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.
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.
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 <0.001). Furthermore, obesity was associated with risk of any CD3+ high or low and any CD68+ high or low tumors in both sexes, and with any PD1+ high or low tumors in men. In age and BMI-adjusted survival analysis, PD1+, CD8+, CD20+, and CD68+ high were favorable prognostic factors only in women, and FoxP3+ high only in men. High PD-L1+ and CD3+ expression was prognostic in both sexes.
Anthropometric factors may influence the immune landscape of colorectal cancer, possibly in a sex-dependent manner. Thus, obesity and sex may be important factors to take into account when stratifying patients for immunotherapy.
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Legal entity responsible for the study
Swedish Cancer Society, Swedish Research Council, the Swedish Government Grant for Clinical research, the Mrs Berta Kamprad Foundation, Lund University Faculty of Medicine, University Hospital Research Grants.
All authors have declared no conflicts of interest.