COVID-19 IN PATIENTS WITH CHRONIC MYELOID LEUKEMIA IN TREATMENT-FREE REMISSION: DISEASE SEVERITY AND IMPACT ON TFR STATUS

ABSTRACT

Background: Severe SARS-CoV-2 infections associated with high mortality rates are reported in a higher percentage of patients (pts) with hematologic malignancies compared to general population. In chronic myeloid leukemia (CML), pts with uncontrolled disease have a higher mortality risk. The impact of SARS-CoV-2 infection on CML pts in treatment-free remission (TFR) has not been studied so far. In particular, as immune control of residual disease may be important for TFR, the concern is that the infection could induce loss of TFR. Aims: To evaluate the outcome of SARS-CoV-2 infection in CML pts in TFR and assess any impact on maintenance of TFR. Methods: From March 2020 to December 2021, the CANDID study organized by the international CML Foundation has collected data on COVID-19 positive CML pts worldwide. Details on the registry were presented recently (Pagano ASH 2021). For this sub-analysis on pts in TFR additional information were collected including;molecular remission status (BCRABL1 ratios) before, during and after SARS-CoV-2 infection covering at least 6 months. For molecular analyses, BCRABL1 ratios were classified according to Cross et al (Leukemia 2015). In addition, ratios of 0% without indication of sensitivity were allocated as MR4 i.e. 0.01%IS. PCR outlier results were identified using the ROUT method by nonlinear regression with a maximum false discovery rate (FDR) of 1% (Motulsky et al 2006). Time to molecular relapse (MR) was measured from the date of COVID-19 diagnosis to the date of MR defined as loss of major molecular remission (MMR, BCRABL1 >0.1%IS) or the date of last molecular test. Molecular relapse-free survival (MRFS) and overall survival (OS) were estimated with the Kaplan-Meier method. The statistical difference between groups was performed using log-rank test. Results: By December 2021, 1050 COVID-19 positive CML pts were registered. 95 pts were in TFR at the time point of SARS-CoV-2 infection of which 89 (93.68%) recovered and 6 deceased (6.32%). Median age of TFR pts was 57 years, male were 51 (53.68%). Median time from CML diagnosis to reporting date was 13 years (range 3.7-27.0 years). TFR duration was 2.83 years in median (range 0.5 months - 10.1 years) including 19 pts with a duration < 1 year. From the 89 recovered TFR pts, 74 pts completed the 6-month follow up (83%), a further 6 pts with molecular follow-up of 3-5 months after COVID-19 diagnosis were still in TFR, 9 pts were lost to follow-up. Of 74 pts with complete reports, 69 pts remained in TFR (93%) and 5 pts lost TFR. For 71 pts, PCR results were obtained before, during and after infection. With the ROUT method 10 pts demonstrated outlier PCR tests, 61 pts demonstrated stable PCR results. There was no statistically significant difference in PCR results before and during/after infection (p>0.2). MRFS for these 71 pts 15 months after COVID-19 diagnosis was 86%. Probability of TFR loss was higher in pts with a TFR duration < 6 months compared to pts with TFR duration >6 months (27% vs 10%, Fig 1A). Additionally, there were no statistically differences in hospitalization rate (16% vs 23%, p=0.12) and severity of COVID-19 symptoms (12.6% vs 12%, p=0.87) comparing TFR and TKI treated pts. OS of COVID-19 positive TFR pts did not differ from COVID-19 positive pts on TKI therapy (HR 1.1, CI 0.47-2.54) (Fig 1B). Summary/Conclusion: In this sub-analysis of the CANDID study, CML pts in TFR had similar severity and survival to CML pts who were on TKI therapy and there was no evidence of an increased risk of TFR loss after SARS-CoV-2 infection.