Solid tumour models for the assessment of different treatment modalities: IV. the combined effects of radiation and 5-fluorouracil.

Neither radiation alone (375 to 1500 rad) nor5-fluorouracil (FU) alone (50-250 mg/kg) is sufficient to prevent an increase in the volume of the solid tumour model hepatoma 3924A. However, as little as 750 rad with 100 mg/kg FU can reduce the tumour below the volume at the time of treatment for as long as 14 days. A series of combined FU and radiation doses given every 11 days should then result in successively smaller tumour volumes until the tumour is eradicated. Changes in tumour volume were analysed by two different methods: (1) tumours in each treatment mode were grouped together and the average response to treatment determined, and (2) tumour volume changes in individual tumours were analyzed utilizing the chi2 technique, which fits the logarithmic tumour volume change with time to polynomials. This two-directional method of analysis has the advantage of permitting both an overview of the main effects of treatment via the averages, and at the same time a detailed examination of the mechanism by which these effects occur through the analysis of individual response. The results suggest that, in addition to concentrating on the cellular response immediately after therapy, greater emphasis should be placed on the kinetic changes of the tumour 1-3 weeks after single or multiple modality therapy. These findings demonstrate how the sequencing of single and/or combined treatment modalities may be investigated in order to detemine how best to obtain maximum effects of treatment on different types of tumours following recovery of the host from the previous treatment series.