Women with ductal carcinoma in situ (DCIS) and elevated decision scores had a significantly higher risk of ipsilateral breast events and a greater relative benefit from radiation therapy compared to women with lower decision scores, according to research presented by Mann et al at the Society of Surgical Oncology 2021 International Conference on Surgical Cancer Care (Abstract 5).
Radiation therapy after breast-conserving surgery for DCIS reduces the risk of ipsilateral breast events without altering survival. Its use varies widely due to differing assessments of the risk/benefit ratio of this treatment. Precise assessment of post–breast-conserving surgery radiation therapy benefit would allow individualized treatment decisions.
Study Methods
Researchers performed a validation of a commercially available biologic risk signature, DCISionRT, to assess ipsilateral breast events risk after breast-conserving surgery and the benefit of radiation therapy.
The team identified 183 women with DCIS who met eligibility criteria from a retrospective Australian cohort. Medical records were reviewed to collect treatment and outcomes, and formalin-fixed paraffin-embedded tissue was provided to the PreludeDx CLIA lab for blinded testing of a panel of biomarkers (HER2, PR, Ki-67, COX2, p16, FOXA1, and SIAH2) scored by board-certified pathologists, and determination of the patented decision scores.
The prognostic effect of decision scores for ipsilateral breast events risk was assessed by multivariate Cox proportional hazards analyses, adjusting for adjuvant treatments. The predictive effect of decision scores for radiation therapy ipsilateral breast events benefit was assessed by multivariate Cox proportional hazards analysis, including the radiation therapy:decision scores interaction.
Risk of Events
Of the 183 women analyzed, 72 received radiation therapy (39%) and 66 received endocrine therapy (36%). The total cohort had 5-year ipsilateral breast events risk of 10%, while women treated with radiation therapy had 4% risk and those treated without radiation therapy had 14% risk. For those treated without radiation therapy, those with low decision scores had a 7% rate of ipsilateral events, while those with elevated decision scores had a 23% rate.
After breast-conserving surgery without endocrine therapy, those with low decision scores had a non–statistically significant difference of 2% with and without radiation therapy, while those with elevated decision scores had a highly significant 27% difference, indicating radiation sensitivity. Findings were similar when all patients were included: 2% and 20% absolute differences with radiation therapy.
“This validation in a contemporary cohort supports previous findings that DCISionRT provides prognostic and predictive information to allow personalized treatment decisions,” concluded the authors.
