Better Efficacy of Synchrotron Spatially Microfractionated Radiation Therapy Than Uniform Radiation Therapy on Glioma

Synchrotron Microbeam Radiation Therapy as a New Approach for the Treatment of Radioresistant Melanoma: Potential Underlying Mechanisms

“…34 MRT significantly attenuated melanoma growth during the 20 days of follow-up, whereas BB irradiation did not manage to temporarily stop melanoma growth and progression. Our results are in line with studies previously published 17,35 showing that MRT had superior efficacy in slowing brain tumor growth in comparison to BB. As shown recently, a unidirectional microbeam irradiation (400 Gy and 17.4 Gy as peak and valley doses, respectively) induced better tumor control and survival than BB irradiation (17.9 Gy) in glioma-bearing rats.…”

“…However, more recent results show that the valley dose is most likely the deciding factor in regard to biological effects. 17,32 This view has been supported by other authors who demonstrated that (1) the valley dose of MRT is the most relevant parameter for acute toxicity 33 and (2) the integrated dose is not a useful indicator of the biological equivalence of MRT and BB. 34 MRT significantly attenuated melanoma growth during the 20 days of follow-up, whereas BB irradiation did not manage to temporarily stop melanoma growth and progression.…”

“…As shown recently, a unidirectional microbeam irradiation (400 Gy and 17.4 Gy as peak and valley doses, respectively) induced better tumor control and survival than BB irradiation (17.9 Gy) in glioma-bearing rats. 17 It was suggested that part of the better tumor control achieved by MRT could be attributed to the immediate cell death caused by the high dose delivered by the microbeams. 14,17 However, only one-quarter of the total targeted tissue was exposed to the high dose in microbeams, whereas three-quarters was exposed to the low valley dose.…”

“…17 It was suggested that part of the better tumor control achieved by MRT could be attributed to the immediate cell death caused by the high dose delivered by the microbeams. 14,17 However, only one-quarter of the total targeted tissue was exposed to the high dose in microbeams, whereas three-quarters was exposed to the low valley dose. Therefore, this discrete dose distribution achieved significant tumor growth delay while sparing the normal tissue.…”

“…8,9 The mechanisms and the chronology underlying the MRT-induced antitumor response are not well understood, but studies have reported preferential effects of MRT on immature over mature blood vessels, 10-12 a differential gene expression between MRT and uniform broad beam (BB) irradiation regarding cell death, [13][14][15] and effects on immune and inflammatory responses. [16][17][18] To gain a better understanding of the mechanisms involved in the efficiency of MRT, a melanoma model was selected. Malignant melanoma is among the most aggressive cancers, radioresistant and often producing metastases.…”