Pulsed reduced dose-rate radiotherapy: a novel locoregional retreatment strategy for breast cancer recurrence in the previously irradiated chest wall, axilla, or supraclavicular region

Abstract

With a median follow-up of 18 months, PRDR appears to be an effective method to reirradiate large volumes of previously irradiated tissue in selected patients with locoregional chest wall, axilla, and supraclavicular recurrences.

Tissue TGF-β expression following conventional radiotherapy and pulsed low-dose-rate radiation

“…[1][2][3][4] This involves spreading out a conventional radiation therapy dose into short pulses of dose with breaks in between. By example, a PLDR regimen may involve delivering a dose of 2 Gy as 10 pulses of 0.2 Gy, each 3 minutes apart.…”

Pulsed reduced dose rate radiation therapy is likely to become the treatment modality of choice for recurrent cancers

“…2 For PRDR re-treatment of locally recurrent breast cancer described in his third reference, 3 a trend toward higher local control was indeed found compared to re-treatment with electron beams in a 1978 study with a similar follow-up period, 92% versus 69%. The 17 patients of the study, however, was a number too small for meaningful statistical significance, and, furthermore, the acute toxicity rate was 23%, which is higher than the 8% reported for the electron-beam re-treatments.…”

“…The improvement in radiobiological understanding has for a long time lagged behind this technological development, but it is expected to play a more significant role in the further advancement of radiotherapy for both curative and palliative care. The favorable outcomes of some pilot studies on radioresistant malignant tumors (8 patients), recurrent breast carcinoma (17 patients), and glioblastoma multiforme (103 patients) 2,3,14 not only demonstrated the clinical effectiveness of the PRDR technique for these body sites but also provided convincing evidence to support future large scale and=or randomized clinical trials to determine the efficacy of the PRDR technique for other recurrent and potentially radioresistant cancers.…”

“…Limited clinical outcome data suggest that the PRDR treatment is well tolerated with minimal acute and late toxicities with accumulative doses up to 236 Gy, and with local control comparable to other irradiation techniques. 3 AGAINST THE PROPOSITION: Gary Luxton, Ph.D.…”

“…The rich in-vitro and in-vivo experimental results have laid a strong radiobiological foundation for the PRDR technique and these have been used to guide pilot studies to find optimal doses, dose rates, and fractionation schemes for particular body sites. 2,3,8,14,15 A clear advantage of the PRDR technique over conventional radiotherapy is the reduced normal tissue damage at lower dose rates, which has offered hope for some recurrent patients with severe and=or life threatening symptoms, who have been otherwise considered unsuitable for re-irradiation with conventional radiotherapy. The fact that many radioresistant tumor cells exhibit higher RHS=IRR ratios at lower doses and dose rates 6 also suggests that the PRDR technique may be a better choice than conventional radiotherapy for some recurrent cancers because of the possible existence of such radioresistant tumor cells.…”