Pelvic bone anatomy vs implanted gold seed marker registration for image-guided intensity modulated radiotherapy for prostate carcinoma: Comparative analysis of inter-fraction motion and toxicities

Objectives we compared the prostate motion variability and toxicities between patients treated with gold marker registration based ig-imrt (ig-imrt-m) and bony landmark registration based ig-imrt (ig-imrt-b). methods t1c-t3b (node negative),intermediate and high risk (non-metastatic) adenocarcinoma of prostate,age ≥18 years,karnofsky performance status of ≥70 were included in this retrospective study. the prostate motion variability,acute and late radiation toxicities between the two treatment arms (ig-imrt-m versus ig-imrt-b) were compared. results total of 35 patients (17 for ig-imrt-m and 18 for ig-imrt-b) were treated with a median radiotherapy dose of 76 gray. the prostate variability observed with and without markers in millimeter was 4.1 ± 2.3 vs 3.7 ± 2.1 [antero-posterior (a-p); p = 0.001],2.3 ± 1.5 vs 2.1 ± 1.2 [superior-inferior (s-i); p = 0.095] and 1.1 ± 1.7 vs 0.4 ± 1.4 [left-right (l-r); p = 0.003]. there was higher acute toxicity in ig-imrt-b arm compared to ig-imrt-m arm in terms of grade ≥2 diarrhea [50% vs 11% or = 7.5 (1.3–42.7); p = 0.02] and grade ≥2 proctitis [38% vs 5.8%,or = 10.1 (1.09–94.1); p = 0.04]. at a median follow up of 36 months,the late genitourinary toxicities grade ≥2 [27% vs 0%; p = 0.04] were higher in the ig-imrt-b arm compared to ig-imrt-m arm. conclusions ig-imrt-m detects higher prostate motion variability as compared to ig-imrt-b,inferring a significant prostate motion inside fixed pelvic bony cavity. the addition of marker based image guidance results in higher precision of prostate localization and lesser acute and late toxicities. © 2017 national cancer institute,cairo university