Treatment intensity significantly influencing fibrosis in bone marrow independently of the cytogenetic response: meta-analysis of the long-term results from two prospective controlled trials on chronic myeloid leukemia

Myelofibrosis at diagnosis is associated with the failure of treatment-free remission in CML patients

The management of patients with chronic myeloid leukemia (CML) has been revolutionized by the introduction of tyrosine kinase inhibitors (TKIs), which induce deep molecular responses so that treatment can eventually be discontinued, leading to treatment-free remission (TFR) in a subset of patients. Unfortunately, leukemic stem cells (LSCs) often persist and a fraction of these can again expand in about half of patients that attempt TKI discontinuation. In this study, we show that presence of myelofibrosis (MF) at the time of diagnosis is a factor associating with TFR failure. Fibrotic transformation is governed by the action of several cytokines, and interestingly, some of them have also been described to support LSC persistence. At the cellular level, these could be produced by both malignant cells and by components of the bone marrow (BM) niche, including megakaryocytes (MKs) and mesenchymal stromal cells (MSCs). In our cohort of 57 patients, around 40% presented with MF at diagnosis and the number of blasts in the peripheral blood and BM was significantly elevated in patients with higher grade of MF. Employing a CML transgenic mouse model, we could observe higher levels of alpha-smooth muscle actin (α-SMA) in the BM when compared to control mice. Short-term treatment with the TKI nilotinib, efficiently reduced spleen weight and BCR::ABL1 mRNA levels, while α-SMA expression was only partially reduced. Interestingly, the number of MKs was increased in the spleen of CML mice and elevated in both BM and spleen upon nilotinib treatment. Analysis of human CML-vs healthy donor (HD)-derived MSCs showed an altered expression of gene signatures reflecting fibrosis as well as hematopoietic support, thus suggesting MSCs as a potential player in these two processes. Finally, in our cohort, 12 patients qualified for TKI discontinuation, and here we observed that all patients who failed TFR had BM fibrosis at diagnosis, whereas this was only the case in 25% of patients with achieved TFR, further supporting the link between fibrosis and LSC persistence.

Increased megakaryocytic proliferation, pro-platelet deposition and expression of fibrosis-associated factors in children with chronic myeloid leukaemia with bone marrow fibrosis

Paediatric chronic myeloid leukaemia (ped-CML) is rare and ped-CML with fibre accumulation in the bone marrow (MF) is thought to be even rarer. In adults (ad-CML), fibrosis represents an adverse prognostic factor. So far, the pro-fibrotic changes in the bone marrow microenvironment have not been investigated in detail in ped-CML. From a total of 66 ped-CML in chronic phase, biopsies were analysable and 10 had MF1/2 (MF1, n=8/10; MF2, n=2/10). We randomly selected 16 ped-CML and 16 ad-CML cases with and without fibrosis (each n=8) as well as 18 non-neoplastic controls. Bone marrow samples were analysed with a real-time PCR-based assay (including 127 genes for paediatric cases) and by immunohistochemistry. We found increased expression of megakaryocytic genes in ped-CML. The number of megakaryocytes and pro-platelets are increased in CML patients, but the most significant increase was noted for ped-CML-MF1/2. Anti-fibrotic MMP9 expression was lower in children than in adults. Cell mobilisation-related CXCL12 was decreased in young and adult patients with CML but not the corresponding receptor CXCR4. In summary, fibre accumulation in ped-CML-MF1/2 is associated with increased megakaryocytic proliferation and increased interstitial pro-platelet deposition. Deregulated expression of matrix-modulating factors shifts the bone marrow microenvironment towards fibrosis.

Bone marrow fibrosis may be an effective independent predictor of the 'TKI drug response level' in chronic myeloid leukemia

OBJECTIVES

The aim of this study was to assess bone marrow (BM) fibrosis and dysplasia in chronic myeloid leukemia (CML) patients receiving the first-generation tyrosine kinase inhibitor (TKI), imatinib, or second-generation TKIs, dasatinib, and nilotinib. We further investigated whether CML under TKI is associated with dysplastic BM changes during the clinicopathological course of the disease.

METHODS

In total, pre-treatment BM paraffin blocks of biopsy specimens were available for 41 adult patients diagnosed with chronic phase CML. Post-treatment BM aspirate clot and core biopsy samples were reviewed for fibrosis and dyshematopoiesis.

RESULTS

Overall, 13 (31.7%) patients achieved a complete cytogenetic response with imatinib treatment, with no events. In 25 patients, imatinib was discontinued owing to primary or secondary resistance. In patients with initial dysmyelopoiesis, the rate of BM fibrosis was 82.4 versus 47.6% for other patient groups (P = 0.02). Overall, 24 patients with newly diagnosed CML showed marrow fibrosis, among which 19 (79.1%) had imatinib resistance. However, only 5 out of 15 patients (33.5%) without marrow fibrosis had imatinib resistance (P = 0.08). Discussion Our findings indicate that BM fibrosis is an independent predictor of the 'TKI drug response level' in CML and support its inclusion as a critical pathobiological parameter for decision-making with regard to TKI drug selection de novo, calculation of prognosis at the onset of disease, and monitoring response to TKI in the long-term disease course of CML.

Assessment of fibrosis and vascularization of bone marrow stroma of chronic myeloid Leukemia patients treated with imatinib mesylate and their relationship with the cytogenetic response

Chronic Myeloid Leukemia (CML) is a myeloproliferative disease characterized by the presence of the Philadelphia chromosome (translocation between chromosomes 9 and 22), resulting in the formation of the hybrid BCR-ABL protein. Currently, the treatment of CML patients is performed with imatinib mesylate (IM), which promotes the elimination of leukemic cells by inhibiting the kinase activity of BCR-ABL. This study evaluated the effectiveness of IM by monitoring 22 CML patients in a chronic phase treated at the CEPON/SC with IM for a minimum follow-up period of two years. Cytogenetic Response (CR) and bone marrow biopsies (BMB) were evaluated before and after IM treatment. BMB were evaluated by detection of reticulin degree and vascularization. The results were correlated to the CR. Mean time to achieve CR was 9 months and was attained by 77.27% of the patients. The results from the initial BMB analysis showed that 59.09% presented reticulin of between 2+ and 4+ whereas after treatment, only 27.17% presented this degree. With regard to vascularization of the initial sample, 90.91% were graded between II and IV, whereas after treatment, 40.91% had this degree. The results suggest a positive correlation of degree of reticulin and vascularization with CR.

Marrow fibrosis and its relevance during imatinib treatment of chronic myeloid leukemia

In chronic myeloid leukemia (CML), imatinib may reverse bone marrow fibrosis (MF). Whether the unfavorable prognosis of MF is also reversed and whether imatinib guarantees against evolution of MF are unclear as yet. Fifty-nine patients with Ph+ CML treated with > or = 400 mg imatinib/day were examined for MF in 6- to 12-month intervals. Imatinib effectively reversed initial MF (P<0.0005). However, during a follow-up period of up to 4.8 years, small foci with abnormal fiber increase (FFI) emerged in 8 of 30 pretreated and 6 of 29 non-pretreated patients. Patients with FFI showed a significantly lower probability of achieving a complete cytogenetic or major molecular response (36 versus 81%; P<0.007). During the further follow up, 57% of patients with FFI but none of the other patients suffered from full-blown MF (P=0.00005). None of the patients with FFI or MF showed a Janus kinase-2 mutation (V617F). Evolutions of FFI and MF were independent significant predictors of imatinib failure (P=0.0031), accelerated phase and death of patients (P=0.0001; multivariate analyses). Imatinib effectively reverses initial MF in CML, but neither eliminates its unfavorable prognosis nor guarantees completely against new evolution of MF.

Diagnosis and quantification of bone marrow fibrosis are significantly biased by the pre-staining processing of bone marrow biopsies

AIMS

Marrow fibrosis (MF) is an unfavourable, often lethal complication of haematological neoplasms. Although biopsy technique and staining procedure are standardized, the prestaining processing of bone marrow biopsies (BMBs) varies markedly without any existing data on its significance for the diagnosis of MF.

METHODS AND RESULTS

In this study on 712 BMBs from 296 patients with chronic idiopathic myelofibrosis (CIMF), chronic myeloid leukaemia (CML), or healthy bone marrow, MF was a characteristic complication of CML and CIMF. However, diagnosis and quantification of MF and detection of its prognostic significance were significantly biased by fixation, decalcification, embedding, marrow tissue shrinkage during biopsy processing and the thickness of marrow sections (P < 0.000005). The relevance of these influences was explained by their effect on the marrow volume to which the fibre content was related, whereas the stainability of fibres was not affected. Semiquantitative grading of fibrosis and measurements of fibre density could not be adjusted to various methods of processing of bone marrow biopsies (P < 0.003).

CONCLUSIONS

Evaluations of MF and its prognostic significance should consider the bias due to the prestaining processing of BMBs and the necessity of an adjustment to the thickness of tissue sections and the degree of marrow tissue shrinkage.