The combination of radiotherapy and granulocyte-macrophage colony-stimulating factor (GCSF) generated objective abscopal responses in some patients with metastatic solid tumors, a new study published online ahead of print in the journal The Lancet Oncology has shown.
The abscopal effect is a phenomenon by which localized treatment of a tumor causes shrinking of both the treated tumor and tumors in other compartments.
For the study, researchers enrolled 41 patients with stable or progressing metastatic solid tumors who were receiving single-agent chemotherapy or hormonal therapy. Patients were eligible if they had at least three different measurable sites of disease.
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All patients were treated concurrent radiotherapy 10 times over 2 weeks to one metastatic site and GCSF for 2 weeks beginning in the second week of radiotherapy. Patients then received a second course of therapy at a second metastatic site.
Results showed that abscopal responses occurred in 26.8% (95% CI: 14.2, 42.9) of the 41 patients. Of those, four had non-small cell lung cancer, five had breast cancer, and two had thymic cancer.
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In regard to safety, the most common grade 3-4 adverse events included fatigue and hematological toxicity. One patient experienced a grade 4 pulmonary embolism.
“This finding represents a promising approach to establish an in-situ anti-tumor vaccine,” the authors conclude.
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