Assessing the Viability of an Online Adaptive Method for Prostate Cancer

A study described the feasibility of the online adaptive radiotherapy (oART) method for prostate cancer. The results appeared in Practical Radiation Oncology.

Researchers analyzed the first 18 patients treated at the Hospital Quirónsalud Barcelona with the developed oART. They employed an ultra-hypofractionated radiotherapy (UHRT) scheme. The population of interest were treated on two conventional Varian C-arm linacs. Each patient was provided a reference plan based on a planning computed tomography (pCT) was generated using the Eclipse system. During each treatment session, the pCT scan was registered with the daily cone-beam computed tomography (CBCT) scan. Subsequently, the pCT-based target (prostate) and organs-at-risk (OAR) were mapped onto the CBCT images and manually adapted.

The reference plan was then copied to the CBCT scan and re-optimized for the current anatomy (adapted plan). For each treatment session, the unaltered reference plan recomputed on the daily CBCT scan by mimicking the soft-tissue alignment performed in our standard procedure (non-adapted plan). Over the 126 adapted sessions from the 18 patients, researchers performed a dosimetric comparison of adapted against non-adapted plans.

Following analysis, the researchers observed a significant difference in the target coverage between the adapted and non-adapted plans (97.1 vs. 90.4, P <0.001), in favor of adapting. According to the findings, without online adaptation, the optimal coverage of the prostate was not attained in 35% of fractions. Adapting allows improving the target coverage with compliance of all OAR dose constraints in all treatment fractions.

“The oART technique described in this study is technically feasible with a C-arm linac. To our knowledge, this is the first clinical experience with oART for prostate cancer including full re-planning and delivered with a C-arm linac without AI capability,” the researchers concluded.