Dr. Shak Discusses Study Evaluating RSClin, Tool to Guide Breast Cancer Treatment

A study that was presented during the 2020 San Antonio Breast Cancer Symposium validated a new tool, RSClin, to provide more individualized data on patients with breast cancer and help guide treatment decisions. Study author Steve Shak, MD, chief medical officer at Exact Sciences, discussed the findings of the study further during an interview with DocWire News.

DocWire News: What prompted you to undertake this study?

Dr. Shak: It is widely accepted that not all breast cancers are the same. For over a decade, physicians have been using genomic testing, such as the Oncotype DX Breast Recurrence Score to help personalize treatment decisions. Specifically, the Oncotype DX test helps determine whether patients who have hormone receptor-positive, HER2-negative early breast cancer benefit from adjuvant chemotherapy.

Historically, prior to genomic testing becoming the standard of care, physicians often used clinicopathologic tumor features such as age, tumor size, tumor grade, and nodal involvement to help inform prognosis and treatment decisions. However, there has not been a tool that integrates both the Recurrence Score result as well as clinical-pathologic features to predict individualized chemotherapy benefit – the development of such a tool has the potential to inform adjuvant chemotherapy treatment decisions with more precision than either alone.

With this in mind, the researchers performed a new patient-specific meta-analysis to develop and validate a new tool—called RSClin. The meta-analysis included data from more than 10,000 patients with node-negative disease, including the results of the TAILORx study, and assessed individualized estimates of distant recurrence risk and absolute chemotherapy benefit.

The meta-analysis was conducted by the ECOG-ACRIN Cancer Research Group (ECOG-ACRIN) primarily with funding from the National Cancer Institute. The data was presented in an oral session at SABCS by lead author Joseph A. Sparano, M.D., associate director for clinical research at Albert Einstein Cancer Center and associate chair for clinical research in the department of oncology at Montefiore Health System in New York, and leader of the TAILORx study for the ECOG-ACRIN Cancer Research Group. The data was published concurrently in the December 2020 issue of the Journal of Clinical Oncology.

DocWire News: What are the key takeaways from the study?

Dr. Shak: The meta-analysis-based RSClin tool further builds on the TAILORx study which continues to shape clinical practice and the future of breast cancer care. While the treatment choice is typically clear based on their Recurrence Score result for the great majority of patients, the RSClin tool will be a valuable resource for physicians and their patients to facilitate treatment decisions, particularly in specific situations where nuanced understanding is desired, as in cases of clinical equipoise or where traditional clinicopathologic features seem discordant. The analysis found that integrating clinicopathologic information and the Recurrence Score result was more informative for distant recurrence risk than either factor alone (P<0.001). By providing individualized estimates of distant recurrence risk and absolute chemotherapy benefit, the study shows that the incorporation of clinicopathologic information can add value in these cases where additional clarity is needed.

The inclusion of data from TAILORx, in addition to data from the NSABP B-14 and NSABP B-20 studies, ensured that the analysis incorporates insights reflective of contemporary treatment and outcomes. Furthermore, the estimation of distant recurrence risk was externally validated in an independent cohort of 1,098 women with node-negative disease from the Clalit Health Services registry.

DocWire News: Did any of the study’s findings surprise you?

Dr. Shak: Given that physicians often used clinicopathologic tumor features to help inform treatment decisions prior to genomic testing becoming the standard of care, the findings of the meta-analysis were not surprising. The analysis now provides an evidence-based framework to formally integrate these features in context with the Recurrence Score result, which provides valuable insight in these nuanced cases.

DocWire News: What limitations did the study have?

Dr. Shak: As a meta-analysis, this study incorporates data-sets from existing published data and as such, is subject to the limitations in each individual study incorporated. In addition, it is of note while these findings can provide valuable information in situations where additional clarity is needed, the tool does not provide specific treatment recommendations.

DocWire News: Do you have any future research plans pertaining to this area?

Dr. Shak: The RSClin tool has been developed only for node-negative disease, but now that data from the RxPONDER trial in patients with 1 to 3 positive nodes is now available, I anticipate that researchers may study RSClin in the future to include the positive-node scenario.

DocWire News: Any information not addressed by the previous questions that you would like to share?

Dr. Shak: RSClin will be accessible as of December 2020 through the Oncotype DX online ordering portal to U.S.-based physicians. It will be offered by Exact Sciences as a complimentary and optional service. To learn more about using the RSClin tool, physicians can call 866-ONCOTYPE (866-662-6897).