Magnetic Resonance-Guided Reirradiation for Local Recurrence Within the Prostate or in the Prostate Bed: Preliminary Results of a Prospective Registry Study.

This prospective registry study evaluated the feasibility of stereotactic magnetic resonance imaging (MRI)-guided radiation therapy for the local treatment of isolated prostate cancer recurrence within the gland or prostate bed after primary radiation therapy.

Patients with isolated recurrence without any regional or distant extension after treatment by external radiation therapy of the prostate gland/bed or by prostate brachytherapy were included. A 173-second Fast Imaging with Steady state Precession (TrueFISP) sequence was used for MRI simulation, and the gross tumor volume was delineated using multimodal images. The initial treatment plan varied from 27.5 Gy in 5 fractions to 38.7 Gy in 9 fractions and was adapted at each session, if necessary. The primary endpoint was acute toxicities (according to the Common Terminology Criteria for Adverse Events v5.0 criteria). Secondary endpoints were the effects of the adaptive treatment on target volume coverage, late toxicities, and oncologic events.

Twenty patients were included. After a minimum follow-up of 6 months, grade 2 dysuria (from grade 1 at baseline; n = 1), grade 2 polyuria (n = 1), grade 1 urinary incontinence (n = 1), grade 1 urinary pain (n = 2), and grade 1 diarrhea (n = 1) were reported.All initial treatment plans met the tumor coverage objectives, with a mean 95% planning target volume value of 95.7%. No plan exceeded the bladder and rectum dose constraints, but 8 exceeded the urethra dose constraints because of urethra proximity to the planning target volume. The initial plan was adapted in 7 patients (35%). The tumor coverage improved by 3.7% compared with the predicted plan (P = .0001) without increase in the dose to organs at risk. The biochemical control rate for the whole cohort was 75% (15/20 patients) including the 4 patients who received androgen-deprivation therapy.

MRI-guided reirradiation for isolated recurrence within the prostate or in the prostate bed appears to be safe with excellent dosimetric results.

Advances in radiation oncology. 2021 Jul 01*** epublish ***

Morgan Michalet, Olivier Riou, Simon Valdenaire, Pierre Debuire, Norbert Ailleres, Roxana Draghici, Marie Charissoux, Carmen Llacer Moscardo, Marie-Pierre Farcy-Jacquet, Pascal Fenoglietto, David Azria

University Federation of Radiation Oncology of Mediterranean Occitanie, Montpellier Cancer Institute, Univ Montpellier, INSERM U1194 IRCM, Montpellier, France., University Federation of Radiation Oncology of Mediterranean Occitanie, Institut de Cancérologie du Gard, CHU Carémeau, Nîmes, France.