Prostate alpha/beta Ratio & Transition to Hypofractionation, part 1/2
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Prostate α/β Ratio and Transition to Hypofractionation MN Lakshmanan
Transcript of Prostate alpha/beta Ratio & Transition to Hypofractionation, part 1/2
Prostate α/β Ratio and Transition to Hypofractionation
MN Lakshmanan
“It is rare that nature hands us a cancer situation where an improved treatment goes hand in hand with a shorter and more convenient one.”
J.F. Fowler. Development of radiobiology for oncology - a personal view. Physics in medicine and biology, 51(13):263, 2006.
1) Hypofractionation to improve therapeutic gain2) Calculation of α/β Ratio 3) Opposing Arguments4) Additional Considerations
1) Hypofractionation to improve therapeutic gain
J.F. Fowler. The radiobiology of prostate cancer including new aspects of fractionated radiotherapy. Acta Oncologica, 44(3):265-276, 2005.
J.F. Fowler. The radiobiology of prostate cancer including new aspects of fractionated radiotherapy. Acta Oncologica, 44(3):265-276, 2005.
Modeling Hypofractionation
J.F. Fowler. The radiobiology of prostate cancer including new aspects of fractionated radiotherapy. Acta Oncologica, 44(3):265-276, 2005.
2) Calculation of α/β Ratio
J. Fowler, R. Chappell, and M. Ritter. Is α/β for prostate tumors really low? International Journal of Radiation Oncology Biology Physics, 50(4):1021-1031, 2001.
J. Fowler, R. Chappell, and M. Ritter. Is α/β for prostate tumors really low? International Journal of Radiation Oncology Biology Physics, 50(4):1021-1031, 2001.
3) Opposing Arguments
• A) Repopulation times
• B) Tumor Heterogeneity
• C) Hypoxia
J.Z. Wang, M. Guerrero, and X.A. Li. How low is the α/β ratio for prostate cancer? International journal of radiation oncology, biology, physics, 55(1):194-203, 2003.
Assumed a fast repopulation time to get
α/β = 3 Gy
J.F. Fowler. The radiobiology of prostate cancer including new aspects of fractionated radiotherapy. Acta Oncologica, 44(3):265-276, 2005.
Tumor Heterogeneity
C.R. King and C.S. Mayo. Is the prostate α/βratio of 1.5 from Brenner & Hall a modeling artifact? International Journal of Radiation Oncology, Biology, Physics, 47(2):536-538, 2000.
Obtained α/β = 5 Gy.
A.E. Nahum, B. Movsas, E.M. Horwitz, C.C. Stobbe, and J.D. Chapman. Incorporating clinical measurements of hypoxia into tumor local control modeling of prostate cancer: implications for the α/β ratio. International journal of radiation oncology, biology, physics, 57(2):391-401, 2003.
4) Additional Considerations
-acute mucosal reaction of rectum
-d = 10 Gy has been used
-improvements in IMRT
Conclusions & Future Work
• Low- & Intermendiate-risk patients
• Hypoxia?
