Volume and time factors in interstitial gamma-ray therapy.
The two suppositions which have dictated time-dose and volume relationships in interstitial gamma ray implantation have been examined in the light of recent publications. The first of these assumptions, that total dose reduction is required when the dose rate exceeds 6,000-7,000 rads in seven days, does not appear to be substantiated by clinical experiences. It appears that total dose is the critical treatment parameter and that dose rate may be increased by a factor of two or three without requiring alteration of the total dose. Although the second classical assumption, "volume increase requires dose decrease," has been shown throughout radiation therapy experience to be generally correct, it should not be applied rigidly to interstitial gamma-ray therapy. In fact, recent experiences seem to indicate that compensation with respect to volume is not an absolute necessity. Larger lesions require, if anything, higher doses than small ones. To obtain a high percentage of controlled, lesions there must be no dose reduction, regardless of increased volume treated.
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D006801:Humans; D066298:In Vitro Techniques; D009369:Neoplasms / Q000532:radiotherapy*; D011830:Radiation Effects; D011879:Radiotherapy Dosage / Q000592:standards*; D012878:Skin Neoplasms / Q000532:radiotherapy; D013997:Time Factors