Look sharp for pseudoprogression
Pseudoprogression is a phenomenon whereby immunotherapy results in inflammatory changes bringing about a temporary increase in tumor size that precedes tumor shrinkage. It’s uncommon, occurring in 3 of 16 patients in the phase 1 study. The mechanism probably involves tumor infiltration by massive numbers of activated T cells. And there is evidence from other PD-1 inhibitor studies in advanced cancers that pseudoprogression may actually be a marker for increased likelihood of survival beyond 1 year.
“Pseudoprogression is important to recognize because the patients you treat with cemiplimab can get worse before they get better,” the dermatologist explained. “So you don’t want to prematurely discontinue treatment because you’re misclassifying it as tumor progression.”
The rationale for anti-PD-1 therapy in CSCC
Tumors that express PD-1 bind to PD–ligand 1 on T cells, switching off T-cell mediated tumor destruction and thereby allowing the malignancy to thrive.
“Simplified, the strategy here is to interfere with the interaction at the T-cell off switch, either with an antibody to PD–ligand 1, such as atezolizumab [Tecentriq], or an antibody to the PD-1 receptor, where cemiplimab works. By turning off the off switch, we get a T cell fully on and attacking the tumor cell,” Dr. Migden said.