title: Radiation carcinogenesis: time-dose relationships.
abstract: The present studies were undertaken to examine the time-dose relationships for the induction of lung adenocarcinomas and mammary adenocarcinomas in female BALB/c mice following gamma irradiation. Twelve-week-old female BALB/c/An NBd mice were irradiated with 137Cs gamma rays, and lifetime tumor incidences following high-dose-rate, low-dose-rate, or fractionated exposure regimens were compared. Analysis of the results indicated that the data could be fitted by linear-quadratic dose-response models for the induction of both tumors following acute doses and a linear model with a slope similar to that for the linear portion of the linear quadratic following low-dose-rate exposure regimens. When doses were fractionated the response was dependent upon the dose per fraction. If the dose per fraction was a dose which was predominantly on the linear portion of the acute dose response curve, then the response was linear and similar to that after low-dose-rate exposures. If the dose per fraction was in a region where the quadratic portion of the acute dose-response was significant, then the tumor incidence was higher than that following low-dose-rate exposures.
mesh_terms: D000230:Adenocarcinoma / Q000209:etiology*; D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D008175:Lung Neoplasms / Q000209:etiology*; D008325:Mammary Neoplasms, Experimental / Q000209:etiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009381:Neoplasms, Radiation-Induced / Q000209:etiology*; D011829:Radiation Dosage