Pre-diagnostic anthropometry, sex, and risk of colorectal cancer according to tumor-infiltrating immune cell composition

Background: Obesity is a well-established risk factor for colorectal cancer (CRC), but whether this risk differs according to CRC subtype defined by the tumor immune microenvironment has been sparsely described. Herein, we examined the relationship between pre-diagnostic anthropometry and CRC risk according to tumor-infiltrating immune cell composition, with particular reference to potential sex differences. Methods: The density of immune cells expressing PD1, PD-L1 (PD-L1/IC), CD3, CD8, FoxP3, CD20, CD68, CD163, and tumor cells expressing PD-L1 (PD-L1/TC) was assessed by immunohistochemistry in tissue microarrays with tumors from 584 incident CRC cases in the Malmö Diet and Cancer Study (n = 28098). Multivariable Cox regression models, adjusted for age, smoking and alcohol intake, were applied to calculate hazard ratios (HR) for CRC risk according to height, weight, bodyfat %, waist- and hip circumference, waist-hip ratio (WHR), body mass index (BMI), and different immune cell subsets. Results: Obesity, measured as several anthropometric factors, was significantly associated with PD-L1+/TC low, CD8+ high, FoxP3+ low, CD20+ low, and CD163+ low tumors in both sexes, and with PD1+ low tumors in women. A contrasting risk between sexes was seen for PD-L1/IC+ tumors, in that obesity was significantly associated with risk of PD-L1/IC+ high tumors in women (ptrend for weight = 0.008, ptrend for BMI = 0.039), but with risk of PD-L1/IC+ low tumors in men (ptrend for weight = 0.005, ptrend for bodyfat % = 0.003, ptrend for waist <0.001, ptrend for hip = 0.012, ptrend for BMI = 0.001, ptrend for WHR