Exact Sciences, a provider of cancer screening and diagnostic tests, today shared initial clinical validation data for its breast cancer radiation signature, Profile for the Omission of Local Adjuvant Radiotherapy (POLAR), at the 2022 San Antonio Breast Cancer Symposium® (SABCS®). The meta-analysis of three independent, randomized clinical trials identified which early-stage breast cancer patients benefited from radiotherapy after breast-conserving surgery.
POLAR is a genomic signature that is both prognostic for the risk of local regional recurrence and predictive of radiotherapy benefit. The analysis found that patients at low risk for local regional recurrence following breast-conserving surgery did not benefit from radiotherapy (~25% of patients). SABCS selected this meta-analysis as part of its press program.
"Exact Sciences' POLAR signature addresses a significant clinical need for those with early-stage, hormone receptor positive breast cancer, identifying which patients may benefit from radiotherapy and which may not," said Rick Baehner, M.D., chief medical officer of Precision Oncology at Exact Sciences. "Like chemotherapy, radiation therapy has significant physical, mental, and monetary costs associated with it. These data are a critical step toward providing patients with a new tool to help ensure better breast cancer treatment decisions."
The meta-analysis included 623 patients with lymph node-negative, estrogen receptor-positive, HER2-negative breast cancer who were enrolled in one of three randomized clinical trials, the Swedish SweBCG91RT trial, Scottish Conservation Trial, and Canadian trial from the Princess Margaret Hospital, examining the efficacy of breast-conserving surgery with and without local breast radiation therapy.
"In a patient-level meta-analysis, the POLAR gene profile successfully predicted which patients would and would not benefit from local radiation therapy," said lead author Per Karlsson, M.D., professor of oncology at the Sahlgrenska Comprehensive Cancer Center and the University of Gothenburg in Sweden. "To our knowledge, POLAR is the first genomic classifier that is both prognostic for the risk of local regional recurrence and predictive of radiotherapy benefit following breast-conserving surgery.
To validate the POLAR signature as both prognostic and predictive, the investigators analyzed gene expression in breast tumor samples to assign each patient a POLAR score. They then examined the impact of radiation therapy for patients with high and low scores. Among the 479 patients with high POLAR scores, those who did not receive adjuvant radiation therapy after breast-conserving surgery had a 63 percent greater risk of local recurrence compared with those who did receive adjuvant radiation therapy. For the 194 patients with low POLAR scores, there was no significant difference in local recurrence rate between those who received adjuvant radiation therapy and those who did not. After 10 years, five percent of patients who received radiation therapy experienced a local recurrence, compared with seven percent of those who did not receive radiation therapy.