Robert J. Kreitman, MD: Hairy cell leukemia is a rare chronic B-cell leukemia that accounts for 2% of all leukemias, with approximately 1200 new cases reported in the United States each year. Major advances in the treatment and understanding of the biology and genomic landscape have been made, which have increased median survival.

In this OncLive Peer Exchange® panel discussion, we will be discussing diagnosis, prognosis, as well as current and new treatment options, to shed light on how the most recent data will be used to shape the way we treat our patients.

I am Dr Robert J. Kreitman. I work at the NIH [National Institutes of Health] in Bethesda, Maryland.

Today I am joined by my colleague, Dr Farhad Ravandi, the Janiece and Stephen A. Lasher professor of medicine and the chief of the section of developmental therapeutics in the Department of Leukemia at The University of Texas MD Anderson Cancer Center in Houston, Texas.

Thank you so much for joining us. Let’s begin.

Let’s start by talking about the first line, or what we call up-front therapy in hairy cell leukemia. First, let’s talk about the recent updates to the NCCN [National Comprehensive Cancer Network] Guidelines.

Farhad Ravandi-Kashani, MD: The NCCN Guidelines is by a group of experts who report on what are the important changes that are in the management of patients with hairy cell leukemia. They continue to consider purine nucleoside analogs. That’s the first line of therapy, but there are now some considerations for second line and subsequent lines of therapy. I don’t know if you would like to expand on that.

Robert J. Kreitman, MD: We’ll talk about a new drug that was approved for hairy cell leukemia—moxetumomab pasudotox. We’ll talk about that in a little bit. There are also some BRAF inhibitors that have been tested but not approved for hairy cell leukemia, even though many people are getting them. We’ll also touch on those subjects.

Farhad Ravandi-Kashani, MD: Regarding the decision to initiate therapy in a patient with hairy cell leukemia, the NCCN Guidelines as well as all the other guidelines—including the ones recommended by the Hairy Cell Leukemia Foundation—consider initiation of therapy only if the patient is symptomatic. That means they have constitutional symptoms—weight loss, fever, significant fatigue—or there is evidence of bone marrow failure with reduction in the blood counts, including platelet counts below about 100,000 per mm³, hemoglobin below 11 g/dL, and neutrophil count below 1000. I don’t think there has been any change in that in terms of NCCN Guidelines.

Robert J. Kreitman, MD: Right. Some people use 10 instead of 11 for the hemoglobin, so there’s a little bit of variability. But that’s how it’s been for many years. I would add that the reason for that is you don’t want to be throwing in chemotherapy for a patient who has good blood counts because that patient could be watched and waited. We used that to say that we can wait on treatment. How often would you follow patients who were being watched and waited?

Farhad Ravandi-Kashani, MD: It really depends on the degree of symptoms and the degree of the decline in the blood counts. For example, if a patient has a platelet count of 99 per mm³, I don’t follow them weekly to make sure it doesn’t drop dramatically because the decline in these counts in most patients will be gradual. However, if a patient is becoming symptomatic, I will start thinking about making the decision to treat the patient. It’s very important to remember that fatigue per se can be a coexisting symptom from other conditions. You clearly want to make sure that the symptoms that the patient is attributing to the hairy cell are truly related to the hairy cell leukemia. But in general, in an asymptomatic patient with mild decline in the blood counts, I probably would see them every 2 to 3 months. If the symptoms start progressing significantly, I would probably see them more frequently.

Robert J. Kreitman, MD: One important question is, if you have a patient who is having infections, and that’s the reason they need treatment, do you want to jump in right away with these chemotherapy drugs in such a patient?

Farhad Ravandi-Kashani, MD: Well, it’s important to remember that the standard—the most commonly used standard therapy—cladribine, is itself myelosuppressive and will produce a period of about a month of significant neutropenia, and probably decline in the immune function of the patient for several months and thereafter. Recurrent infections are an important consideration for therapy, but in my practice, I make sure that the patients are well educated about neutropenia and neutropenic fever. I tend to use prophylactic antibiotics. This is not a standard and not used by everyone, but I tend to use an antiviral prophylaxis with valacyclovir and also antibacterial prophylaxis with levofloxacin. It is very important to remember that initiation of therapy with cladribine will actually predispose the patients more to infections.

Robert J. Kreitman, MD: It sounds like you don’t use anything to prevent pneumocystis, and we also do not. We’re also not concerned about pneumocystis, particularly in patients who are not on steroids and only getting treated for the first time.

Farhad Ravandi-Kashani, MD: Yes. Again, some groups or some experts do use Bactrim [sulfamethoxazole-trimethoprim], but I don’t use it because in a straightforward, uncomplicated hairy cell leukemia, I have yet to see a patient who develops a pneumocystis infection.

Transcript Edited for Clarity