S2911
RTT- RTT operational practice and workflow innovations
ESTRO 2026
optimization approach. Each fraction was also replanned using the conventional reference plan cost function-based method. Dosimetric comparisons were performed in Monaco (constrained mode), and planning time was recorded for each fraction.The structured approach consisted of two Stage 1 fluence optimizations to adjust constraints based on daily anatomy, followed by a Stage 2 dosimetric optimization. Results:
For the 50 analyzed fractions, organ-at-risk (OAR) sparing was comparable between the reference plan cost function and the step-by-step approach, with differences of ±2% in volume indices and ±1 Gy in dose metrics—favoring either method depending on the case. These variations were negligible across full treatment courses.In contrast, target volume coverage consistently favored the step-by-step method: 41 fractions showed superior coverage, 8 were equivalent (within 1% difference), and only 1 favored the reference plan cost function. The average gain in V100% for the planning target volume (PTV) was 7.73±7.36%.Planning time averaged 8±5 minutes for prostate SBRT fractions and 15±10 minutes for other sites. This included verification of layers and electron density mapping, plan optimization, acquisition of the Comprehensive Motion Management (CMM) template, cine sequence launch, and multidisciplinary review involving the radiation therapist, medical physicist, and radiation oncologist. This represents an increase of approximately 2 minutes compared to the reference plan cost function approach. Conclusion: Target coverage (V100%) was significantly improved using the structured step-by-step approach (ANOVA p = 0.003). Organ-level post-hoc contrasts demonstrated
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