Prognostic phenotypic subtypes to predict recurrence and response to adjuvant chemotherapy for colorectal cancer.
205 Background: Histological phenotypic subtypes have been proposed that stratify survival in a discovery cohort of patients with stage I-III colorectal cancer (CRC). However, clinical utility has not been validated nor associations with recurrence and chemotherapy assessed. Therefore, this study assessed prognostic value in patients with stage I-III CRC as well as predictive value for recurrence and chemotherapy response. Methods: Two independent stage I-III CRC patient cohorts were utilized to assess associations between phenotypic subtypes, survival, and recurrence. Stage II-III patients, from the SCOT adjuvant chemotherapy trial, were utilized to assess associations between phenotypic subtypes and adjuvant chemotherapy response. Log rank analysis compared immune and stromal subtypes. Results: In an 867-patient internal cohort, phenotypic subtype stratified patients by disease-free survival (DFS) (HR 2.18 95% CI 2.26-4.47, p < 0.001); independent of stage and location. The stromal subtype also predicted increased local and distant recurrence (p < 0.001). In a 146-patient external validation cohort, phenotypic subtype significantly stratified patients by DFS (HR 3.43 95% CI 1.60-7.35, p = 0.001). In 1343 SCOT trial patients, phenotypic subtype significantly stratified patients by DFS (HR 1.59 95% CI 1.13-2.25, p = 0.010). Furthermore, there was evidence that the effect of regimen depended on phenotypic subtype (p = 0.048), only significantly stratifying DFS in patients receiving FOLFOX (HR 3.73 95% CI 1.58-8.81, p = 0.003) but not CAPOX (HR 0.84 95% CI 0.56-1.26, p = 0.396) adjuvant chemotherapy. Interestingly, the immune subtype associated with improved DFS in patients receiving FOLFOX compared to CAPOX adjuvant chemotherapy (HR 3.40 95% CI 1.41-8.19, p = 0.006). Whereas patients with a stromal subtype trended towards improved DFS in patients receiving CAPOX compared to FOLFOX adjuvant chemotherapy (HR 0.72 95% CI 0.50-1.05 p = 0.088). Conclusions: Histological phenotypic subtypes are an effective independent prognostic classification for patients with stage I-III CRC that can predict response to FOLFOX adjuvant chemotherapy as well as the presence of local and distant recurrence.