Physical activity and the Neuro-Immuno-Fascial interface in cancer patients: mechanisms, clinical evidence, and therapeutic integration.

Physical activity has progressed from supportive care to an evidence-based oncologic intervention, with large cohort studies showing dose-dependent reductions in all-cause cancer mortality of roughly 20-47% across multiple tumor entities, and randomized trial evidence supporting a pooled reduction of approximately 26%. The CCTG CO.21 CHALLENGE trial, the first randomized controlled trial powered for survival endpoints, demonstrated that structured post-adjuvant exercise reduced disease recurrence by 28% and mortality by 37% in stage II-III colon cancer survivors, with an effect size comparable to adjuvant chemotherapy. This narrative review proposes the Neuro-Immuno-Fascial (NIF) interface as a hypothetical integrative axis that may help explain how exercise influences tumor-related biology. Clinical trials have established that physical activity improves function, mitigates fatigue, and lowers recurrence risk in selected cohorts; however, the multi-step causal chain linking mechanical fascial remodeling to anti-tumor outcomes in humans remains speculative. Accordingly, the NIF construct is presented as a conceptual framework for translational research rather than a clinical decision-making tool. At the fascial-stromal interface, preclinical data suggest that exercise-induced mechanical loading may activate Piezo1/YAP-TGF β1 mechanotransduction cascades in cancer-associated fibroblasts and modulate immunosuppressive architecture via three convergent, yet exploratory, mechanisms: viscoelastic and hydration-driven remodeling of the extracellular matrix that may improve compliance and interstitial fluid dynamics; Piezo channel-mediated mechanosensing that may influence myokine release (e.g., interleukin 6, irisin, SPARC) and associate with downstream changes in fibroblast behavior and natural killer cell trafficking; and autonomic rebalancing, reflected in 20-50% improvements in heart rate variability, which may attenuate pro-tumorigenic sympathetic tone. Direct human evidence that training-induced changes in fascial dynamics causally drive anti-tumor immunity is currently lacking. Preclinical findings further indicate that exercise-induced vascular normalization can increase tumor vessel perfusion and reduce hypoxia, although the magnitude and clinical relevance of these shifts in patients require further validation. On this basis, we outline three priorities for translational exercise oncology: standardized fascial and autonomic phenotyping using shear-wave elastography and heart rate variability spectral analysis; tumor microenvironment phenotype-specific exercise dosing algorithms; and prospective trials combining aerobic and resistance training with myofascial interventions and immune checkpoint inhibition. Structured physical activity should remain a standard component of oncologic care, while NIF-informed phenotyping and dosing strategies warrant systematic investigation.