# The Feasibility of Omission of Postoperative Radiotherapy in Japanese Patients With Early Breast Cancer Treated With Breast-Conserving Surgery

## TL;DR

This study suggests that skipping post-surgery radiation may be safe for low-risk Japanese breast cancer patients who had breast-conserving surgery.

## Contribution

The study identifies a low-risk group of Japanese patients for whom omitting postoperative radiotherapy may be feasible without compromising outcomes.

## Key findings

- Postoperative radiotherapy improved local control but not breast cancer-specific survival in the total population.
- In low-risk patients, omitting radiotherapy did not significantly affect local recurrence rates or survival outcomes.
- Equivalent outcomes were observed in low-risk patients with and without radiotherapy after propensity-score matching.

## Abstract

Background

This study was aimed at analyzing the impact of postoperative radiotherapy (PORT) after breast-conserving surgery (BCS) on Japanese patients with early-stage breast cancer and exploring the potential of PORT omission.

Materials and methods

Data from 794 patients with early-stage breast cancer (T1-2, N0-1), who underwent BCS with (n = 310) or without PORT (n = 484) were retrospectively analyzed. Local control (LC) rate and breast cancer-specific survival (BCSS) were compared between the groups that received and did not receive PORT in the whole cohort and low-risk cohort (i.e., the cohort with negative surgical margin, lymph node negativity, and estrogen receptor positivity, excluding young age of 49 or less), and in low-risk subgroup using propensity-score matching.

Results

PORT was associated with better LC but not BCSS in the total population. In the low-risk cohort, the incidence of local recurrence in patients without and with PORT was 5.3% and 4.8%, respectively, at 10 years (p = 0.591), and 7.8% and 4.8%, respectively, according to propensity-score matching (p = 0.485).

Conclusion

PORT improved LC in the total population, but not BCSS or overall survival (OS). In the low-risk group analysis (negative surgical margin, lymph node negativity, estrogen receptor positivity, and age 50 years or more), equivalent LC, BCSS, and OS were found including propensity-matched comparison. Therefore, this study showed that the omission of PORT could be a treatment option for low-risk Japanese patients. Further multi-center prospective studies are warranted to validate these findings and reduce the unnecessary burden of PORT for patients and institutions.