This transcript has been edited for clarity.
Hello. It’s Mark Kris, from Memorial Sloan Kettering. In my discussions with doctors around the world, I’ve come upon a huge amount of confusion and difference in what we call progression. Today I’d like to talk about what I’ll call the many faces of progression in systemic therapy.
The first thing to remember is that we don’t have a definition of progression for care. Many people turn to Response Evaluation Criteria in Solid Tumors (RECIST), but please remember that RECIST is something that talks about tumor measurements, part of clinical investigation, and drug development. It doesn’t apply to decision-making for the care of individual patients.Again, these standards have been set up for consistency and reproducibility, not to guide the doctor to make a decision about whether to continue with therapy or not.
First, a couple of thoughts as to what you need to consider when you’re making this decision about whether progression is happening and what to do.I think the single most important thing is to focus on symptoms. Does a growing lesion lead to a symptom? Does a growing lesion lead to a disruption of somebody’s lifestyle and their ability to live the kind of life they want?
A second very important thing is the availability of an alternative therapy.If there’s an alternative therapy available with a high likelihood of benefit and side effects that are either equal to or less than the treatment that people are on, then that’s a very important consideration as to what is next.
Last is the reliability of the documentation of progression, particularly in imaging studies.Please remember, you need about a 25% change in lesion size to be sure that a lesion has truly grown or shrunk on a CT scan. For a PET scan, it’s closer to 35%. You have to be careful when determining whether people really progressed, and sadly, has their cancer shrunk.
Also, there are some things that occur that can cloud the interpretation. One of the common ones — and many more people know about this now — is that lytic bony lesions under effective therapy often are inapparent, but they become apparent and become sclerotic a s the healing process takes place. I think all of us have seen these cases where people had a “negative” PET scan that suddenly became positive while a patient was clearly benefiting from the therapy. You have to be really careful there in the case of sclerotic bone metastases.
Also, please note that bone metastases are not part — even in RECIST — of the decision-making for whether or not a cancer has grown or shrunken.Bone metastases are a special situation, and you see this often with targeted therapies. It’s very common that people can be misled by that.
Again, I think how a drug is tolerated is important. A drug that has had virtually no adverse effects doesn’t affect somebody’s life quality or the ability to live the life they want.You have to think hard about changing that treatment. You need a strong reason for that.
Last is whether the disease is growing in an existing metastatic site or whether there’s a new metastatic site. That’s something else that influences our decision on how to go ahead with assessing whether a patient has progressed.
I’m going to post a second part of this discussion soon.