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Abstract

The results of a retrospective study carried out at the University of California, Los Angeles, USA, and published in BMC Cancer, suggest that targeting stem cells with radiation could double the progression-free survival time in patients with glioblastoma. Cancer stem cells have been implicated in many cancer types. Frank Pajonk and his team hypothesized that, in addition to healthy stem cells, the neural stem cell niche may also harbor cancer stem cells and that eliminating or damaging these cells may delay the onset of cancer recurrence. Neural stem cells reside in the subventricular zone (SVZ). In order to analyze the impact of irradiating this region, Pajonk and his colleagues compared the outcomes of 55 patients with grade 3 or 4 glioblastoma, treated with radiation between 2003 and 2009. They found that patients who received greater than the median dose (43 Gy) to the bilateral SVZ had a significantly longer survival than those who received less than 43 Gy to the SVZ (progression-free survival: 15.0 vs 7.2 months; p = 0.028), and a mean dose of more than 43 Gy yielded a hazard ratio of 0.73 (p = 0.019). A similar ana lysis of total radiation dose failed to identify a significant impact on survival, suggesting that the improved survival was not due to increased overall dose. However, the authors cautioned that prospective studies are needed to confirm these results. “Our study found that if you irradiated a part of the brain that was not necessarily part of the tumor, the patients did better,” Pajonk commented. “We have been struggling for years to come up with new combinations of drugs and targeted therapies that would improve survival for patients with glioblastoma. It may be that by reshaping our radiation techniques we can extend survival for these patients.”