EARLY-ONSET COLORECTAL CANCER: A COHORT STUDY
Margarida Rajão Saraiva*, Joana Lemos Garcia, Isadora Rosa, Grupo MCCR, Cristina Albuquerque, Inês Francisco, Patrícia Silva, Bruno Filipe, Ricardo Fonseca, Pedro Lage, Isabel Claro
Gastroenterology, Instituto Portugues de Oncologia de Lisboa Francisco Gentil EPE, Lisboa, Lisboa, Portugal
Background: Colorectal cancer's (CRC) incidence above 50 years old has been decreasing globally in the last decades, but its incidence in patients below 50 years old (early-onset colorectal cancer, EO-CRC) has been increasing, for reasons not yet fully understood.
Methods: A unicentric cohort study was conducted in a tertiary centre, including all patients admitted for a first diagnosis of CRC and evaluated by the Multidisciplinary Colorectal Cancer Group from 01.01.2017 until 31.12.2018. Patients with a previous diagnosis of a Hereditary Colorectal Cancer Syndrome were excluded.
Results: A total of 438 patients were included, 58.2% males, with a mean age at diagnosis of 67.7±11.1 years old. Mean follow-up time was 41.49 months. There were 25 EO-CRC patients (5.7%), 17 males (68%), mean age 43.1±6.0 years old.
Globally, 32.4% of the patients were current or past smokers, 18.5% had previous non-colorectal cancer, 7.5% and 3.4% were previously exposed to immunosuppressive drugs or abdominal/pelvic radiotherapy, respectively. The majority presented with normal(29.7%) to high Body Max Index (39.7%), median 25.6 (IQR:22.6-28.4) Kg/m2. The most common CRC location was the rectum (42.9%) and 56.1% were stage I or II (AJCC 8th edition).
In the univariate analysis, a significant association was found between EO-CRC and: smoking status (past or current smokers 52% in EO-CRC vs. 31.2% in older cases p=0.009); lymphovascular invasion (40.0% in EO-CRC vs. 17.4% in over 50, p=0.018) No significant differences were found for histological subtype (p=0.447), perineural invasion (p=0.474), or tumor stage at diagnosis, although a relevant proportion of the younger patients had metastatic disease at diagnosis (28.0% vs. 12.8%, p=0.064).
Immunohistochemistry for mismatch-repair proteins showed loss of expression of at least one protein in 1/18 EO-CRC patients and 22/179 of older patients (p=0.728).
From the EO-CRC patients, 16 were evaluated in the Familial Cancer Clinic and 14 underwent germline mutation analysis: 13 patients had inconclusive results, one of them presented a MUTYH heterozygote mutation and another was diagnosed with MUTYH-associated Polyposis (composed heterozygote mutation).
Conclusion: Colorectal cancer showed distinctive features in the younger population, with a higher prevalence of lymphovascular invasion and, possibly, a higher incidence of metastatic disease at diagnosis. Smoking had a significant association with CRC, especially in this younger population. Whether this means there is a biological difference is not yet clear. More evidence is needed in order to clarify EO-CRC aetiology and to develop screening and improve management strategies.
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