VMAT technique enables concomitant radiotherapy of prostate cancer and pelvic bone metastases.

Background. Prostate cancer (PCa) patients with metastatic disease often suffer from skeletal pain and urinary retention impairing their quality of life. Prophylactic radiotherapy to bone metastases planned concomitantly with primary PCa radiotherapy could enable more precise control of combined dose in healthy tissues when compared to sequential palliative treatment. Materials and methods. Volumetric modulated arc therapy (VMAT) was planned for 14 PCa patients with primary bone metastases. The bone planning target volume (PTV_bone) was contoured together with the PTVs of prostate (pr), pelvic lymph nodes (ln) and seminal vesicles (sv). Another virtual plan was calculated excluding PTV_bone for dose volume histogram (DVH) comparison. DVHs were additionally compared to a set of actual VMAT treatment plans of a control cohort of 13 high risk PCa patients treated with PTV_pr, PTV_sv and PTV_ln. The prescribed doses varied between 42 and 76 Gy for PTV_bone. Results. Recommended healthy tissue tolerances (Quantec) were not exceeded except for one patient's rectum V_50Gy value. Rectum doses did not increase significantly due to the inclusion of PTV_bone. For bladder, there was a slight increase for V_65Gy and V_50Gy (2.7% and 7.4%). The DVHs of metastatic and non-metastatic patients were comparable. There were no differences in the PTV_pr DVH parameters, while mean PTV_ln dose increased by 3.7 Gy-4.4 Gy due to the increased treatment volume related to PTV_bone. All side effects were < grade 3 during the mean follow-up duration of 25 months. Conclusions. VMAT offers a good optimization tool for adding extra PTVs to the radiotherapy plan. Radiotherapy of bone metastases concomitantly with irradiation of the primary prostate tumor is a safe and well-tolerated approach and deserves to be studied in a randomized setting. [ABSTRACT FROM AUTHOR]