Prognostic tools are widespread throughout all medical specialities, enabling physicians to make the best clinical decisions for patients. For breast cancer, the 21-gene recurrence score (RS) is one such tool, assessing the activity of 21 oncogenes and providing a score that can be used to indicate the clinical benefit a patient might gain from chemotherapy, as well as a prognostic estimation on the likelihood of recurrence.
However, this assay relies solely on a genetic model, which, as our understanding of cancer biology grows, is evidently not fully understood. Breast oncologists also rely on histological models for prognostic estimation, creating risk groups based on clinic-pathological features such as age, tumour size and grade, as well as nodal involvement. In reality, both approaches provide useful clinical insight, and in an effort to combine the two, to produce a more accurate prognostic tool, Dr. Joseph A. Sparano, MD, of the Montefiore Medical Center and Albert Einstein Cancer Center, New York, United States, leads a research team to produce a new tool, RSClin, that was presented at SABCS 2020, for use in HR+/HER2-, node-negative breast cancer patients.
“The 21-gene recurrence score has been available for about 15 years and used in more than 1 million patients worldwide,” Dr. Sparano says. “For patients who have a very high or very low recurrence score, the treatment choice is often very clear. But for most patients who have a mid-range score, this new tool will be a valuable resource for use by health care professionals that will facilitate a better informed, shared decision-making process.”
To validate the tool, a meta-analysis was conducted of 10,000 women with HR+/HER2-, node-negative breast cancer who received either endocrine therapy alone in the B-14 trial, or endocrine therapy plus chemotherapy in the TAILORx trial, with the aim of evaluating RSClin to RS, as well as comparing the tool’s performance to using just clinical-pathological features for prognostic estimation.
“The RSClin tool provided more prognostic information for distant recurrence than did RS or clinical-pathologic factors independently,” explains Dr. Sparano. “Further, in external validation in an independent real-world cohort that included 1,098 patients, the RSClin risk estimate was significantly prognostic for distant recurrence, and the estimated risk closely approximated the observed 10-year risk.”
Potentially providing a greater scientific insight, the RSClin estimation of chemotherapy benefit found that the presence of certain ‘classical’ risk factors alone were not sufficient indicators of benefit, and that instead, the potential benefit from chemotherapy relied on both the individuals RS score, as well as their distant recurrence risk, calculated by both RS and the clinical-pathological features. The tool does present with some limitations, however, with this prognostic tool is only applicable to women with node-negative disease.
In Belgium alone, over 6,176 women are diagnosed with node-positive disease (stage II or above), accounting for 56.7% of all breast cancer diagnoses in the country. Despite this, Dr. Sparano hasn’t ruled out updating this new prognostic tool to include node-positive women in the future.
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