Hypofractionation Results in Reduced Tumor Cell Kill Compared to Conventional Fractionation for Tumors With Regions of Hypoxia

Journal Article · Tue Mar 15 00:00:00 EDT 2011 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2010.10.007· OSTI ID:21491644

Keall, Paul J; Loo, Billy W ^[1]; Chen, Zhe J ^[2]; Brown, J Martin ^[1]

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1. Stanford University School of Medicine, Department of Radiation Oncology, Stanford, CA (United States)
2. Yale University School of Medicine, Department of Therapeutic Radiology, New Haven, CT (United States)

Purpose: Tumor hypoxia has been observed in many human cancers and is associated with treatment failure in radiation therapy. The purpose of this study is to quantify the effect of different radiation fractionation schemes on tumor cell killing, assuming a realistic distribution of tumor oxygenation. Methods and Materials: A probability density function for the partial pressure of oxygen in a tumor cell population is quantified as a function of radial distance from the capillary wall. Corresponding hypoxia reduction factors for cell killing are determined. The surviving fraction of a tumor consisting of maximally resistant cells, cells at intermediate levels of hypoxia, and normoxic cells is calculated as a function of dose per fraction for an equivalent tumor biological effective dose under normoxic conditions. Results: Increasing hypoxia as a function of distance from blood vessels results in a decrease in tumor cell killing for a typical radiotherapy fractionation scheme by a factor of 10{sup 5} over a distance of 130 {mu}m. For head-and-neck cancer and prostate cancer, the fraction of tumor clonogens killed over a full treatment course decreases by up to a factor of {approx}10{sup 3} as the dose per fraction is increased from 2 to 24 Gy and from 2 to 18 Gy, respectively. Conclusions: Hypofractionation of a radiotherapy regimen can result in a significant decrease in tumor cell killing compared to standard fractionation as a result of tumor hypoxia. There is a potential for large errors when calculating alternate fractionations using formalisms that do not account for tumor hypoxia.

• OSTI ID: 21491644
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Vol. 79, Issue 4; Other Information: DOI: 10.1016/j.ijrobp.2010.10.007; PII: S0360-3016(10)03424-3; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ANOXIA
CELL KILLING
FRACTIONATED IRRADIATION
HEAD
NECK
NEOPLASMS
OXYGEN
PARTIAL PRESSURE
PROBABILITY DENSITY FUNCTIONS
PROSTATE
RADIOTHERAPY
SURVIVAL CURVES
TUMOR CELLS
ANIMAL CELLS
BODY
DISEASES
ELEMENTS
FUNCTIONS
GLANDS
IRRADIATION
MALE GENITALS
MEDICINE
NONMETALS
NUCLEAR MEDICINE
ORGANS
PHYSICAL PROPERTIES
RADIOLOGY
THERAPY
THERMODYNAMIC PROPERTIES