Impact Of Cancer And Chemotherapy On Autonomic Nervous System Function

Abstract

Cancer- and chemotherapy-related autonomic nervous system (ANS) dysfunction may contribute to increased cardiovascular (CV) morbidity- and mortality-risks in cancer survivors. However, inconsistent participant screening and assessment methods may compromise the reliability of the supporting evidence. Thus, good laboratory practices must be established before the presence and nature of cancer-related autonomic dysfunction can be characterized. PURPOSE: To assess the feasibility of conducting concurrent ANS and CV evaluations in young adult cancer patients, by: i) identifying methodological pitfalls and proposing good laboratory practice criteria for ANS testing in cancer, and ii) providing composite autonomic scoring scale (CASS)-based evidence of autonomic perturbations in cancer patients. METHODS: We assessed 13 patients (mixed diagnoses) before and after 4 cycles of chemotherapy. Their results were compared to 12 sex- and age-matched controls. ANS function was assessed using standardized tests of resting CV (tilt-table, respiratory sinus arrhythmia and Valsalva maneuver) and sudomotor (quantitative sudomotor axon reflex test) reactivity. CV reactivity during exercise was assessed using a modified Astrand-Ryhming cycle ergometer protocol. Our feasibility criteria addressed: i) recruitment potential, ii) retention rates, iii) pre-chemotherapy assessment potential, iv) test performance/tolerability, and v) identification and minimizing the influence of potentially confounding medication. Repeated measures ANOVAs were used to assess between- and within-group differences at baseline and follow-up. RESULTS: The overall success rate in achieving our feasibility criteria was 98.4%. We found greater CASS-based evidence of ANS impairment in patients compared to controls at baseline and follow-up (38.5% vs. 0% and 33.1% vs. 9.1%, respectively). CONCLUSIONS: Our feasibility results suggest the study of ANS function in young adult cancer patients receiving chemotherapy is possible. To our knowledge, this is the first study to report CASS-based evidence of ANS and sudomotor dysfunction in any cancer population. We found support for cancer/chemotherapy-related parasympathetic dysfunction - as a possible contributor to CV disease pathogenesis in cancer survivors.