Pathologic stage of ypT0N+ rectal cancers following neo-adjuvant treatment: clinical interpretation of an orphan status

Approximately 20% of locally advanced rectal cancers treated with neoadjuvant therapy achieve a pathologic complete response, but approximately 10% of them present residual nodal metastases (ypT0N+). We aimed this research to compare the survival rates of ypT0/ypTisN+ and stage 3a rectal cancer patients. A large multicenter study recently investigated ypT0/ypTis rectal cancers treated between 2005 and 2015 in Italy and Spain. ypT0/ypTisN+ were selected and compared with stage 3a rectal cancers treated at the same institutions with upfront surgery (ySICO group). Additionally, the SEER database was searched for patients with stage 3a rectal cancers treated with surgery in the same years. Overall survival (OS), disease-free survival (DFS), and disease-specific survival (DSS) were analyzed using Kaplan-Meier curves and random survival forest analysis (RSF). The ySICO study population consisted of 19 ypT0/2ypTisN+ (mean follow-up 41.8 months) and 72 Stage 3a patients (mean follow-up 56.9 months). These subgroups were comparable, but stage 3a patients were treated more frequently with adjuvant therapy (90.5% vs 61.9%, p 0.0001). No significant differences were reported between the ySICO subgroups for the OS, DFS, and DSS curves. When the 1213 SEER patients were added to Stage 3a, the RFS model failed to differentiate OS between groups that presented identical survival. Root analysis showed that adjuvant therapy was the only variable differentiating OS and DSS in the ySICO population. These findings suggest that ypT0/ypTisN+ and stage 3a rectal cancers could be ranked together based on their similar outcomes and pathologic assessment, and they stress the importance of adjuvant therapy in patients presenting with residual nodal metastases.