Influence of intrinsic radiosensitivity on the survival of breast cancer patients.

Purpose : The association between enhanced intrinsic radiosensitivity, measured by the level of chromosome damage induced in either the G 2 or G 0 phases of the cell cycle, and the risk of breast cancer has been well demonstrated. Although not originally designed for this purpose, early studies are now sufficiently mature (median follow-up 4.2 years) to enable an assessment of the impact of radiosensitivity on patient outcome. Materials and methods : Breast cancer patients assessed in previous studies of G 2 and G 0 lymphocyte chromosomal radiosensitivity between 1993 and 1997 were identified. Tumour characteristics, recurrence and survival data were obtained from clinical records and outcomes were compared between those identified as having normal and elevated radiosensitivity in the two assays. Results : There was a significant association between G 0 sensitivity and tumour grade ( p =0.03), but otherwise there were no associations in these series between radiosensitivity in the two assays and tumour characteristics. Overall survival in this cohort of patients was high (94% at 5 years) and there was no association between the G 2 or G 0 assay results and outcome as measured by cancer-specific survival or local recurrence. Conclusions : Radiosensitivity, as measured by these two assays, was not a strong prognostic factor following standard radiotherapy treatment. However, the statistical power of the present study was limited and modest prognostic utility could not be discounted. Further studies designed specially to investigate outcome are needed, possibly in association with trials of altered radiotherapy fractionation. [ABSTRACT FROM AUTHOR]