Clinicopathological and demographic spectrum of colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) is the third most common cancer worldwide and is one of the leading causes of cancer-related morbidity and mortality.^[1,2] Colorectal cancer incidence is markedly higher in the West as compared to the East; however, this trend is slowly changing, likely due to continued westernisation of Eastern nations.

Colorectal cancer, like many other cancers, results from genetic mutations in oncogenes or tumour suppressor genes.

Most commonly, colorectal cancer presents sporadically; the pathogenesis of most of these cancers follows a well-defined adenoma carcinoma sequence.^[3]

Colorectal cancer has many recognised risk factors, which include but are not limited to age, presence of IBD, a family history of colorectal neoplasms, and a sedentary lifestyle.^[3-7]

Despite the lower incidence rates of colorectal cancer in India, there are still recognised differences in the clinical and pathological characteristics of colorectal cancer in India when compared to the west, mainly a lower age at presentation, preponderance for left-sided tumours, and increased proportion of signet ring cell morphology.^[8,9]

Data regarding the demography and clinical characteristics of colorectal cancer, especially in a country as diverse as India, remains incomplete. This study aims to further examine the clinical and pathological features of colorectal cancer in a cancer centrein South India.

MATERIAL AND METHODS

This study was a retrospective cross-sectional study of a prospectively maintained CRC institutional database in a tertiary care cancer centrein South India.

All patients with histologically confirmed colorectal cancers undergoing treatment at Kidwai Memorial Institute of Oncology from January 2021 to February 2025 were included in this study. Patients with secondary or recurrent colorectal cancers were excluded. Patients whose records were incomplete were also excluded.

Patient data such as age, sex, religion, literacy, as well as tumour characteristics such as location, histology, and stage at presentation were recorded.

Location (subsite) of the tumourwas classified broadly into colon and rectum. Under the colon, the tumour was further classified into right (cecum, appendix, ascending colon, transverse colon) or left colon (descending colon and sigmoid colon). Rectosigmoid tumours were considered as rectal tumours for the sake of analysis. Histological information was recorded by a trained pathologist. Data was extracted into SPSS, and descriptive statistics were calculated.

The patient characteristics (age and sex) were analysedwith respect to sex, location, differentiation, signet and mucinous morphology, and staging (both tumour node metastasis and American Joint Committee on Cancer stage grouping).

The chi-square test was used to determine the association between groups of categorical variables, while the t-test was used to determine the association between means. P values < 0.05 were considered statistically significant as per convention. Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) version 25.0 for Windows.

RESULTS

A total of 831 consecutive patients were enrolled in the study. The mean age of the study participants was 52.74 ± 14.27 years, of which 57.8% were male.

Rectal cancers formed the bulk of incident colorectal cancers (64.0%), while 36% were of colonic origins. The most common tumourhistological subtype was moderately differentiated adenocarcinoma. Mucinous and signet ring cell subtypes were the next most commonly encountered, at 11.4% and 7.6% respectively. Over half of the patients (58.2%) presented in stage III, and 25.5% were stage IV.

CRC showed sex differences concerning T staging at diagnosis, in which females were found to have a higher T stage at diagnosis than males (87.1% vs 81.6%, p = 0.03). There was also a significantly increased rate of illiteracy among females diagnosed with CRC when compared to males [Table 1].

Generally, colonic and rectal tumoursdid not show many significant differences. Of note, colon cancers were more likely to be of a mucinous subtype than rectal cancers (p = 0.000). In addition, colon cancers were more likely to have poor differentiation when compared to their rectal counterparts (p = 0.012) [Table 2].

DISCUSSION

Colorectal cancer is an emergingcancer epidemic, constituting 10% of the global cancer burden.^[10,11] We studied the clinicopathological characteristics of CRC with the help of available data from a quaternary care cancer centre in South India. The analysis of patient demographics, sex-based characteristics, tumour characteristics, and their variation by tumour location was conducted. A total of 831 patients with colorectal malignancy were part of the study from 2020 to 2025.

Etiologically, increasing age is known to be a key factor in the development of colorectal malignancy. Studies worldwide have indicated that the risk of colorectal cancer increases 2-fold every 5 years till the age of 50 and plateaus from the age of 50, as early detection of pre-cancerous lesions after the age of 50 is more likely due to improved screening. While the mean age range of incidence of colorectal cancer ranges from 55 to 70 across various studies, our study detected colorectal cancer at a mean age of 52.7 ± 14.2 years. We found that patients were diagnosed with CRC at a marginally younger age in comparison to the current world trends, which may be contributing to the rise of early onset of colorectal cancer.^[12–15] This rising trend of young-onset colorectal cancer is particularly pronounced in the Indian subcontinent, known to be a low-prevalence area for colorectal cancer, with multiple studies done in high-volume cancer centres showing a reduced age of incidence across the country.^[8,10,16]

Based on tumourlocation, our data indicated that rectal cancers have a slightly higher incidence than colonic tumours since the majority of the patients (64%) were diagnosed with rectal cancer. This is in line with data reported from other Indian centres. In contrast, data reported from other countries, such as the US or South Korea, indicate higher prevalence rates of colon cancer.^[8,10,14,17]

Analysis of the histopathological type of cancer indicated that adenocarcinoma constituted the majority of the cases (653 cases) (78.6%), followed by Mucinous and Signet Ring cell subtypes - 11.4% and 7.6% respectively. This corresponds with studies worldwide, which demonstrate that the adenocarcinoma subtype is the most common histopathological variant. The signet ring cell subtype and the mucinous subtype have higher percentages than other regions worldwide. This could be attributed to the younger age of our cohort, as young-onset colorectal cancer tends to be associated with aggressive histological features. Signet ring subtypes, in particular, are known for their aggressive behaviour and poor outcomes. They are rare subtypes, composing about 1% of colorectal adenocarcinomas. However, this subtype is more prevalent in India, with prevalence rates reaching 19% in some regions of the country.^[18–20]

We also recognisedthat by the time of diagnosis, most patients are already at advanced stages, both histopathologically and radiologically, compared to the data and studies conducted in higher-income countries. Lower literacy rates of the population, lack of early screening protocols, and limited accessibility to healthcare may have contributed to this trend. Less than 10% of adults eligible for screening actually undergo screening in India, which presents an area of unmet need that, if tackled, may drastically improve outcomes.^[21] The majority of the patients were diagnosed to have moderately differentiated and poorly differentiated histopathological characteristics in our study. Moderately differentiated and poorly differentiated carcinomas are known to be aggressive carcinomas with a poorer prognosis. The indication of the majority of patients presenting with aggressive carcinoma highlights the need for early screening policies and equitable access to healthcare in low-and middle-income countries (LMIC).

In conclusion, there is a rising trend of young-onset CRC according to our study, where rectal cancers were found to be of higher prevalence. Histopathologically, these cancers are usually of the Adenocarcinoma subtype, while mucinous and signet ring subtypes also showed significantly higher percentages. We also highlight that the delay in diagnosis poses a significant challenge, contributing to the progression of the disease and diagnosis at an advanced stage. Hence, routine screening, health education, and identification of risk factors of CRC can help in early detection and management of Young-Onset CRC.

TAKE HOME MESSAGE

Colorectal cancer in India demonstrates a distinct clinical and pathological profile, with a substantial proportion of patients presenting at a younger age, advanced stage, and with aggressive pathological features. These findings underscore the need for improved screening strategies, heightened clinical vigilance, and tailored public health interventions.