Cell kinetics and repopulation parameters of irradiated xenograft tumours in SCID mice: comparison of two dose-fractionation regimens.
The extent and mechanism(s) of repopulation were assessed in SiHa (human cervical squamous cell carcinoma) xenografts in SCID mice for two fractionated irradiation regimens. Mice in one arm of the study received 50 Gy in 20 fractions over 23 days with a 14 day split between 10 fraction, 5 day courses. The other tumours were treated with 50 Gy in 20 fractions over 10 consecutive days. Cell kinetics and tumour regrowth parameters were monitored during and after treatment by measuring tumour volume and analysing cellular DNA content and proliferation parameters with flow cytometry. Repopulation occurred rapidly, beginning during irradiation and largely attributable to an increased growth fraction and decreased potential doubling time, apparently triggered by increased cell loss. Cell cycle time, in contrast, remained relatively constant throughout. Extrapolation of these results to humans suggests that treatment times should be minimised whenever possible, since regrowth rates exceeded those predicted from pretreatment Tpot measurements.
Sham
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British Columbia Cancer Agency, Department of Radiation Oncology, Vancouver, Canada.
Durand
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D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy*; D002455:Cell Division / Q000528:radiation effects; D005260:Female; D051379:Mice; D016513:Mice, SCID; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*