Prospective multi‐institutional study of library‐based adaptive radiotherapy for cervical cancer: Evaluation of plan‐of‐the‐day selection and population analysis
Abstract
Purpose
Plan‐of‐the‐day (PoD) adaptive radiation therapy (ART) is based on a library of treatment plans, with 3D daily imaging guiding the plan selection. In a phase II multi‐institutional trial of cone‐beam CT (CBCT)‐guided PoD‐ART for locally advanced cervical carcinoma (LACC), this study aimed at evaluating the PoD selection, its geometric and dosimetric impact and characterizing a sub‐population of patients associated with dosimetric improvement from ART.
Material and methods
For 49 cervical cancer patients, three planning CT scans [empty bladder (EB), intermediate bladder (IB) and full bladder (FB)] were acquired to generate a treatment plan library. A dose of 45 Gy was prescribed to the planning target volume in 25 fractions. Daily CBCT were acquired to visually select the best plan in the library (Manual‐ART strategy). A deep learning model was used to segment daily clinical target volume (CTVt) and organs‐at‐risk (OAR). Manual‐ART was compared to two strategies: (i) “Non‐ART” strategy (IB‐CT treatment plan only); (ii) PoD‐ART strategy selecting the PoD maximizing CTVt coverage (“Cov‐ART”). Geometrical and dosimetric coverages of daily CTVt and OAR were assessed. Decision trees were developed to predict the subpopulation of patients associated with dosimetric benefit from PoD‐ART.
Results
The agreement in PoD selection between Manual‐ART and Cov‐ART was 63.5%. Compared to the Non‐ART strategy (D95%‐CTV: 43.6 ± 4.1 Gy), PoD‐ART significantly increased the dose to the target, with Manual‐ART achieving 44.0 ± 3.0 Gy and Cov‐ART with 44.1 ± 2.0 Gy. Decision trees using IB‐CT plan and first two treatment fractions correctly classified 85.4% and 93.8% of patients as benefiting or not from PoD‐ART.
Conclusions
In PoD‐ART for LACC, selected treatment plans by the radiation oncologist had 63.5% concordance with treatment plans maximizing target coverage. PoD‐ART increased dose to target, without compromising dose to OARs, with the largest benefit observed in a sub‐population identifiable after two treatment fractions.