MRI and PET to Assess Pembrolizumab Response

There is a growing body of evidence that demonstrates that tumor proliferation, measured classically by immunohistochemical evidence of increased Ki-67 expression, can be reliably determined in vivo using radiolabeled thymidine. The development of \[18F\]-fluorothymidine (FLT) PET has been reliably identified as a marker of cellular proliferation, and has been shown to identify changes in proliferation in successfully treated patients.