Close collaboration between treating clinicians and pathologists is required in order to understand the performance of each laboratory, and also so that we understand these results can actually help inform the choice of patients.— Michael Boyer, MD
According to Michael Boyer, MD, a medical oncologist at the Chris O’Brien Lifehouse in Sydney, Australia, the development of testing for programmed cell death ligand 1 (PD-L1) has been complex. Efforts at harmonization have been made, but most laboratories actually use a single immunohistochemistry platform, and even if the correct platform is available, kits that work with that platform are often not used.
“So what we have is the development of so-called laboratory-developed tests where the antibody is used without the kits and sometimes not on the correct immunohistochemistry platform,” Dr. Boyer said. “If we’re going to do this, it’s very important that these are validated.”
He pointed out the low concordance between some of the immunohistochemistry platforms and antibodies. “This is of great concern because it means that in an individual laboratory, with a particular combination of antibody and platform, the result you get will almost certainly not be the same as if a different laboratory performed that same test using some sort of reference standard.”
Dr. Boyer observed, “It’s interesting that one particular antibody (SP263) stands out, which is important because these tests are the basis on which we’ll be selecting patients for first-line treatment, at least for the moment.” He said it is also clear that laboratories must validate their own results, even when antibodies are used on the appropriate platforms.
“Close collaboration between treating clinicians and pathologists is required in order to understand the performance of each laboratory, and also so that we understand these results can actually help inform the choice of patients,” he added. ■
Disclosure: Dr. Boyer has received research support from Genentech/Roche, Pfizer, Eli Lilly, Merck Sharpe and Dohme, AstraZeneca, and Clovis.