To evaluate prostate volume change during daily-adaptive prostate SBRT on 1.5T MR-linac and to correlate it with treatment toxicity.
a series of patients affected by low-to-intermediate risk prostate cancer was treated by 5-fraction SBRT within a prospective study (Prot. n° 23748). Total dose was 35 Gy and 36.25 Gy delivered every day or on alternate days. Treatment toxicity was recorded with the following patient reported outcomes (PROMs): IPSS, ICIQ-SF, and EPIC-26.
254 patients were included in the analysis. Baseline median CTV volume was 55 cc (range 15.3-163.3). Mean prostate volume were 58.9 cc, and 62.7 cc at first and last fraction respectively (mean volume increase 6.4%; p=<0.0001). We observed prostate swelling (mean 15.4% increase) in 50% of cases, stable volume (≤5% volume change) in 39% of patients, and prostate shrinkage in 11% of cases (mean 12.2% reduction). Baseline CTV >55 cc showed a trend towards higher CTV shrinkage (-10.5% versus -14.5%; p=0.052). We found no correlation between CTV change and PROMs. Prostate swelling was generally compensated by the planned PTV expansion, even though the mean setup volume dropped from 47.4 cc to 38.9 cc at last fraction, with few cases not covered by initial setup margins.
the present study reported a significant prostate volume change during prostate SBRT on 1.5T MR-linac. We observed both prostate swelling in half of cases and few cases of prostate shrinkage. No correlations were found with PROMs in this population treatment with daily-adaptive strategy.
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2023 Dec 04 [Epub ahead of print]
Luca Nicosia, Paolo Ravelli, Michele Rigo, Niccolò Giaj-Levra, Rosario Mazzola, Edoardo Pastorello, Francesco Ricchetti, Andrea Gaetano Allegra, Ruggero Ruggieri, Filippo Alongi
Advanced Radiation Oncology Department, IRCCS Sacro Cuore Don Calabria Hospital, Cancer Care Center. Electronic address: ., Advanced Radiation Oncology Department, IRCCS Sacro Cuore Don Calabria Hospital, Cancer Care Center., Advanced Radiation Oncology Department, IRCCS Sacro Cuore Don Calabria Hospital, Cancer Care Center; University of Brescia, Brescia, Italy.