Low Risk DCIS clinical trials

Radiotherapy Omission in Low Risk Ductal in Situ Carcinoma Breast

Following breast-conserving surgery (BCS) for localized ductal carcinoma in situ (DCIS) of the breast, whole-breast irradiation (WBRT) is a standard of care, reducing the absolute rate of in-breast recurrences (IBR) by more than 15% at 10 years, from 28% without radiotherapy to 13 % with radiotherapy. Half of the recurrences occurred as invasive disease. Whereas in the comparative trials, WBRT did not impact on overall survival, survival of patients who recurred with invasive cancers was impaired in comparison to patients who did not recur, or to patients with DCIS-only recurrences. Using criteria based on age, tumor size, nuclear grade, and margins status, several trials and cohort studies failed to identify subgroups of patients at low risk, who could be safely spared the need for WBRT. The Radiation Therapy Oncology Group (RTOG) DCIS trial included patients treated with BCS for low- or intermediate grade DCIS revealed by unifocal microcalcifications, size ≤25 mm, margins ≥3 mm, and no residual microcalcifications after surgery. The 5-year rates of IBR were 3.5 % without radiotherapy, versus 0.4 % with radiotherapy, and 6.7 % and 0.9 % at 7 years, respectively (p <0.001). Sixty percent of the patients received tamoxifen in both groups. Several studies showed that the same molecular classes were identified in DCIS as in invasive cancers. Studies suggested that low proliferation, hormone receptors expression, and lack of ERBB2 amplification were associated with a low risk of IBR in patients not receiving radiotherapy. A combined signature was tested in the Eastern Cooperative Oncology Group (ECOG) trial, showing a 10% IBR rate at ten years in patients with a low-risk. Identifying very low-risk DCIS, using biological markers in addition to the clinical and histological markers of low-risk DCIS, could help to select patients who could be safely avoided WBRT following BCS. It would avoid over-treatment in these women and could decrease the cost of management.