Treatment Optimization in Linac-Based SBRT for Localized Prostate Cancer: A Single-Arc versus Dual-Arc Plan Comparison

Abstract

This study aimed to comprehensively present data on treatment optimization in linac-based SBRT for localized prostate cancer at a single institution. Moreover, the dosimetric quality and treatment efficiency of single-arc (SA) versus dual-arc (DA) VMAT planning and delivery approaches were compared. Re-optimization was performed on twenty low-to-intermediate-risk- (36.25 Gy in 5 fractions) and twenty high-risk (42.7 Gy in 7 fractions) prostate plans initially administered with the DA FFF-VMAT technique in 2021. An SA approach was adopted, incorporating new optimization parameters based on increased planning and clinical experience. Analysis included target coverage, organ-at-risk (OAR) sparing, treatment delivery time, and the pre-treatment verification’s gamma analysis-passing ratio. The SA optimization technique has consistently produced superior plans. Rectum and bladder mean doses were significantly reduced, and comparable target coverage and homogeneity were achieved in order to maintain a urethra protection strategy. The mean SA treatment delivery time was reduced by 22%; the mean monitor units increased due to higher plan complexity; and dose measurements demonstrated optimal agreement with calculations. The substantial reduction in treatment delivery time decreased the probability of prostate motion beyond the applied margins, suggesting potential decrease in treatment-related toxicity and improved target coverage in prostate SBRT. Further investigations are warranted to assess the long-term clinical outcomes.

Stereotactic body radiation therapy (SBRT) for prostate cancer: Improving treatment delivery efficiency and accuracy

“…In our work, despite a higher fraction dose (8 Gy), we achieved a lower mean BOT (1.3 min) using 10 MV FFF SA. Moreover, differently from [36] we obtained a larger reduction of delivery time (up to more than half) while maintaining the same plan quality and complexity. The reason of these discrepancies is probably related to the different degree of complexity in SA and DA plans between the two studies.…”

“…The same authors, in a very recent retrospective study [36] re-planned DA treatments with single partial arcs (300° length) achieving a mean delivery time of 1.5 min, delivering 7.25 and 6.1 Gy/fraction and using 10 MV FFF. With increased planning and clinical experience, Panizza et al [36] obtained higher quality SA plans increasing plan complexity while reducing the delivery time by 22 %.…”