Patterns of radiation treatment planning for localized prostate cancer in Japan: 2003-05 patterns of care study report.

OBJECTIVE: The purpose of this study is to identify the treatment planning process for Japanese patients with localized prostate cancer. METHODS: The Patterns of Care Study conducted a random survey of 61 institutions nationwide. Detailed information was collected on prostate cancer patients without distant metastases who were irradiated during the periods 2003-05. Radiation treatment planning and delivery were evaluated in 397 patients who were treated radically with external photon beam radiotherapy. RESULTS: Computed tomography data were used for planning in approximately 90% of the patients. Contrast was rarely used for treatment planning. Simulations and treatments were performed in the supine position in almost all patients. Immobilization devices were used in only 15% of the patients. Verification of the treatment fields using portal films or electric portal imaging devices was performed in most of the patients. However, regular or multiple verifications in addition to initial treatment and/or portal volume changes were performed in only 30% of the patients. Typical beam arrangements for treatment of the prostate consisted of a four-field box. Three-dimensional conformal techniques were applied less frequently in non-academic hospitals than in academic ones. Modernized multileaf collimators with leaf widths < or =10 mm were used in about two-thirds of the patients. Although the total doses given to the prostate were affected by the leaf widths, there were no significant differences between leaf widths of 5 and 10 mm. CONCLUSIONS: The results of the survey identified certain patterns in the current treatment planning and delivery processes for localized prostate cancer in Japan.