What guides a CLL treatment choice? Dr. Catherine Coombs discusses genetic mutations and factors that may help determine a CLL patient’s therapy .
Dr. Catherine Coombs is an Assistant Professor of Medicine in the Division of Hematology at The UNC Lineberger Comprehensive Cancer Center. Learn more about Dr. Coombs here.
There’s not necessarily a one-size-fits-all approach to treating CLL, so how do you decide which treatment is right for a patient?
I always look at their underlying disease biology. There’s a couple really important tests that I send for all of my CLL patients by the time that they need therapy. The first is to see what their underlying cytogenetics and molecular findings are. There are certain good findings, and then certain bad findings.
One of the bad findings is having a deletion in the 17th chromosome in the short arm of that chromosome. The chromosomes are the big pieces of DNA within everyone’s cells. There are findings that are common in CLL: a 17p deletion is a poor prognostic feature. There’s a separate test where we can actually identify mutations in a gene called TP53. And these behave largely the same as 17p deletions, so I always check for both. It’s two different tests.
Oftentimes patients have both of these findings: a 17p deletion and a TP53 mutation. But sometimes you can have the mutation without the deletion and vice versa. That is one finding that’s important when talking about different therapies. The other really important prognostic test is the IGHV gene mutation status. This is another specialized sequencing test. It looks to see if the patient’s heavy chain, if their immunoglobulin protein has undergone something called somatic hypermutation or not.
It’s actually good to be mutated. What we know about people who are mutated is that they typically have better responses to most therapies and their disease typically is one that grows slower. So, I use those factors and then I have a conversation with the patient. The two main treatment classes that I spoke about – so the BTK inhibitors, those work actually really well and even the people with these bad prognostic features.
So, people with the 17p deletion, people with the TP53 mutation, they can have disease control for six plus years on a BTK inhibitor, which is really good.
That was not the case a decade ago when we didn’t have these drugs. That’s something that’s been hugely beneficial for our patients. The venetoclax/obinutuzumab regimen, that still works when people have the 17p or the TP53, but it probably doesn’t work as well.
I’d mentioned the median time for disease to come back hadn’t been reached yet. It had been reached for that poor risk subset. The expectation for people with that poorest marker is that the median PFS, progression-free survival. So, again, when after someone starts therapy, when the disease then progresses is 49 months. It kind of gives me a rough estimate of, “Gosh, these are your therapy options and based on your underlying biologic factors unique to your disease, this is what you can expect out of therapy A or therapy B.”
The mutated or unmutated IGHV, similarly, those BTK inhibitors work extremely well, even in people with the bad unmutated finding. I think those are always an option. The other treatment is an option, but the people with that bad finding do have a shorter time until they progress of just under five years.