Benefit of Chemotherapy for Breast Cancer Observed With Midrange Gene Assay Score

Endocrine therapy was found to be noninferior to chemoendocrine therapy in the analysis of invasive disease-free survival with a hazard ratio of 1.08. The study showed that the two treatment arms had similar rates of invasive disease-free survival (83.3% in the endocrine-therapy group vs 84.3% in the chemoendocrine-therapy group) at 9 years. The findings were similar for freedom from disease recurrence at a distant site (94.5% vs 95.0%) and at a distant or local/regional site (92.2% vs 92.9%). 

There were no differences found in terms of overall survival between the two arms (93.9% vs 93.8%). However, the chemotherapy benefit for invasive disease-free survival varied with the combination of RS and age. The researchers found women 50 or younger with a RS of 16 to 25 derived some benefit from chemotherapy.“Adjuvant chemotherapy is commonly recommended for women with early stage breast cancer to reduce the risk of recurrence, but more precision is needed in identifying who benefits most from chemotherapy,” Dr Sparano told Oncology Nurse Advisor.

Dr Sparano and colleagues note that these new findings contrast with those of previous biomarker validation studies that were performed retrospectively. Those previous studies used archival tumor specimens. In this study, researchers were able to adjust for nonadherence. The rate of nonadherence to the assigned treatment was 12% overall, but investigators were able adjust the sample size to compensate for it.

The investigators concluded that the 21-gene assay may identify up to 85% of women with early breast cancer who can be spared adjuvant chemotherapy. In addition, the assay may be especially beneficial to women older than 50 who have a recurrence score of 25 or lower, as well as women 50 and younger with a recurrence score of 15 or lower.

Dr Sparano said oncology nurses now can more accurately and precisely counsel women about the benefits and limitations of the 21-gene assay based on their RS score. “The use of adjuvant chemotherapy in this setting may be guided by the use of the 21-gene assay, similar to use of ER/PR testing to guide the use of adjuvant endocrine therapy, and HER2 testing to guide the use of anti-HER2 therapy.” 

John Schieszer is a medical reported based in Seattle, Washington. 

Reference

Sparano JA, Gray RJ, Makower DF, et al. Adjuvant chemotherapy guided by a 21-gene expression assay in breast cancer. N Engl J Med.2018;379(2):111-121.