CAR T and secondary cancers

A recent perspective article by Nicole Verdun and Peter Marks in NEJM suggests that controlling insertional mutagenesis risk during CART T generation may help elucidate the risk of T cell lymphoma development in CAR T treated patients.

Genetic sequencing has shown detection of the CAR transgene in the malignant clone in some cases. Could this be due to the LV-mediated insertional mutagenesis or to the survival of CAR T expressing cells in conditions with elevated IL-7/IL-15 conditions? Should additional immunological markers be included to predict risk?