Is Whole-Breast Radiation Better in Older Women?

Nick Mulcahy

February 06, 2014

In an observational study of breast cancer treatment strategies, standard external-beam radiation therapy (EBRT) provided a higher 5-year breast preservation rate than 2 other methods in women 66 years and older, researchers say.

For patients with invasive cancer, the 5-year subsequent mastectomy risk was 4.7% after lumpectomy alone, 2.8% after brachytherapy, and 1.3% after EBRT (P < .001).

All of the patients receiving brachytherapy, also known as partial-breast irradiation, also underwent lumpectomy, as did those receiving EBRT, also known as whole-breast irradiation.

The median follow-up was 3.5 years.

The findings were published in the February 1 issue of the International Journal of Radiation Oncology * Biology * Physics.

This study is the first to directly compare breast brachytherapy with lumpectomy alone and EBRT, according to the study authors.

"Brachytherapy offered a breast-preservation benefit, although in general this benefit was slightly less than the benefit derived from standard external-beam radiation therapy," said senior author Benjamin D. Smith, MD, from the University of Texas M.D. Anderson Cancer Center in Houston, in a press statement.

The authors provide some clinical context, and say that "controversy persists over whether this technique should be considered a standard of care." They explain that brachytherapy is nonetheless "increasingly popular" and "increasingly used" in lieu of standard whole-breast radiation.

That's not likely to change, a pair of experts suggest in an accompanying editorial. Brachytherapy is "more convenient" (with only a 5-day schedule), and "exposes less normal tissue to ionizing radiation," they say.

Furthermore, the "reported differences may be statistically significant, but [are] clinically trivial," write Robert R. Kuske, MD, from Arizona Breast Cancer Specialists in Scottsdale, and S. Stanley Young, PhD, from the National Institute of Statistical Sciences in Research Triangle Park, North Carolina.

This study is a lot like a 2012 study from the same M.D. Anderson researchers, according to the editorialists. That study found that breast brachytherapy was associated with more complications than whole-breast irradiation and a decreased likelihood of long-term breast preservation, as reported at the time by Medscape Medical News.

The new study adds 2 wrinkles: a control group of patients treated with lumpectomy alone and outcomes that follow American Society for Radiation Oncology (ASTRO) guidelines and classify patients by suitability for brachytherapy, the editorialists report.

However, wrinkles or not, the new study, just like the old study, used information from the Surveillance, Epidemiology, and End Results (SEER)–Medicare database and, thus, has "significant limitations," they write.

"Obviously, great care needs to be exercised in the analysis of observational studies, and readers need to be wary of reported claims and conclusions," Drs. Kuske and Young note.

Furthermore, both studies used data from the early to mid-2000s. This is the "early period of applicator-based accelerated partial-breast irradiation, and was limited to single-lumen balloon applicators," they explain.

"It's a study of older technology that has been subsequently improved upon," Dr. Kuske previously told Medscape Medical News. In the early to mid-2000s, there was only 1 form of breast brachytherapy in use — the single-catheter MammoSite "balloon," which was approved by the US Food and Drug Administration in 2002.

"There has been a mass movement away from this single-channel brachytherapy device," Dr. Kuske said.

Single-channel brachytherapy has largely been replaced by a number of newer catheters and devices. However, all patients in these 2 observational studies were treated with the older technology, which weakens the real-world applicability of the findings, he explained.

ASTRO Suitability Groupings

The ASTRO suitability criteria, which direct patient selection for brachytherapy, have not been empirically validated, the study authors point out.

So, in addition to evaluating 5-year breast preservation for the different radiation methods, the authors looked at suitability and outcomes by treatment type.

They used the SEER–Medicare linked database to identify 35,947 women, 66 years and older, diagnosed with invasive breast cancer (79.9%) or ductal carcinoma in situ (DCIS) (20.1%) from 2002 to 2007. The patients were treated with lumpectomy alone (23%), lumpectomy followed by brachytherapy (3.6%), or lumpectomy followed by EBRT (73.4%).

ASTRO's Accelerated Partial-Breast Irradiation Consensus Statement was used to classify patients with invasive breast cancer as suitable for brachytherapy (34.7%), cautionary (17.6%), or unsuitable (35.2%); 12.5% of patients were unclassified.

The relative risk for mastectomy after initial treatment did not differ by ASTRO suitability classification (P = .84 for interaction). In addition, patients in the suitable category (estrogen-receptor-positive tumors, ≤2 cm, etc.) had a low absolute subsequent mastectomy risk, with a minimal absolute difference in risk after brachytherapy (1.6%) and EBRT (0.8%).

In other words, when stratifying patients by certain ASTRO criteria, the authors found that patients classified as suitable were the least likely to undergo subsequent mastectomy and had the smallest absolute difference, compared with those treated with brachytherapy or EBRT.

The small number of patients with DCIS in this cohort who were treated with brachytherapy did not allow for strong conclusions to be reached on the effectiveness of brachytherapy in this patient group.

The study was supported in part by Varian Medical Systems, the Cancer Prevention & Research Institute of Texas, and the National Cancer Institute. The authors, Dr. Kuske, and Dr. Young have disclosed no relevant financial relationships.

Int J Radiation Oncol Biol Phys. 2014;88: 266-268, 274-284. Editorial, Abstract

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