Magnetic resonance image-guided adaptive stereotactic body radiotherapy for prostate cancer: preliminary results of outcome and toxicity

Abstract

Objectives: Using moderate or ultra hypofractionation, which is also known as stereotactic body radiotherapy (SBRT) for treatment of localized prostate cancer patients has been increased. We present our preliminary results on the clinical utilization of magnetic resonance image-guided adaptive radiotherapy (MRgRT) for prostate cancer patients with the workflow, dosimetric parameters, toxicities and prostate specific antigen (PSA) response. Methods: Fifty prostate cancer patients treated with ultra-hypofractionation were included in the study. Treatment was performed with IMRT (step and shoot) technique and daily plan adaptation using MRgRT. The SBRT consisted of 36.25 Gy in five fractions with a 7.25 Gy fraction size. The time for workflow steps was documented. Patients were followed for the acute and late toxicities and PSA response. Results: The median follow-up for our cohort was 10 months (range between 3 and 29 months). The median age was 73.5 years (range between 50 and 84 years). MRgRT was well tolerated by all patients. Acute genitourinary (GU) toxicity rate of Grade one and Grade 2 was 28 and 36%, respectively. Only 6% of patients had acute Grade one gastrointestinal (GI) toxicity and there was no Grade ≥ 2 GI toxicity. To date, late Grade 1 GU toxicity was experienced by 24% of patients, 2% of patients experienced Grade 2 GU toxicity and 6% of patients reported Grade 2 GI toxicity. Due to the short follow-up, PSA nadir has not been reached yet in our cohort. Conclusion: In conclusion, MRgRT represents a new method for delivering SBRT with markerless soft tissue visualization, online adaptive planning and real-time tracking. Our study suggests that ultra-hypofractionation has an acceptable acute and very low late toxicity profile. Advances in knowledge: MRgRT represents a new markerless method for delivering SBRT for localized prostate cancer providing online adaptive planning and real-time tracking and acute and late toxicity profile is acceptable.

Interfractional Geometric Variations and Dosimetric Benefits of Stereotactic MRI Guided Online Adaptive Radiotherapy (SMART) of Prostate Bed after Radical Prostatectomy: Post-Hoc Analysis of a Phase II Trial

“…There is a paucity of data reporting the feasibility and efficacy of online ART for prostate cancers and most publications have focused on intact prostate treatment with SMART [ 26 , 27 , 28 ]. A prospective phase II study of SMART reported a low incidence of early toxicity in patients with localized PCa treated on the same 0.35T MR-LINAC as in this study, with an average treatment fraction time of 45 min [ 26 ].…”

“…Alongi et al reported a single-institution prospective study using a 1.5T MR-LINAC with daily adaptive SBRT for 25 patients with localized PCa [ 27 ], with a median adaptive fraction time of 53 min. In another study of SBRT for localized PCa with daily adaptive planning on the same 0.35T MR-LINAC, the median treatment time was reported to be 45 min [ 28 ]. Of the treatment fractions, 76% were adapted, with 33.2% of them accounting for target coverage, 24.7% for OAR dose violations, and 36.3% for both.…”

MR-Guided Hypofractionated Radiotherapy: Current Emerging Data and Promising Perspectives for Localized Prostate Cancer

“…A further recent paper has been published by Uguerler et al [38] reporting in a series of 50 patients with a median follow-up of 10 months with no evidence of G3 acute or late toxicity. Although observing a 36% rate of G2 GU adverse events, when available, late GI and GU toxicity rates were respectively 2% and 6%.…”

“…For both devices, given the relatively longer treatment time per session, the simulation process is a crucial factor in order to perform an accurate and refined treatment delivery. Based on available literature, most experiences reported a similar protocol in terms of bladder filling and rectal emptying ( [32][33][34][35][36][37][38]-see Table 1). For both the CT scan (performed for dose calculation purposes) and the MRI scan, patients were educated to have a half-full bladder in order to take into account residual volume changes during the plan adaptation phase (Figure 2).…”

1.5T Magnetic Resonance-Guided Stereotactic Body Radiotherapy for Localized Prostate Cancer: Preliminary Clinical Results of Clinician- and Patient-Reported Outcomes

“…This distinctive feature of MRgRT holds the potential to achieve better tumor control and lower toxicities of PC SBRT. However, reports of clinical outcomes of MR-guided SBRT (MRgSBRT) in PC remain sparse [ 20 , 21 , 22 , 23 ]. The longitudinal clinical outcome of 1.5T MRgSBRT in localized PC is not yet available.…”