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Pencil Beam Scanning Proton Therapy Planning for Low-Risk Prostate Cancer Based On Proton Collaborative Group (PCG)-GU002-10 (NCT01230866) Protocol

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S Rana

B Arjomandy1 , H Gayar1 , B Tesfamicael1 , S Rana2*, (1) McLaren Cancer Institute, Flint, MI, (2) Miami Cancer Institute, Miami, FL


SU-I-GPD-T-160 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The purpose of this study is to investigate whether proton collaborative group (PCG)-GU002-10 (NCT01230866) protocol’s dosimetric criteria can be applied for low-risk prostate cancer treatment plans generated by pencil beam scanning (PBS) technique in Eclipse treatment planning system (TPS).

Methods: Computed tomography (CT) data set of ten low-risk prostate cancer cases previously treated with photons were included in this retrospective study. Clinical target volume (CTV) included prostate only, whereas planning target volume (PTV) was expanded from the CTV (margin:2 mm to the posterior and 3 mm elsewhere). Optimization target volume (OTV) was generated from the CTV (margin:2 mm to the posterior, 5 mm left and right, and 3 mm elsewhere). Scanning target volume (STV) was generated from the OTV (margin:7 mm). For each case, two PBS plans were generated using single field optimization (SFO) and multi-field optimization (MFO) techniques in Eclipse TPS (version 11) for prescription dose (PD) of 79.2 Gy(RBE). Each plan was generated using two parallel opposed lateral fields. Both sets of plans (SFO and MFO) were optimized using identical dose constraints with an objective of meeting the protocol criteria. Treatment plans were then normalized such that at least 95% of the OTV received the PD.

Results: All ten cases produced PTV D99.5%>75.24 Gy(RBE) (SFO:77.17±0.98 Gy(RBE);MFO:77.21±1.02 Gy(RBE)). The CTV D99% was 100.85±0.74% of PD in SFOIMPT plans and 100.81±0.70% of PD in MFO plans. For the rectum, V50 was less than <35% (SFO:10.11±6.12%; MFO: 10.30±6.20%) and V70 was less than 10% (SFO:3.82±2.76%; MFO: 3.83±2.64%). For the bladder, V80 was less than 8 cc (SFO:2.85±3.04 cc; MFO:2.75±2.94 cc). For the femoral heads, V45 was 0 in all ten cases.

Conclusion: It is feasible to apply dosimetric criteria of PCG-GU002-10 (NCT01230866) protocol for low-risk prostate cancer plans generated by PBS technique (SFO and MFO) in Eclipse TPS.

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