CHHiPvsPROFIT for Localized Prostate Cancer:A Retrospective Dosimetric Comparison of Organs at Risk.
PO-1202
Abstract
CHHiPvsPROFIT for Localized Prostate Cancer:A Retrospective Dosimetric Comparison of Organs at Risk.
Authors: RAMIA|, Paul(1)*[pr04@aub.edu.lb];Mkanna|, Abbas(1);Shahine|, Bilal(1);Makke|, Zeinab(2);Hilal|, Lara(1);Geara|, Fady(1);Adel|, Mohammed(1);Olleik|, Farah(1);Youssef|, Bassem(1);
(1)American University of Beirut, Radiation Oncology, Beirut, Lebanon;(2)Lebanese University, Physics, Beirut, Lebanon;
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Purpose or Objective
Moderate hypofractionation for localized prostate cancer has become a standard of care in many radiotherapy centers worldwide. Several fractionation and planning protocols exist, with CHHiP and PROFIT (60 Gy in 20 fractions) being two of the most commonly used. We retrospectively compared the doses received by organs at risk using these 2 protocols.
Material and Methods
We retrospectively reviewed the charts of 15 randomly selected de-identified patients treated with intensity modulated radiation therapy (IMRT) for prostate cancer in a single tertiary care center. Each of these patients had a planning CT simulation with full bladder and empty rectum. For each patient, we generated 2 sets of contours for target volumes and organs at risk in accordance with both CHHiP and PROFIT protocols. The CHHiP protocol requires the contouring of 3 different target volumes planned to different doses utilizing simultaneous integrated boost technique, whereas the PROFIT protocol requires only a single target volume.Using Panther software (Prowess Inc, Concorde, CA) version 5.10. IMRT plans were generated (total 30 plans), using the respective planning targets and normal tissue constraints. Dependent t-tests were used to evaluate average mean dose as well as V60, V50 and V40 of the rectum, bladder and penile bulb.
Results
Patients had a mean age of 72.6, average PSA of 11.9, and mostly a Gleason score 7. Average mean dose,and V40 of the bladder and rectum were not significantly different between the two protocols. However, both bladder and rectum V60 and V50 were significantly lower in CHiPP as compared to PROFIT. The dose to the penile bulb was also significantly higher in terms of mean dose, V50 and V40 in the PROFIT arm. (Table 1)
Conclusion
In this retrospective dosimetric study comparing doses to organs at risk using CHHiP and PROFIT protocols, we observed statistically significant higher V60 and V50 to the bladder and rectum when using the PROFIT protocol. For the penile bulb,V40, V50 and mean dose were also significantly higher using PROFIT protocol. While contouring and planning using CHHiP protocol are usually more demanding, our results show that doing so, decreases the radiation dose to the organs at risk, specifically the penile bulb, and potentially minimizes the risk of impotence. These results need to be validated in a larger cohort of prospectively treated patients.