ASTRO 2017: Accelerated Breast Radiation Therapy Following Mastectomy Can Shorten Treatment Time While Maintaining Tumor Control

Key Points

Radiation therapy following mastectomy for intermediate-stage, high-risk breast cancer can be shortened from 5 to 3 weeks while maintaining tumor control rates in the breast and surrounding region that are equivalent to conventional treatment, according to research presented by Sun et al at the 59th Annual Meeting of the American Society for Radiation Oncology (ASTRO).

Radiation therapy following mastectomy for intermediate-stage, high-risk breast cancer can be shortened from 5 to 3 weeks while maintaining tumor control rates in the breast and surrounding region that are equivalent to conventional treatment, according to research presented by Sun et al at the 59th Annual Meeting of the American Society for Radiation Oncology (ASTRO).

Five-year results of a Chinese clinical trial with more than 800 postmastectomy breast cancer patients confirmed that tumor recurrence rates following 15 daily fractions of radiation delivered over 3 weeks were not inferior to those following 25 fractions. Patients also experienced fewer side effects following accelerated treatment, indicating that hypofractionated radiation following mastectomy is a safe and effective treatment for locally advanced disease.

“Patients with invasive breast cancer receive radiation therapy after tumor-removal surgery to destroy any remaining cancer cells and prevent this very aggressive disease from returning,” said Shulian Wang, MD, one of the study’s lead authors and a radiation oncologist at the Chinese Academy of Medical Sciences in Beijing, China. “This trial demonstrates that we can safely accelerate adjuvant radiation therapy and reduce treatment time by 2 weeks. This option makes treatment more convenient for patients, reduces medical expenses, and allows providers to treat more patients with limited resources.”

Study Background

Of the 820 patients with high-risk breast cancer who enrolled in the trial from 2008 to 2016, 810 were eligible for analysis. The median age was 49 years (range, 24–74 years). Nearly all patients (93.9%) had stage III breast cancer, and the remaining 6.1% had stage II disease.

All patients underwent mastectomy and received chemotherapy consisting of taxanes and/or anthracycline-based regimens (specifically, 88.6% taxanes and anthracycline, 8.9% taxanes-based, 1.9% anthracycline-based, and 0.6% unknown), and some patients received trastuzumab targeted therapy (16.8%) and/or hormonal therapy (76.5% of all patients; 94.5% of those eligible). Patient and disease characteristics did not differ significantly between the treatment groups.

Following mastectomy, patients were randomly assigned in even proportions to receive either accelerated (ie, hypofractionated) or standard (ie, conventionally fractionated) external-beam radiation therapy to the chest wall and supra-infraclavicular nodal region. The accelerated regimen consisted of 43.5 Gy delivered in 15 fractions over 3 weeks, and the standard regimen consisted of 50 Gy delivered in 25 fractions over 5 weeks. Treatment was delivered via two-dimensional radiation therapy. Median follow-up for surviving patients was 55 months, with an interquartile range of 36 to 79 months.

Major Findings

At 5 years following accelerated treatment, the rate of locoregional recurrence was noninferior to the rate for standard treatment. Locoregional recurrence rates were 8.3% following accelerated treatment and 8.1% following standard treatment (hazard ratio [HR] = 1.10, 95% confidence interval [CI] = 0.67–1.83), with a difference of 0.2% (95% CI = –4.1 to 4.5).  

Among all patients, the 5-year overall survival rate was 84.4%, and the disease-free survival rate was 72.7%. Five-year overall survival rates were 83.2% following accelerated treatment and 85.6% following standard treatment (HR = 1.13, 95% CI = 0.78–1.62). Five-year disease-free survival rates were 74.6% for the accelerated-treatment arm and 70.7% following standard treatment (HR = 0.88, 95% CI = 0.67–1.16).

Rates of distant metastases were 23.2% and 26.2% at 5 years for accelerated and standard treatment, respectively (HR = 0.90, 95% CI = 0.67–1.20). Survival and recurrence rates were calculated using the Kaplan-Meier method and analyzed using Cox regression models.

The two cohorts did show some differences in terms of treatment-related side effects. Fewer patients in the accelerated treatment group experienced grade 3 acute skin toxicity (3.5% vs 7.8% of standard-treatment patients; P = .008). Rates between the treatment arms were similar for symptomatic radiation pneumonitis, lymphedema, and shoulder disorder, and no patients experienced brachial plexopathy. Toxicity rates were compared using Chi-square tests.

Commentary

“Clinicians have seen clear benefits with accelerated radiation therapy to the whole breast after breast-conserving surgery, but questions remain about its safety and effectiveness with treating nodal regions. Our trial demonstrates a similar benefit for intermediate-stage breast cancer after mastectomy, in that we reduced treatment time from 5 weeks to 3 weeks while preserving high rates of tumor control and tolerability,” said Dr. Wang.

“The accelerated approach also has practical value for patients. With fewer treatment sessions, patients spend less time away from work and family, enjoy lower transportation costs, and, as our findings show, experience fewer side effects.”

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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