Hairy cell leukemia medical therapy overview

# Overview
Patients with hairy cell leukemia who are symptom-free typically do not receive immediate treatment. They engage in "watchful waiting" with routine bloodwork and exams every three to six months to monitor disease progression and identify any new symptoms.

# Indication
Treatment is generally considered necessary when the patient shows signs and symptoms such as low blood cell counts (e.g., infection-fighting neutrophil count below 1.0 K/ul), frequent infections, unexplained bruises, anemia, or fatigue that is significant enough to disrupt the patient's everyday life.
Patients who need treatment, which includes most newly diagnosed HCL cases, usually receive either cladribine or pentostatin, which are both in a class of chemotherapeutic drugs known as purine analogs or nucleosides. In most cases, one round of treatment will produce a prolonged remission.

# Other treatments
Other treatments include rituximab infusion or self-injection with Interferon-alpha.  In limited cases, the patient may benefit from splenectomy (removal of the spleen). These treatments are not typically given as the first treatment for a new patient because their success rates are lower than cladribine or pentostatin.
In the short term, especially when neutrophil counts are low, an immune system hormone called granulocyte colony-stimulating factor may be taken to increase white blood cell counts.  This is believed to help prevent or treat an infection.  Many patients also take antibiotics until their white blood cell counts have recovered to normal levels.

# Control disease
Several treatments are available, and successful control of the disease is common.

### Not everyone needs treatment
Treatment is usually given when the symptoms of the disease interfere with the patient's everyday life, or when white blood cell or platelet counts decline to dangerously low levels, such as an absolute neutrophil count below one thousand cells per microliter (1.0 K/uL).  Not all patients need treatment immediately upon diagnosis, and about 10% of patients will never need treatment.

### Treatment delays are less important than in solid tumors
Unlike most cancers, treatment success does not depend on treating the disease at an early stage.  Because delays do not affect treatment success, there are no standards for how quickly a patient should receive treatment.  However, waiting too long can cause its own problems, such as an infection that might have been avoided by proper treatment to restore immune system function.  Also, having a higher number of hairy cells at the time of treatment can make certain side effects somewhat worse, as some side effects are primarily caused by the body's natural response to the dying hairy cells.  This can result in the hospitalization of a patient whose treatment would otherwise be carried out entirely at his hematologist's office.

### Single-drug treatment is normal
Unlike most cancers, only one drug is normally given to a patient at a time.  While monotherapy is normal, combination therapy -- typically using one first-line therapy and one second-line therapy -- is being studied in current clinical trials and is increasingly used for refractory cases.  It is unclear whether combining rituximab with cladribine or pentostatin will produce any practical benefit to the patient.  Combination therapy is almost never used with a new patient.  Because the success rates with purine analog monotherapy are already so high, the additional benefit from immediate treatment with a second drug in a treatment-naive patient is very low.  For example, one round of either cladribine or pentostatin gives the median first-time patient a ten-year remission; the addition of rituximab, which gives the median patient only three or four years, is reasonably expected to provide no additional value for this easily treated patient.  In a more difficult case, however, the benefit from the first drug may be substantially reduced and therefore a combination may provide some benefit.