Drug-free, single-center, prospective observational pilot study in hairy Cell Leukemia patients

The V600E gene lesion of B-raf, specific and almost always present in patients with hairy cell leukemia, correlates with the presence of neoplastic cells, therefore of active disease. The measurement of the fractional abundance of the mutated gene, by ddPCR, could therefore constitute a method of molecular assessment of the minimal residual disease. In addition, the values of fractional abundance (FA) of the mutated allele obtained can be integrated coherently in patients' clinical context, along with their PB counts and BM findings.

Primary objective Verify whether the absence of mutation at the end of treatment, indicative of a state of complete molecular response to therapy, can represent a predictor of long treatment-free survival.

Secondary objectives Verify the association between the absence of mutation and the duration of response in patients who do not need treatment for at least 5 years after only one treatment with purine analogues (cladribine and pentostatin) and judged in CR according to current criteria.

Inclusion Criteria:

1. Histologically confirmed diagnosis of HCL patients:

   1. newly diagnosed and candidates for first-line cytoreductive treatment with analogues purines or
   2. in relapse after a previous line of treatment, with indication for rescue therapy (repetition of a purine analogue; use of targeted or innovative drugs), except splenectomy or
   3. in CR for at least 5 years after a first line of treatment, in the absence of clinical alterations indicative of a state of hematological relapse, or in any case in the absence of an indication for a new line of cytoreductive therapy (time-to-next treatment exceeding 5 years).

2. Age ≥ 18 years at enrollment

3. Signature of written informed consent

Exclusion Criteria:

1. Concomitant second malignancy.