Switching the immunotherapy?
Some U.S. oncologists have been telling patients with mTNBC that the atezolizumab withdrawal is “not an issue” because the new full approval of pembrolizumab in this setting will allow prescriptions to be switched, said patient advocate Ms. Cowden.
However, experts have said that no patient who is responding to or whose condition is stable with atezolizumab should switch immunotherapies. “This is a very aggressive disease,” reminded Dr. Lustberg.
Switching the immunotherapies is complicated by the difference in the respective drugs’ companion biomarker assays used to establish the presence of PD-L1.
Dr. Lustberg explained that patients who are not responding to atezolizumab and who now want to try pembrolizumab will have to be assessed with the CTS assay.
“About 22% of the patients who are positive for the atezolizumab biomarker assay SP-142 are not going to be positive for the CTS,” she said.
In other words, about one in four patients with mTNBC who are taking atezolizumab will not qualify for treatment with pembrolizumab.
Rebecca Shatsky, MD, of the University of California, San Diego, echoed those comments in an email to this news organization – and emphatically discouraged switching off atezolizumab (and going on pembrolizumab) if a patient is having success (i.e., stable disease or positive response).
“The two groups don’t always overlap, so it isn’t an easy switch. That’s why if they are already responding, I would NOT have them stop the drug,” she said.
Not every mTNBC patient receiving – and responding to – atezolizumab has had the unfortunate experience of having their prescription canceled.
Johanna Rauhala, of San Francisco, who is a former middle-school teacher and who writes the blog Pink Stinks, has been taking atezolizumab for 2 years. She has had a partial response and now, after taking the immunotherapy in combination with chemotherapy (gemcitabine and carboplatin), has stable disease. Currently, she is taking single-agent atezolizumab..
Ms. Rauhala has been living with mTNBC for 5 years. She said in an interview that she was “very surprised and concerned” to learn about Genentech’s withdrawal of its accelerated approval. She said that at her next treatment appointment, she was “probably going to ask the oncology nurse first [about the atezolizumab withdrawal] – because they are the front line, and I will then follow-up with my doctor. But I can’t imagine that they will take away something that is working.”
Dr. Shatsky, Dr. Horton, and Dr. Lunsberg report no relevant financial disclosures.
A version of this article first appeared on Medscape.com.