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Relative Effects of Brachytherapy and Beam Radiation for DCIS on Subsequent Invasive Events.
Thomas J O'Keefe1, Nicolas D Prionas2, Anne M Wallace1
1Department of Surgery, University of California San Diego, San Diego, CA 92037, USA.
Biomedicines
|November 27, 2025
Summary
Brachytherapy did not reduce invasive breast cancer recurrence compared to no radiation for ductal carcinoma in situ (DCIS). For DCIS patients, brachytherapy showed a higher invasive recurrence risk than external-beam radiation, suggesting caution with partial breast irradiation.
Area of Science:
- Oncology
- Radiotherapy
- Breast Cancer Research
Background:
- Patients with ductal carcinoma in situ (DCIS) were underrepresented in trials comparing partial vs. whole-breast irradiation.
- DCIS recurrence patterns differ from invasive cancers, with similar risks at the original site and new sites within the ipsilateral breast.
- Partial breast irradiation (PBI) techniques like brachytherapy require evaluation for DCIS efficacy.
Purpose of the Study:
- To compare the efficacy of brachytherapy (a PBI technique) versus external-beam radiation (EBRT) in reducing subsequent ipsilateral invasive breast cancers in DCIS patients.
- To assess the risk of ipsilateral invasive events following brachytherapy compared to no radiation and EBRT.
Main Methods:
- Retrospective analysis of women diagnosed with unilateral DCIS and treated with breast-conserving surgery without endocrine therapy, identified via the SEER database.
- 1:2 matching was performed between brachytherapy patients and those receiving EBRT or no radiation.
- Competing risks methods were used to estimate 10-year cumulative incidence of invasive breast events and subdistribution hazard ratios (sHRs).
Main Results:
- No significant difference in 10-year ipsilateral invasive cancer incidence between brachytherapy (5.7%) and no radiation (5.5%) (p=0.92).
- Brachytherapy showed an initial reduction in risk within 3 years (sHR=0.19) but a non-significant increase after 3 years (sHR=1.66).
- Compared to EBRT, brachytherapy was associated with a higher 10-year ipsilateral invasive cancer incidence (5.7% vs. 3.1%) and an increased risk after 3 years (sHR=2.20, p=0.009).
Conclusions:
- Brachytherapy may be linked to a higher invasive recurrence risk in DCIS patients not receiving endocrine therapy.
- Brachytherapy was less effective than EBRT in reducing ipsilateral invasive events and showed no benefit over no radiation.
- Further research is needed to determine if these findings are specific to brachytherapy or applicable to all PBI modalities.
