Pilot trial testing the effects of exercise on chemotherapy-induced peripheral neurotoxicity (CIPN) and the interoceptive brain system

Purpose: Chemotherapy-induced peripheral neurotoxicity (CIPN) is a prevalent, dose-limiting, tough-to-treat toxicity involving numbness, tingling, and pain in the extremities with enigmatic pathophysiology. This randomized controlled pilot study explored the feasibility and preliminary efficacy of exercise during chemotherapy on CIPN and the role of the interoceptive brain system, which processes bodily sensations.

Methods: Nineteen patients (65 ± 11 years old, 52% women; cancer type: breast, gastrointestinal, multiple myeloma) starting neurotoxic chemotherapy were randomized to 12 weeks of exercise (home-based, individually tailored, moderate intensity, progressive walking, and resistance training) or active control (nutrition education). At pre-, mid-, and post-intervention, we assessed CIPN symptoms (primary clinical outcome: CIPN-20), CIPN signs (tactile sensitivity using monofilaments), and physical function (leg strength). At pre- and post-intervention, we used task-free ("resting") fMRI to assess functional connectivity in the interoceptive brain system, involving the salience and default mode networks.

Results: The study was feasible (74-89% complete data across measures) and acceptable (95% retention). We observed moderate/large beneficial effects of exercise on CIPN symptoms (CIPN-20, 0-100 scale: - 7.9 ± 5.7, effect size [ES] = - 0.9 at mid-intervention; - 4.8 ± 7.3, ES = - 0.5 at post-intervention), CIPN signs (ES = - 1.0 and - 0.1), and physical function (ES = 0.4 and 0.3). Patients with worse CIPN after neurotoxic chemotherapy had lower functional connectivity within the default mode network (R² = 40-60%) and higher functional connectivity within the salience network (R² = 20-40%). Exercise tended to increase hypoconnectivity and decrease hyperconnectivity seen in CIPN (R² = 12%).

Conclusion: Exercise during neurotoxic chemotherapy is feasible and may attenuate CIPN symptoms and signs, perhaps via changes in interoceptive brain circuitry. Future work should test for replication with larger samples.

Trial registration: Registered Jan 2017 on ClinicalTrials.gov as NCT03021174.