Challenging Suitability Criteria for Accelerated Partial Breast Irradiation in DCIS

Researchers investigated breast cancer outcomes after accelerated partial breast irradiation (APBI) in patients with ductal carcinoma in situ (DCIS) in a study published at the ASCO 2023 Annual Meeting in Chicago, IL. They considered that guideline-recommended suitability criteria for APBI in DCIS were too stringent, given that landmark APBI studies included limited explorations of DCIS subgroups.

The study’s first author, Diana Roth O’Brien, MD, and colleagues reported that early analysis of patients with DCIS who underwent lumpectomy and adjuvant APBI showed excellent local disease control, even among those classified as “cautionary” for APBI according to the American Society for Radiation Oncology (ASTRO) criteria.

Patient Selection Guidelines for APBI Potentially Too Strict

The researchers enrolled 176 patients from a prospectively-maintained institutional database of individuals with DCIS who underwent lumpectomy and APBI from 2000-2022 at the Memorial Sloan Kettering Cancer Center. Primary endpoints included local recurrence (LR), overall survival (OS), and duration of follow-up.

The cohort had a median age of 60 years (interquartile range [IQR], 52-66), median tumor size of 9 mm (IQR, 4-15), and approximately 20% had multifocal disease. The authors noted 160 (91%) patients had negative final surgical margins for DCIS, with 10 and 6 patients having ≤2 and ≤1 mm margins, respectively. Most patients (91%) had estrogen receptor-positive DCIS, and 72% received endocrine therapy.

Overall, 18 (10%) patients had nuclear grade 1 disease, 111 (63%) had grade 2 disease, 33 (19%) had grade 3 disease, and a small subset had grade 1-2 or grade 2-3 disease. Per ASTRO guidelines, 118 (67%) participants were classified as suitable for APBI, 57 (32%) as cautionary, and 1 (0.6%) as unsuitable.

After a median follow-up of 24 months (range, 2-127), investigators observed 1 LR event in the cautionary subgroup, representing a 2-year LR rate of 0.6% for the overall cohort and 1.8% for the cautionary subgroup.

“Although our findings are limited by short follow up,” the authors summarized, “these results suggest that broadening the application of APBI for patients with DCIS may warrant further investigation.”

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