Prognostic relevance of prediagnostic weight loss and overweight at diagnosis in patients with colorectal cancer.

Studies on the association between body mass index (BMI) and colorectal cancer (CRC) prognosis after diagnosis have yielded inconsistent results. Few studies have investigated associations between prediagnostic BMI change and CRC prognosis.

The associations of BMI at diagnosis and prediagnostic BMI change with relevant prognostic outcomes were evaluated in a large population-based cohort of CRC patients.

A total of 3130 patients diagnosed with CRC between 2003 and 2010 were interviewed on sociodemographic and lifestyle factors, medication, and comorbidities. Cancer recurrence, vital status, and cause of death were documented for a median follow-up time of 4.9 y. With the use of Cox proportional hazards regression, associations between BMI at diagnosis and BMI change (difference between 1-10 y before diagnosis and at diagnosis) and overall, CRC-specific, recurrence-free, and disease-free survival were analyzed.

Compared with normal weight, overweight [BMI (in kg/m2): 25 to <30] and obesity (BMI: ≥30) were associated with improved overall [adjusted HR (aHR): 0.82; 95% CI: 0.70, 0.95 and aHR: 0.80; 95% CI: 0.66, 0.98, respectively] and CRC-specific (aHR: 0.84; 95% CI: 0.71, 1.01 and aHR: 0.78; 95% CI: 0.62, 0.99, respectively) survival, with associations being even stronger when the analysis was restricted to nonmetastatic disease. Compared with stable BMI, a strong prediagnostic BMI decrease of >5 was associated with poorer prognosis for all survival outcomes (overall survival-aHR: 1.83; 95% CI: 1.43, 2.34; CRC-specific survival-aHR: 1.78; 95% CI: 1.33, 2.39), and associations were particularly pronounced in men (overall survival-aHR: 2.31; 95% CI: 1.65, 3.22; CRC-specific survival-aHR: 2.56; 95% CI: 1.72, 3.81; P-interaction = 0.08).

Overweight and obesity are associated with enhanced survival after a CRC diagnosis. A major decrease in BMI in the years before diagnosis is a strong independent predictor of decreased survival. This trial was registered at www.studybox.de as ST-D066.