Constance D. Lehman, MD, PhD
In a prospective cohort clinical trial reported in JAMA Oncology, Constance D. Lehman, MD, PhD, and colleagues found that multiple factors, including magnetic resonance imaging (MRI) findings, played a role in conversion to mastectomy among women with ductal carcinoma in situ (DCIS) who were candidates for wide local excision based on conventional imaging. In patients undergoing wide local excision, adherence to radiotherapy guided by the DCIS 12-gene assay was high.
The study included 339 women from the Eastern Cooperative Oncology Group–American College of Radiology Imaging Network trial E4112, which enrolled women with DCIS on core biopsy who were candidates for wide local excision from 75 institutions between March 2015 and April 2016. Participants underwent breast MRI before surgery, with MRI findings being incorporated into choice of surgery. The DCIS 12-gene score was used to guide radiotherapy recommendations for patients with DCIS who had wide local excision as the final surgical procedure and had tumor-free excision margins of ≥ 2 mm. The primary objective of the study was to determine the conversion rate to mastectomy and identify reasons for conversion.
Conversion to Mastectomy and Adherence to DCIS 12-Gene Assay-Guided Radiotherapy
Among the 339 evaluable women eligible for wide local excision before MRI, 65 (19.2%) converted to mastectomy. Among these 65 patients, conversion to mastectomy was based on MRI findings in 25 (38.5%), patient preference in 25 (38.5%), positive margins after attempted wide local excision in 10 (15.4%), positive genetic test results in 3 (4.6%), and contraindication to radiotherapy in 2 (3.1%).
Among the 285 women who underwent wide local excision after MRI as first surgical procedure, 274 (96.1%) had successful breast conservation. Of 171 eligible for radiotherapy guided by DCIS score (clear margins, absence of invasive disease, and DCIS score), DCIS score was low (< 39) in 82 (48.0%) and intermediate/ high (≥ 39) in 89 (52.0%). Among these 171 patients, 159 (93.0%) had radiotherapy adherent to recommendations.
The investigators concluded, “Among women with DCIS who were wide local excision candidates based on conventional imaging, multiple factors were associated with conversion to mastectomy. This study may provide useful preliminary information required for designing a planned randomized clinical trial to determine the effect of MRI and DCIS score on surgical management, radiotherapy, overall resource use, and clinical outcomes, with the ultimate goal of achieving greater therapeutic precision.”