Introduction and Epidemiology of Hairy Cell Leukemia

Jae Park, MD: Hello and welcome to this OncLive® Peer Exchange, entitled “Updates in the Management of Hairy Cell Leukemia.” I'm Dr Jae Park from Memorial Sloan Kettering Cancer Center in New York. Joining me today in this virtual discussion are my colleagues, Dr. Steven Coutre from Stanford University Medical Center; Dr. Farhad Ravandi-Kashani from MD Anderson Cancer Center; Dr Alan Saven from Scripps Health; and Dr Andrea Sitlinger from Duke University Cancer Institute. Hairy cell leukemia is a rare, slow-growing cancer of the blood involving excess abnormal B cells. Today we're going to discuss a number of topics pertaining to the management and practical application of the most recent data on the disease. Our first topic is disease state and biology of a hairy cell leukemia. Dr Saven, can you share with us an overview of the hairy cell leukemia epidemiology, risk factors, and clinical presentations?

Alan Saven, MD: Hairy cell leukemia is a relatively uncommon hematologic malignancy. There are about 600 to 800 cases annually in the United States. I think that's underestimated. That was before the introduction of flow cytometry, where it's easier to detect hairy cell leukemia circulating in the peripheral blood. It's a disease of males rather than females. The ratio’s about 4:1, usually middle-aged patients, but there’s great variability. The youngest patient I’ve seen is 26, and I've seen the disease in 90-year-olds. It's mostly a disease of Caucasians. Why it doesn't affect other ethnic groups to the same degree I’m uncertain, but it certainly occurs in Hispanics. Of the 800 patients I've seen, probably only 1 has been African American, and I've seen a handful of Asian Americans with this disorder. What predisposes patients to this disorder? No one really knows. There are various theories about pesticides, organic solvents, but I don't think they've been definitively proven. Among the Caucasians, there’s a higher incidence among Ashkenazi Jews. The reason for that is unclear. It is a disorder of the memory pre-plasma cell, and circulating lymphocytes can accumulate in the spleen, less commonly in lymphocytes in the bone marrow, and hence the clinical presentation of splenomegaly, cytopenias. Monocytopenia is a hallmark of untreated hairy cell leukemia. This is a disease with a very indolent and protracted clinical course, and we'll get into the various factors associated with it.

Jae Park, MD: Sometimes we see very young patients with hairy cell leukemia. It is a disease of relatively younger patients compared to other blood cancers that we may see, or the leukemias. Do any of you have thoughts about patients in their 20s and 30s, which are very rare, but any differences in terms of the clinical, not so much presentations, but in terms of the prognosis? Are there any other factors to consider for younger patients?

Alan Saven, MD: When it occurs in younger patients, it tends to be somewhat more aggressive. The prognosis in younger people isn't as good as in older people, but older patients can also die of unrelated causes. It's probably a little bit more biologically active in younger patients. I rarely see patients in their 20s. The youngest patient I've ever seen is 26, and I'm not sure if it occurs in childhood.

Jae Park, MD: Dr Sitlinger, what are the laboratory findings for these patients? How do they determine it’s hairy cell?

Andrea Sitlinger, MD: Similar to other indolent lymphoproliferative disorders, there are 3 big buckets in which patients are diagnosed. One is that they present to their primary care doctor and have laboratory tests drawn for whatever reason, screening, and are found to have significant cytopenias. About 60% to 80% of people are found to have pancytopenia, and neutropenia particularly, as well as monocytopenia. They're both in the range of 80% of patients who will have this disorder. They will often present to us because they were found to have lab abnormalities. Neutropenia and pancytopenia are by far the predominant lab abnormality. There are about 10% of patients that present with a leukocytosis, and these tend to be the more aggressive and maybe even patients with variant hairy cell leukemia. For the general practitioner, or general oncologist, just because you're seeing leukocytosis doesn't rule out hairy cell.

One of the very profound features would be splenomegaly. Up to 90% or more of patients have splenomegaly. Some patients can present with profound, even splenic rupture just with how big their spleen is. That's less common now with imaging, but that has been a problem in the past. What's interesting with hairy cell compared to other leukemias and lymphomas is it's much less common to have lymph nodes involved. Clear splenomegaly is a clue that hairy cell is in the differential, among other things as well.

Then finally, people also present with systemic complaints. It's usually fatigue, weakness, sometimes weight loss, particularly a large spleen was causing early satiety and people are not eating as well. They also can present with profound thrombocytopenia, leading to bleeding. The other thing is there are either recurrent infections or recurrent autoimmune complications that will also alert patients. What’s interesting with hairy cell compared to other leukemias and lymphomas is it's not as common to have fevers and night sweats with hairy cell. Usually if I see a patient with fever or night sweats, I'm either starting to think something else is going on, or it’s just the infections that come along with these patients since they are immunocompromised. When I talk to patients, those are the 3 main presentations that we see initially that alert us to that hairy cell diagnosis.

Steven Coutre, MD: Anecdotally, the uncommon patient who presents with the leukocytosis, I've been impressed that they often have extremely high fevers.

Farhad Ravandi-Kashani, MD: I also wanted to mention that the situation of massive splenomegaly and significant constitutional symptoms is becoming less common, mainly because people are getting routine blood screening. Frequently patients are found to be slightly cytopenic on a routine blood evaluation, and then further work-up shows hairy cell leukemia. There are unusual presentations. Lymphadenopathy is not that common, but I've had patients with very unusual presentations. I had a young lady who had a paravertebral mass, which turned out to be hairy cell leukemia. I had a gentleman who had a renal mass. The thinking was renal cell carcinoma. It turned out to be hairy cell leukemia. I had another gentleman who was managed by orthopedics for almost a year because of back pain and severe bone pains. Eventually, he had a blood count and he had massive involvement of all of his skeletal system with hairy cell leukemia. Unusual presentations do exist.

Andrea Sitlinger, MD: Especially when you're seeing a lot of hairy cell, you're going to see a lot of the unusual and uncommon variants. That's an excellent point. It is interesting, and certainly the vasculitis and some of the autoimmune manifestations that go with it as well can present in other organ manifestations. There are a lot of different ways, but it's interesting to highlight that in a majority of patients, you will see less of some of the other common things. It’s fortunate that we are catching these patients a lot earlier, and we’re not having the massive splenomegaly and splenic ruptures that used to be seen.

Transcript Edited for Clarity