LACK OF CORRELATION OF HUMAN FIBROBLAST RADIOSENSITIVITY IN-VITRO WITH EARLY SKIN REACTIONS IN PATIENTS UNDERGOING RADIOTHERAPY

Fibroblasts from breast cancer patients were obtained as outgrowths in vitro from punch biopsies and their radiosensitivity tested in early passages. Skin erythema reactions in the same patients were also measu red, as degree of redness using reflectance spectrophotometry. Measure ments were taken before and during a 4-week radiotherapy treatment wit h electrons to the thoracic wall. Of 59 biopsies studied, radiosensiti vity and erythema were concurrently studied in 32. In 24, evaluable da ta from both clinic and laboratory were obtained. A population growth assay in 96-well plates, using absorption of sulphur rhodamine B as th e stain for cell numbers, showed good agreement with the colony-format ion assay. Plating efficiencies and growth rates in the colony assay w ere higher using human serum in place of foetal calf serum. Cell survi val curves with human serum were mostly exponential with little should er. The parameters of survival at 2 Gy (SF2) and the dose required to give 10% survival (D10) were used in the correlations with clinical da ta; these were 0.25 +/- 0.09 and 3.03 +/- 0.50 Gy, respectively. There was a strong correlation between these two survival curve parameters (r = 0.98). Skin redness was found to linearly increase with time duri ng radiotherapy. The slope of the increase differed markedly from pati ent to patient, with a range of a factor approx. 10. No correlation wa s found between SF2 and erythema response in the 24 evaluable patients (r = 0.13, p > 0.5). A similar lack of correlation was found using D1 0 as the radiosensitivity parameter (r = 0.12, p > 0.5). These data in dicate that fibroblast radiosensitivity measured in vitro cannot be us ed to predict erythema reactions to radiotherapy in breast cancer pati ents.