Testicular dose during prophylaxis of heterotopic ossification with radiation therapy

Aim: A single-institution, retrospective study was performed to investigate potential techniques to minimize radiation exposure to the testicles during heterotopic ossification (HO) prophylaxis. We report the impact of splitbeam technique (SBT) and different photon energies on the total dose of radiation received by the testicles during prophylaxis of HO. Materials and Methods: Between 2008 and 2010, we identified 64 patients with traumatic acetabular fractures who underwent surgery followed by radiation therapy (RT) without testicular shielding. Postoperative RT was delivered within 72 h in a single fraction of 700 cGy using 6-18 MV photons, without testicular shielding due to patient refusal. All patients underwent 3-D RT planning in which the testicles were contoured as a region of interest and dosevolume histograms (DVH) were generated. Additional treatment planning trials were created for each patient by utilizing a SBT medially and by using different photon energies (6, 10 and 18 MV) to study the effects of these maneuvers on the delivered dose to the testicles. Results: In reviewing the DVH, it was noted that the mean dose delivered to the testicles was 10 cGy (range=3-40). The maximum dose was 31 cGy (range=7-430). When SBT was utilized, a significant reduction in the mean (44%) and maximum (47%) doses delivered to the testicles was noted. Further reductions in the mean (26%) and maximum (14%) doses were achieved by using higher-energy (10-18 MV) beams. The radiation doses to the testicles from the CT simulation and the two portal images were estimated to be 4 and 1.5 cGy, respectively. Conclusion: Low-dose prophylactic RT to prevent HO around the hip causes a low, but likely biologically meaningful, radiation dose to be delivered to the testicles. This dose could be further reduced by using a medial SBT and photon energies above 6 MV. Testicular shielding should be offered to all male patients receiving such RT. In addition, all patients should be informed about the consequences of testicular radiation as part of their informed consent.