Effect of Radiotherapy Boost for Ductal Carcinoma in Situ After Whole-Breast Radiotherapy
In an analysis reported in JAMA Oncology, Moran et al found that a radiotherapy boost for ductal carcinoma in situ with local control after whole-breast radiotherapy was associated with a reduction in the risk for ipsilateral breast tumor recurrence.
Study Details
The analysis pooled de-identified patient-level data on 4,131 patients from 10 academic institutions in the United States, Canada, and France from January 1980 through December 2010. All patients had newly diagnosed ductal carcinoma in situ with no microinvasion, underwent breast-conserving surgery, received whole-breast radiotherapy with (n = 2,661) or without (n = 1,470) the boost, and had a minimum follow-up of 5 years.
Patients had a median age of 56 years and a median follow-up of 9 years. The median radiotherapy boost dose was 14 Gy.
Effect of Boost
Receipt of a radiotherapy boost was more likely in patients with positive margins, an unknown estrogen receptor status, and comedo necrosis. Among all patients, receipt of a boost was significantly associated with lower ipsilateral breast tumor recurrence (hazard ratio [HR] = 0.73, P = .01); ipsilateral breast tumor recurrence–free survival was 97.1% vs 96.3% at 5 years, 94.1% vs 92.5% at 10 years, and 91.6% vs 88.0% at 15 years (P = .04 overall).
On multivariate analysis including age, ductal carcinoma in situ grade, tumor size, margin status, comedo necrosis status, estrogen receptor status, and tamoxifen use (all significant on univariate analysis), receipt of a boost remained an independent predictor for reduced ipsilateral breast tumor recurrence (HR = 0.68, P = .01).
No significant interactions were observed between age and boost treatment effect (HR for age ≥ 50 years = 0.64, 95% confidence interval [CI] = 0.45–0.92; HR for age < 50 years = 0.77, 95% CI = 0.53–1.11; P = .46 for interaction) or between margin status and boost (HR for negative margin status = 0.55, 95% CI = 0.41–0.76; HR for positive margin status = 0.93, 95% CI = 0.30–2.93; P = .31 for interaction).
The investigators concluded: “This patient-level analysis suggests that the [radiotherapy] boost confers a statistically significant benefit in decreasing [ipsilateral breast tumor recurrence] across all [ductal carcinoma in situ] age groups, similar to that seen in patients with invasive breast cancer. These findings suggest that a [ductal carcinoma in situ radiotherapy] boost to the tumor bed could be considered to provide an added incremental benefit in decreasing [ipsilateral breast tumor recurrence] after a shared discussion between the patient and her radiation oncologist.”
The authors reported no conflicts of interest.
Meena S. Moran, MD, of Yale University School of Medicine, is the corresponding author of the JAMA Oncology article.
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