Predicting pubic arch interference in permanent prostate brachytherapy based on the specific parameters derived from nuclear magnetic resonance imaging

Purpose
The aim of this study was to establish a more reliable method to predict pubic arch interference (PAI) before permanent prostate brachytherapy.

Material and methods
We retrospectively analyzed the nuclear magnetic resonance imaging (MRI) results of forty patients with prostate cancer, who were treated with permanent implantation of 125I seeds (permanent brachytherapy). We measured and calculated six parameters based on the MRI results: 1. The prostate volume (PV); 2. The angle of the pubic arch (AoPA); 3. The angle of PAI (AoPAI, pubic symphysis level); 4. The height of PAI (hPAI, pubic symphysis level); 5. The maximum angle of PAI (AoPAIMax); 6. The maximum height of PAI (hPAIMax). We then tested which parameters could accurately predict PAI through receiver operating characteristic (ROC) curve analysis.

Results
The results of this study demonstrated that AoPAI, hPAI, hPAIMax, and AoPAIMax could predict PAI. Out of forty cases in our research, 10 cases were with PAI and 30 cases without PAI during the operation. The areas under the ROC curve for PV, AoPA, AoPAI (pubic symphysis level), hPAI (pubic symphysis level), AoPAIMax, and hPAIMax were 0.592, 0.567, 0.957, 0.940, 0.927, and 0.877, respectively. The AoPAI (pubic symphysis level), hPAI (pubic symphysis level), AoPAIMax, and hPAIMax were statistically correlated with PAI. The boundary values were 26.32°, 1.13 cm, 28.37°, and 1.51 cm, respectively.

Conclusions
This new method derived from MRI has predictive value, as AoPAI, hPAI, hPAIMax, and AoPAIMax could predict PAI. Taking other factors into consideration, we suggest the use of AoPAI as a novel and very reliable predictor of PAI.