Excellent Outcomes Achieved with Medical Management of Chronic Phase CML Patients with Non-Hematologic TKI Intolerance

Introduction:Tyrosine kinase inhibitor (TKI) intolerance is commonly encountered in patients with chronic myeloid leukemia in chronic phase (CML-CP). Clinical trials define non-hematologic TKI intolerance as grade 3-4 toxicities, but lower grade toxicities may also impair patients' quality of life and lead to changes in medical management. We sought to compare TKI-intolerant and -tolerant CML-CP patients and their clinical outcomes, including molecular responses, rates of progression, survival, and utilization of allogeneic stem cell transplant (alloSCT).

Methods:We performed a single-center, retrospective cohort study of active CML-CP patients in our Hematology clinic between January 2017 and December 2019. We defined TKI intolerance as any grade non-hematologic toxicity that led to a change in TKI management, such as dose reduction or change of TKI. We also reviewed CML-CP patients who underwent alloSCT in the TKI era (2002-2019). AlloSCT patients were identified for chart review by ICD-10 codes and query of the institution's transplant database. Descriptive statistics, Chi-Square tests, and two-tailed t-tests were used to summarize the data.

Results:We identified 216 CML-CP patients (Table 1), and 161 (74.5%) met criteria for non-hematologic TKI intolerance. The median age was 59 years-old in TKI-intolerant patients and 49 in tolerant patients (P=0.011). Most patients experienced TKI-intolerance from symptoms (93.2%, n=150); symptoms included fatigue (n=77, 59.2%), arthralgias (n=36, 27.7%), nausea (n=29, 22.3%), headache (n=16, 12.3%), and edema (n=15, 11.5%). The remaining patients were TKI-intolerant based on abnormal laboratory findings such as transaminitis or hyperglycemia (6.8%, n=11/161).

Of the 161 TKI-intolerant patients at last follow-up, 130 (80.7%) remained on TKI, 19 (11.8%) were on prescribed discontinuation, 6 (3.72%) were non-adherent, 5 (3.1%) were off TKI for non-CML medical problems, and 1 (0.6%) was on omacetaxine. Dose reductions occurred in the majority who remained on TKIs (n=103/130, 79.2%) and prior to TKI discontinuation (n=13/19, 68.4%). Most TKI-intolerant patients (n=122/161, 75.8%) switched TKIs, with a median of 2 agents used (range 1-5). Of 55 TKI-tolerant patients, 46 (83.6%) were on TKI, 8 (14.5%) were on discontinuation, and 1 (1.8%) was non-adherent. Only 19.6% (n=9/46) patients were dose-reduced, and they rarely changed TKIs (median of 1 agent used).

MR4.5 was achieved in 49% (n=79/161) of TKI-intolerant and 41.8% (n=23/55) of TKI-tolerant patients. Only 1 patient in each group progressed to accelerated phase. TKI-intolerant and -tolerant patients had similar times since diagnosis (with a median follow up of 81.7 months and 79.7 months, respectively). Five of 161 (3.1%) TKI-intolerant patients died, all from causes unrelated to CML and TKI therapy. None of the TKI-tolerant patients died during the abstraction period.

Twenty CML-CP patients underwent alloSCT from year 2002-2019; 10 (50%) were transplanted for TKI intolerance without other transplant indications (Tables 2 and 3). Three of those 10 patients also had hematologic intolerance. Four (40%) TKI-intolerant patients resumed TKI post-transplant: 3 for disease relapse, 1 for sclerotic GVHD. Seven (70%) developed GVHD, with most cases being chronic (n=6), extensive (n=6), and severe/moderate (n=6). While 80% of patients achieved MR4.5 post-transplant (n=8/10), 30% (n=3/10) experienced transplant-related mortality (TRM) with a mean post-transplant survival of 38.5 months; the remaining 7 patients were alive at a median follow-up of 37.1 months.

Conclusion: CML-CP patients with non-hematologic TKI-intolerance achieved similar clinical outcomes as TKI-tolerant patients despite dose reductions and/or switching TKIs. The use of alloSCT was rare in our practice, and CML-CP patients transplanted for TKI intolerance commonly resumed TKI post-alloSCT and frequently developed extensive GVHD. In light of the high survival rate achieved with medical management in CML-CP patients with non-hematologic TKI-intolerance, including no disease- or treatment-related deaths, this analysis does not support the use of alloSCT for patients with non-hematologic TKI-intolerance.

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