Whole-breast radiation significantly decreased local recurrence and invasive local recurrence among a subset of women with favorable-risk ductal carcinoma in situ, according to data from a randomized study presented at American Society for Radiation Oncology Annual Meeting.
“I think the most surprising thing was that the recurrence rate in patients randomized to receive radiation therapy was so low. Radiation reduced recurrence by half, and this was a much more profound impact than we expected,” Beryl McCormick, MD, FASTRO, lead investigator of the NRG Oncology/RTOG multicenter trial, chief of the external beam radiotherapy service at Memorial Sloan Kettering Cancer Center, and professor of radiation oncology at Cornell University, said in a press release.
DCIS accounts for about 25% of all new breast cancers, with an estimated 60,000 cases diagnosed in the U.S. each year, according to the press release. The current standard of care for DCIS is lumpectomy with radiotherapy.
In the prospective, randomized NRG/RTOG 9804 trial, McCormick and colleagues evaluated 636 women (median age, 58 years; 76% menopausal) with “good-risk” DCIS, meaning tumors were 2.5 cm or smaller (mean, 0.6 cm; 61% 0.5 cm or smaller) with margins 3 mm or larger (65% 1 cm or greater or completely negative re-excision specimen) and low or intermediate nuclear grade (44% grade 1, 56% grade 2).
The researchers randomly assigned the women to whole-breast radiation with standard doses or observation; no boosts were permitted.
The long-term update included analyses for 585 women with follow-up data and sensitivity analysis for all 629 patients with follow-up.
Tamoxifen was optional, with 69% of women, equally between treatment groups, intending to use the hormonal therapy but fewer actually using it (58% whole-breast radiation vs. 65% observation; P= .05).
Median follow-up was 12.4 years.
At 12 years, cumulative incidence of local recurrence was 2.8% (95% CI, 1.1-5.6) with whole-breast radiation vs. 11.4% (95% CI, 7.7-15.8) with observation (HR = 0.26; 95% CI, 0.13, 0.54). The 12-year cumulative incidence of invasive local recurrence was 1.5% (95% CI, 0.4-4) with radiation vs. 5.8% (95% CI, 3.2-9.5) with observation (HR = 0.34; 95% CI, 0.14-0.85).
local recurrence was reduced only with whole-breast radiation (HR = 0.25; 95% CI, 0.12-0.53) and the use of tamoxifen (HR = 0.5; 95% CI, 0.27-0.91).
Age (younger than 50 vs. 50 and older) and pathologic tumor size were not significant in predicting local or invasive local recurrence. There were no significant disparities among the groups in terms of OS, DFS or mastectomy.
McCormick said in the press release.
“All of us have a different definition of what is an acceptable risk,” she added. “Some patients with DCIS will still want radiation therapy. But, for others, the risk is so low they may opt not to treat, and that should be considered a viable option.” – by Jennifer Byrne
McCormick B, et al. Abstract LBA1. Presented at: ASTRO Annual Meeting; Oct. 21-24, 2018; San Antonio.
Disclosures : The authors report no relevant financial disclosures.