Early-onset colorectal cancers (EO-CRC) are clinically and genomically similar to and also not more aggressive than average-onset CRC (AO-CRC), except that they tend to occur more on the left side and are more likely to present with rectal bleeding and abdominal pain, suggests a recent study published in the Journal of the National Cancer Institute.¹

EO-CRC are defined as CRC diagnosed in individuals under the current recommended screening age of 50 years.²

The retrospective study undertook to find out the differences in clinical or genomic characteristics of 759 patients with early-onset colorectal cancer (EO-CRC) and 687 patients with average-onset colorectal cancer (AO-CRC). Patients with AO-CRC were ≥50 years, while patients with EO-CRC were further grouped into two by their age at the point of diagnosis: ≤35 years (n=151) and 36-49 years (n=608). These patients had presented to the Memorial Sloan Kettering Cancer Center between 2014 and 2019 and underwent treatment there.

The incidence of left sided tumors was nearly 81% in EO-CRC patients ≤35 years and 83.7% in the 36-49 years age group, whereas the incidence in the AO-CRC patients was around 64% suggesting that EO-CRC were more commonly left-sided in the younger patients.

The incidence of rectal bleeding was also higher in the EO-CRC (≤35 years = 41.1%; 36-49 years = 41.0%) compared to AO-CRC, where the incidence of rectal bleeding was 26%. Similarly, more patients with EO-CRC complained of abdominal pain than those with AO-CRC; ≤35 years = 37.1%, 36-49 years = 34.0%, AO = 26.8%). 

No differences in tumor characteristics were observed in microsatellite stable tumors on histopathology. The prevalence of pathogenic germline mutations was higher in the younger patients (EO-CRC aged 35 years or younger) compared to patients with AO-CRC; 23.3% vs 14.1%, respectively. This finding highlights the significance of family history in younger patients as well as the need for germline testing and genetic counseling in young adults.

The clinical outcomes and response to chemotherapy was comparable between the three groups as was the median overall survival, which was: 46.9 months for patients ≤35 years, 56.4 months for patients 36-49 years and 54.5 months for AO-CRC patients, which was not statistically significant.

Hence, based on their findings, the study authors concluded that “aggressive treatment regimens based solely on the age at CRC diagnosis are not warranted”.

Reference

1. Cercek A, et al. A comprehensive comparison of early-onset and average-onset colorectal cancers. J Natl Cancer Inst. 2021 Aug 18:djab124. doi: 10.1093/jnci/djab124.
2. Loomans-Kropp HA, et al. Increasing incidence of colorectal cancer in young adults. J Cancer Epidemiol. 2019 Nov 11;2019:9841295

Dr Dinesh Pendharkar

Consultant Medical Oncologist

Founder Innovative Healthcare Delivery Model-(Cancer Care- Pendharkar Model)