Chronic myeloid leukemia-transplantation in the tyrosine kinase era

Questions concerning tyrosine kinase-inhibitor therapy and transplants in chronic phase chronic myeloid leukaemia

In this provocative commentary, we consider several questions posed by the late chronic myeloid leukaemia (CML) expert Prof. Michele Baccarani, which he challenged us to address after his death. He noted only a small proportion of people with chronic phase CML receiving tyrosine kinase-inhibitor (TKI)-therapy are likely to achieve sustained therapy-free remission (TFR) and even fewer are likely to be cured. Persons most likely to fail TKItherapy can be identified at diagnosis or soon after starting TKI-therapy. These persons are likely to need lifetime TKI-therapy with attendant risks of adverse events, cost and psychological consequences. Allogeneic transplants achieve much higher rates of leukaemia-free survival compared with TKI-therapy but are associated with transplant-related adverse events including an almost 20 percent risk of transplant-related deaths within 1 year post-transplant and a compromised quality-of-life because of complications such as chronic graft-versus-host disease. Subject-, disease- and transplant-related co-variates associated with transplant outcomes are known with reasonable accuracy. Not everyone likely to fail TKI-therapy is a transplant candidate. However, in those who candidates are physicians and patients need to weigh benefits and risks of TKI-therapy versus a transplant. We suggest transplants should be more often considered in the metric when counseling people with chronic phase CML unlikely to achieve TFR with TKI-therapy. We question whether we are discounting a possible important therapy intervention; we think so.

Cost-Effectiveness of First-Line Tyrosine Kinase Inhibitor Therapy Initiation Strategies for Chronic Myeloid Leukemia

OBJECTIVES

Overall survival in chronic myeloid leukemia (CML) in chronic phase is not significantly different by treatment with first-line tyrosine kinase inhibitors (TKIs), but emerging evidence reveals differences in costs and safety profiles. We evaluated the 1-year cost-effectiveness of TKI initiation with imatinib, dasatinib, or nilotinib among a hypothetical cohort of incident patients with CML from a US payer's perspective.

METHODS

We constructed a decision analytic model to assess quality-adjusted life years (QALYs), healthcare costs, net monetary benefit, and incremental cost-effectiveness of treatment strategies. We used published studies and data from the IBM Watson Health MarketScan database for model parameters. To calculate TKI costs, we used the 2018 Federal Supply Schedule estimates for generic imatinib and branded second-generation TKIs. We evaluated cost-effectiveness under various willingness-to-pay thresholds. We accounted for uncertainty with deterministic and probabilistic sensitivity analyses.

RESULTS

In the base-case analysis, imatinib was favored over dasatinib and nilotinib at a lower cost per QALY gained. Imatinib remained the favored strategy after 1-way variations in TKI costs, TKI switching, QALYs, adverse event risk, and CML progression. When we assessed model uncertainty with prespecified parameter distributions, imatinib was cost-saving compared with dasatinib in 40% of 100 0000 simulations and was favored over all simulations compared with nilotinib. First-line treatment with second-generation TKIs was cost-effective in 50% of simulations at a $200 000/QALY willingness-to-pay threshold.

CONCLUSIONS

Generic availability of imatinib provides a more cost-effective treatment approach in the first year compared with other available TKIs for newly diagnosed patients with CML.

Late mortality after bone marrow transplant for chronic myelogenous leukemia in the context of prior tyrosine kinase inhibitor exposure: A Blood or Marrow Transplant Survivor Study (BMTSS) report

BACKGROUND

Late mortality was investigated in patients with chronic myelogenous leukemia (CML) who underwent blood or bone marrow transplant (BMT) with or without prior tyrosine kinase inhibitor (TKI) therapy.

METHODS

By using data from the Blood or Marrow Transplant Survivor Study, the authors examined late mortality in 447 patients with CML who underwent BMT between 1974 and 2010, conditional on surviving ≥2 years post-BMT. For vital status information, the medical records, the National Death Index, and the Accurint database were used. Standardized mortality ratios (SMRs) were calculated using general population age-specific, sex-specific, and calendar-specific mortality rates. Kaplan-Meier techniques and Cox regression were used for all-cause mortality analyses. Cumulative incidence and proportional subdistribution hazards models for competing risks were used for cause-specific mortality analyses.

RESULTS

The 10-year overall survival rate was 65.7% and 73% for those who underwent transplant with and without pre-BMT exposure to TKI therapy, respectively. Patients who underwent transplant with and without pre-BMT TKI experienced SMRs of 6.4 and 6.4, respectively (P = .8); and the SMRs were 11.6 and 8.1, respectively, for those with high-risk disease (P = .2). Independent predictors of non-CML-related mortality included chronic graft-versus-host disease (hazard ratio [HR], 2.8; 95% CI, 1.8-4.4) and busulfan/cyclophosphamide conditioning (HR, 0.5; 95% CI, 0.3-0.9; reference, total body irradiation/cyclophosphamide conditioning). The 20-year cumulative incidence of CML-related and non-CML-related mortality was 6% and 36%, respectively, for the entire cohort. Both CML-related mortality (HR, 1.0; 95% CI, 0.1-12.6) and non-CML-related mortality (HR, 1.3; 95% CI, 0.6-3.1) were comparable for those with and without pre-BMT TKI therapy.

CONCLUSIONS

The similar late mortality experienced by patients with CML who undergo transplantation with or without pre-BMT TKIs suggests that allogeneic BMT can be considered in the context of TKI intolerance or nonadherence. The prevention of post-BMT non-CML-related mortality could favorably affect long-term survival.

Cellular and Molecular Networks in Chronic Myeloid Leukemia: The Leukemic Stem, Progenitor and Stromal Cell Interplay

The use of imatinib, second and third generation ABL tyrosine kinase inhibitors (TKI) (i.e. dasatinib, nilotinib, bosutinib and ponatinib) made CML a clinically manageable and, in a small percentage of cases, a cured disease. TKI therapy also turned CML blastic transformation into a rare event; however, disease progression still occurs in those patients who are refractory, not compliant with TKI therapy or develop resistance to multiple TKIs. In the past few years, it became clear that the BCRABL1 oncogene does not operate alone to drive disease emergence, maintenance and progression. Indeed, it seems that bone marrow (BM) microenvironment-generated signals and cell autonomous BCRABL1 kinase-independent genetic and epigenetic alterations all contribute to: i. persistence of a quiescent leukemic stem cell (LSC) reservoir, ii. innate or acquired resistance to TKIs, and iii. progression into the fatal blast crisis stage. Herein, we review the intricate leukemic network in which aberrant, but finely tuned, survival, mitogenic and self-renewal signals are generated by leukemic progenitors, stromal cells, immune cells and metabolic microenvironmental conditions (e.g. hypoxia) to promote LSC maintenance and blastic transformation.

Impact of drug development on the use of stem cell transplantation: a report by the European Society for Blood and Marrow Transplantation (EBMT)

Hematopoietic stem cell transplantation (HSCT) is used with increasing frequency in Europe with 40 000 transplants reported in 2014. Transplant-related mortality remains high in allogeneic HSCT (10-20%); high-dose chemotherapy is toxic and demanding for patients. Drug development is accelerating and with limited toxicity of some targeted drugs may replace HSCT, whereas others may function as a 'bridge to transplant'. We analyzed HSCT reported to the activity survey for selected diseases in which major advances in drug development have been made. Tyrosine kinase inhibitors markedly changed the number of allogeneic HSCT in early CML. In myelodysplastic syndromes, hypomethylating agents show no effect on HSCT activity and Janus kinase inhibitors for myeloproliferative neoplasm appear to have only a temporary effect. For CLL autologous HSCT decreased after publication of trials showing improved PFS but no overall survival advantage and allogeneic rates are dropping after the introduction of Bruton kinase and PI3K Inhibitors. Whether these are 'game changers' as was imatinib for CML requires additional follow-up. For myeloma, proteasome inhibitors and new immunomodulatory drugs do not appear to impact transplant rates. Drug development data show different effects on HSCT use; highly effective drugs may replace HSCT, whereas other drugs may improve the patient's condition to allow for HSCT.

Cost-effectiveness of Tyrosine Kinase Inhibitor Treatment Strategies for Chronic Myeloid Leukemia in Chronic Phase After Generic Entry of Imatinib in the United States

Background:

We analyzed the cost-effectiveness of treating incident chronic myeloid leukemia in chronic phase (CML-CP) with generic imatinib when it becomes available in United States in 2016. In the year following generic entry, imatinib’s price is expected to drop 70% to 90%. We hypothesized that initiating treatment with generic imatinib in these patients and then switching to the other tyrosine-kinase inhibitors (TKIs), dasatinib or nilotinib, because of intolerance or lack of effectiveness (“imatinib-first”) would be cost-effective compared with the current standard of care: “physicians’ choice” of initiating treatment with any one of the three TKIs.

Methods:

We constructed Markov models to compare the five-year cost-effectiveness of imatinib-first vs physician’s choice from a US commercial payer perspective, assuming 3% annual discounting ($US 2013). The models’ clinical endpoint was five-year overall survival taken from a systematic review of clinical trial results. Per-person spending on incident CML-CP treatment overall care components was estimated using Truven’s MarketScan claims data. The main outcome of the models was cost per quality-adjusted life-year (QALY). We interpreted outcomes based on a willingness-to-pay threshold of $100 000/QALY. A panel of European LeukemiaNet experts oversaw the study’s conduct.

Results:

Both strategies met the threshold. Imatinib-first ($277 401, 3.87 QALYs) offered patients a 0.10 decrement in QALYs at a savings of $88 343 over five years to payers compared with physician’s choice ($365 744, 3.97 QALYs). The imatinib-first incremental cost-effectiveness ratio was approximately $883 730/QALY. The results were robust to multiple sensitivity analyses.

Conclusion:

When imatinib loses patent protection and its price declines, its use will be the cost-effective initial treatment strategy for CML-CP.

Long-term outcome of patients with newly diagnosed chronic myeloid leukemia: a randomized comparison of stem cell transplantation with drug treatment

Tyrosine kinase inhibitors represent today's treatment of choice in chronic myeloid leukemia (CML). Allogeneic hematopoietic stem cell transplantation (HSCT) is regarded as salvage therapy. This prospective randomized CML-study IIIA recruited 669 patients with newly diagnosed CML between July 1997 and January 2004 from 143 centers. Of these, 427 patients were considered eligible for HSCT and were randomized by availability of a matched family donor between primary HSCT (group A; N=166 patients) and best available drug treatment (group B; N=261). Primary end point was long-term survival. Survival probabilities were not different between groups A and B (10-year survival: 0.76 (95% confidence interval (CI): 0.69–0.82) vs 0.69 (95% CI: 0.61–0.76)), but influenced by disease and transplant risk. Patients with a low transplant risk showed superior survival compared with patients with high- (P<0.001) and non-high-risk disease (P=0.047) in group B; after entering blast crisis, survival was not different with or without HSCT. Significantly more patients in group A were in molecular remission (56% vs 39% P=0.005) and free of drug treatment (56% vs 6% P<0.001). Differences in symptoms and Karnofsky score were not significant. In the era of tyrosine kinase inhibitors, HSCT remains a valid option when both disease and transplant risk are considered.