Does Variation in the in Vitro Cellular Radiosensitivity Explain the Shallow Clinical Dose—control Curve for Malignant Melanoma?

Summary

In radiotherapy, clinical dose—control curves are generally more shallow than what should be expected from in vitro dose—survival curves for human cells of the same histology. One possible explanation is that a considerable inter-tumor heterogeneity in radiosensitivity flattens out the presumably steep individual dose—control curves. This paper compares dose—control curves for malignant melanomas derived from clinical data with curves derived from in vitro cell-survival experiments. Although inter-tumour variability in the in vitro dose and fractionation sensitivity may explain parts of the discrepancy between the steepness of clinical and in vitro dose—control curves, the present calculation indicates that a considerable additional variability, undetected by current in vitro assays, must be assumed to exist in order to resolve the discrepancy.