High dose proton and photon-based radiation therapy for 213 liver lesions: a multi-institutional dosimetric comparison with a clinical perspective.

BACKGROUND: Stereotactic radiotherapy (SRT) and Proton therapy (PT) are both options in the management of liver lesions. Limited clinical-dosimetric comparison are available. Moreover, dose-constraint routinely used in liver PT and SRT considers only the liver spared, while optimization strategies to limit the liver damaged are poorly reported. METHODS: Primary endpoint was to assess and compare liver sparing of four contemporary RT techniques. Secondary endpoints were freedom from local recurrence (FFLR), overall survival (OS), acute and late toxicity. We hypothesize that Focal Liver Reaction (FLR) is determined by a similar biologic dose. FLR was delineated on follow-up MRI. Mean C.I. was computed for all the schedules used. A so-called Fall-off Volume (FOV) was defined as the area of healthy liver (liver-PTV) receiving more than the isotoxic dose. Fall-off Volume Ratio (FOVR) was defined as ratio between FOV and PTV. RESULTS: 213 lesions were identified. Mean best fitting isodose (isotoxic doses) for FLR were 18Gy, 21.5 Gy and 28.5 Gy for 3, 5 and 15 fractions. Among photons, an advantage in terms of healthy liver sparing was found for Vmat FFF with 5mm jaws (p = 0.013) and Cyberknife (p = 0.03). FOV and FOVR resulted lower for PT (p < 0.001). Three years FFLR resulted 83%. Classic Radiation induced liver disease (RILD, any grade) affected 2 patients. CONCLUSIONS: Cyberknife and V-MAT FFF with 5mm jaws spare more liver than V-MAT FF with 10 mm jaws. PT spare more liver compared to photons. FOV and FOVR allows a quantitative analysis of healthy tissue sparing performance showing also the quality of plan in terms of dose fall-off.

Stereotactic Body Radiation Therapy for Oligoprogressive Pleural Mesothelioma: Fine-Tuning the Optimal Doses.

There is growing evidence of a role of stereotactic body radiation therapy (SBRT) in the treatment of patients with oligoprogressive pleural mesothelioma (PM). The objective of this study was to investigate the optimal radiation therapy doses and schedules in this setting. The records of patients treated with SBRT (>5 Gy per fraction) for oligoprogression of PM at 2 institutions from June 2014 to September 2022 were reviewed. Patients were divided into 2 groups: "intermediate-dose" SBRT (i-SBRT; total dose, 30-36 Gy in 5-6 fractions) and "high-dose" SBRT (h-SBRT; total dose, 45-50 Gy in 4-8 fractions). The comparison between the 2 groups in terms of local control (LC) and toxicity was the primary endpoint of the study. Overall, 23 patients were treated for 25 pleural lesions. All had received upfront chemotherapy with platinum/pemetrexed. Fifteen patients were treated with i-SBRT and 8 patients with h-SBRT. The median equivalent dose was 40 Gy (range, 40-49.6) in the i-SBRT group and 74.46 Gy (range, 64-88) in the h-SBRT group. Six-month, 1-year, and 2-year LC were 100%, 100%, and 80% in the i-SBRT group and 100%, 100%, and 67% in the h-SBRT group, respectively (p =.94). Only 2 patients (1 for each dose group) had a recurrence in the radiation therapy field, both after experiencing a distant relapse. No severe acute and late toxicities were observed in the i-SBRT group, whereas in the h-SBRT group, 2 patients experienced G2 acute and late thoracic pain and 1 patient experienced G2 acute and G3 chronic thoracic pain. In our experience, SBRT is a safe and effective option for selected patients with oligoprogressive PM. Use of intermediate total doses keeping the dose per fraction high seems to offer an excellent LC, avoiding the risk of severe toxicity.

Stereotactic prostate radiotherapy with or without androgen deprivation therapy, study protocol for a phase III, multi-institutional randomized-controlled trial.

Objective: The therapeutic landscape for localized prostate cancer (PC) is evolving. Stereotactic radiotherapy (SRT) has been reported to be at least not inferior to standard radiotherapy, but the effect of androgen deprivation therapy (ADT) in this setting is still unknown and its use is left to clinical judgment. There is therefore the need to clarify the role of ADT in association with SRT, which is the aim of the present study. Methods: We present a study protocol for a randomized, multi-institutional, Phase III clinical trial, designed to study SRT in unfavorable intermediate and a subclass of high-risk localized PC. Patients (pts) will be randomized 1:1 to SRT + ADT or SRT alone. SRT will consists in 36.25 Gy in 5 fractions, ADT will be a single administration of Triptorelin 22.5 mg concurrent to SRT. Primary end point will be biochemical disease-free survival. Secondary end points will be disease-free survival, freedom from local recurrence, freedom from regional recurrence, freedom from distant metastasis and overall survival (OS); quality of life QoL and patient reported outcomes will be an exploratory end point and will be scored with EPIC-26, EORTC PR 25, IPSS, IIEF questionnaires in SRT + ADT and SRT alone arms. Moreover, clinician reported acute and late toxicity, assessed with CTCAE v. 5.0 scales will be safety end points. Results: Sample size is estimated of 310 pts. For acute toxicity and quality of life results are awaited after 6 months since last patient in, whereas, for efficacy end points and late toxicity mature results will be available 3-5 years after last patient in. Conclusion: Evidence is insufficient to guide decision making concerning ADT administration in the new scenario of prostate ultra-hypofractionation. Hence, the need to investigate the ADT role in SRT specific setting. Advances in knowledge: The stereotactic prostate radiotherapy with or without ADT trial (SPA Trial) has been designed to establish a new standard of care for SRT in localized unfavorable intermediate and a subclass of localized high risk PC.