Farhad Ravandi-Kashani, MD: That is an important topic because, as you mentioned, despite the success of purine nucleoside analogs, there’s still a significant proportion of patients who would relapse even within the first few years. Also if you follow patients long enough, there will be more relapses later. So the question is how does one decide on second-line therapy in hairy cell leukemia? Perhaps you can expand on your practice.

Robert J. Kreitman, MD: This is an important topic. The first thing I would say is don’t make the mistake, which is commonly made in hairy cell leukemia, of doing a bone marrow at 1 or 2 months and finding that there is a small amount of hairy cell present. Then you feel that the treatment has been a failure, say it was single-agent cladribine. The decision is to give another course of cladribine. It’s amazing how often that happens. If you do nothing and you just follow that patient, oftentimes by 6 months they will be a complete responder in complete remission. Hairy cell is one of those diseases where it takes a while to respond to the treatment. We don’t know exactly why, but it’s important not to jump in too quickly upfront with a second course of treatment. That’s a first point that I would make.

The next point is when do you decide that a patient really does need second-line treatment? We use the criteria, which really are the same for first-line treatment. In other words, the criteria are that they have to have cytopenias, they have to have a hemoglobin less than 10 or 11, a platelet count less than 100, neutrophil count less than 1, painful splenomegaly, or enlarging large lymph nodes, frequent infections, etcetera. But here we have to be careful because the low blood counts could be due to the prior treatment if it’s too close to that prior treatment. So we have to be cognizant of any potential other reasons why their blood counts might be low.

The other thing that I think is important to mention is that when a patient is newly diagnosed, they tend to have a lot of disease because they didn’t know that they had hairy cell leukemia. No one is really following them. When a patient’s had hairy cell leukemia, they’re being followed a lot more closely. They tend not to have overwhelmingly large tumor burden when they need second-line treatment. Oftentimes, you can see the counts go up and down. For example, 1 day their platelet count might be 90, and so you think that they’re qualifying for second-line treatment. Then the next month or 2, their platelet count is 120. So sometimes we like to see several CBCs [complete blood counts] in a row that indicate that the patient really does need treatment or to develop some sort of trend where it looks like the patient actually does need treatment.

We feel that even though a patient might qualify for re-treatment by having a low blood count, if it’s just a low platelet count—say in the 90s or 80s and otherwise the patient is doing fine and really wants to avoid additional treatment—sometimes those patients can go for not only months but years being followed. However, if a patient is developing neutropenia down to 0.5 or below, or platelet counts below 50, 40, 30, then we’re getting a little anxious that that patient really does need treatment. Or else, they might develop significant cytopenias from the treatment itself that might put them at risk for complications during the second-line treatment.

Transcript Edited for Clarity