Association of objectively assessed physical activity with immune cell infiltration of the tumor microenvironment in non-metastatic colon cancer.

PURPOSE: Physical activity and immune cell infiltration of the tumor microenvironment are associated with improved prognosis in colon cancer. There is also evidence that physical activity may mobilize immune cells against colon tumors. One possible mechanism behind the positive effect of physical activity on colon cancer prognosis could thus be increased immune cell infiltration of the tumor microenvironment. There are few previous studies examining this association, and none has included an objective assessment of physical activity. METHODS: This was a study on 69 patients enrolled in the Physical Activity and its impact on COlon cancer Surgery (PACOS) prospective cohort, all diagnosed with colon cancer stages I-III, all eligible for curative surgery, and with no previous treatment. Prior to surgery, the participants underwent physical tests, dual-energy X-ray absorptiometry, and wore an accelerometer to quantify their physical activity and physical fitness. Tumor infiltration by cytotoxic T cells, T-helper 1 cells, regulatory T cells, B cells, and macrophages was objectively assessed with multispectral quantitative automated pathology imaging. Odds ratios for associations between physical activity and immune cell infiltration were estimated. RESULTS: A higher number of repetitions in the 30-s sit-to-stand test was associated with a lower density of T-helper 1 cells in the stromal compartment of the tumor, in the model adjusted for age and sex. When correcting for multiple testing, the association was considered non-significant. No other significant association was seen for any of the physical tests or immune cell types. CONCLUSIONS: No consistent evidence was found to support the hypothesis of an association between physical activity or fitness and increased immune cell tumor infiltration in colon cancer. TRIAL REGISTRATION: This study was registered at clinicaltrials.gov (ID NCT03947840), registration date 2019-05-19.