title: Fractionation sensitivity and immunological status in radiation treated murine sarcomas.
abstract: The fractionation sensitivity of a strongly immunogenic murine fibrosarcoma (FSa1) was tested in highly immunosuppressed (18 Gy whole body irradiation, 10 fractions, 4 days and bone marrow salvage) and control mice (C3Hf/Sed). Radiation was delivered to extremity-transplanted tumors after reaching a volume of 250 mm3. Two, 4 and 10 fractions were used, delivering the radiation treatments to uniformly hypoxic tumors (by extremity clamping). Doses needed to attain a 10 day tumor-growth delay (TGD) over the volume range 250 mm3 to 1000 mm3, and doses necessary to reach a tumor-control probability of 50% (TCD50), were calculated for the three fractionation schedules. Immunosuppression influenced the TCD50 values profoundly: 56.2, 71.5, and 101.4 Gy in control mice versus 76.6, 104.2, and 141.1 Gy in immunosuppressed mice for 2, 4, and 10 fractions, respectively. The alpha/beta ratios estimated by reciprocal-dose analysis using the TGD and TCD50 assays were not significantly different, nor were the alpha/beta ratios of tumors grown in immunosuppressed mice (TGD 5.7 Gy; TCD50 5.3 Gy) as compared with tumors in control recipients (TGD 3.5 Gy; TCD50 4.9 Gy). In addition, direct analysis was used with the fractionated TCD50 data from control and immunosuppressed animals to calculate a immunity-related-cell-kill factor. For 250 mm3 tumors a 1.29 [0.99 . . . 1.59, 95% confidence interval] log10-kill factor was obtained.
authors.affiliation: Department of Radiation Medicine, Massachusetts General Hospital, Boston.
authors.forename: R
authors.initials: R
authors.lastname: Miralbell
authors.forename: A
authors.initials: A
authors.lastname: Zietman
authors.forename: P
authors.initials: P
authors.lastname: Okunieff
authors.forename: H D
authors.initials: HD
authors.lastname: Thames
authors.forename: H D
authors.initials: HD
authors.lastname: Suit
mesh_terms: D000818:Animals; D005260:Female; D005354:Fibrosarcoma / Q000276:immunology / Q000532:radiotherapy*; D007165:Immunosuppression Therapy; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009368:Neoplasm Transplantation; D011879:Radiotherapy Dosage