Accelerated partial-breast irradiation confers similar toxicity, cosmetic results as whole-breast irradiation

Women with breast cancer experienced comparable toxicity and cosmetic results whether they underwent accelerated partial-breast irradiation using interstitial brachytherapy or whole-breast irradiation with tumor bed boost, according to results of a new analysis from the GEC–ESTRO study presented at the European Society for Therapeutic Radiology and Oncology conference.

Accelerated partial breast irradiation (APBI) also was associated with fewer late skin adverse events and better cosmetic results; however, these data were not statistically significant.

“APBI with interstitial multicatheter brachytherapy offers a significantly shorter treatment course with equivalent local tumor control, less late skin side effects and better cosmetic results compared to conventional whole-breast irradiation [WBI],” Csaba Polgár, MD, PhD, MSc, head of the radiotherapy center at the National Institute of Oncology in Budapest, Hungary, said in a press release. “The convenience of this 5-day treatment coupled with excellent cosmetic outcomes make this a very attractive treatment option for women with early breast cancer.”

The GEC–ESTRO trial is a phase 3 study that evaluated APBI with multicatheter interstitial brachytherapy compared with WBI with boost in 1,184 patients aged at least 40 years who had invasive breast cancer or ductal carcinoma in situ who underwent breast-conserving surgery (BCS).

Women in the standardized arm (n = 551) received 50 Gy of WBI with tumor bed boost of 10 Gy, whereas women in the investigative arm (n = 633) received APBI using high dose-rate or pulsed dose-rate interstitial brachytherapy.

Median follow-up was 6.6 years.

Primary results from GEC–ESTRO — published in The Lancet — showed that after BCS, APBI conferred equivalent 5-year OS (97.27% vs. 95.55%) and DFS (recurrence rates, 0.92% vs. 1.44%) compared with WBI with boost.

Polgár and colleagues presented new data regarding late toxicity — graded by the RTOG/EORTC late radiation morbidity scoring scheme — as well as cosmetic results, scored using four-scale Harvard criteria.

Toxicity and cosmetic data were available from 82% (n = 969) of the women at 5-year follow-up.

There were no grade 4 toxicities. Compared with the WBI arm, patients in the APBI arm experienced fewer cumulative incidence of grade 2 to grade 3 late skin toxicity (3.2% vs. 5.7%; P = 0.08), grade 3 fibrosis (0% vs. 0.2%), and grade 2 to grade 3 breast pain (1.4% vs. 3.2%; P = 0.04).

However, fewer patients in the WBI arm experienced subcutaneous tissue adverse events than in the APBI arm (6.3% vs 7.6%).

Patients in the APBI arm rated cosmetic results as excellent or good 90.4% of the time, compared with 87.2% of women who underwent WBI.

Physicians also more frequently rated the cosmetic results as excellent or good in the APBI arm than the WBI arm (88.2% vs. 86.7%).

These secondary findings further validate growing evidence supporting APBI with interstitial multicatheter brachytherapy as a safe, effective alternative to WBI, Polgár said.

“Early-stage breast cancer has high unmet medical needs and places an enormous physical, emotional and economic burden on women, families and health care systems,” study co-author Vratislav Strnad, MD, PhD, chair of the GEC-ESTRO Breast Cancer Working Group and radiation oncologist in the department of radiology at University Hospital in Erlangen, Germany, said in a press release. “We anticipate these data will drive significant changes in how clinicians approach early-stage breast cancer treatment in patients 50 years and older and place APBI multicatheter brachytherapy as an accepted standard alternative to whole-breast irradiation." – by Nick Andrews

Reference:

Polgár C, et al. Abstract OC–0481. Presented at: ESTRO 35 Conference; April 29-May 3, 2016; Turin, Italy.

Disclosure: HemOnc Today was unable to confirm the researchers’ relevant financial disclosures.