Abstract: To evaluate the difference in testicular dose between dual-arc conventional VMAT (dac-VMAT) and split-arc partial-field VMAT (sapf-VMAT) in postoperative radiotherapy for penile cancer, so as to provide a reference for preserving testicular function in clinical plan, ten patients aged 33 to 56 years with penile squamous cell carcinoma (PSCC) with lymph node metastasis were treated with the uRT-TPOIS plan system of United Imaging, and the range of jaw locking and arc of testicular avoidance were discussed. A paired t-test was employed and the dosimetry parameters of the plan target volume (PTV) and the radiation dose of organs at risk (OAR) were compared. All plans are normalized to a prescribed dose of 50.4 Gy covering 95% of the volume of PTV. The statistical results of machine unit (MU) in the dac-VMAT were 706.85±107.97, which were lower than those of 874.70±106.08 in the sapf-VMAT. The treatment time (T, s) of the dac-VMAT and sapf-VMAT was 174.44±13.61 and 183.89±14.33 respectively and the V1, V2, V3 of testes in the sapf-VMAT were 49.77±14.52, 5.42±5.60 and 0.40±0.69 respectively, all of which are significantly lower than 97.97±3.17, 83.15±19.14 and 7.35±4.81 in dac-VMAT; the P values were all less than 0.001. There were no significant differences in other outcomes. For patients of postoperative radiotherapy for penile cancer, compared with dac-VMAT, the testicular dose can be significantly reduced by sapf-VMAT, and the dose received is lower than the dose threshold that causes functional impairment. This suggests that patients can preserve fertility without the need for gonadal occlusion or pre-radiation sperm banking.

Key words: linear accelerators, penile cancer, testicular dose, jaw lock