January 08, 2019
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Data support accelerated radiotherapy as standard of care for breast cancer

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Benjamin Smith
Benjamin D. Smith

When followed by a tumor bed boost, hypofractionated and conventionally fractionated whole-breast irradiation appeared to yield comparable 3-year outcomes among patients with breast cancer, according to a randomized noninferiority phase 3 study published in Journal of Clinical Oncology.

Thus, hypofractionated whole-breast irradiation (HF-WBI) should be the standard of care regardless of tumor bed boost, chemotherapy and larger breast size.

“Our study adds to the existing literature additional evidence relevant to recent patients treated in the United States, confirming prior trials that demonstrate HF-WBI is similar to conventionally fractionated [CF]-WBI with regard to tumor control and side effect profile,” Benjamin D. Smith, MD, associate professor in the radiation oncology department at The University of Texas MD Anderson Cancer Center, told HemOnc Today. “We specifically showed that HF-WBI was similar, if not better than, CF-WBI among patients with large breasts, specifically D cup or larger. Previously, there was controversy as to whether or not HF-WBI would still be safe in patients with large breasts.”

ASTRO guidelines recommend HF-WBI for patients with breast cancer of all ages, tumor stages and chemotherapy exposures. Still, there has been a reluctance among U.S. clinicians to adopt HF-WBI, partially due to cosmetic outcomes of this procedure, especially when used with a tumor bed boost or for women with larger breast sizes who undergo chemotherapy.

Smith and colleagues evaluated 287 women with stage 0 to stage 2 breast cancer who were enrolled at MD Anderson Cancer Center and four nearby centers between February 2011 and February 2014. Eligible participants were aged 40 years or older, had stage Tis-T2N0-N1M0 breast cancer, and were treated with margin-negative segmental mastectomy.

Researchers randomly assigned women to undergo CF-WBI (n = 149) — 50 Gy in 25 fractions — or HF-BWI (n = 138), 42.56 Gy in 16 fractions. Randomization was stratified by baseline physician-evaluated cosmesis, bra cup size, chemotherapy receipt, margin status and location of treatment.

The percentage of patients with an adverse cosmetic outcome 3 years after treatment — according to a score of 2.5 or higher on the Breast Cancer Treatment Outcomes Scale — served as the study’s primary endpoint.

Median follow-up was 4.1 years.

Overall, 286 patients received the protocol-specified radiation dose, 30% underwent chemotherapy and 36.9% were classified as having large breast size.

Researchers found that at 3 years, adverse cosmetic outcomes were 5.4% lower with HF-WBI (P for noninferiority = .002); absolute risks were 8.2% (n = 8) with HF-WBI and 13.6% (n = 15) with CF-WBI.

Patients treated with chemotherapy and HF-WBI had a 4.1% higher rate of adverse cosmetic outcomes (90% upper confidence limit, 15%), leading to inconclusive noninferiority results for this subgroup.

Among patients with large breast size, adverse cosmetic outcomes were 18.6% lower (90% upper confidence limit, –8%) with HF-WBI vs. CF-WBI.

Researchers observed no difference in 3-year poor or fair photographically evaluated cosmesis (28.8% vs. 35.4%) and 3-year local RFS (99% for both) between the CF-WBI and HF-WBI groups.

“Our study has helped to change our practice at MD Anderson,” Smith told HemOnc Today. “We now treat over 90% of our patients with HF-WBI. We believe our study findings, which strongly support the new ASTRO guideline on whole-breast irradiation, should lend additional evidence to support widespread adoption of the ASTRO guideline recommendations.” – by Jennifer Byrne

For more information:

Benjamin Smith , MD, PhD, can be reached at The University of Texas MD Anderson Cancer Center, Building 318, 1515 Holcombe Blvd., Houston, TX 12345; email: bsmith3@mdanderson.org.

Disclosures : The study was supported by a Career Development Award from ASCO’s Conquer Cancer Foundation funded by the Breast Cancer Research Foundation. Smith reports research funding from Varian Medical Systems He also reports having an equity interest in Oncora Medical as part of a partnership agreement. Please see the study for a list of all other authors’ relevant financial disclosures.