SSTR2 and neoplasm: To determine if the observed toxicity of high-affinity MSLN VHH CAR T cells was due to off-tumor targeting and excessive expansion of T cells, we employed PET/CT imaging using the SSTR2-specific tracer, 1,4,7-Triazaclononane-1,4,7-triacetic acid-octreotide (18F-NOTA-Octreotide), to detect CAR T cell biodistribution at a whole-body level on day 7 after treatment.