Stereotactic body radiotherapy for oligometastatic castration sensitive prostate cancer using 1.5 T MRI-Linac: preliminary data on feasibility and acute patient-reported outcomes

Objectives To report preliminary data on feasibility and patient-reported outcomes following PSMA-PET/CT guided SBRT by means of 1.5 T MRI-Linac. Methods and materials Between October 2019 and April 2020, twenty consecutive castration sensitive oligorecurrent prostate cancer patients were enrolled in an ethical committee approved prospective observational study (Protocol n. XXXX) and treated with PSMA-PET/CT guided SBRT by means of 1.5 T MRI-Linac (Unity, Elekta AB, Stockholm, Sweden). The mean delivered dose was 35 Gy in 5 fractions. Clinicians reported toxicity was prospectively collected according to Common Terminology Criteria for Adverse Events v5.0. Quality of life (QoL) assessment was performed using EORTC-QLQ C30 questionnaires administered at baseline, end of treatment and at first follow-up. Results Twenty-five lesions in 20 castration sensitive oligorecurrent patients were treated: the most commonly treated anatomic sites were nodal (n = 16) and pelvic bone (n = 9). Median PSA-value preMRI guided SBRT was 1.16 ng/mL (range, 0.27-8.9), whereas median PSA value at first follow-up after SBRT was 0.44 ng/mL (range, 0.06-8.15). At first follow-up, for 16 patients showing detectable PSA, PSMA-PET/CT was performed detecting, respectively, in 6 cases partial response and in 10 cases complete response. In the remaining cases, PSA-value was undetectable after SBRT. Radiotherapy treatment was safe and well tolerated according to the PROMs. No acute G2 or higher toxicities were recorded. Conclusions The current series represent the largest one exploring the feasibility and patient-reported outcomes following PSMA-PET/CT guided SBRT by means of 1.5 T MRI-Linac. The preliminary findings here reported are encouraging in terms of effectiveness and tolerability.

Automated summary

This study investigated the feasibility and patient-reported outcomes of PSMA-PET/CT guided SBRT using a 1.5 T MRI-Linac for castration sensitive oligorecurrent prostate cancer patients. The preliminary results showed promising effectiveness and tolerability, with a majority of patients experiencing a decrease or disappearance in PSA levels at the first follow-up. No severe toxicities were reported during the treatment.