NEUROMUSCULAR FATIGUE IN PROSTATE-CANCER PATIENTS UNDERGOING RADIATION-THERAPY

Objective: To determine the etiology of fatigue in prostate cancer pat ients undergoing radiation therapy (RT). Methods: Thirteen prescreened men (60 to 76 years in age, 58 to 130kg in body weight) were evaluate d for neuromuscular fatigue (NMF) of the tibialis anterior (TA) muscle , cardiopulmonary fatigue (CPF), and psychological-subjective fatigue (PSF) at 1 to 2 weeks before RT (Pre), at the end of 8 weeks of RT (RT ), and at 5 to 6 weeks after completion of RT (Post). Outcome Measures : For NMF, the TA muscle was fatigued by sustained isometric contracti on at 80% of maximum voluntary contraction for 60 seconds on a force d ynamometer. Neuromuscular efficiency (NME) expressed as a ratio of iso metric force (in Newtons) and respective integrated electromyograms we re measured. For CPF, stress testing was performed on a treadmill usin g the modified Bruce protocol. Piper Fatigue Scale, Beck Depression In ventory, and Epworth Sleepiness Scale were administered to evaluate PS F. Data Analysis: Paired t tests, single factor analysis of variance, and nonparametric analysis. Results: At RT, there was a significant de cline in NME of TA at the beginning (18.4%, p < .01) and the end (29.2 %, p < .001) of sustained muscle contraction for 60 seconds. Post valu es were lower but nonsignificant in comparison with Pre values. NME re covered within 5 to 6 weeks after RT. No abnormalities were detected i n CPF or PSF. No correlation was found between the decline in NME and psychological status of the patients. Conclusion: Results provide defi nitive evidence of transient decline in NME in prostate cancer patient s at the completion of RT. The effect seems to be specific for neuromu scular performance alone and is independent of the cardiovascular or p sychological status of the patients. (C) 1997 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medic ine and Rehabilitation.