BOSTON -- Hypofractionated radiotherapy is a safe and efficient alternative to conventional fractionation in women with high breast cancer after mastectomy, according to a study presented September 28 at the American Society for Radiation Oncology (ASTRO) annual meeting.     

Guang-Yi Sun, MD, of the Chinese Academy of Medical Sciences in Beijing, China, discussed 10-year outcomes from a phase III trial comparing the two techniques, with results suggesting that adopting hypofractionated radiotherapy could improve patient convenience and healthcare efficiency without compromising long-term disease control. 

“Hypofractionated postmastectomy radiotherapy provides durable locoregional control, comparable survival outcomes, and acceptable long-term toxicity in high-risk breast cancer,” Sun said. 

Radiotherapy after mastectomy is standard of care for high-risk breast cancer patients to reduce the risk of recurrence. Hypofractionated radiotherapy delivers larger daily doses of radiation over a shorter total number of sessions, whereas conventional fractionation delivers smaller daily doses over a longer period of weeks. 

While hypofractionated radiotherapy is well established for whole-breast irradiation after breast-conserving surgery, there is little long-term data on its use post-mastectomy, Sun added. 

To bridge the gap, Sun and colleagues enrolled 820 women with high-risk breast cancer (≥ 4 positive axillary nodes or T3–T4 disease) who had undergone modified radical mastectomy and axillary dissection at a national cancer center in China between 2008 and 2016. Participants were randomized 1:1 to either conventional radiotherapy (50 Gy in 25 fractions over 5 weeks) or hypofractionated radiotherapy (43.5 Gy in 15 fractions over 3 weeks) to the chest wall and supraclavicular region. 

The primary endpoint was five-year locoregional recurrence (LRR), with a pre-specified non-inferiority margin of five percentage points. Median follow-up was 11.5 years. 

At five years, LRR was 8.6% with conventional fractionation and 9.6% with hypofractionation, meeting the non-inferiority margin. At 10 years, rates remained stable at 10.3% and 12.0%, with curves showing no late separation. No significant differences were observed in 10-year disease-free survival (65.2% vs. 69.9%) or overall survival (72.9% vs. 77.5%). 

In addition, no grade 4–5 late toxicities or brachial plexopathy were reported. Grade 1–2 pulmonary fibrosis occurred more frequently with hypofractionation (19.7% vs. 11.7%; p = 0.008), although all events were asymptomatic, Sun noted. 

"These long-term results further establish hypofractionated postmastectomy radiotherapy with regional nodal irradiation as a standard of care for patients with high-risk breast cancer," Sun concluded. 

Including the present study, there are now three long-term clinical trials worldwide that support a 3-week schedule of hypofractionated radiotherapy in this patient population, Sun concluded.

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