Long Term Survival of Chronic Myeloid Leukemia Patients with Chromosomal Aberrations in Philadelphia Negative Metaphases During Treatment with Tyrosine Kinase Inhibitors

    


    


    Figure 1: A) K/T 46,XY,t(2;10)(q23;q24). B) Similar OS between b3a2 and b2a2 (p=0.355).

    

Examination of the bone marrow aspiration showed normal bone marrow in 7 patients, increase of lymphocytes and/or plasma cells in 6 patients, mild dysmegakaryopoiesis in 3 patients and dry tap in 3 patients. Moreover, none of the bone marrow aspirations and biopsies revealed signs suggestive of myelodysplastic syndrome.

At the end of the study, 2 out of 21 patients died, due to complications irrelevant to CML or TKI treatment, while 3 underwent allogeneic hematopoietic cell transplantation (HCT) - 1 in AP, 1 in BC and 1 in CP but with persistent monosomy 7 in all metaphases. Among the remaining 16 patients still on TKIs, all achieved complete cytogenetic response (CCyR), while 2 are in major molecular response (MMR) and 14 in deep molecular response (MR^4.5). Furthermore, we investigated the persistence of these ACAs in Ph- cells in these 16 patients. Persistent ACA was defined as continuously positive ACA results in sequential three or more times of cytogenetic follow-up. Eight patients had a persistent clone for a median time of 76 months (range 2-192). Five were found to have loss of chromosome Y, 2 trisomy 8 and 1 patient del(20q),+8 and +9.

Potential association between number of ACAs and number of treatments before TKI initiation

Ten patients with additional chromosomal abnormalities received only TKIs before the emergence of Ph (-) clone, while 11 patients received 1-5 (lines of treatment) prior to the initiation of TKIs. Moreover, the number of these aberrations was associated with the number of treatments before TKIs (p=0.030). Among these patients, 3 had undergone autologous HCT before the initiation of TKIs. Importantly, 2 of them still demonstrate persistent ACAs

Potential association between Overall Survival (OS) and type of BCR-ABL transcript or loss of chromosome Y

Our study revealed that the probability of OS at 15 years was 87.1%. Fourteen out of 21 patients (66.6%) were diagnosed with b2a3 transcripts (e14a2), 6 patients with b2a2 (e13a2) and 1 with b3a2 (e13a3). OS was found to be similar between b3a2 and b2a2 transcripts (p=0.355) as it can be seen in Figure 1B. Additionally, the loss of chromosome Y did not seem to affect OS compared to the non -Y ACAs (p=0.777). Survival measures were not significantly different in patient in which -Y was the only clonal abnormality versus others (p=0.458, 75% versus 92%). Moreover, response to TKI did not affect this difference because all patients in which -Y was the only clonal abnormality achieved optimal response.

Discussion

In this study, we investigated the occurrence of ACAs in Ph- cells in patients with CML. Twenty-one out of 200 patients with history of CML developed chromosomal abnormalities in the Ph- cells during the treatment with TKIs. The observed frequency is 10.5% which is similar to that reported in previous studies [12]. Consistent with previous reports, our study demonstrates that trisomy 8 and monosomy 7/7q- are common chromosomal abnormalities in Ph- cells [10]. Moreover, loss of chromosome Y was also common, appearing in 8 patients (in 7 patients as a single abnormality). In addition to these ACAs, we have detected other rare abnormalities, such as +X, +9, +13, +21, add(6)(q27), del(20)(q11), t (4;15)(q31;q26) and t(2;10)(q23;q24). Importantly, the latter two have never been reported by other studies before according to the International Library (https://mitelmandatabase.isb-cgc.org/).

Most reports demonstrated that the presence of ACAs in the Ph-cells is transient. The persistence of these ACAs was documented in less than 30% of patients [8]. Our study also showed that 8 out of 21 patients (38%) carried persistent chromosomal aberrations as demonstrated by subsequent follow-up cytogenetic analyses. These results suggest that ACA in Ph- cells can be persistent.

The prognostic significance of ACAs remains unclear. Some studies have shown that chromosome 7 clonal aberrations are associated with an increased risk of evolution to myelodysplastic syndrome and acute myeloid leukemia [13]. In agreement with these reports and after a thorough follow-up, our patients with persistent monosomy 7 ultimately underwent allogeneic HCT. The significance of -Y in this setting is unclear. It has been reported that this phenomenon is a common occurrence in male individuals with aging, where up to 6% may at some time develop -Y but one of our patients was only 23 years old [14]. It is also reported that this abnormality may be significantly more frequent among patients with hematologic malignancies, suggesting that there might be an element of genetic instability [15]. In the present study, no evidence of myelodysplastic syndrome or acute leukemia was documented.

Furthermore, and in agreement with most reports, we demonstrated that the emergence of ACA’s does not seem to have an effect on the outcome of CML and its treatment plan [6]. Previous studies revealed that patients with ACAs in Ph- cells did not have inferior response to TKI treatment in comparison with patients without ACAs [16]. Similarly, most cases in our present study showed satisfactory responses to TKI treatment (CCyR, MMR, MR^4.5). Sixteen out of 21 patients achieved optimal response. Two patients died, while 3 underwent allogeneic HCT due to the association of their ACAs and the possible evolution to myelodysplastic syndrome or acute leukemia (2 patients with monosomy 7 and 1 with trisomy 8). However, it should be noted that time to CCyR and MMR was significantly longer in patients that received allogeneic HCT (median 33 versus 6 months, and 48 versus 13 months, respectively). The same results were found for patients that had more than 1 ACA (median 27 versus 3 months, and 38 versus 6 months, respectively).

Conclusion

We found ACAs in 10.5% of CML patients treated with TKIs after long term follow up. Beyond previously reported ACAs, we also describe novel ACAs such as add(6)(q27), t (4;15)(q31;q26) and t(2;10)(q23;q24) that have never been reported. The significance of –Y needs to be further elucidated, since our study reports this aberration in rather young patients. Importantly, our study confirms that ACAs do not impact outcomes of CML. However, the potential of cure with allogeneic HCT in patients with monosomy 7, should be kept in mind. Larger cohorts are needed to define the significance of ACAs, since the underlying pathophysiology remains unknown.

Declaration

Acknowledgements: We would like to thank all the personnel of the Cytogenetics and Molecular Biology laboratory for their assistance.

Statement of Ethics: The research was conducted ethically in accordance with the World Medical Association Declaration of Helsinki and in agreement with institutional guidelines. Subjects have given their written informed consent. No further ethics approval was required according to our Institution’s Ethics Committee.

Authorship Contributions: C. Var, A. At and E G: Designed the study, recorded and analyzed the data and wrote the manuscript. G. P, C. Vad, C. L and N.S: Treated the patients and edited the manuscript. A. At, G. P and M. G: Performed cytogenetic analysis. T. T and A. P: Conducted PCR analysis. I. S and A. An: Analyzed the data and edited the manuscript.

References

1. Ren R. Mechanisms of BCR-ABL in the pathogenesis of chronic myelogenous leukaemia. Nat Rev Cancer. 2005; 5: 172-183.
2. Choi SM, Goldenson B, Peterson LA, et al. Diagnostic and therapeutic implications of genetic heterogeneity in myeloid neoplasms uncovered by comprehensive mutational analysis. Leuk Res Rep. 2017; 8: 11-13.
3. Gambacorti-Passerini C, Antolini L, Mahon FX, et al. Multicenter independent assessment of outcomes in chronic myeloid leukemia patients treated with imatinib. J Natl Cancer Inst. 2011; 103: 553-561.
4. Cortes JE, Talpaz M, Giles F, et al. Prognostic significance of cytogenetic clonal evolution in patients with chronic myelogenous leukemia on imatinib mesylate therapy. Blood. 2003; 101: 3794-3800.
5. Athanasiadou A, Stavroyianni N, Salloum R et al. Novel chromosomal aberrations in Philadelphia negative cells of chronic myelogenous leukemia patients on imatinib: report of three cases. Leukemia. 2004; 18: 1029-1031.
6. Deininger MWN, Cortes J, Paquette R, et al. The prognosis for patients with chronic myeloid leukemia who have clonal cytogenetic abnormalities in philadelphia chromosome-negative cells. Cancer. 110: 1509-1519.
7. Ni H, Sun X, Xu Y, et al. Clinical implications of clonal chromosomal abnormalities in Philadelphia negative cells in CML patients after treated with tyrosine kinase inhibitors. Cancer Gen. 2019; 238: 44-49.
8. Jabbour E, Hagop M Kantarjian, et al. Chromosomal abnormalities in Philadelphia chromosome–negative metaphases appearing during imatinib mesylate therapy in patients with newly diagnosed chronic myeloid leukemia in chronic phase. Blood. 2007; 110: 2991-2995.
9. Larsson N, Billström R, Lilljebjörn H, et al. Genetic analysis of dasatinibtreated chronic myeloid leukemia rapidly developing into acute myeloid leukemia with monosomy 7 in Philadelphia-negative cells. Cancer Gen. 2010; 199: 89-95.
10. Bozkurt S, Uz B, Buyukasik Y, et al. Prognostic importance of additional cytogenetic anomalies in chronic myeloid leukemia. Med Oncol. 2013; 30: 443.
11. McGowan-Jordan J, Simons A. An International System for Human Cytogenomic Nomenclature. S Karger AG Basel Switzerland. 2016.
12. Krishna Chandran R, Geetha N, Sakthivel KM, et al. Impact of Additional Chromosomal Aberrations on the Disease Progression of Chronic Myelogenous Leukemia. Front. Oncol. 2019; 9: 88.
13. Bidet A, Dulucq S, Smol T, et al. Poor prognosis of chromosome 7 clonal aberrations in Philadelphia-negative metaphases and relevance of potential underlying myelodysplastic features in chronic myeloid leukemia. Haematologica. 2019; 104: 1150-1155.
14. Pierre RV, Hoagland HC. Age-associated aneuploidy: loss of Y chromosome from human bone marrow cells with aging. Cancer. 1972; 30: 889-894.
15. Wiktor A, Rybicki BA, Piao ZS, et al. Clinical significance of Y chromosome loss in hematologic disease. Genes Chromosomes Cancer. 2000; 27: 11-16.
16. Issa GC, Kantarjian HM, Gonzalez GN, et al. Clonal chromosomal abnormalities appearing in Philadelphia chromosome-negative metaphases during CML treatment. Blood. 2017; 130: 2084-2091.