The influence of daily localization during treatment of prostate cancer on acute toxicity.

Abstract

214 Background: Various localization techniques are used in clinical practice but little comparative effectivess data exists. The purpose of this investigation is to assess the impact of daily localization (L) of the prostate on toxicity during definitive treatment of prostate cancer with intensity modulated radiotherapy (IMRT). Methods: This study details an IRB approved retrospective review of three cohorts of patients treated for prostate cancer utilizing IMRT and different L technologies at four academic hospitals. Patients were treated with no technique (N), gold markers (G), or electromagnetic beacons [Calypso] (C) for daily L. Acute genitourinary (GU) and gastrointestinal (GI) toxicity was assessed according to RTOG toxicity criteria; toxicity rates between the groups were compared using the chi-square test. Ordered logit regression of all major demographic (age, race), disease (PSA, Gleason grade, and T-stage) and treatment (hormones, pelvic nodal treatment, total dose, and prior TURP) characteristics on GU and on GI toxicity were performed. Results: One hundred fifty four men who received definitive dose escalated IMRT (no brachytherapy or post-prostatectomy patients) for prostate cancer from 2006 to 2010 and were included (G: n=47; C: n=47; N: n=60). The cohorts were balanced except race (higher percentage of African Americans in the N group, due to hospital demographics) and higher grade and use of pelvic nodal treatment (which were more common in the G and C groups). Bladder V40 and V70 were higher in the N group (45.4%/24.3%) compared to C (27.9%/12.3%) and G (37.4%/18.4%) groups; however, rectal V40 and V70 were similar among all 3 groups. Toxicity results are shown in the Table; as shown the C and G groups had lower GU toxicity (p <0.001) respectively compared to the N group; no significant differences in GI toxicity were seen among the 3 groups. Ordered logit regression showed only daily L (p=0.041) reached significance in lowering GU toxicity, and only pelvic RT use (p =0.008) reached significance in increasing GI toxicity. Conclusions: In patients treated with IMRT, daily L was associated with lower acute GU toxicity but not acute GI toxicity.