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Postmastectomy Hypofractionated vs Conventionally Fractionated Radiotherapy for High-Risk Breast Cancer

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Key Points

  • No difference in 5-year locoregional recurrence was observed between hypofractionated and conventionally fractionated radiotherapy.
  • Acute and late toxicities were similar in both the groups.

In a Chinese, single-center, noninferiority phase III trial reported in The Lancet Oncology, Wang et al found that postmastectomy hypofractionated radiotherapy was noninferior to and associated with similar toxicities vs conventionally fractionated radiotherapy in patients with high-risk breast cancer.

Study Details

In the open-label trial, 810 eligible patients (modified intent-to-treat population) from a single academic hospital in China were randomly assigned between June 2008 and June 2016 to receive postmastectomy hypofractionated radiotherapy (n = 401) or conventionally fractionated radiotherapy (n = 409). Patients had to have at least four positive axillary lymph nodes or primary tumor stage T3–4 disease. Hypofractionated radiotherapy consisted of chest wall and nodal irradiation at 43.5 Gy in 15 fractions over 3 weeks; conventionally fractionated radiotherapy consisted of 50 Gy in 25 fractions over 5 weeks.

The primary endpoint was 5-year locoregional recurrence, with a 5% margin establishing noninferiority (equivalent to a hazard ratio [HR] < 1.883).

Treatment Outcomes

Median follow-up was 58.5 months. Locoregional recurrence was observed in 60 patients (7%), including 31 in the hypofractionated group and 29 in the conventionally fractionated group. The 5-year cumulative incidence of locoregional recurrence was 8.3% in the hypofractionated group vs 8.1% in the conventionally fractionated group (absolute difference = 0.2%, 90% confidence interval [CI] = –3.0–2.6; HR = 1.10, 90% CI = 0.72–1.69; P < .0001 for noninferiority). At 5 years, disease-free survival was 74% vs 70% (HR= 0.88, P = .429) and overall survival was 84% vs 86% (HR = 1.13, P = .526).  

Toxicity

A lower incidence of grade 3 acute skin toxicity was observed in the hypofractionated group (3% vs 8%, P < .0001). Apart from this, there were no significant differences between groups in the incidence of other acute or late toxicities, including symptomatic radiation pneumonitis, lymphedema, ischemic heart disease, and shoulder dysfunction.

The investigators concluded, “Postmastectomy hypofractionated radiotherapy was noninferior to and had similar toxicities to [conventionally] fractionated radiotherapy in patients with high-risk breast cancer. Hypofractionated radiotherapy could provide more convenient treatment and allow providers to treat more patients.”

Ye-Xiong Li, MD, of the National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, is the corresponding author for The Lancet Oncology article.

Disclosure: The study was funded by National Key Projects of Research and Development of China, Chinese Academy of Medical Science Innovation Fund for Medical Sciences, and Beijing Marathon of Hope, Cancer Foundation of China. The study authors' full disclosures can be found at thelancet.com.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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