PS2-2 [Encore] - SUNRISE-DI Study: Decision Impact of the 12-Gene RS Assay on Adjuvant Chemotherapy for Stage II and IIIA/B Colon Cancer.

Validation studies demonstrated that the 12-RS assay, known as Oncotype DX Colon Cancer Assay, can identify a wide range of recurrence risk in stage II/III colon cancer (CC). The objective of this prospective study was to evaluate the decision impact of the 12-RS assay on adjuvant chemotherapy recommendation for stage II/III CC patients (UMIN000028784). Patients who had curatively resected stage II, IIIA or IIIB CC were eligible. Physicians formulated a treatment recommendation and completed a pre-assay questionnaire, and then the 12-RS assay was performed. Following receipt of the 12-RS result, the treatment recommendation was revised in a post-assay questionnaire. The primary endpoint was the proportion of changes in a treatment recommendation between pre- and post- assay. The threshold value for the proportion of changes was assumed 20%. The target enrollment was 300 patients (100 stage II and 200 stage III CC). Between November 2017 and January 2019, 305 patients were registered from 14 centers. Of 275 who were evaluable, stage II/III was 97/178 patients. The RS < 30 was observed in 82% (low-risk), between 30 and 40 in 15% (intermediate-risk) and ≥41 in 4% (high-risk) of patients. The primary analysis showed that a treatment recommendation change was observed in 109 (40%) out of 275 patients (95% CI, 34-45%; P < 0.001). In patients with stage III CC, a change was observed in 80 (45%) out of 178 patients (39-51%; P < 0.001). In patients with stage II CC, a change was observed in 29 (30%) out of 97 patients (24-35%; P < 0.001). Physicians reported that the 12-RS assay increased the confidence in a change between pre- and post-assays for 36% of overall (P < 0.001), 38% of stage III (P < 0.001), and 31& of stage II patients (P < 0.001), respectively. This is the first study to evaluate the impact of the 12-RS assay on adjuvant treatment recommendations for stage III CC. The 12-RS results significantly influenced treatment recommendations. [ABSTRACT FROM AUTHOR]