Between May 2020 and October 2021, total 43 patients (Arm A – 20, Arm B – 23) were treated by 3D Conformal Radiation Therapy in VARIAN TrueBeam, and were followed-up till December 2024. Over a median follow-up of 42 months, 1 patient in Arm A (5%) and 2 in Arm B (8.7%) had chest wall recurrence (Odds ratio 0.5526, p-value 0.6392). Mean RFS for Arm A and Arm B were 51.150 months (95% CI 49.526 – 52.774) and 50.633 months (95% CI 48.805 – 52.460) respectively (p-value 0.691). No significant difference in acute skin toxicity was observed between two arms. At 3 years of follow-up, grade 1 chronic cough was seen in 5% of Arm A and 8.7% of Arm B (p-value 0.6392), grade 1 pulmonary fibrosis in 5% of Arm A and 4.35% of Arm B (p-value 0.9194), and grade 1 cardiac chest pain in 10% of Arm A and 4.35% of Arm B (p-value 0.4799) without any serious cardiovascular event.

Conclusion: No statistically significant difference was observed between the 1-week (26Gy in 5 fractions) schedule and the standard 3-weekly regimen of adjuvant radiotherapy in post-mastectomy node-negative breast cancer patients in terms of local control, and acute and late skin, pulmonary and cardiac toxicities.