Response of EMT-6 tumors to single fractions of x rays and cyclotron neutrons
Journal Article
·
· Radiat. Res.; (United States)
EMT-6 cells growing in vitro or as solid tumors were treated with single fractions of 250-kVp x rays or cyclotron neutrons (21.5-MeV d/sup +/ on Be). The neutron RBEs for cell survival in vitro are 1.5 to 1.6 in the exponential region, less than the RBEs of 1.8 to 2.5 for mitotic delay. The relatively greater delay produced by neutrons can influence cell progression and also response of survivors to subsequent doses of radiation in a manner different from that occurring after an x-ray dose isoeffective for cell killing. The in vivo endpoints of tumor response examined were clonogenic cell survival, local tumor control, and growth delay. RBEs for growth delay range from 2.3 to 2.4, but are not statistically significantly different from RBEs for cure or clonogenic cell survival. The large neutron RBE of 3.0 for clonogenic cell survival at intermediate as well as high doses is based on apparent tumor hypoxia caused by anesthesia. The low neutron RBE of 1.7 for local control is due to immunosuppression caused by leakage and scatter neutron radiation to the animal's body during localized treatment of the tumor; leakage and scatter whole-body photon exposure is neglibible. Low-dose whole-body neutron irradiation reduces the TD/sub 50/ in mice preimmunized with heavily irradiated tumor cells. This is consistent with the above explanation of the lowered RBE for local tumor control.
- Research Organization:
- Univ. of Washington, Seattle
- OSTI ID:
- 7291134
- Journal Information:
- Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 71:2; ISSN RAREA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
560121* -- Radiation Effects on Cells-- External Source-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACCELERATORS
ANIMAL CELLS
BARYONS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CYCLIC ACCELERATORS
CYCLOTRONS
DISEASES
DOSE-RESPONSE RELATIONSHIPS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
FERMIONS
FRACTIONATED IRRADIATION
HADRONS
IONIZING RADIATIONS
IRRADIATION
NEOPLASMS
NEUTRONS
NUCLEONS
RADIATION EFFECTS
RADIATIONS
RBE
SURVIVAL CURVES
TUMOR CELLS
X RADIATION
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACCELERATORS
ANIMAL CELLS
BARYONS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CYCLIC ACCELERATORS
CYCLOTRONS
DISEASES
DOSE-RESPONSE RELATIONSHIPS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
FERMIONS
FRACTIONATED IRRADIATION
HADRONS
IONIZING RADIATIONS
IRRADIATION
NEOPLASMS
NEUTRONS
NUCLEONS
RADIATION EFFECTS
RADIATIONS
RBE
SURVIVAL CURVES
TUMOR CELLS
X RADIATION