Analysis of DNA mismatch repair proteins expression and BRAF V600E mutation in a subset of early- and late-onset colorectal carcinoma patients in Mexico

The Clinicopathological Characteristics of Young-Onset Versus Adult-Onset Colorectal Cancer: A Tertiary Hospital-Based Study

Background

The prevalence of colorectal cancer (CRC) among young individuals is rising worldwide, especially in Malaysia. Investigations are currently employed to distinguish the features of young-onset CRC (YOCRC) from adult-onset CRC (AOCRC). This study aimed to compare the characteristics of patients with YOCRC and AOCRC diagnosed at Hospital Universiti Sains Malaysia (HUSM).

Methods

This was a retrospective study of CRC cases from January 2013 to December 2021. The details of YOCRC (< 50 years old) and AOCRC (≥ 50 years old) patients were retrieved from the laboratory system and medical records. The Pearson's chi-square test, Fisher's exact test and multiple logistic regression were used to compare the AOCRC and YOCRC cases. Statistical significance was defined at a P-value of ≤ 0.05.

Results

The AOCRC (254/319, 79.6%) was more prevalent than YOCRC (65/319, 20.4%), with a predominance of males (53.9%) and Malay sub-population (90.2%). AOCRC and YOCRC shared similarities in left-sided location, high occurrence of adenocarcinoma with moderately differentiated histology and advanced stage of diagnosis. More patients with YOCRC (23.1%) had a family history of cancer than patients with AOCRC. YOCRC also differed from AOCRC by having more specific histological subtypes, such as mucinous adenocarcinoma (15.4%) and signet ring carcinoma (6.2%). In addition, patients with YOCRC commonly presented with a low density of tumour-infiltrating lymphocytes (TILs) (60%). Multiple logistic regression showed a family history of CRC (adjusted odds ratio [AOR] = 3.75, P = 0.003) and histological type (AOR = 15.21, P < 0.001) are more likely to cause YOCRC than diabetes (AOR = 0.06, P < 0.001) and hypertension (AOR = 0.14, P < 0.001) comorbidities, which are associated with AOCRC.

Conclusion

Our descriptive study presented the epidemiological and histopathological characteristics of AOCRC and YOCRC in HUSM, providing current information on distinguishing features between the groups.

Mismatch repair system in colorectal cancer. Frequency, cancer phenotype, and follow-up

INTRODUCTION AND AIMS

A frequent task in the study of colorectal carcinomas (CRC) is to identify tumors harboring deficient DNA mismatch repair systems (dMMR), which are associated with microsatellite instability. Given that there is scant information on those tumors in Mexican patients, our aim was to describe their frequency, clinical and pathologic characteristics, and results, which are necessary for future trials.

MATERIALS AND METHODS

A consecutive series of CRC patients, treated and followed at a tertiary care center was performed. The clinical and pathologic variables and the risk of hereditary or familial cancer syndrome were retrieved. The original slides and hMLH1, hPMS2, hMSH2, hMSH6 immunohistochemistry were evaluated. Tumors with an absence of at least one protein were considered dMMR. Differences were contrasted, utilizing non-parametric tests.

RESULTS

One hundred and forty-four patients were included, with a median age of 65 years. A total of 134/93% patients presented with sporadic CRC, 8/5.6% had a family history of CRC, and 2/1.4% met the diagnostic criteria for hereditary non-polyposis colon cancer, according to the Amsterdam and Bethesda criteria. dMMR tumors were found in 39 patients, distributed among the three groups. They were locally advanced (p<0.001), right-sided, had the mucinous phenotype, and harbored a Crohn's-like lymphoid reaction (all three features, p<0.04). Adjuvant or palliative chemotherapy was administered to 57 (39.6%), concomitant chemoradiotherapy to 24 (16.7%), but 63 (43.8%) patients received no additional treatment to surgery. Five-year follow-up was completed in 131 of the patients and the outcomes alive-with-disease or died-of-disease were more frequently observed in the proficient (pMMR) lesions.

CONCLUSIONS

In the present pre-FOLFOX case series, outcomes were better in dMMR CRC than in proficient lesions.

Prevalence of the BRAF p.v600e variant in patients with colorectal cancer from Mexico and its estimated frequency in Latin American and Caribbean populations

This study aimed to investigate the frequency of the somatic BRAF p.V600E in patients with colorectal cancer (CRC) in Mexico and compare it with those estimated for Latin American and Caribbean populations. One hundred and one patients with CRC with AJCC stages ranging I–IV from Western Mexico were included, out of which 55% were male and 61% had AJCC stage III–IV, with a mean age of 60 years. PCR-Sanger sequencing was used to identify the BRAF p.V600E variant. In addition, a systematic literature search in PubMed/Medline database and Google of the 42 countries in Latin America and the Caribbean led to the collection of information on the BRAF p.V600E variant frequency of 17 population reports. To compare the BRAF variant prevalence among populations, a statistical analysis was performed using GraphPad Prism V.6.0. We found that 4% of patients with CRC were heterozygous for the p.V600E variant. The χ² test showed no significant difference (p>0.05) in p.V600E detection when comparing with other Latin American and Caribbean CRC populations, except for Chilean patients (p=0.02). Our observational study provides the first evidence on the frequency of BRAF p.V600E in patients with CRC from Western Mexico, which is 4%, but increases to 7.8% for all of Latin America and the Caribbean. The patient mean age and genetic descent on the observed frequencies of the variant in populations could influence the frequency differences.