Recovery kinetics in mouse skin and CaNT tumours.
Recovery kinetics and recovery capacity were studied in a fast proliferating normal tissue, skin, and in an anaplastic mouse mammary carcinoma, CaNT. Three fractions per day of X-rays, repeated over 5 days, were given at varying interfraction intervals from 0 to 8 h. The rate of recovery in tumours (t1/2 = 0.31 +/- 0.15 h for local control) was significantly faster than in skin (t1/2 = 0.96 +/- 0.10 h). By contrast, the fractionation sensitivity of CaNT tumours was less than that of skin (alpha/beta = 43.3 +/- 8.5 Gy vs. alpha/beta = 7.9 +/- 0.2 Gy). Tissues with recovery half-times similar to or longer than that determined for skin would be at risk if interfraction intervals less than 6 h are used in regimes which involve the use of two or more fractions per day. This would be especially true for tissues that show a greater sensitivity to dose fractionation, and hence more sparing of radiation damage with hyperfractionation.
Rojas
A
A
CRC Gray Laboratory, Mount Vernon Hospital, Northwood, Middlesex, U.K.
Joiner
M C
MC
Johns
H
H
D000230:Adenocarcinoma / Q000532:radiotherapy*; D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006207:Half-Life; D007700:Kinetics; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000532:radiotherapy*; D051379:Mice; D008808:Mice, Inbred CBA; D012867:Skin / Q000503:physiopathology / Q000528:radiation effects*