Molecular Profiling of Colorectal Cancer in Indian Patients: New Insights for Personalized Treatment

What is the Global Perspective on Colorectal Cancer?

Colorectal cancer (CRC) represents a significant global health burden, ranking third in worldwide newly diagnosed cancer cases and accounting for 9.2% of cancer-related deaths according to GLOBOCAN 2018. With an incidence of 19.7 per 100,000 population globally (23.6 in males and 16.3 in females), CRC also stands as the third most common cause of cancer-specific mortality in the Asian continent. The heterogeneous nature of CRC, with varying biological, histological, and molecular profiles depending on tumor site, highlights the importance of understanding these distinctions for effective treatment and prognostication. While numerous studies have examined the molecular classification of CRC in Western populations and some Asian countries, there remains a significant knowledge gap regarding the clinical and pathological correlations with molecular profiles in the Indian population. A recent prospective study conducted at the Rajiv Gandhi Cancer Institute and Research Centre in Delhi has addressed this gap by investigating the molecular subtypes of CRC and their clinicopathological correlations in an Indian cohort, providing valuable insights into the molecular landscape of this disease in a previously understudied population.

Who Are the Study Participants?

The study enrolled 50 CRC patients (both inpatients and outpatients) between February 2019 and March 2020, including those with localized, locally advanced, or metastatic disease. Patients younger than 18 years or with insufficient tissue for testing at least three molecular markers (KRAS, NRAS, BRAF, MSI, and MLH1 methylation) were excluded. The demographic profile revealed a median age of 53 years at presentation, with a slight male predominance (54%). Regarding tumor location, 44% were right-sided colon tumors, 38% left-sided, and 18% rectal tumors. Most patients presented with advanced disease, with 28% having stage III and 54% having stage IV CRC. No stage I cases were identified, highlighting the challenge of early detection in this population. Interestingly, 30% of patients presented with upfront obstruction or perforation, and among those with metastatic disease at diagnosis, 48% had liver metastases. This demographic and clinical profile provides important context for understanding the molecular findings and their implications for this specific patient population.

What Do Molecular Profiling Results Tell Us?

The molecular analysis revealed several significant findings. KRAS mutations were identified in 40% of cases, consistent with global data showing KRAS mutation prevalence ranging from 33.5% to 44% across different populations. Notably, no NRAS mutations were detected, which aligns with the known rarity of these mutations. BRAF mutations were found in only 4% of patients, lower than some Western reports but consistent with data from other Asian countries. Deficient mismatch repair (dMMR) status was observed in 22% of patients, with MLH1 loss accounting for the majority (72%) of dMMR cases. Among the patients tested for MLH1 promoter methylation, 52% showed positive results. These molecular alterations demonstrated specific correlations with clinicopathological features that could have important implications for patient management and prognosis. RAS-mutated tumors, for instance, were significantly associated with upfront liver metastases (69% vs. 31%, p=0.019) and poor differentiation (92% vs. 50%, p=0.020) compared to RAS wild-type tumors, suggesting a more aggressive phenotype. The study also confirmed the mutually exclusive nature of KRAS and BRAF mutations, with no cases showing both alterations simultaneously.

The dMMR status showed particularly interesting correlations with clinicopathological features. Females had a higher proportion of proficient MMR (pMMR) tumors (91% vs. 67%, p<0.046), while dMMR tumors showed a male preponderance (81%). Most dMMR tumors were stage II cancers (67%, p<0.001) and demonstrated a lower propensity for bowel wall invasion (p=0.010), nodal metastases (p=0.006), and distant metastases compared to pMMR tumors. Regarding tumor location, 72% of dMMR tumors were right-sided, consistent with global patterns. Histologically, dMMR tumors showed associations with mucinous features and higher levels of intraepithelial lymphocytes and peritumoral lymphocytic infiltration. These findings reinforce the distinct biological behavior of dMMR tumors and their potential implications for treatment strategies, particularly regarding immunotherapy response. The study also explored MLH1 methylation status and found no significant association with dMMR status or KRAS/BRAF mutations, though the limited sample size may have affected these results.

How Could These Findings Impact Clinical Practice?

The study's findings have important clinical implications, particularly for the management of CRC in the Indian population. The molecular subtyping approach allows for a more precise classification of tumors beyond traditional histopathological assessment, potentially guiding treatment decisions and prognostic assessments. For instance, the identification of dMMR tumors, which tend to have distinct clinical behaviors and potential responsiveness to immunotherapy, could influence treatment strategies. Similarly, the detection of KRAS mutations, which are associated with resistance to anti-EGFR therapies, is crucial for appropriate treatment selection. The study also highlighted the importance of universal screening for Lynch syndrome using immunohistochemistry rather than relying solely on family history, as none of the patients with germline deficiency in the MLH1 gene had a personal or family history of Lynch syndrome-related cancers. This approach could lead to the identification of more Lynch syndrome cases and enable appropriate genetic counseling and surveillance for affected families. The molecular subgrouping according to dMMR and KRAS status (dMMR/KRAS mutation, dMMR/KRAS wild-type, pMMR/KRAS mutation, and pMMR/KRAS wild-type) provides a framework for prognostic stratification, as previous studies have shown that MSS/KRAS mutant tumors have the worst survival outcomes.

What Are the Study Limitations and Future Directions?

Despite its valuable contributions, the study acknowledged several limitations. The relatively small sample size (50 patients) may have affected the statistical significance of some associations and could have led to under- or overestimation of the relationships between molecular markers and clinicopathological characteristics. Missing histopathological and molecular data for certain parameters, particularly in cases with small biopsies or biopsies from metastatic sites, further limited comprehensive analysis. Additionally, the short study period and the inclusion of molecular testing for all CRC patients, regardless of stage or other factors, may have introduced selection biases. Nevertheless, this study represents the first comprehensive effort in India to correlate complete RAS and BRAF analysis, dMMR status, and MLH1 methylation with CRC clinicopathological features and to explore associations between different molecular subtypes. It provides a foundation for future research and clinical practice in this area, particularly in guiding targeted therapies and prognostic assessments for Indian CRC patients.

Looking ahead, there are several important questions that emerge from this study. How might the integration of molecular profiling into routine CRC management improve patient outcomes in the Indian population, particularly given the high proportion of advanced-stage presentations? What challenges do clinicians face in standardizing molecular tests across diverse healthcare settings in India, and how can these be addressed to ensure equitable access to precision oncology approaches? Could the molecular subtypes identified in this study inform the development of targeted therapies or clinical trials specifically designed for the Indian CRC population? These questions underscore the need for larger, multicenter studies to validate the findings and further explore the molecular landscape of CRC in the Indian context. Such research could ultimately lead to more personalized and effective treatment strategies, improved prognostic assessments, and better outcomes for CRC patients in India and beyond.

Summary

A prospective study conducted at the Rajiv Gandhi Cancer Institute and Research Centre in Delhi investigated the molecular subtypes of colorectal cancer and their clinicopathological correlations in an Indian cohort of 50 patients. The research revealed that KRAS mutations were present in 40% of cases, BRAF mutations in 4%, and deficient mismatch repair status in 22% of patients. The study found significant associations between RAS-mutated tumors and upfront liver metastases as well as poor differentiation, suggesting a more aggressive phenotype. Deficient mismatch repair tumors demonstrated distinct characteristics, including male preponderance, predominantly stage II disease, right-sided location, and lower propensity for invasion and metastases. These findings provide crucial insights into the molecular landscape of colorectal cancer in the Indian population, highlighting the importance of molecular profiling for treatment selection, particularly regarding anti-EGFR therapies and immunotherapy. The study emphasized the need for universal screening for Lynch syndrome using immunohistochemistry rather than relying solely on family history. Despite limitations including a relatively small sample size and missing data for certain parameters, this research represents the first comprehensive effort in India to correlate complete RAS and BRAF analysis, deficient mismatch repair status, and MLH1 methylation with colorectal cancer clinicopathological features, providing a foundation for personalized treatment strategies and improved patient outcomes in this previously understudied population.