COVID-19 vaccines that employ new messenger RNA (mRNA) technology may require further testing before it becomes clear they are safe for cancer patients with solid tumors, cancer treatment experts say. The vaccines — including those from Pfizer Inc with partner BioNTech SE and from Moderna Inc. — work by carrying genetic instructions for making a protein from the virus that the immune system learns to recognize and defend against. The mRNA is encased in lipid nanoparticles that protect and deliver the fragile molecule into cells. While this technique is new for vaccines, it has long been used to carry cancer drugs into tumors, because tumors easily take up liposomes. This raises the possibility that tumor tissues would capture some of the liposomes carrying the vaccine's mRNA, said Gerard Milano of Nice University in France. The potential for part of the vaccine dose to become sequestered in tumors and the resulting effect on cancer patients "is an open question to which there is currently no answer," Milano said. In a paper in the British Journal of Cancer, his team calls for "a careful evaluation of the efficacy of these promising mRNA COVID-19 vaccines administered as lipid carriers for patients with solid tumors, including a possible re-appraisal of the dosing for optimal protection of this specific and frail population." —Reuters Staff Source
