Advertisement

Breast Induration Risk With Partial- vs Whole-Breast Irradiation After Breast-Conserving Surgery for Node-Negative Early Disease


Advertisement
Get Permission

As reported in the Journal of Clinical Oncology by Offersen et al, the phase III Danish Breast Cancer Group Partial Breast Irradiation Trial showed that partial-breast irradiation was noninferior to whole-breast irradiation in terms of the risk for breast induration in women aged ≥ 60 years undergoing breast-conserving surgery for node-negative early breast cancer. No increased risk of locoregional recurrence was observed with partial-breast irradiation.

Study Details

In the open-label multicenter trial, 865 evaluable patients were randomly assigned between 2009 and 2016 to receive external-beam partial-breast irradiation (n = 431) or whole-breast irradiation (n = 434) with a dose of 40 Gy in 15 fractions. The primary endpoint was the incidence of grade 2 or 3 breast induration at 3 years.

Key Findings

Median follow-up was 5 years for induration and 7.6 years for locoregional recurrence. The 3-year incidence of grade 2 or 3 induration was 9.7% (95% confidence interval [CI] = 7.0%–12.9%) in the whole-breast irradiation group vs 5.1% (95% CI = 3.2%–7.6%) in the partial-breast irradiation group (risk difference = –4.6%, 95% CI = –8.2% to –0.9%, P = .014). Since the upper 90% confidence interval for the difference in incidence was below 0% (–1.5%), the statistical criterion (< 10%) for noninferiority of partial-breast irradiation was satisfied.

The hazard ratio for grade 2 or 3 induration for partial-breast irradiation vs whole-breast irradiation was 0.50 (95% CI = 0.29–0.86). At 5 years, overall induration risk was 12% in the whole-breast irradiation group vs 8% in the partial-breast irradiation group (odds ratio [OR] = 0.59, 95% CI = 0.43–0.82).

At 5 years, patients with large vs small breasts had an increased risk of induration (12% vs 7%; OR = 1.71, 95% CI = 1.23–2.38, P = .0014). At 3 years, risks with whole-breast irradiation vs partial-breast irradiation were 13% vs 6% among large-breasted patients and 6% vs 5% among small-breasted patients.

Partial-breast irradiation was not associated with an increased risk of dyspigmentation, telangiectasia, edema, or pain. Excellent or good cosmetic outcome was reported by 85% of the whole-breast irradiation group and 89% of the partial-breast irradiation group. Letrozole use and current smoking were not associated with the risk of radiation-associated morbidity.

No significant difference in locoregional recurrence risk was observed; 5-year risks were 0.7% (95% CI = 0.2%–1.9%) in the whole-breast irradiation group vs 1.2% (95% CI = 0.4%–2.6%) in the partial-breast irradiation group (P = .47). Estimated 9-year risks were 1.7% vs 3.1% (P = .30). No differences between the whole-breast irradiation and partial-breast irradiation groups were observed for contralateral breast cancer (7 vs 13 patients overall; 4 vs 6 during the first 5 years); distant failure (5 vs 3 patients); or nonbreast second cancers (observed in 8.4% of patients overall).

The investigators concluded, “External-beam [partial-breast irradiation] for patients with low-risk breast cancer was noninferior to [whole-breast irradiation] in terms of breast induration. Large breast size was a risk factor for radiation-associated induration. Few recurrences were detected and unrelated to [partial-breast irradiation].”

Birgitte V. Offersen, MD, PhD, of Aarhus University Hospital, is the corresponding author for the Journal of Clinical Oncology article.

Disclosure: The study was supported by the Danish Cancer Society, Centre for Interventional Research in Radiation Oncology, and others. For full disclosures of the study authors, visit ascopubs.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
Advertisement

Advertisement



Advertisement