Anthony K. Mills

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Most patients with chronic myeloid leukemia (CML) treated with imatinib will relapse if treatment is withdrawn.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.

Patients with chronic myeloid leukemia who maintain a complete molecular response after stopping imatinib treatment have evidence of persistent leukemia by DNA PCR

Around 40–50% of patients with chronic myeloid leukemia (CML) who achieve a stable complete molecular response (CMR; undetectable breakpoint cluster region-Abelson leukemia gene human homolog 1 (BCR–ABL1) mRNA) on imatinib can stop therapy and remain in CMR, at least for several years. This raises the possibility that imatinib therapy may not need to be continued indefinitely in some CML patients. Two possible explanations for this observation are (1) CML has been eradicated or (2) residual leukemic cells fail to proliferate despite the absence of ongoing kinase inhibition. We used a highly sensitive patient-specific nested quantitative PCR to look for evidence of genomic BCR–ABL1 DNA in patients who sustained CMR after stopping imatinib therapy. Seven of eight patients who sustained CMR off therapy had BCR–ABL1 DNA detected at least once after stopping imatinib, but none has relapsed (follow-up 12–41 months). BCR–ABL1 DNA levels increased in all of the 10 patients who lost CMR soon after imatinib cessation, whereas serial testing of patients in sustained CMR showed a stable level of BCR–ABL1 DNA. This more sensitive assay for BCR–ABL1 provides evidence that even patients who maintain a CMR after stopping imatinib may harbor residual leukemia. A search for intrinsic or extrinsic (for example, immunological) causes for this drug-free leukemic suppression is now indicated.

Impact of early dose intensity on cytogenetic and molecular responses in chronic- phase CML patients receiving 600 mg/day of imatinib as initial therapy

We conducted a trial in 103 patients with newly diagnosed chronic phase chronic myeloid leukemia (CP-CML) using imatinib 600 mg/day, with dose escalation to 800 mg/day for suboptimal response. The estimated cumulative incidences of complete cytogenetic response (CCR) by 12 and 24 months were 88% and 90%, and major molecular responses (MMRs) were 47% and 73%. In patients who maintained a daily average of 600 mg of imatinib for the first 6 months (n = 60), MMR rates by 12 and 24 months were 55% and 77% compared with 32% and 53% in patients averaging less than 600 mg (P = .037 and .016, respectively). Dose escalation was indicated for 17 patients before 12 months for failure to achieve, or maintain, major cytogenetic response at 6 months or CCR at 9 months but was only possible in 8 patients (47%). Dose escalation was indicated for 73 patients after 12 months because their BCR-ABL level remained more than 0.01% (international scale) and was possible in 45 of 73 (62%). Superior responses achieved in patients able to tolerate imatinib at 600 mg suggests that early dose intensity may be critical to optimize response in CP-CML. The trial was registered at www.ANZCTR.org.au as #ACTRN12607000614493.

TIDEL-II: first-line use of imatinib in CML with early switch to nilotinib for failure to achieve time-dependent molecular targets

The Therapeutic Intensification in De Novo Leukaemia (TIDEL)-II study enrolled 210 patients with chronic phase chronic myeloid leukemia (CML) in two equal, sequential cohorts. All started treatment with imatinib 600 mg/day. Imatinib plasma trough level was performed at day 22 and if <1000 ng/mL, imatinib 800 mg/day was given. Patients were then assessed against molecular targets: BCR-ABL1 ≤10%, ≤1%, and ≤0.1% at 3, 6, and 12 months, respectively. Cohort 1 patients failing any target escalated to imatinib 800 mg/day, and subsequently switched to nilotinib 400 mg twice daily for failing the same target 3 months later. Cohort 2 patients failing any target switched to nilotinib directly, as did patients with intolerance or loss of response in either cohort. At 2 years, 55% of patients remained on imatinib, and 30% on nilotinib. Only 12% were >10% BCR-ABL1 at 3 months. Confirmed major molecular response was achieved in 64% at 12 months and 73% at 24 months. MR4.5 (BCR-ABL1 ≤0.0032%) at 24 months was 34%. Overall survival was 96% and transformation-free survival was 95% at 3 years. This trial supports the feasibility and efficacy of an imatinib-based approach with selective, early switching to nilotinib. This trial was registered at www.anzctr.org.au as #12607000325404.

Selective accumulation of virus-specific CD8+ T cells within the peripheral blood stem cell compartment.

To the editor: The absence of cellular immunity is central to the pathogenesis of herpesvirus-mediated diseases after allogeneic hemopoietic stem cell transplantation (HSCT).[1][1],[2][2] For both bone marrow (BM)– and granulocyte-colony stimulating factor–mobilized peripheral blood stem cells

How we mobilize haemopoietic stem cells.

Mobilization and collection of haemopoietic stem and progenitor cells (HSPC) is the cornerstone of autologous and allogeneic stem cell transplantation for a wide variety of haematological and some non‐haematological malignancies. Centres providing this service face the challenge of optimizing the likelihood of successful collection of transplantable doses of cells, while maximizing the efficiency of the apheresis unit and minimizing the risk of toxicity as well as mobilization failure. Recent developments in the understanding of the molecular mechanisms of mobilization have led to the emergence of novel strategies for HSPC mobilization, which may assist in meeting these imperatives. The task for clinicians is how to incorporate the use of these strategies into practice, in the light of emerging evidence for efficacy and safety of these agents. Herein, the literature is reviewed, and a proposed algorithm for HSPC mobilization is presented.

Idarubicin Dose Escalation During Consolidation Therapy for Adult Acute Myeloid Leukemia

Purpose Higher doses of the anthracycline daunorubicin during induction therapy for acute myeloid leukemia (AML) have been shown to improve remission rates and survival. We hypothesized that improvements in outcomes in adult AML may be further achieved by increased anthracycline dose during consolidation therapy. Patients and Methods Patients with AML in complete remission after induction therapy were randomly assigned to receive two cycles of consolidation therapy with cytarabine 100 mg/m2 daily for 5 days, etoposide 75 mg/m2 daily for 5 days, and idarubicin 9 mg/m2 daily for either 2 or 3 days (standard and intensive arms, respectively). The primary end point was leukemia-free survival (LFS). Results Two hundred ninety-three patients 16 to 60 years of age, excluding those with core binding factor AML and acute promyelocytic leukemia, were randomly assigned to treatment groups (146 to the standard arm and 147 to the intensive arm). Both groups were balanced for age, karyotypic risk, and FLT3-internal tandem duplication and NPM1 gene mutations. One hundred twenty patients in the standard arm (82%) and 95 patients in the intensive arm (65%) completed planned consolidation ( P < .001). Durations of severe neutropenia and thrombocytopenia were prolonged in the intensive arm, but there were no differences in serious nonhematological toxicities. With a median follow-up of 5.3 years (range, 0.6 to 9.9 years), there was a statistically significant improvement in LFS in the intensive arm compared with the standard arm (3-year LFS, 47% [95% CI, 40% to 56%] v 35% [95% CI, 28% to 44%]; P = .045). At 5 years, the overall survival rate was 57% in the intensive arm and 47% in the standard arm ( P = .092). There was no evidence of selective benefit of intensive consolidation within the cytogenetic or FLT3-internal tandem duplication and NPM1 gene mutation subgroups. Conclusion An increased cumulative dose of idarubicin during consolidation therapy for adult AML resulted in improved LFS, without increased nonhematologic toxicity.

Successful maintenance of molecular remission in chronic myelogenous leukaemia during pregnancy with transition from imatinib to pegylated interferon

We present the case of a 30-year-old woman with chronic myelogenous leukaemia (CML) who successfully maintained a major molecular response (MMR) during pregnancy after transition from imatinib mesylate to pegylated interferon (PEG-IFN). Our patient was originally diagnosed with chronic phase CML in October 2009. She was enrolled on the Australian Leukaemia and Lymphoma Group CML9 (Trial ID: ACTRN12607000325404) trial and initially commenced on imatinib at 600 mg daily. At diagnosis, her Sokal score was indicative of high-risk disease and at her 3-month assessment, her quantitative BCR-ABL reverse transcription-polymerase chain reaction had only reduced to 13% on the international scale (IS), a marker of suboptimal response. In accordance with the trial protocol, her dose was increased to 400 mg twice daily, which she tolerated with minimal toxicity. At her 6-month assessment, she was in MMR with 0.1% BCRABL (Fig. 1). Thereafter she remained on this dose of imatinib in sustained MMR for the next 36 months, achieving a molecular response (MR) (BCR-ABL <0.01% IS) at 27 months but never MR (BCR-ABL <0.0032% IS). In early discussions with the patient, we advised deferring pregnancy until maximal response to imatinib had occurred. At 41 months, her response appeared to have reached a plateau, and it appeared unlikely she would achieve sustained MR, to allow a trial of imatinib cessation within a period acceptable to her. We sought opinions from three national experts and presented the case during a panel discussion at an international CML meeting. There was a surprising degree of consensus that it would be safe and reasonable at that point to cease imatinib and commence PEG-IFN to enable pregnancy (although some advised deferring PEG-IFN until progression). Pregnancy was confirmed 4 months after ceasing imatinib. Throughout her pregnancy, she succeeded in maintaining MMR. Initially she was treated with PEG-IFN 180 mcg weekly. In the second half of her pregnancy, the dose was reduced to 90 mcg/weekly due to anaemia and thrombocytopenia. She had no significant non-haematological toxicity. She successfully delivered a healthy low-normal birth weight (2559 g), term infant. As she remained in MMR, she continued on PEG-IFN for 2 months post-partum to allow breast-feeding. She was then transitioned from PEG-IFN to nilotinib with the goal of achieving a deeper molecular response with a view to eventual drug cessation. On her most recent assessment, 3 months postpartum, BCR-ABL was 0.006%. This patient had 3-month BCR-ABL of >10%, which has been shown to predict shorter progression free and overall survival, although more recent studies suggest the rate of decline of BCR-ABL transcripts may help to identify the poor-risk group among these patients. Following dose escalation, the patient rapidly obtained MMR. However, it was felt that given the Sokal score and initial response to imatinib, the relapse risk was too high to consider isolated cessation of tyrosine kinase inhibitor (TKI) during pregnancy, as described elsewhere. Additionally, only 2 of 12 (17%) of Sokal high-risk patients achieved treatment-free remission in combined results

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.

Chronic myeloid leukaemia and tyrosine kinase inhibitor therapy: assessment and management of cardiovascular risk factors

Several BCR‐ABL1 tyrosine kinase inhibitors (TKIs) are approved for the first‐line treatment of chronic phase chronic myeloid leukaemia (CML). Disease control is achieved in the vast majority of patients and disease‐specific survival is excellent. Consequently, there is now emphasis on managing comorbidities and minimising treatment‐related toxicity. Second‐generation TKIs have cardiovascular risks that are greater than with imatinib treatment, but these risks must be balanced against the superior CML responses encountered with more potent TKIs. Cardiovascular risk should be assessed at baseline using a locally validated model based on the Framingham risk equation. Clinicians involved in the care of CML patients should be aware of the vascular complications of TKIs and manage cardiovascular risk factors early to mitigate treatment‐related risks. Reversible risk factors, such as dyslipidaemia, smoking, diabetes and hypertension, should be addressed. We summarise the available data on cardiovascular complications in CML patients treated with TKIs. Using the latest evidence and collective expert opinion, we provide practical advice for clinicians to assess, stratify and manage cardiovascular risk in people with CML receiving TKI therapy.