CML TKI interruption: Swedish registry results

With a median follow-up of 9 years, discontinuation of tyrosine kinase inhibitor (TKI) therapy in chronic phase chronic myeloid leukaemia (CML) was reported in 43% of 548 evaluable CML patients, in a population-based setting. Patients interrupting TKI therapy outside a clinical trial setting had good outcomes.

Dr Hjalmar Flygt (Uppsala University Hospital, Sweden) presented data extracted from the Swedish CML registry about patients stopping TKI therapy outside of clinical trials in chronic phase CML [1]. Studies have shown that 40-50% of patients with a deep molecular response (DMR, defined as MR^4.0 or lower) successfully remained TKI treatment-free. In the current Swedish Guidelines for CML, stopping TKI therapy can be considered in patients treated with a TKI ≥5 years and an MR^4.0 or lower for at least 2 years.

CML patients diagnosed between 2007-2012 (n=584) were analysed, of whom 234 of the 548 evaluable patients (43%) had stopped treatment with TKI ≥1 month. Most interrupted TKI therapy because they had achieved durable MR (56%); other reasons included adverse events (18%), or stem cell transplantation (13%).

In an analysis aimed at determining outcomes of patients treated outside of a clinical trial setting, Dr Flygt pointed out that 29% stopped while enrolled in a clinical trial, whereas 70% stopped their TKI therapy outside a study setting. Median time from diagnosis to TKI stop while in a study was 4.2 years (IQR: 3.6-5.2), and 6.0 years (IQR: 4.0-7.5) for those not enrolled in a study. In total, 48.9% patients had re-initiated TKI treatment at a median of 0.4 years (IQR 0.3-0.6) after stopping TKI. Of those stopping TKI outside a study setting, the probability of remaining TKI treatment-free at 22 months was 61%.

1. 1. Flygt H, et al. High level of successful TKI discontinuation outside clinical trials – a population-based study from the Swedish CML registry. EHA25 Virtual, 11-21 June 2020, Abstract S174.