Safety and efficacy of imatinib cessation for CML patients with stable undetectable minimal residual disease: results from the TWISTER study.

Most patients with chronic myeloid leukemia (CML) treated with imatinib will relapse if treatment is withdrawn. We conducted a prospective clinical trial of imatinib withdrawal in 40 chronic-phase CML patients who had sustained undetectable minimal residual disease (UMRD) by conventional quantitative polymerase chain reaction (PCR) on imatinib for at least 2 years. Patients stopped imatinib and were monitored frequently for molecular relapse. At 24 months, the actuarial estimate of stable treatment-free remission was 47.1%. Most relapses occurred within 4 months of stopping imatinib, and no relapses beyond 27 months were seen. In the 21 patients treated with interferon before imatinib, a shorter duration of interferon treatment before imatinib was significantly associated with relapse risk, as was slower achievement of UMRD after switching to imatinib. Highly sensitive patient-specific BCR-ABL DNA PCR showed persistence of the original CML clone in all patients with stable UMRD, even several years after imatinib withdrawal. No patients with molecular relapse after discontinuation have progressed or developed BCR-ABL mutations (median follow-up, 42 months). All patients who relapsed remained sensitive to imatinib re-treatment. These results confirm the safety and efficacy of a trial of imatinib withdrawal in stable UMRD with frequent, sensitive molecular monitoring and early rescue of molecular relapse.

Ultra-low dose external beam radiotherapy for presumed choroidal lymphoma: a case report.

Primary choroidal lymphoma is a rare, slowly progressive intraocular malignancy. Most are low grade B cell lymphomas, often involving tissues adjacent to the choroid such as the subconjunctival space, lacrimal gland or orbit. Ideally, these lesions are biopsied to establish histopathological diagnosis. The most accessible ocular structure is biopsied. Obtaining tissue by transvitreal choroidal biopsy imparts a small but significant risk of ocular morbidity, including the need for multiple surgeries, retinal detachment and vision loss.External beam radiotherapy (EBRT) is a common and effective treatment of low-grade lymphomas. EBRT has been found to very successfully treat primary marginal zone lymphomas of the ocular adnexa, which are typically of the same cell type as most primary choroid lymphomas. Ultra-low dose EBRT, most commonly using a total dose of 4 Gy, has been shown to be as effective as higher doses of radiotherapy for follicular or marginal zone lymphomas. The use of this low dose regimen for conjunctival lymphomas has been recently explored. The role of EBRT, and especially ultra-low dose EBRT, for treatment of primary choroidal lymphoma has been confined to case reports.We describe a case of presumed primary choroidal lymphoma diagnosed on clinical findings alone as the risks of ocular biopsy were deemed too high, and report outcome following treatment with ultra-low dose EBRT.

Long-term treatment-free remission of chronic myeloid leukemia with falling levels of residual leukemic cells.

Following the achievement of deep molecular response on tyrosine kinase inhibitors (TKIs), approximately half of patients with chronic myeloid leukemia (CML) can discontinue TKI and remain in treatment-free remission (TFR). The ALLG CML8 study enrolled 40 imatinib-treated patients with undetectable BCR-ABL1 mRNA (approximately MR4.5). Molecular relapse was defined as detectable BCR-ABL1 on two consecutive tests or any single value >0.1%. With a median follow-up of 8.6 years (range 5.7-11.2 years), 18 patients remain in continuous TFR (45.0%; 95% confidence interval 31.9-63.4%). The latest relapse detected was 27 months after stopping imatinib. No patient progressed to advanced phase. Twenty-two patients met criteria for imatinib re-treatment and all regained undetectable molecular response. Nine patients in long-term TFR were monitored by highly sensitive individualized BCR-ABL1 DNA PCR in a sufficient number of samples to enable more precise quantification of residual leukemia. BCR-ABL1 DNA decreased from a median of MR5.0 in the first year of TFR to MR6.1 in the sixth year of TFR. Our results support the long-term safety and remarkable stability of response after imatinib discontinuation in appropriately selected CML patients. Serial high sensitivity testing provides a new and unexpected finding of gradually reducing CML cells in patients in long-term TFR.

Cytokines in haemopoietic progenitor mobilisation for peripheral blood stem cell transplantation.

Haemopoietic progenitors mobilised into peripheral blood are now almost universally used in autologous haemopoietic stem cell transplantation in the treatment of a range of malignant and some nonmalignant disease. Although chemotherapy alone was initially used, all modern protocols now involve the use of cytokines, with or without chemotherapy. Important developments have included an in understanding of the importance of prior cancer therapy on progenitor yield, knowledge of the kinetics of mobilisation and development of necessary skills to collect and cryopreserve progenitors. More accurate measurement of haemopoietic progenitors and definitions of target cell yields for optimal haemopoietic recovery after high-dose therapy have also contributed to more predictable outcomes and provide a reference point for newer mobilisation approaches. Although G-CSF based regimens are usually successful, some patients either fail to mobilise sufficient progenitors or require an excessive number of collections. Clinical studies with the early acting cytokine, stem cell factor, in combination with G-CSF have demonstrated increased progenitor yields in a range of patients which may translate to clinical benefit in selected situations. In animal models and to a lesser extent in humans, other cytokines such as thrombopoietin and Flt-3 ligand or a number of engineered small molecules with single or dual agonist activity for cytokine receptors (IL-3, Flt-3L, TPO, G-CSF), have also been found to be promising mobilising agents. Further research into the relative importance of cell proliferation, cellular adhesion and the role of accessory cells and other signalling events is leading to an improved understanding of the underlying mechanisms of haemopoietic progenitor mobilisation. Administration of appropriate high-dose chemotherapy followed by re-infusion of haemopoietic progenitor cells capable of long-term reconstitution has long had a place in the treatment of a number of malignant (largely haematological) and non-malignant diseases. For many years these progenitor cells were obtained by direct aspiration of bone marrow under general anaesthetic, hence the term bone marrow transplantation. However, it has also been recognized that haemopoietic stem cells may be recovered from peripheral blood, albeit in low numbers, and also from umbilical cord blood. Further empirical observations showed that the number of haemopoietic progenitors circulating in the blood could be transiently augmented after chemotherapy and/or administration of one or more of a number of cytokines. Refinements to the clinical practice of progenitor mobilisation, collection and enumeration have proved very successful such that in many cases peripheral blood stem cells (PBSC) have largely replaced bone marrow as the preferred source.