In patients with metastatic colorectal cancer (mCRC), body mass index (BMI) was prognostic for overall survival (OS) and progression-free survival (PFS), investigators reported online in Journal of Clinical Oncology.
Risks were highest at the lowest BMI values, decreased as BMI increased to 28 kg/m2, and plateaued at higher BMI values.
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This slide shows colorectal cancer metastasis.
By pooling data from more than 21,000 patients enrolled worldwide in 25 randomized trials for frontline treatment, “we have shown that BMI is prognostic for OS and PFS in this population, but with a shape of the risk curve across the BMI spectrum, different than that observed in the adjuvant setting,” wrote Lindsay Renfro, Ph.D., of the Mayo Clinic, Rochester, Minn., and her colleagues (Jour Clin Onc. 2015 Oct 26 [doi: 10.1200/JCO.2015.61.6441]).
Patients with a BMI of 18.5 kg/m2 had a 50% increased risk of death (95% confidence interval, 43%-56%). After researchers adjusted for age, sex, performance status, and clinical characteristics, the prognostic significance of BMI remained (P less than .001).
Previous studies showed that obese patients with stage II or III colon cancer were at increased risk for disease recurrence or death, but results of the current study showed obese patients with mCRC were not at increased risk.
Men with low BMIs had a greater risk of death than did women. Both men and women with moderate and higher BMIs had similar risks. Previous studies have shown that the prognosis for women with colorectal cancer is improved over men, possibly because of the protective effect of estrogen.
The results suggest that patients with mCRC and low BMI are likely cachectic, a condition that affects approximately 50% of patients with colon cancer and is associated with a 20% mortality rate, the authors noted.