Background:
Variable prognosis of right versus left colonic malignancy has been linked to disparate expression at genetic and epigenetic level. Study aims to map differences in molecular profile of colon carcinoma with respect to location.

Methodology:
Study was performed at Department of Surgical Gastroenterology, Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow from December 2019 to February 2022. Stage II and III colon adenocarcinoma patients were subjected to oncologic surgery and resected specimens sent for histology examination and NGS(next generation sequencing) and MSI testing. Among total 48 patients, 26 were right sided and 22 left sided tumors. Data was compared between two groups, using Chi-square/Fisher’s exact test(with Yates correction) considering p value of <0.05 as statistically significant.

Results:
Demographic characteristics were comparable between two groups. While 27% among right sided had mucinous adenocarcinoma, it was 10% on left side(p value 0.115). Both sides were comparable stagewise. Frequency of mutations on right side were p53(46.1%), KRAS(34.6%), PIK3CA(30.7%), SMAD4(15.4%), MET(15.4%), ERBB2(11.5%), PTEN(11.5%), BRAF(7.7%), CTNNB1(7.7%), FBXW7(3.84%), DDR2(3.84%) and NRAS(0), while on left side, p53(68.2%), KRAS(36.4%), PIK3CA(36.3%), MET(27.2%), SMAD4(22.7%), CTNNB1(18.18%), FBXW7(9.9%), ERBB2(4.5%), BRAF(4.45%), NRAS(4.5%) and PTEN(0). Both right and left sides showed similar genetic profiles, although right-sided colon cancer group tended to have more gene mutations in BRAF, PTENand MSI-high, while left sided tumors had more mutationsinp53, NRAS, CTNNB1, MET.Mutual exclusion was noted between KRAS BRAF, BRAF NRAS, NRAS PIK3CA.

Conclusion:
Likely, this is first molecular study in Indian patients comparing right and left colon tumors. Both sides had comparable molecular profile. Studies with larger sample size are paramount to come to conclusion.