Rotational radiotherapy for prostate cancer in clinical practice

Background and purpose: Radiotherapy is the standard treatment in locally advanced prostate cancer. The latest technological improvement is modulated rotational radiotherapy, where one single rotation of the treatment machine is used to conform the dose delivery to the target and spare organs at risk, requiring less than 2 min of beam-on time per treatment fraction. Materials and methods: We report herein our experience from the first 46 patients treated for prostate cancer, clinical stage T1-3 with rotational therapy ('RapidArc (registered) ', Varian Medical systems) (RA). This patient group is compared to a group of 50 patients treated with a 5-field Intensity Modulated Radiation Therapy (IMRT) technique over the same period. The comparison parameters include target coverage, dose to OAR, treatment time and number of monitor units. Daily-IGRT using implanted gold markers is used before and after treatment to investigate intra-fractional prostate displacement. Results: RA results in improved sparing of the rectum and achieves desired dose distributions with fewer monitor units and a shorter treatment time (<1.5 min versus up to 8.9 min with IMRT). This shorter treatment time also translates in a decreased risk of patient motion during treatment: daily-IGRT demonstrates reduced prostate motion (<3 mm 3D vector) from 16.7% to 4.7% in RA patients. Only slight side-effects were seen in the two groups of patients. Conclusions: RA results in improved sparing of the rectum, however, at the expense of an increase in dose to the femoral heads in prostate patients. The treatment time is significantly reduced from 4.9 min on average with 5-field IMRT to 1.1 min with RA, which allows for a reduction of infractional prostate motion.