| Response | Criteria for response |
| Timing of response assessment | The bone marrow examination for evaluating response in patients treated with cladribine should not be done before four to six months after therapy. In those patients being treated with pentostatin, the bone marrow can be evaluated after the blood counts have nearly normalized and the physical examination shows no splenomegaly. |
| Complete response (CR) | Near normalization of peripheral blood counts: hemoglobin >11 g/dL (without transfusion); platelets >100,000/microL; absolute neutrophil count >1500/microL. Regression of splenomegaly on physical examination. Absence of morphologic evidence of HCL on both the peripheral blood smear and the bone marrow examination. |
| CR with or without MRD | In patients who achieved a CR, an immunohistochemical assessment of the percentage of MRD will enable patients to be separated into those with CR with or without evidence of MRD. |
| Partial response (PR) | A PR requires near normalization of the peripheral blood count (as in CR) with a minimum of 50% improvement in organomegaly and bone marrow biopsy infiltration with HCL. |
| Stable disease (SD) | Patients who have not met the criteria for an objective remission after therapy are considered to have SD. Because patients with HCL are treated for specific reasons, including disease-related symptoms or decline in their hematologic parameters, SD is not an acceptable response. |
| Progressive disease (PD) | Patients who have an increase in symptoms related to disease, a 25% increase in organomegaly, or a 25% decline in their hematologic parameters qualify for PD. An effort must be made to differentiate a decline in blood counts related to myelosuppression effects of therapy versus PD. |
| HCL in relapse | Morphologic relapse is defined as the reappearance of HCL in the peripheral blood, the bone marrow biopsy, or both by morphologic stains in the absence of hematologic relapse. Hematologic relapse is defined as reappearance of cytopenia(s) below the thresholds defined above for CR and PR. Whereas no treatment is necessarily needed in case of morphologic relapse, treatment decisions for a hematologic relapse are based upon several parameters (eg, hematologic parameters warranting intervention, reoccurrence of disease-related symptoms). |
