Survey data analysis of treatment planning methods in particle therapy facilities.

[PURPOSE] We conducted a survey on various parameters and methods of treatment planning for particle therapy.

[METHODS] A questionnaire was distributed among particle therapy facilities in Japan. The data collection period was from October 2024 to December 2024.

[RESULT] Responses were collected from 21 facilities. For prostate, the largest number of facilities used a posterior PTV margin of 5 mm. The majority of facilities used 3 mm, 5 mm and 5 mm PTV margins for the treatment of head and neck cancer, liver cancer, and lung cancer, respectively. The majority of facilities used 2-4 fields for each site. For robustness considerations, 48% of the facilities used robust optimization, with the largest number of 10 facilities using a range uncertainty of 3-4%. Set-up uncertainties of 3-5 mm were most frequently used for each site. Regarding optimization methods, single field uniform dose (SFUD) was most commonly used for the prostate, liver, and lung treatments, and intensity modulated particle therapy (IMPT) for the head and neck treatment. While the majority of facilities created treatment plans with the stopping power ratio (SPR) for intestinal gas as is, 28.6% of the facilities replaced it with a water SPR. The majority of facilities did not replace the lipiodol and metal marker SPRs with tissue SPRs and no replacement, respectively.

[CONCLUSION] The trend of setting parameters regarding particle therapy planning was identified. These data could contribute to the launch of new treatments and facilities. They could provide important data for assuring treatment quality in future clinical trials.