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

Abstract 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.