Preclinical data suggest that combining radiotherapy and immunotherapy will improve the abscopal effect.

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“Preliminary data are promising, but still inconclusive,” Dr Scorsetti told Cancer Therapy Advisor. To date, in-human studies testing the combination of radiotherapy and immunotherapy included small, retrospective, or single institution series, each of which yielded inconsistent results. Several studies reported abscopal responses in patients with melanoma who received radiotherapy or SRS after ipilimumab.8,9,10

Two small studies, 1 retrospective and the other a case series, demonstrated that patients with melanoma brain metastases treated with SRS and ipilimumab had prolonged overall survival, in contrast with those who did not receive ipilimumab.11,12 Two other small studies, however, found no difference in overall survival or local control among patients who received the combination of SRS and ipilimumab and those who received SRS alone.13,14

The timing of SRS and ipilimumab may be important. A small study found that treatment with SRS before or during ipilimumab therapy improved overall survival and regional recurrence, in contrast with SRS administered after ipilimumab.15

According to Dr Scorsetti, “the combination of CTLA-4 blockade or PD-1/PD-L1 blockade plus radiotherapy still needs prospective trials. There are a lot of ongoing trials that will hopefully answer our questions.”

In the studies to-date, the combination is well tolerated. There was, however, an increased risk of radiation necrosis in some studies. “According to the available data, I do not see any significant problems in terms of side effects or toxicity. There are some contradictory results about radiation necrosis in the brain, but it is also true that radionecrosis can be regarded as a marker of good response and better prognosis,” Dr Scorsetti said.

Disclosures: the author has no relevant relationships to report.


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