Chromosomal radiosensitivity and acute radiation side effects after radiotherapy in tumour patients--a follow-up study

Abstract

Background: Radiotherapists are highly interested in optimizing doses especially for patients who tend to suffer from side effects of radiotherapy (RT). It seems to be helpful to identify radiosensitive individuals before RT. Thus we examined aberrations in FISH painted chromosomes in in vitro irradiated blood samples of a group of patients suffering from breast cancer. In parallel, a follow-up of side effects in these patients was registered and compared to detected chromosome aberrations.

Methods: Blood samples (taken before radiotherapy) were irradiated in vitro with 3 Gy X-rays and analysed by FISH-painting to obtain aberration frequencies of first cycle metaphases for each patient. Aberration frequencies were analysed statistically to identify individuals with an elevated or reduced radiation response. Clinical data of patients have been recorded in parallel to gain knowledge on acute side effects of radiotherapy.

Results: Eight patients with a significantly elevated or reduced aberration yield were identified by use of a t-test criterion. A comparison with clinical side effects revealed that among patients with elevated aberration yields one exhibited a higher degree of acute toxicity and two patients a premature onset of skin reaction already after a cumulative dose of only 10 Gy. A significant relationship existed between translocations in vitro and the time dependent occurrence of side effects of the skin during the therapy period.

Conclusions: The results suggest that translocations can be used as a test to identify individuals with a potentially elevated radiosensitivity.

Figure 1

Distribution of aberrant cells and of colour junctions in in vitro irradiated lymphocytes of 47 patients. Symbols represent individual frequency of the respective cytogenetic endpoint. Filled symbols represent cases with significantly increased or decreased frequency. Exposure 3 Gy.

Figure 2

Distribution of translocation types t(Ba), t(Ab), and of dicentrics (dic) in in vitro irradiated lymphocytes of 47 patients. Symbols represent respective individual frequency of respective aberration type. Filled symbols represent cases with significantly increased or decreased frequency. Exposure 3 Gy.

Figure 3

Box plot analysis of t(Ba) frequencies in 4 patient groups ordered according to temporal occurence of any side effects of the skin during the period of radiation therapy. Box area, 50% of data [lines in box denote medians; bars include at most 1.5 of interquartile distance, difference between first and third quartiles of data; circles indicate values out of the 1.5-fold box area (outliers)]. A significant correlation between the frequencies of t(Ba) from lymphocytes irradiated in vitro (3 Gy) and the time-dependent occurence of side effects is demonstrated.