Assessing rectal toxicity in a pilot study using intrarectal amifostine and concurrent radiation

Abstract

18579 Background: There is evidence that daily intrarectal amifostine can protect rectal mucosa during prostate cancer treatment. Instruments more sensitive than the RTOG score may discriminate small but clinically important reductions in proctitis, however these tools need further evaluation. This study used both the RTOG GI toxicity score and expanded prostate cancer index composite (EPIC), a patient-administered quality of life instrument, to evaluate toxicity. Methods: In this pilot study, patients with localized prostate cancer were given daily amifostine (MedImmune, INC., Gaithersburg, MD) which was placed per rectum 30–45 min before 3D conformal radiation (66–76 Gy in 2 Gy fractions to a volume based on PSA, Gleason score and clinical stage). The first 18 patients enrolled received 1gram of amifostine and the next 12 patients were given 2 grams. Toxicity was assessed at baseline, 5, and 7 weeks during treatment and 3, 6, 12, 18, and 24 months after radiation and amifostine treatment. RTOG grading, an EPIC score and proctoscopic examination were done. The EPIC questionaire is a validated instrument that consists of 50 quality of life questions related to urinary, bowel, sexual and hormonal domains. Two subsets of the bowel domain were used: “bowel function” (BF) targets symptom severity and “bowel bother,” (BB) assesses quality of life subscales. Results: Previously reported results demonstrate a clear trend towards protection from rectal toxicity using 2 gm as compared to a 1 gm amifostine dose. Here, we report that the EPIC-BF and EPIC-BB scores are both highly correlated with the RTOG toxicity score with a pearsons coefficient of 0.98 and 0.97 respectively at a median follow up of 24 mos. There was no significant change in the RTOG GI toxicity score over the course of treatment for either amifostine dose group. There was a statistically significant decrease in EPIC-BF score at 7 weeks (p = 0.04) and the EPIC-BB score showed a trend toward improvement (p = 0.07) at the same time point. The EPIC scores at all other time points were not statistically different from baseline. Conclusions: The EPIC score may be a more sensitive measure to detect acute toxicity associated with prostate cancer treatment but needs further investigation in the acute setting. No significant financial relationships to disclose.