Introduction: The IDEA collaboration demonstrated that shortening the duration of oxaliplatin-based adjuvant chemotherapy may be possible according to a patient’s risk and treatment regimen for stage III colon cancer (CC). In addition, validation studies including the Japanese SUNRISE study 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 CC and may enable physicians to ascertain a patient’s risk of recurrence to guide treatment decision-making. Accordingly, the objective of this prospective study was to evaluate the decision impact of the 12-RS assay on adjuvant chemotherapy recommendations for stage II/III CC patients in an era informed by the IDEA study results (Study Identifier, UMIN000028784).
Methods: Patients who had curatively resected stage II, IIIA, or IIIB CC were eligible. Treating 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-assays. The threshold value for the proportion of changes was assumed to be 20%. Secondary endpoints included the proportion of changes by stage; the proportion of changes in the duration of oxaliplatin-based chemotherapy (3 or 6 months); the proportion of switching to fluoropyrimidine monotherapy or surgery alone; and changes in the declared confidence level. The target enrollment was 300 patients with 100 stage II and 200 stage III CC.
Results: Between November 2017 and January 2019, 305 patients were registered from 14 centers. Of 275 who were evaluable, 97/178 patients were stage II/III. RS < .001). In patients with stage III CC, it was observed in 80 (45%) out of 178 patients (39–51%; P < .001); of these, treatment recommendations for 28 (16%) patients changed from chemotherapy to surgery alone, 20 (11%) had a shorter duration of oxaliplatin-based chemotherapy from 6 to 3 months, 19 (11%) spared oxaliplatin (i.e., fluoropyrimidine monotherapy), and the remaining 13 (7%) patients had other recommendations. In patients with stage II CC, a treatment recommendation change was observed in 29 (30%) out of 97 patients (24–35%; P < .001). Physicians reported that the 12-RS assay increased their confidence in a treatment recommendation between pre- and post-assays for 36% of overall (P < .001), 38% of stage III (P < .001), and 31% of stage II patients (P < .001), respectively.
Conclusion: 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 decisions for stage II/III patients and their physicians. The decisions were affected in nearly half of stage III and one-third of stage II patients, respectively.
© 2019 THE AUTHORS. Published by Elsevier Inc.