Keywords: low dose-rate brachytherapy, inverse dose-rate effect, IDRE, potential therapeutic gain, normal tissue complications, hyper-radiosensitivity, radiation induced radioresistance, low radiation, cell killing, tumour control, prostate cancer, cervical cancer
The correlation of hypersensitivity for HRS/IRR and the 'inverse' dose-rate effect – its potential influence on LDR brachytherapy: a review
The 'Inverse' Dose-Rate Effect (IDRE) has been extensively studied (Leonard, 2000; 2007a; Leonard and Lucas, 2008a?b). We here consolidate these results. We have shown a correlation between Hyper-radiosensitivity and the Induced Radioresistance effect (HRS/IRR), and IDRE has the same threshold and transition behaviours. This supports a conclusion that IDRE is the dose-rate manifestation of HRS/IRR. We show that the low dose-rate hyper-radiosensitivity of IDRE can have a significant influence on cell killing in low dose-rate brachytherapy if the tumour tissues and/or the peripheral tissues and organs experience IDRE. We show that there can be a therapeutic gain in tumour control or there can be significant excess cell killing of the peripheral tissues increasing the normal tissue complication probability. We suggest and outline a coordinated dose and dose-rate cellular dose response programme of measurements on both carcinogenic and normal human tissues related to low dose-rate brachytherapy.