Abstract
Pulsed Reduced Dose Rate (PRDR) is an external beam re-irradiation technique that may be appropriate for recurrent tumors in patients who have previously undergone radiation treatment. PRDR is thought to effectively target dividing neoplastic cells that display Low-Dose Hyper-Radiosensitivity (LDHRS) while permitting sub-lethal damage repair in non-proliferating normal tissues. To date, only a few case reports and several retrospective studies have reported on efficacy after PRDR retreatment across several disease sites, including CNS, breast, and nasopharyngeal tumors. In this article, we review available publications of PRDR re-irradiation in patients. Taken together, this research demonstrates that PRDR offers a treatment option for large volume recurrent disease at previously irradiated sites. More research is needed to establish therapeutic benefit and late adverse effects for each disease site.
Highlights
Recurrent cancer after initial standard treatment is devastating for patients and physicians alike
Until survival for recurrent cancer improves substantially, we argue that any improvement in normal tissue tolerance that is achieved is not as significant a consideration when weighing the merits of Semi-Continuous LowDose-Rate teletherapy (SLDR) against Pulsed-Reduced Dose Rate (PRDR)
A valid criticism of PRDR as a re-irradiation technique is that current evidence comprises case reports and retrospective studies, often with limited patient numbers
Summary
Recurrent cancer after initial standard treatment is devastating for patients and physicians alike. Data about tumor control following re-irradiation is often lacking. Pulsed-Reduced Dose Rate (PRDR) is a re-irradiation technique that potentially overcomes volume and dose limitations in the setting of recurrent tumors. Tomé and Howard proposed a pulsed radiation strategy in glioma cell lines that exhibit Low-Dose HyperRadiosensitivity (LDHRS) [1]. In their analysis, models of glioma cell survival after low-dose, pulsed irradiation predicted greater tumor control than with standard dose-rates. Models of glioma cell survival after low-dose, pulsed irradiation predicted greater tumor control than with standard dose-rates
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