Evoluzione clonale in relazione ai fattori prognostici nella Leucemia Linfatica Cronica

Chronic lymphocytic leukemia (CLL) display a variable clinical behaviour, with many patients living for years without symptoms and other patients requiring early therapeutic intervention attaining short lasting responses and succumbing to their disease in a few years. Several adverse prognostic features have been identified including stage, CD38 positivity, the unmutated configuration of the variable region of the immunoglobulin heavy chain gene (IGHV), ZAP70 positivity, chromosome aberrations and molecular abnormalities. Even though most of CLL patients with favorable prognostic features, i.e. CD38-, mutated IGHV, absence of chromosome lesions or isolated 13q-, live for long periods without any treatment, some cases may show progression to a more aggressive leukemia. The biologic and molecular characteristics predicting disease progression in these patients are unknown. Clonal evolution (CE) was more recently reported in 15–42% of CLLs using conventional karyotyping or fluorescence in situ hybridization (FISH) methods. Besides the classical CLL-associated aberrations, attention was recently devoted to 14q32 translocation involving the immunoglobulin heavy chain gene (IGH). To better define the incidence and significance of CE, including the late appearance of 14q32/IGH translocations, we performed a study including 105 cases of CLL analyzed sequentially at our institution between 1995 and 2004. These patients were submitted to sequential FISH analysis on peripheral blood using a panel of probes for the identification of deletions at 13q14/D13S25, 11q23/ATM and 17p13/TP53, as well as for the detection of trisomy 12 and translocations at 14q32/IGH. Clonal evolution (CE) was observed in 15/105 patients after 24–170 months (median 64). Recurring aberrations at CE were 14q32/IGH translocation in seven patients. CE was detected in 15/58 pre-treated patients; in contrast, none of 47 untreated patients developed CE (p & 0.0001). In two cases the appearance of 14q32/IGH translocation was first detected in the bone marrow (BM) or in the lymph node (LN) and 13–58 months later in the peripheral blood (PB). Shorter time to first treatment (TTT) and time to chemorefractoriness (TTCR) were noted in 15 patients with CE when compared to patients without CE (TTT: 35 vs. 71 months, p=0.0033 and TTCR: 34 vs. 86 months, 0.0046, respectively). Survival after the development of CE was 32 months (standard error 8.5). We arrived at the following conclusions: (i) 14q32/IGH translocation may represent one of the most frequent aberrations acquired during the natural history of CLL and (ii) it may be detected earlier in BM or LN samples; (iii) CE including 14q32/IGH translocation occurs in pre-treated patients with short TTT and TTCR; (iv) survival after CE is relatively short. The heterogeneity in the subclonal architecture of the leukemic cells was suggested to correlate with a poor clinical outcome. In order to better understand the biologic and molecular features predicting disease progression in CLL patients with favorable prognostic features we analized a cohort of untreated CD38- CLL patients with normal FISH or isolated 13q-. We found that, by fluorescence in situ hybridization (FISH), 16/28 cases presented, within immunomagnetic sorted CD38+ cells, genetic lesions undetectable in the CD38- fraction. These patients showed a shorter time to first treatment (TTFT, p=0.0162) in comparison to cases without FISH lesions in CD38+ cells. Patients with FISH abnormalities in CD38+ cells showed a distinctive microRNA profile, characterized by the down-regulation of miR-125a-5p both in the CD38- and CD38+ populations. In an independent cohort of 71 consecutive untreated CD38- CLL with normal FISH or isolated 13q-, a lower miR125a-5p expression was associated with a shorter TTFT both in univariate and multivariate analysis (p=0.003 and 0.016, respectively) and with a higher prevalence of mutations (7/12 vs 0/8, p=0.015) as assessed by next-generation sequencing. In conclusion, our data showed previously unrecognized subclonal heterogeneity within the CD38+ fraction of CD38- CLL patients with low-risk FISH findings and suggested an association between down-regulated miR-125a-5p expression, genetic complexity and worse outcome. Treatment of chronic lymphocytic leukemia (CLL) has dramatically changed over the last years, with significant improvement in overall survival (OS) and increased efficacy in genetically defined “high-risk” disease. Retrospective studies were performed comparing the outcome of patients belonging to different age groups and showing longer survival in patients diagnosed in the most recent periods. Improved outcome derived in part by the introduction of effective regimens in genetically defined “high-risk” disease (i.e., 17p_, 11q_, TP53, NOTCH1, SF3B1 mutations), especially in the younger and/or fit patients. The unfavorable prognostic significance of 11q_ was overcome by chemoimmunotherapy. High-dose steroids with anti-CD52 appeared to improve the response rate in 17p-/TP53 mutated cases and allogeneic transplantation achieved prolonged disease control irrespective of high-risk disease. Further improvement is being generated by the new anti-CD20 obinutuzumab in the elderly and by mechanism-based treatment using kinase-targeting agents or anti-BCL2 molecules yielding high-response rate and impressive progression-free survival in the chemorefractory setting as well as in previously untreated patients. The cost of hemopoietic neoplasms is an issue in highincome countries and the development on novel treatment in CLL is likely to become soon a real challenge for the national health systems. The predicted efficacy of very potent, targeted, and nonchemotherapeutic drugs in CLL along with the development of sensitive predictors of response offer a unique opportunity to intensify coordinated research programmes aimed at providing compelling evidence of the positive cost/efficacy ratio of these novel agents.