S Parsai¹*, J Alfonso² , J Donaghue³ , N Joshi⁴ , A Godley⁵ , C Shah⁶ , S Koyfman⁷ , J Caudell⁸ , C Fuller⁹ , H Enderling¹⁰ , J Scott¹¹ , (1) Cleveland Clinic, Cleveland, Ohio, (2) Helmholtz Centre for Infection Research, Braunschweig, --, (3) The Cleveland Clinic Foundation, Cleveland, OH, (4) Cleveland Clinic, Cleveland, Ohio, (5) The Cleveland Clinic, Cleveland, OH, (6) Cleveland Clinic, Cleveland, Ohio, (7) Cleveland Clinic, Cleveland, Ohio, (8) Moffitt Cancer Center, Tampa, FL, (9) MD Anderson Cancer Center, Houston, TX, (10) Moffitt Cancer Center, Tampa, FL, (11) ,Cleveland Heights, OH

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(Saturday, 4/7/2018)  

Room: Foyer

Purpose: We introduce a novel strategy of radiotherapy planning using canonical radiobiology principles, idealizing fractional doses and timing delivered to organs at risk (OAR) to decrease normal tissue complication probability (NTCP). This strategy is termed temporally feathered radiation therapy (TFRT). A dynamical model of normal tissue radiation response with respect to tissue recovery is used to compare TFRT and conventionally fractionated radiotherapy.

Methods: Dynamic NTCP modeling was performed to simulate the cumulative effects of normal tissue damage and recovery. Normal tissue damage was determined by the Linear-Quadratic (LQ) model. TFRT plans were generated by altering the fractional dose delivered to normal tissues. Each OAR receives a rotation of a higher than standard dose of radiation (DH) once weekly followed by lower than standard doses (DL) the remaining four fractions that week. We developed a term, “success potential�, to demonstrate reduction in NTCP with TFRT as compared to conventional RT under various recovery rates and standard daily fractional doses. Finally, we created patient-specific plans using TFRT through RayStation treatment planning system, creating in silico models of head and neck plans treated to 70 Gy in 35 fractions.

Results: TFRT is beneficial in reducing toxicity compared to conventional RT schemes. Delivering a combination of DH and DL to OARs allows increased sublethal damage recovery despite higher total radiation doses delivered to OARs. The magnitude of clinical benefit of TFRT plans is dependent on the standard dose delivered to OAR with conventional plans as well as the organ-specific recovery rate of radiation damage.

Conclusion: TFRT offers a novel technique for radiation planning optimization. Application of this technique to carefully selected cases can reduce normal tissue toxicity. With widening of the therapeutic ratio, isotoxic radiation therapy plans can be delivered in an effort to allow dose intensification to the target volume.

ePosters

• 134-38537-437584-134997-2024255341.pdf (S Parsai)

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