Background: To establish the impact of re-stratification on the outcomes of patients (stage I-III right-sided colon cancer) based on the presence/absence of occult tumor cells (OTC) and/or metastatic lymph nodes in the different levels of surgical dissection.

Methods: Consecutive patients were drawn from a multicenter prospective trial. After surgery, the surgical specimen was divided into the D1/D2 and D3 volumes before being further analyzed separately. All lymph nodes were examined with cytokeratin CAM 5.2 immunohistochemically. Lymph nodes containing metastases and OTC (micrometastases; isolated tumor cells) were identified. Re-stratification was as follows: RS1, stages I/II, no OTC in D1/D2 and D3 volumes; RS2, stages I/II, OTC in D1/D2 and/or D3; RS3, stage III, lymph node metastases in D1/D2, with/without OTC in D3; RS4, stage III, lymph node metastases in D3, with/without OTC in D3.

Results: Eighty-seven patients (39 men, 68.4 + 9.9 years) were included. The standard stratified (SS) group contained the following: stages I/II (SS1) 57 patients; stage III (SS2) 30 patients. Re-stratified (RS) contained RS1 (38), RS2 (19), RS3 (24), and RS4 (6) patients. Lymph node ratio (OTC) RS2: 0.157 D1/D2; 0.035 D3 and 0.092 complete specimens. Lymph node ratio RS3: 0.113 D1/D2; complete specimen 0.056. Overall survival and disease-free survival were p = 0.875 and p = 0.049 for SS and p = 0.144 and p = 0.001 for RS groups, respectively.

Conclusion: This re-stratification identifies a patient group with poor prognosis (RS4). Removing this group from SS2 eliminates all the differences in survival between RS2 and RS3 groups. The level of dissection of the affected nodes may have an impact on survival.

Clinical trial: "Safe Radical D3 Right Hemicolectomy for Cancer through Preoperative Biphasic Multi-Detector Computed Tomography (MDCT) Angiography" registered at https://clinicaltrials.gov/ct2/show/NCT01351714.