Radiotherapy after breast-conserving surgery for the treatment of ductal carcinoma in situ (DCIS) reduces the risk of ipsilateral breast events without changing survival
Between March 18th and 19th, SSO 2021 (International Conference on Surgical Cancer Care) took place in virtual format. At this event, a validation trial of a commercially available genetic signature, the DCISionRT, was presented in order to assess the risk of ipsilateral breast events after conservative surgery and the benefit of adjuvant radiotherapy.
Researchers identified 183 women with DCIS who met the eligibility criteria of a retrospective Australian cohort. Medical records were reviewed to assess treatment and clinical outcomes. The anatomopathological specimen was analyzed for several biomarkers (HER2, progesterone receptor, Ki-67, COX2, p16, FOXA1 and SIAH2) from a blinded and scored review by certified pathologists.
Of the 183 women analyzed, 72 received radiotherapy (39%) and 66 received endocrine therapy (36%). The total cohort had a 10% risk of ipsilateral breast events in 5 years; women exposed to radiotherapy had a 4% risk and those treated without radiotherapy had a 14% risk.
Additionally, in the group of women without radiotherapy, the rate of ipsilateral events was 7% for those whose decision score was low, while those who obtained high scores had an event rate of 23%.
After breast-conserving surgery without adjuvant endocrine therapy, women with low decision scores had a non-statistically significant difference of 2% with and without radiotherapy, while those with high scores showed a significant difference of 27%, indicating sensitivity to radiation. The results were similar when all patients were included: 2% and 20% of absolute differences with radiotherapy.
Authors conclude that such validation in a contemporary cohort supports previous observations that DCISionRT provides prognostic and predictive information that allows even more personalized treatment decisions.