SU-E-J-97: Pretreatment Test and Post-Treatment Evaluation for Iso-NTCP Dose Guided Adapive Radiotherapy (DGART), Experience with Prostate Cancer Patients Treated with Rectal Balloons
- The University of Wisconsin-Madison, Madison, WI (United States)
- Thomas Jefferson UniversityHospital, Philadelphia, PA (United States)
Purpose: To explore the feasibility of pretreatment test for iso-NTCP DGART and to compare the pretreatment test results with post-treatment evaluations. Methods: NTCP here refers to late rectal wall toxicity only and is calculated with the ring rectal wall DVH. Simulation for one time iso- NTCP DGART starts after half of the total dose was done for 10 patients to investigate if TCP gains could be achieved. Six patients were treated using a 12-fraction 4.3Gy technique and four using 16-fraction 3.63Gy technique. For each of the 12-fraction cases a VMAT plan was generated in Pinnacle3™ using the daily CT obtained prior to the 6th fraction. A pretreatment simulation was performed using only the first 6 daily CTs. The idea is to add the 6 original plan delivered doses with 6 DGART plan delivered doses by deformable dose accumulation (DDA) on each of the first 6 CTs, resulting in 6 rectal wall doses (RWDs) and NTCPs. The 95% confidence interval (95%CI) for the 6 NTCPs were computed.The posttreatment evaluation was done by: a) copy the DGART plan to 6 CTs for fraction 7–12 and calculate the 6 actual DGART delivered fractional doses; b) sum the 6 actual DGART doses with the 6 original plan delivered doses by DDA on each of the 12 CTs resulting in 12 post-treatment RWDs and NTCPs; c) boxplot the 12 post-treatment NTCPs. Results: Target dose gain is 0.76–1.93 Gy. The 95%CI widths of the pretreatment tests NTCPs were 1.1–2.7%. For 5 patients, the planned NTCP fell within the 95%CI. For 4 patients, the planned NTCP was lower than the 95%CI lines. Post-treatment results show that for 7 patients, the upper quartile was within the 95%CI; for 2 patients, the upper quartile were higher than the 95%CI. Conclusion: The pretreatment test yields conservative prediction of the actual delivered NTCP.
- OSTI ID:
- 22325251
- Journal Information:
- Medical Physics, Vol. 41, Issue 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
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