Materials/Methods:
667 cases treated with prostate IMPT using proton scanning beams between 2019 and 2024 at a single institution were reviewed retrospectively, with 303 patients meeting inclusion criteria. Patients with a history of hip arthroplasty or arthritis prior to IMPT were excluded. In each prostate IMPT course, 76 GyE were delivered to the target over 38 fractional days using two oblique lateral proton scanning beams, administered either from alternating ipsilateral sides or bilaterally. Because the transmission beams from the ipsilateral side irradiate each hip, the average dose delivered to each hip or femoral head ranged from 25 and 27 GyE per calculated dosimetry. Cone beam CT and surface mapping image-guidance were used during daily treatment to ensure precise dose delivery. Data collection included demographics, radiation dosimetry, and patient-reported outcomes using the Oxford Hip Score (OHS). Linear, logistic, and ordinal logistic regression models were employed to assess the association between femoral head radiation dose and hip pain severity. Secondary analysis was performed using a case-control format to further evaluate this relationship.
Results:
The mean follow-up period was 30.07 ± 14.96 months. The majority of patients (87.8%) reported satisfactory hip function, with only 4.6% experiencing moderate or severe hip pain. Linear regression demonstrated no significant relationship between radiation dose of femoral head and OHS scores (p=0.198). Similarly, multivariate logistic regression revealed no significant association with the presence of hip pain (p=0.541) and multivariate ordinal logistic regression showed no dose-response trend across OHS severity categories (p=0.331). Data formatted in a case-control manner yielded an odds ratio of 1.34 (95% CI: 0.84–2.12), indicating no significant association for hip pain in patients receiving above-median femoral head doses.
Conclusion:
Incidental femoral head radiation doses during prostate IMPT using two oblique lateral proton scanning beams, whether delivered from alternating ipsilateral sides or bilaterally, are not significantly associated with hip pain. These results support the safety of IMPT in prostate cancer management without contributing to short- or medium-term hip-related complications.
