Obesity and overweight are associated with worse survival in early-onset colorectal cancer

Background: Obesity and its associated lifestyle are known risk factors for early-onset colorectal cancer and are associated with poor postoperative and survival outcomes in older patients. We aimed to investigate the impact of obesity on the outcomes of early-onset colorectal cancers.

Methods: Retrospective review of all patients undergoing primary resection of colon or rectal adenocarcinoma at our institution between 2015-2022. Patients who had palliative resections, resections performed at another institution, appendiceal tumors, and were underweight were excluded. The primary endpoint was survival according to the patient's body mass index: normal weight (18-24.9 kg/m²), overweight (25-29.9 kg/m²), and obesity (≥30 kg/m²). Patient and tumor characteristics and survival were compared between the three groups.

Results: A total of 279 patients aged <50 years with colorectal cancer were treated at our hospital; 120 were excluded from the analysis for the following reasons: main treatment or primary resection performed at another hospital (n = 97), no resection/palliative resection (n = 23), or body mass index <18 kg/m² (n = 2). Of these, 157 patients were included in the analysis; 61 (38.9%) were overweight and 45 (28.7%) had obesity. Except for a higher frequency of hypertension in the overweight (P = .062) and obese (P = .001) groups, no differences in patient or tumor characteristics were observed. Mean overall survival was 89 months with normal weight, 92 months with overweight, and 65 months with obesity (P = .032). Mean cancer-specific survival was 95 months with normal weight, 94 months with overweight, and 68 months with obesity (P = .018). No statistically significant difference in disease-free survival (75 vs 70 vs 59 months, P = .844) was seen.

Conclusion: Individuals with early-onset colorectal cancer who are overweight or obese present with similar tumor characteristics and postoperative morbidity to patients with normal weight. However, obesity may have a detrimental impact on their survival. Addressing obesity as a modifiable risk factor might improve early-onset colorectal cancer prognosis.