Olga Sevriukova, Aista Plieskienė, Kamilė Guogytė, Rima Ladygienė, Julius Žiliukas, Vinsas Janušonis
Ionizing radiation is commonly used for cancer treatment. Human response to the same dose of ionizing radiation can vary among individuals, therefore individual radiosensitivity (IRS) was proposed to be an important factor for development of radiotherapy (RT) related side effects. Ionizing radiation especially at low doses can modify organism sensitivity causing its sensitization or adaptation to further exposure, thus IRS of cancer patient can change during RT and so effect the development of normal tissue toxicity as well. Therefore, objective of our study was to determine the correlation between IRS of prostate cancer patients during RT and outcome of treatment adverse reactions. This pilot study included six prostate cancer patients without previous exposure to ionizing radiation treated with salvage RT. IRS was assessed using G2 chromosomal radiosensitivity assay with G2-checkpoint abrogation by caffeine three times for each patient: prior RT, after first fraction, and after completing treatment and acute genitourinary (GU) and gastrointestinal (GI) toxicity were reported. It was found that three of selected patients experienced grade 1-2 RT acute GU/GI toxicity. According to IRS tests, before RT two patients were classified as normal, two – as radiosensitive, and two – as highly radiosensitive. After the first fraction there were three individuals classified as nor-mal, one patient remained radiosensitive and two others felt to the highly radiosensitive group. After completion of treatment, the distribution of IRS in selected patients recovered to that observed before the treatment. Despite that pattern of IRS changes during RT varied in every patient, the common tendencies and their correlation with the development of toxicity was observed. It was found that, IRS of patient experienced adverse reaction riced during RT, meanwhile in patients without side effects it decreased. So, it could be concluded that difference in radiation-induced IRS alteration tendency could be reflected in pattern of adverse reaction development. This phenomenon could be associated with attribute of preexposure to initiate individually either an adaptive response increasing resistance to further irradiation or sensitization. Therefore, further investigations of more RT patients employing G2 assay are foreseen to reveal the possible correlation between IRS and adverse clinical outcome of RT.
Keyword(s): individual radiosensitivity, G2 radiosensitivity assay, radiotherapy.