Breast Cancer Assay Findings Associated With Physician Adjuvant Treatment Decisions

10/27/17

The 70-gene signature assay for early breast cancer provides physicians with actionable information and may be associated with adjuvant therapy decisions, according to research published in JAMA Oncology (online August 26, 2017; doi:10.1001/jamaoncol.2017.3470).

Among the patients with early breast cancer who undergo the 21-gene assay (21-GA), approximately 39% to 67% receive and intermediate risk result. As a result, treatment guidance is often ambiguous. The 70-gene signature assay (70-GS)—an FDA approved molecular diagnostic assay that offers a binary classification for patients with early breast cancer into low or high risk for breast cancer recurrence—may be associated with physician treatment decisions in this population.

Michaela Tsai, MD, Virginia Piper Cancer Center (Minneapolis, MN), and colleagues conducted a study to determine whether 70-GS findings are associated with physician adjuvant treatment decisions. The trial (PROMIS) enrolled 840 patients from 58 national institutions with early-stage breast cancer and a 21-gene assay recurrence score of 18-30. The 70-GS results were given to physicians before beginning adjuvant treatment.

The main outcome of the study was changes in physician treatment decision before vs after receiving the 70-GS result. Odds ratio (OR) was applied after observing a treatment change of at least 20%.

Among the total patient sample, 375 (44.5%) had a low-risk and 466 (55.5%0 had a high-risk result.

Researchers found that a significant change in adjuvant treatment was associated with receiving the 70-GS classifications (OR, 0.64; 95% CI, 0.50-0.82; P < .001). Among patients with low-risk results, 108 (28.9%) had chemotherapy removed from their treatment recommendation. For patients in the high-risk classification, 171 (36.7%) had chemotherapy added to their recommendation.

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Furthermore, researchers noted that varying results of the 70-GS were associated with physicians’ adjuvant treatment recommendation; 409 patients classified as high-risk (87.8%) were recommended adjuvant chemotherapy, and 339 patients classified as low-risk (90.6%) were recommended no chemotherapy.

Physicians reported feeling more confident in their treatment recommendation in 660 cases (78.6%) based on 70-GS results.

Researchers concluded that the 70-GS provides clinically actionable information regarding patients classified as intermediate risk by the 21-GA and was associated with a change in adjuvant treatment recommendations in a significant percentage of patients.—Zachary Bessette