Real-world use of multigene signatures in early breast cancer: differences to clinical trials

Abstract

Abstract Purpose In Italy, Lombardy was the first region to reimburse multigene assays (MGAs) for patients otherwise candidates for chemotherapy. This is a real-world experience of MGAs usage in six referral cancer centers in Lombardy. Methods Among MGAs, OncotypeDX (RS) was used in 97% of cases. Consecutive patients tested with OncotypeDX from July 2020 to July 2022 were selected. The distribution of clinicopathologic features by RS groups (low-RS: 0–25, high-RS: 26–100) was assessed using chi-square and compared with those of the TAILORx and RxPONDER trials. Results Out of 1,098 patients identified, 73% had low-RS. Grade and Ki67 were associated with RS (p < 0.001). In patients with both G3 and Ki67 > 30%, 39% had low-RS, while in patients with both G1 and Ki67 < 20%, 7% had high-RS. The proportion of low-RS in node-positive patients was similar to that in RxPONDER (82%vs83%), while node-negative patients with low-RS were significantly less than in TAILORx (66%vs86%, p < 0.001). The distribution of Grade was different from registration trials, with more G3 and fewer G1 (38% and 3%) than in TAILORx (18% and 27%) and RxPONDER (10% and 24%) (p < 0.001). Patients ≤ 50 years were overrepresented in this series (41%) than in TAILORx and RxPONDER (31% and 24%, respectively) (p < 0.001) and, among them, 42% were node-positive. Conclusions In this real-world series, OncotypeDX was the test almost exclusively used. Despite reimbursement being linked to pre-test chemotherapy recommendation, almost 3/4 patients resulted in the low-RS group. The significant proportion of node-positive patients ≤ 50years tested indicates that oncologists considered OncotypeDX informative also in this population.