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Introduction: Physical activity is associated not only with a decreased risk of developing colorectal cancer but also with improved survival. One putative mechanism is the infiltration of immune cells in the tumor microenvironment. Experimental findings suggest that physical activity may mobilize immune cells to the tumor. We hypothesized that higher levels of physical activity prior to colorectal cancer diagnosis are associated with higher densities of tumor-infiltrating T-lymphocytes in colorectal cancer patients.

Method: The study setting was a northern Swedish population-based cohort, including 109792 participants with prospectively collected health- and lifestyle-related data. For 592 participants who later developed colorectal cancer, archival tumor tissue samples were used to assess the density of CD3⁺ and CD8⁺ cytotoxic T-cells by immunohistochemistry. Odds ratios for associations between self-reported, pre-diagnostic recreational physical activity and immune-cell infiltration were estimated by ordinal logistic regression.

Results: Recreational physical activity >3 times per week was associated with a higher density of CD8⁺ T-cells in the tumor front and center compared to participants reporting no recreational physical activity. Odds ratios were 2.77 (95% CI 1.21-6.35) and 2.85 (95% CI 1.28-6.33) for the tumor front and center, respectively, after adjustment for sex, age at diagnosis, and tumor stage. The risk estimates were consistent after additional adjustment for several potential confounders. For CD3 no clear associations were found.

Conclusion: Physical activity may promote the infiltration of CD8⁺ immune cells in the tumor microenvironment of colorectal cancer.

Impact: The study provides some evidence on how physical activity may alter the prognosis in colorectal cancer.

Purpose: Sarcopenia and myosteatosis, quantified via computed tomography (CT), are associated with poor colorectal cancer outcomes. These body composition estimates can be influenced by physical exercise. We explored the correlation between pre-diagnostic physical exercise, body composition close to diagnosis, and the combined prognosis impact of these factors.

Methods: We studied 519 stage I–III colorectal cancer (CRC) cases diagnosed 2000–2016 with pre-diagnostic self-reported recreational physical exercise data collected in the prospective, population-based Northern Sweden Health and Disease Study, and CT-estimated skeletal muscle index (SMI) or skeletal muscle density (SMD). Risk estimates were calculated by multivariable logistic regression and Cox proportional hazards models.

Results: No association was seen between low pre-diagnostic physical exercise and sarcopenia/myosteatosis in the multivariable model adjusted for age, sex, educational level, tumor stage, and tumor location. In multivariable Cox regression models, the combination of low pre-diagnostic physical exercise and either sarcopenia or myosteatosis at the time of diagnosis was associated with cancer-specific mortality compared to the reference group of high physical exercise combined with no sarcopenia/myosteatosis (adjusted HR 1.94 95% CI 1.00–3.76 for sarcopenia and adjusted HR 2.39 95% CI 1.16–4.94 for myosteatosis).

Conclusions: The combined presence of low pre-diagnostic physical exercise and sarcopenia or myosteatosis was associated with increased CRC-specific mortality. Despite the positive effect on prognosis, physical exercise did not alter body composition estimates at diagnosis, which could indicate attenuation from other factors.

Background: Both 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 and fitness.

Methods: This was a cohort study on 69 patients 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 by logistic regression.

Results: A higher number of repetitions in the 30-second 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 in the multivariable logistic regression models.

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).

BACKGROUND: Physical activity improves survival, reduces postoperative complications, and reduces the risk of developing colon cancer. It is important to maintain physical activity after receiving a diagnosis of colon cancer to improve postoperative recovery. Individuals who are physically active and diagnosed with colon cancer presumably have different motivations to maintain physical activity compared to their sedentary counterparts.

OBJECTIVE: Enlighten how the diagnosis of colon cancer might affect physically active individuals in their attitude and experiences towards physical activity.

METHODS: A qualitative study using content analysis was conducted in northern Sweden based on semi-structured telephone interviews of twenty patients diagnosed with colon cancer. All participants met the recommendations for physical activity issued by the World Health Organization.

RESULTS: Participants were between 50 and 88 years and 50% were male. Three main categories were identified: I'll fight the cancer and come out stronger; The diagnosis makes no difference; and The diagnosis is an obstacle for physical activity. These main categories represent the ways the individuals reacted to the diagnosis of colon cancer regarding their physical activity.

CONCLUSION: Attitudes to and experience of physical activity after colon cancer diagnosis varied from a will to increase physical activity and fight the cancer, to the diagnosis putting a stop to physical activity. It is important that healthcare professionals recommend physical activity even in already physically active individuals, to encourage continued physical activity after diagnosis of colon cancer.