Absorbed dose calculations for 1 MeV, monodirectional photon beams targeted at an idealized neck cancer have been performed using the MCNP computer code. The dose-depth profiles for the individual beams were then used to calculate the cell-killing effects of representative treatment designs using the lethal and potentially lethal (LPL) radiobiological model. Our calculations, which are based on LPL parameter values for colon adenocarcinoma cells, suggest that increasing the time required to deliver each dose fraction from less than a minute up to 1 or 2 hours can decrease the overall cell-killing effects of some treatments by factors as high as 2 to 20. Moreover, dose protraction effects alter the iso-effect treatment dose by factors on the order of 5 to 10%. That is, a 75 Gy treatment produces about the same tumor control probability (TCP) as a 70 Gy treatment if the dose fractions are delivered in 1 to 2 hours instead of a few minutes. American Nuclear Society (ANS) Topical Meeting on Radiation Protection for our National Priorities, Medicine, the Environment, and the Legacy (RPS 2000), Spokane, WA, September 17-21, 2000
Revised: September 13, 2002 |
Published: January 12, 2001
Citation
Stewart R.D., and R.J. Traub. 2001.Temporal Optimization of Radiotherapy Treatment Fractions. In Proceedings of the Topical Meeting on Radiation Protection for our National Priorities: Medicine, the Environment, and the Legacy, Spokane, Washington, September 17-21, 2000., 372-378. La Grange Park, Illinois:American Nuclear Society.PNNL-SA-33246.