Clinical and Dosimetric Comparison Between Non-image Guided Radiation Therapy and Fiducial-Based Image Guided Radiation Therapy With or Without Reduced Margin in Intensity Modulated Radiation Therapy for Prostate Cancer

Purpose: This study aimed to compare the outcomes and toxicities between patients treated with image guided radiation therapy (IGRT) using fiducial markers and non-IGRT in intensity modulated radiation therapy (IMRT) for prostate cancer. Methods and Materials: In total, 518 patients with intermediate- and high-risk prostate cancer received IMRT with 78 Gy in 39 fractions after neoadjuvant androgen deprivation therapy for at least 3 months. Of these patients, 371 were in the non-IGRT group and 147 in the IGRT group, including the IGRT-A group using the same margins as the non-IGRT group and the IGRT-B group using reduced margins. The median follow-up periods for the non-IGRT, IGRT-A, and IGRT-B groups were 99 months, 88 months, and 63 months, respectively. Results: The 5-year biochemical recurrence-free survival rates in the non-IGRT, IGRT-A, and IGRT-B groups were 88%, 95%, and 98% (non-IGRT vs IGRT-A, P = .396; IGRT-A vs IGRT-B, P = .426), respectively. Those for intermediate- and high-risk patients were 94%, 93%, and 96% (non-IGRT vs IGRT-A, P = .916; IGRT-A vs IGRT-B, P = .646), respectively, and 87%, 96%, and 100% (non-IGRT vs IGRT-A, P = .500; IGRT-A vs IGRT-B, P = .483), respectively. For the non-IGRT and IGRT-A groups, the rates of acute grade >= 2 gastrointestinal toxicities and late grade >= 2 genitourinary toxicities were 17% and 7% (P = .019), respectively, and 28% and 16% (P = .028), respectively. In the IGRT-A and IGRT-B groups, the rates of acute grade >= 2 genitourinary toxicities were 45% and 21% (P = .003), respectively. All V60(Gy) = the volume at least received 60Gy and V70(Gy) = the volume at least received 70Gy values of the bladder and rectal walls in the IGRT-B group were smaller than those in the IGRT-A group. Conclusions: IGRT with fiducial markers results in lower acute and late toxicities compared with non-IGRT in IMRT for intermediate- and high-risk prostate cancer. Moreover, the toxicities are further decreased by reducing the margins in the treatment planning under IGRT. These processes do not decrease the biochemical recurrence-free survival rates. (c) 2024 The Authors. Published by Elsevier Inc. on behalf of American Society for Radiation Oncology. This is an open accessarticle under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).