Accelerated breast radiation therapy following mastectomy shortens treatment time while maintaining tumor control

SAN DIEGO, September 25, 2017

Clinical trial for intermediate-stage breast cancer finds equivalent five-year local/regional control following hypofractionated radiation that reduced treatment from five to three weeks

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

Five-year results of a Chinese clinical trial with more than 800 post-mastectomy breast cancer patients confirmed that tumor recurrence rates following 15 daily fractions of radiation delivered over three 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 two weeks. This option makes treatment more convenient for patients, reduces medical expenses and allows providers to treat more patients with limited resources.”

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 percent 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 trasuzumab 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 (i.e., hypofractionated) or standard (i.e., conventionally fractionated) external beam radiation therapy to the chest wall and supra-infraclavicular nodal region. The accelerated regimen consisted of 43.5 Gray (Gy) delivered in 15 fractions over three weeks, and the standard regimen consisted of 50 Gy delivered in 25 fractions over five 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.

At five years following accelerated treatment, the rate of locoregional recurrence, where disease returns in the breast or region near the breast, was noninferior to the rate for standard treatment. Locoregional recurrence rates were 8.3 percent following accelerated treatment and 8.1 percent following standard treatment (Hazard Ratio (HR) = 1.10, 95% CI 0.67-1.83), with a difference of 0.2 percent (95% CI = -4.1 to 4.5).  

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

Rates of distant metastases, where a patient develops tumors outside the region of the original tumor, were 23.2 percent and 26.2 percent at five 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% versus 7.8% of standard-treatment patients; p = 0.008). 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.

“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 five weeks to three 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 abstract, “Hypofractionated radiotherapy after mastectomy for the treatment of high-risk breast cancer: 5-year follow up result of a randomized trial,” will be presented in detail during a news briefing and the plenary session at ASTRO’s 59th Annual Meeting in San Diego (full details below). To schedule an interview with Dr. Wang and/or outside experts in breast cancer,contact ASTRO’s media relations team on-site at the San Diego Convention Center September 24 through 27, by phone at 703-286-1600 or by email at press@astro.org.

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ATTRIBUTION TO THE AMERICAN SOCIETY OF RADIATION ONCOLOGY (ASTRO) ANNUAL MEETING REQUESTED IN ALL COVERAGE.

This news release contains additional and/or updated information from the study author(s). Full original abstract and author disclosures available on the final page of the PDF or from www.astro.org/annualmeeting.

Study Presentation Details

News Briefing: Monday, September 25, 11:00 a.m. – 12:00 p.m. Pacific time, San Diego Convention Center, room 24C, webcast: http://www.bit.do/astro17-2

Scientific Session: Plenary, Monday, September 25, 2:15 – 3:45 p.m. Pacific time, San Diego Convention Center, Ballroom 20

Resources on Breast Cancer and Radiation Therapy

Videos: Radiation Therapy for Breast Cancer (Spanish version), An Introduction to Radiation Therapy (Spanish version)

Digital brochure: Radiation Therapy for Breast Cancer (Spanish version)

Additional brochures, videos and information on radiation therapy from ASTRO’s patient site, RTAnswers.org

ASTRO’s clinical practice statements and guidelines

ABOUT ASTRO’S ANNUAL MEETING

ASTRO’s 59th Annual Meeting, the world’s largest scientific meeting in radiation oncology, will be held September 24-27, 2017, at the San Diego Convention Center. The 2017 Annual Meeting is expected to attract more than 11,000 attendees from across the globe, including oncologists from all disciplines and members of the entire radiation oncology team. More than 2,800 abstracts sharing results from clinical trials and other research studies will be presented in conjunction with educational sessions and keynote addresses that underscore the meeting’s theme, “The Healing Art and Science of Radiation Oncology.” Led by ASTRO President Brian Kavanagh, MD, MPH, FASTRO, the 2017 meeting will feature keynote addresses from Richard D. Zane, MD, FAAEM, Chief Innovation Officer for the University of Colorado Health System; Lucy Kalanithi, MD, FACP, widow of Paul Kalanithi, MD, the best-selling author of “When Breath Becomes Air,” with Heather Wakelee, MD, Paul’s oncologist; and Vinay K. Prasad, MD, MPH, an assistant professor of medicine at the Oregon Health & Science University. During the four-day meeting, more than 200 exhibitors will demonstrate cutting-edge technology and medical device innovations for radiation oncology. Visit us online for more information about ASTRO’s 59th Annual Meeting or press opportunities at the meeting.

ABOUT ASTRO

The American Society for Radiation Oncology (ASTRO) is the world’s largest radiation oncology society, with more than 10,000 members who are physicians, nurses, biologists, physicists, radiation therapists, dosimetrists and other health care professionals who specialize in treating patients with radiation therapies. The Society is dedicated to improving patient care through professional education and training, support for clinical practice and health policy standards, advancement of science and research, and advocacy. ASTRO publishes three medical journals, International Journal of Radiation Oncology • Biology • Physics (www.redjournal.org), Practical Radiation Oncology (www.practicalradonc.org) and Advances in Radiation Oncology (www.advancesradonc.org); developed and maintains an extensive patient website, RT Answers (www.rtanswers.org); and created the Radiation Oncology Institute (www.roinstitute.org), a nonprofit foundation to support research and education efforts around the world that enhance and confirm the critical role of radiation therapy in improving cancer treatment. To learn more about ASTRO, visit www.astro.org and follow us on our blog, Facebook and Twitter