Pelvic radiotherapy and urine substance P levels

Abstract

9607 Background: Pelvic radiotherapy is widely used for the treatment of malignancies localized in the pelvis. Urinary complications are the major side effects of pelvic radiation. Etiopathogenesis of the radiation-induced bladder toxicity is not known. Substance P (SP) which is found in sensory neurons is important in both motor functions and local regulation of immune response in the urinary bladder. There are no clinical studies examining the effects of pelvic radiotherapy on urine SP levels. Hence, the goal of this study was to determine the acute and sub acute effects of RT on SP levels in the urine. Methods: Sixty-three patients were enrolled in the study. Out of 63 patients 15 of them had endometrial, 12 of them had cervical, 12 of them had prostate and 24 of them had rectal carcinoma. Each patient received 2 Gy daily fractions and urine samples were obtained before first fraction, one hour after first, eighth and twenty-fifth fraction and twelve weeks after the completion of RT. Each patient was evaluated for urinary side effects weekly, according to RTOG toxicity criteria. SP levels were determined directly form urine samples by enzyme immune assay. Results: Urinary side effects were reported in 36 % of patients after eighth fraction while most patients developed side effects after 25th fraction. Specifically all the prostate patients had grade one or 2 toxicity while only 66% of the patients with endometrial carcinoma developed toxicity. 93% and 84 % of patients with cervical and rectal carcinoma respectively had toxicity. Radiotherapy altered SP levels in the urine in patients with urinary toxicity. SP levels were decreased in most patients. Specifically SP levels decreased markedly (> 70 %) in 14 %, 24 % and 17 %, and intermediately (50–70 %) in 22 %, 14 % and 19 % of patients after first, eighth and twenty-fifth fractions respectively. In a group of patients, SP levels were increased after RT. SP levels increased markedly (> 90 %) in 6 %, 18 % and 15 % after first, eighth and twenty-fifth fractions respectively. Intermediate increase (50–90 %) was observed in 4 %, 4 % and 6 % of patients after first, eighth and twenty-fifth fractions respectively. Conclusions: These results demonstrate that RT affects peptidergic neurons in the bladder and altered Substance P levels could be responsible from acute and late toxicities of RT. No significant financial relationships to disclose.