ALBERT

Description: Background: MPNs including Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF), are clonal hematopoietic diseases in which the discovery of molecular driver mutations (JAK2, CALR, MPL) has deeply modified diagnostic approach in recent years. To date available data on epidemiology of MPNs and perspective analysis are rare. Our aim is to study the incidence of MPN Ph negative in a specific region of Italy named Latium and its variability across five years. Moreover we prospectively report the general features of our population. Method: We present here the prospective epidemiologic analysis of 1116 adult patients affected by MPNs (PV=289, ET=550, PMF=209) diagnosed according to 2008 WHO criteria, from January 2011 to December 2015 in 15 hematological Centers (5 academic and 10 community-based Hospitals) in Latium. A total of 289 PV, 550 ET and 209PMF were identified. The overall incidence rate of 289PV was 1.0/105 in 2011 and 2012, 1.1/105 in 2013, 0.9/105 in 2014 and 2015. The overall incidence rate of 550ET was 2.0/105 in 2011, 2.4/105 in 2012, 2.2/105 in 2013, 1.8/105 in 2014 and 1,2/105 in 2015 and the overall incidence rate of 209PMF was 0.7/105 in 2011 and 2012, 1.0/105 in 2013, 0.7/105 in 2014 and 0.5/105 in 2015. We have observed also 63 cases of MPNu (36M/32F) and the incidence rate was 0.3/105 in 2011 and 2012, 0.14/105 in 2013, 0.24/105 in 2014 and 0.22/105 in 2015. Baseline features of PV, ET and PMF patients are summarized in table 1. We have also analyzed the presence of comorbidities including obesity, arhythmia and neoplasia observed at the diagnosis in 1.6, 6.2 and 4% of all population, respectively; thirty-five percent of 1116 pts presented other comorbidities such as diabetes, inflammatory bowel disease, renal and liver failure. As thrombotic risk factors we considered diabetes, dislipidemia, smoke, essential hypertension and thrombophilia observed in 11,8, 16,2, 13,2, 51,7 and 3% of total pts, respectively. Conclusions: We confirm in our prospective observational protocol the overall incidence of MPN Ph negative, previously reported in the literature and the major incidence of male gender in PV and PMF, female in of ET. The annual incidence from 2011-2015 in Latium is remained substantially the same during the observation period. The decreasing trend observed in 2015 is probably due to the different update of some Centers that was done in October 2015 not including patients diagnosed in the last two months. Disclosures Latagliata: Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria; Janssen: Consultancy, Honoraria; Shire: Honoraria. Breccia:Pfizer: Honoraria; Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria; Ariad: Honoraria. Cimino:Celgene: Honoraria; Bristol-Mayer: Honoraria.

Description: Key Points INTERIM treatment affects cytogenetic and molecular response, but not the outcome. No patients treated with INTERIM progressed to accelerated or blast phase.

Description: Introduction. Chronic myeloid leukemia (CML) patients (pts) treated with imatinib first line achieve complete cytogenetic response (CCyR) in 〉 70% of cases and major molecular response (MMR) in 18-58%. These pts have a life expectancy similar to the general population. However even undetectable BCR-ABL may not equate to eradication of the disease because of the sensitivity of Q-RT-PCR. A new diagnostic method, the digital-PCR (dPCR), able to detect 1 BCR-ABL+ cell out of 107 cells, has been recently developed (Goh HG et al., 2011). dPCR corresponds to a 100 fold increase in sensitivity as compared to Q-RT-PCR. Therefore, dPCR by assessing the presence of minimal residual disease with higher sensitivity, could potentially identify pts in whom CML has been eradicated. Aims. The Imatinib Suspension And Validation (ISAV) study is aimed at validating the capability of dPCR to predict relapses after imatinib discontinuation in CML pts with negative Q-RT-PCR results. Methods. This study involves 15 sites, 10 in Italy and 1 in each of the following countries: Germany, Spain, The Netherlands, Canada and Israel. CML pts (Chronic or Accelerated Phase) under imatinib therapy since more than 2 years and in complete molecular remission (CMR) were eligible for this study. Patients had to be in CMR for at least 18 months (mts), with a minimum of 3 Q-RT-PCR performed at their own sites. After signing the informed consent, blood samples are obtained for dPCR and the pts discontinue imatinib therapy. Standard Q-RT-PCR is performed monthly (mts 1-6) and then bimonthly for 36 mts to assess the maintenance of the molecular remission. The loss of molecular remission is defined as two consecutive positive Q-RT-PCR tests with at least one BCR-ABL/ABL value above 0.1%. Patients losing molecular remission resume imatinib treatment at the same dosage used before interruption. Patients’ quality of life during imatinib discontinuation/resumption is evaluated through the EORTC – C30 Quality of Life questionnaire. Results. The enrolment in ISAV began in November 2011 and ended in July 2013. The study enrolled 112 pts: Italy 69.6%, Germany 21.4%, Canada 5.3%, Spain 2.6% and Israel 0.9%. Among the 112 pts, 59.3% were male and 37.0% were aged 65 or older; median duration of imatinib treatment was 103.1 mts with median duration of CMR of 25.8 mts before imatinib discontinuation. To date, the median follow-up (FUP) time is 16.6 mts [95% CI: 14.9-18.2]. Forty-seven pts (43.5%, 95% CI: 34.0-53.4) of the 108 eligible pts relapsed and resumed imatinib; 38/47 (80.9%) of them relapsed in the first 9 mts and the last relapse occurred 19.6 mts after imatinib discontinuation. A loss of CCyR occurred in 11 pts (23.4%): 10/11 CCyR losses were recovered; 1 patient withdrew the consent shortly after obtaining a partial cytogenetic response. No case of CML progression was observed. After the resumption of imatinib the median time to either MMR or CMR was 1.9 [95% CI: 1.2-2.4] mts. Of the 61 not-relapsed pts, 43 (39.8% of the total) regained Q-RT-PCR positivity but never lost MMR. The median time to Q-RT-PCR positivity was 3.6 mts [95% CI: 3.0-4.8] and the range of duration of Q-RT-PCR positivity (below 0.1%) was between 5.7 and 29.2 mts. No significant correlation between relapse and previous duration of imatinib treatment, use of interferon, time to CCyR or duration of CMR was identified. An inverse relationship between pts age and risk of relapse is evident: 90% of pts 〈 45 years relapsed vs 37.5% in the class ≥ 45 - 〈 65 years and 27.5% of pts ≥ 65 years, p(χ2)

Description: Background Thrombotic episodes are the major complication in the follow-up of Philadelphia negative Myeloproliferative Neoplasms (MPN), with high morbidity and mortality, as reported in several retrospective studies. At present, however, few prospective data are available on the early incidence of these complications. Methods To address this issue, we report on 1087 patients [M/F 508/579, median age 67.6 years, interquartile range (IQR) 55.2 - 75.9] with newly diagnosed MPN enrolled in the prospective database of our regional cooperative group since January 2011. Of them, 571 (52.5%) had Essential Thrombocythemia (ET), 303 (27.9%) Polycythemia Vera (PV) and 213 (19.6%) Primary Myelofibrosis (PMF). The main clinical features at diagnosis of the whole cohort and according to the different MPNs are reported in the Table 1. Results On the whole, 22 episodes of thrombotic complications were reported in 1087 patients (2.0%) at a median interval from diagnosis of 18.2 months (IQR 7.4 - 29.7): in particular, 15 (68.1%) were arterial (8 cerebral, 2 coronaric, 4 in the lower limbs, 1 splancnic) and 7 (31.9%) venous (5 in the lower limbs and 2 in the upper limbs). As to the incidence of early thrombosis in the different MPNs, they were 13/571 (2.2%) in ET patients, 5/303 (1.6%) in PV patients and 4/213 (1.8%) in PMF patients (p=0.810): median time from diagnosis to thrombotic event was also similar in the 3 MPNs (p=0.311). The 4-year cumulative Thrombosis-Free Survival (TFS) of the whole cohort was 97.3% (95%CI 96.0 - 98.6): there was no difference among the 3 MPNs as to 4-year TFS [96.7% (95%CI 94.8 - 98.6) in ET, 97.8% (95%CI 95.9 - 99.7) in PV and 98.7% (95%CI 96.9 - 100) in PMF, respectively, p=0.668). Several clinical features at diagnosis (age, gender, Hb levels, WBC and PLT counts, spleen enlargement, JAK-2 V617F mutation and previous thrombotic events) were evaluated for a role in predicting thrombotic events: only age (p=0.009) and previous thrombotic events (p=0.009) were significant. Conclusions The incidence of early thrombosis seems low in the first 4 years after diagnosis of MPN based on our prospective database, without any difference among ET, PV and PMF: it is worth of note that only age and previous thrombotic events had a predictive role, thus confirming many retrospective reported data and reinforcing the prognostic value of old scoring system for thrombotic risk in MPN. Table 1 Table 1. Disclosures Breccia: Ariad: Honoraria; Pfizer: Honoraria; Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria. Latagliata:Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria; Janssen: Consultancy, Honoraria; Shire: Honoraria.

Description: Introduction. Eltrombopag is an oral, non-peptide thrombopoietin receptor agonist that has been shown efficacy and safety in chronic immune thrombocytopenia (ITP) patients not responding to previous therapy , by raising the platelets count in both continued long-term administration and in a repeated short-term administration. However, when eltrombopag is discontinued, platelet counts usually return to baseline within 2 weeks. As reported in different case series only 15 % of patients achieve a durable response after treatment discontinuation. The aims of this study was to evaluate the efficacy and safety of eltrombopag given at a dose of 25 mg every 3 days as maintenance therapy in responding patients after an initial standard dose of 50 mg orally once daily. Methods. A total of 7 consecutive adult patients, female (70 %), median age 47 years (range 28 - 79) were enrolled in the study. Patients had ITP for a median of 3.5 years and had failed a median of four prior therapies. Splenectomy was not taken into account because contraindicated or refused. All patients received eltrombopag 50 mg by mouth once a day as induction treatment .A complete blood count was performed at baseline, on day 5, then weekly for 28 days, every 2 weeks during maintenance. Complete Response ( CR) was defined as platelet count ≥ 100 * 10^9/L measured on two occasions 〉 7 days apart and the absence of bleeding. Relapse Free Survival (RFS) was considered to be from the day of initial response until relapse (Plt

Description: Background and rationale In chronic myeloid leukemia (CML) about half of patients (pts) achieving a deep and stable molecular response (MR) with tyrosine kinase inhibitors (TKIs) may discontinue TKI treatment without disease recurrence. As such, treatment free remission (TFR) has become an ambitious goal of treatment. Given the evidence that deepness and duration of molecular response are necessary but not sufficient requisites for a successful TFR, additional biological criteria to possibly identify more and better CML patients suitable for an efficacious discontinuation are today focus of research in CML. Leukemia stem cells (LSCs) are supposed to be the reservoir of disease. We first showed in a cross-sectional study including 112 pts in TFR for a median of 31 months (mos) that residual circulating CD34+/CD38-/CD26+ CML-specific LSCs were still detectable in the majority of CML pts despite stable and deep molecular response. This evidence suggested that the level of BCR-ABL transcript only may not reflect the actual residual CML LSCs burden and that there could be a "threshold" of LSCs predicting a successful TFR. Aims To further study the behavior of residual LSCs during TKI discontinuation we designed a prospective multicentered study (AIRC IG 20133 study) in which we monitored circulating CD26+ LSCs in CML pts from the time of TKI discontinuation until molecular relapse. Methods CML pts meeting the current molecular criteria for TKI withdrawal entered this multicenter study. At TKI stop (baseline) and at +1, +2, +3, +6, + 12 mos after discontinuation and at any time if molecular relapse, CML pts were evaluated for peripheral blood number of CD34+/CD38-/CD26+ LSCs by centralized flow-cytometry analysis and for BCR-ABL transcript level by standard (IS) quantitative RT-PCR assay. Results 49 consecutive CML pts were enrolled in the study so far. Pts characteristics at diagnosis, type of TKI, disease response and treatment duration before discontinuation are shown in Tab. 1. After a median time of 7 mos since TKI stop (range 1-24), 13/49 (26.5%) pts lost their molecular response and restarted TKI treatment. Median time to relapse after discontinuation was 4 mos (range 2-7). 36/49 (73.4%) pts are still in TFR after a median time of 7.5 mos (range 1-24). If considering a cut-off of 6 mos from discontinuation as the period with higher risk of relapse, 14/36 pts actually in TFR have discontinued treatment for ≤ 6 mos (range 1-6) while 22/36 pts are in TFR for a median of 10 mos (range 7-24). Regarding residual CML LSCs evaluation, at baseline 23/49 (46%) pts had still measurable circulating CD26+LSCs with a median number of 0.0204µ/L (range 0.0077-0.1197), while 26/49 (54%) had no detectable CD26+ LCSs. Considering the small number of molecular relapses no statistical difference in number of residual CD26+ LSCs at time of discontinuation was shown between pts losing vs maintaining TFR (13 pts median CD26+ LSC 0.0237/µ/L, range 0-0.1197 and 36 pts median CD26+ LSCs 0.0204/µ/L, range 0-0.1039, respectively). However, the number of pts with undetectable CD26+ LSCs at baseline was 6/13 (45%) and 20/36 (55%) in the two subgroups, respectively. Considering subsequent time points, the 13 relapsed pts showed a small yet progressive increase of residual CD26+ LSCs number until molecular relapse, while the 36 pts in TFR showed a fluctuation of CD26+ cells number. However, Kendall rank correlation coefficient, Mood test and bi-linear relation model of the whole cohort showed no correlation between BCR-ABL/ABLIS ratio and number of residual CD26+ LSCs either at baseline or at each time points after discontinuation, thus confirming our previous observations. Conclusions Yet very preliminary our results showed that CD26+ LSCs are detectable at time of TKI discontinuation and during TFR. Moreover, at least for the observation median time of the study (7.5 mos) the persistence of "fluctuating" values of residual CD26+ LSCs do not hamper the possibility to maintain a stable TFR. Due to the short follow up and the small number of molecular relapsed pts we could not find a threshold of CD26+ LSCs predictive of TFR loss. Our data may suggest other factors then LSCs "burden" to play an active role in controlling disease recurrence. Additional studies evaluating CD26+ LSCs ability to modulate the immune system through a variable expression of immune response inhibitory molecules and through their interactions with effectors cells are ongoing. Table Disclosures Bocchia: Novartis: Honoraria; Incyte: Honoraria; BMS: Honoraria. Pregno:Bristol Myers Squibb: Honoraria; Incyte: Consultancy, Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Abruzzese:Incyte: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; BMS: Consultancy. Crugnola:Novartis: Honoraria; Incyte: Honoraria. Iurlo:Pfizer: Honoraria; BMS: Honoraria; Incyte: Honoraria; Novartis: Honoraria. Galimberti:Roche: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Speakers Bureau. Liberati:Bristol & Mayer: Honoraria; Takeda: Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria.

Description: Background The efficacy and safety of subsequent TKIs in pts who have experienced failure of dasatinib is not fully known. Ponatinib, a pan-BCR-ABL inhibitor, was evaluated in a phase 2, international, open-label clinical trial (PACE). This post-hoc analysis explored the efficacy and safety of ponatinib following failure of dasatinib in CP-CML pts in the PACE trial. Methods The PACE trial enrolled 449 pts, including 270 with CP-CML. Pts had to be resistant or intolerant to dasatinib or nilotinib, or they had to have the T315I mutation at baseline. The primary endpoint in CP-CML was major cytogenetic response (MCyR) at any time within 12 months after treatment initiation. The trial is ongoing. Data as of 1 April 2013 are reported, with a minimum follow-up of 18 months for pts remaining on study. The efficacy and safety of ponatinib (45 mg QD) in 107 CP-CML pts following failure of dasatinib as the most recent prior therapy, irrespective of other TKI therapy, is presented (Group D). Eighteen pts who experienced failure of dasatinib but received ≥1 anticancer therapy, other than hydroxyurea or anagrelide, prior to ponatinib treatment were excluded from the analyses. Data are also presented for 2 subsets of Group D: 52 pts whose only TKI therapy was imatinib followed by dasatinib (Group I-D), and 46 pts whose only TKI therapy was imatinib, then nilotinib, and then dasatinib (Group I-N-D). An analysis of cross-intolerance was also conducted in 69 pts with prior dasatinib treatment at any time who discontinued dasatinib due to intolerance. Results Baseline characteristics are shown in the table. Group I-D tended to be younger, with less time since diagnosis versus Group I-N-D. At the time of analysis, 60%, 65%, and 54% of pts in Groups D, I-D, and I-N-D remained on study. The most common reasons for discontinuation were adverse events (AEs; 16%, 15%, 17%) and progressive disease (9%, 6%, 11%) in Groups D, I-D, and I-N-D. Efficacy end points are shown in the table. In Group D, MCyR was seen in pts with the following dasatinib-resistant mutations at baseline: V299L, 3/4 (75%); T315I, 17/23 (74%); F317L, 3/10 (30%). The most common treatment-related AEs were thrombocytopenia (44%, 37%, 57%), rash (39%, 39%, 39%), and dry skin (39%, 29%, 52%) in Groups D, I-D, and I-N-D. Serious cardiovascular, cerebrovascular, and peripheral vascular AEs occurred in 6%, 3%, and 3% of pts in Group D (treatment-related: 3%, 1%, 0%). Seventy-three of 217 pts receiving prior dasatinib at any time discontinued dasatinib due to intolerance. Of these 73 pts, 27 experienced the same AE(s) with ponatinib that led to dasatinib intolerance; 12 pts had grade 3/4 thrombocytopenia, 6 pts had other grade 3/4 AEs (3 with neutropenia, 1 each with pleural effusion, dyspnea, pulmonary hypertension), 8 pts had grade 1/2 AEs. Six of these 27 pts discontinued ponatinib due to the same AE that led to dasatinib intolerance. Thrombocytopenia was the primary AE involved in cross-intolerance (4 pts); congestive cardiac failure (grade 5) and pleural effusion each occurred once. Conclusions Ponatinib has substantial activity in pts with CP-CML following failure of dasatinib, with a safety profile reflective of this heavily pretreated population. Cross-intolerance between dasatinib and ponatinib was infrequent. Disclosures: Hochhaus: Ariad, Novartis, BMS, MSD, Pfizer: Research Funding; Novartis, BMS, Pfizer: Honoraria. Cortes:Ariad, Pfizer, Teva: Consultancy; Ariad, BMS, Novartis, Pfizer, Teva: Research Funding. Kim:BMS, Novartis,IL-Yang: Consultancy; BMS, Novartis, Pfizer,ARIAD,IL-Yang: Research Funding; BMS, Novartis,Pfizer,IL-Yang: Honoraria; BMS, Novartis,Pfizer: Speakers Bureau; BMS, Pfizer: Membership on an entity’s Board of Directors or advisory committees. Pinilla-Ibarz:Novartis, Ariad: Research Funding; Novartis, Ariad, BMS and Pfizer: Speakers Bureau. le Coutre:Novartis: Research Funding; Novatis, BMS, Pfizer: Honoraria. Paquette:ARIAD, BMS, Novartis: Consultancy, Honoraria, Speakers Bureau. Chuah:Novartis, Bristol-Myers Squibb: Honoraria. Nicolini:Novartis, Ariad and Teva: Consultancy; Novartis & Bristol Myers Squibb: Research Funding; Novartis, BMS, Teva, Pfizer, Ariad: Honoraria; Novartis, BMS, Teva: Speakers Bureau; Novartis, Ariad, Teva, Pfizer: Membership on an entity’s Board of Directors or advisory committees. Apperley:Novartis: Research Funding; Ariad, Bristol Myers Squibb, Novartis, Pfizer, Teva: Honoraria. Talpaz:Ariad, BMS, Sanofi, INCYTE: Research Funding; Ariad, Novartis: Speakers Bureau; Ariad, Sanofi, Novartis: Membership on an entity’s Board of Directors or advisory committees. DeAngelo:Araid, Novartis, BMS: Consultancy. Abruzzese:BMS, Novartis: Consultancy. Rea:BMS, Novartis, Pfizer, Ariad, Teva: Honoraria. Baccarani:Ariad, Novartis, BMS: Consultancy; Ariad, Novartis, BMS, Pfizer, Teva: Honoraria, Speakers Bureau. Müller:Novartis, BMS, Ariad: Consultancy, Honoraria; Novartis, BMS: Research Funding. Gambacorti-Passerini:Pfizer: Research Funding; Pfizer, BMS: Honoraria. Lustgarten:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc Other, Employment. Rivera:ARIAD: Employment. Clackson:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc Other, Employment. Turner:ARIAD: Employment. Haluska:ARIAD: employees of and own stock/stock options in ARIAD Pharmaceuticals, Inc Other, Employment. Deininger:BMS, ARIAD, NOVARTIS: Consultancy; BMS, NOVARTIS, CELGENE, GILEAD: Research Funding; ARIAD, NOVARTIS: Advisory Boards, Advisory Boards Other. Hughes:Novartis, BMS, ARIAD: Honoraria, Research Funding. Goldman:Ariad: Honoraria. Shah:Ariad, Bristol-Myers Squibb: Consultancy, Research Funding. Kantarjian:RIAD, Novartis, BMS, Pfizer: Research Funding.

Description: Abstract 3375 Introduction. Telomere are effective sensors of cell integrity and their accelerated shortening is a marker of genetic and/or proliferative stress in several tissues including the hematopoietic compartment. Severe telomere attrition has been indeed observed in aplastic anemia and post-transplant setting. Little is currently known on the genetic integrity of Ph-negative hematopoietic cells (HCs) repopulating the bone marrow (BM) after successful chronic myeloid leukemia (CML) treatment. We thus decided to verify whether severe telomere shortening might occur in this setting and to assess whether its presence might correlate to genetic and functional impairment of Ph-negative hematopoiesis. Patients and methods. We investigated 81 CML patients with persistent (≥12 months) complete cytogenetic remission (CCyR). Median age was 62 years (23-88), M/F ratio was 1.5. Median time from diagnosis and CCyR were 4 years (1-18) and 3 years (1-12) respectively. 15 patients had acquired cytogenetic abnormalities (CA) (del7: 4 patients, +8: 5 patients, del5q: 2 patients, del or +Y: 2 patients, other CA: 2 patients). Telomere length (TL) analysis was performed by Southern Blotting on polymorphonucleates (PMN) and on monocyte-depleted PBMC (MD-PBMC) to monitor both the myeloid and lymphoid compartments. As control group we analyzed 76 age-matched healthy donors. Prospective follow-up monitoring of TL was performed on 56 CML patients with a median time of 22 months from the first determination (range 12–20). Results. PMN (but not MD-PBMC) from CML patients showed a major erosion of their telomeric DNA (median loss 1294 bp p

Description: Although the success of imatinib mesylate therapy represents an exciting advance in targeted cancer therapy, it has still to be determined whether responses to this p210 inhibitor in chronic myeloid leukemia (CML) patients will be durable. In fact most of clinical studies agree on the evidence of a persistent molecular disease in the majority of treated patients and altough the absolute level of bcr-abl transcript may vary over the treatment, yet a molecular complete response is of rare observation. In addition, discontinuation of imatinib exerts always in rapid loss of response. In accordance to this the persistence of malignant progenitors in patients in complete cytogenetic response (CCR) after short term imatinib treatment, has been recently demonstrated. In particular, Bathia et al. showed in 12/15 patients studied after a median time of 10 months of imatinib treatment a median of 11% of residual CML CD34+ progenitors in the bone marrow (by FISH Dual Fusion bcr/abl analysis)while only 3/15 patients had no detectable residual CD34+ cells. Less is known about residual Ph+/CD34+ cells surviving after a prolonged therapy with this targeting drug. Thus, we evaluated the amount of bone marrow residual CD34+ cells in 17 CML patients in stable CCR after a long lasting treatment with imatinib. At the time of evaluation, the patients were on conventional dose (400mg) Imatinib for a median time of 48 months (range 36–58 months) having achieved a CCR status (conventionally defined as the complete absence of t(9;22) on caryotypic analysis) within 3 to 6 months of treatment. However all of them still showed molecular disease as detected by nested RT-PCR. Bone marrow CD34+ cell-enriched populations were selected from mononuclear cells using immunomagnetic column separation and were evaluated after cytospin by FISH using a bcr-abl Dual Color Extra Signal Probe(LSI bcr-abl ES, Vysis), that is able to detect bcr-abl fusion in interphase nuclei with a false positive signal rate close to 0. A minimum of 100 CD34+ nuclei per each sample were evaluated. Interestingly, in 8/17 patients no Ph+/CD34+ cells were detected, while in the remaining 9/17 patients a median of 2% (range 0.5–11%) of bcr-abl positive progenitors were still observed. In this small selected serie of patients prolonged treatment with imatinib appears to be correlated with a lower, yet detectable, amount of residual bone marrow Ph+/CD34+ cells when compared to previously published data. This result could be partly explained with the different specificity and sensitivity of the probe used (bcr/abl ES

Description: Introduction: Pregnancy requires, and is an important motivator of tyrosine kinase inhibitor (TKI) cessation in patients with chronic myeloid leukemia (CML). While conventional treatment free remission (TFR) attempts may allow observation of limited rise in BCR-ABL prior to expected TKI re-exposure, TKI cessation in pregnancy affords longer observation of BCR-ABL kinetics without automatic TKI re-exposure. Mathematical models and clinical observation of BCR-ABL kinetic rise during TKI discontinuation or planned cessation estimate of 'doubling time' (DT) of roughly 9 days (Branford et al., Blood 2012). In order to explore the impact of pregnancy, we studied BCR-ABL kinetics and response stability during and after pregnancy. Methods: We collected cases of successful pregnancies (conception-〉childbirth) at 4 CML referral centers including the following conditions: 1/conception occurring while on TKI therapy; 2/TKI therapy stopped for the purpose of conception; and 3/ pregnancy during TKI cessation within a TFR clinical trial. Cases with early spontaneous/elective abortion, treated with interferon during pregnancy or with less than 2 BCR-ABL transcripts recorded during pregnancy were excluded. Doubling time (DT) was calculated using the following formula: DT = ln2/k, where k = (ln(b)-ln(a))/d, where (a) and (b) is the value before the rise and at the rise, and (d) is days. Results: In total 50 pregnancies in 39 patients were analyzed; 10 patients had 〉1 pregnancy. Four pregnancies were in the context of TFR study (2 enrolled at conception, 1 patient 28mo in TFR, 1 patient 5mo in TFR). The majority of cases were on first-line treatment at TKI cessation and median duration of TKI therapy was 6.4 years (range 0.5-16.2); 58% were in deeper molecular response (MR4 or deeper) and 34% in major molecular response (MMR) at TKI cessation. Patient characteristics are summarized in Table 1. Median time off TKI was 10.1 months (range 5.4-71.5). Of 44 pregnancy cases within MMR or deeper at TKI cessation, 54.5% maintained MMR or greater; 60.7% of those in MR4 or deeper and 43.7% for those in MMR, respectively. Several cases were associated with decline in BCR-ABL off TKI: 2 cases of improvement from MMR to deep MR (MR5), and among 4 cases not in MMR at TKI cessation, 1 achieved MMR during pregnancy (Table 2). BCR-ABL rise in 2 or more consecutive measurements, and at least one measurement of rise defined as more than 2-fold increase, was observed in 24 patients. The median BCR-ABL doubling time among 54 such instances in these 24 patients was 18.3 days (range 1.8-306.8). Of 20 cases that lost MMR during pregnancy, 17 met these criterions for BCR-ABL rise; the median doubling time among 40 such instances in these cases was 14.7 days (1.8-306.8). Postpartum (n=48), 34 cases have been retreated to date; 14 others remain off therapy with ongoing deep MR (MR5) in 6 cases, MMR in 6 and BCR-ABL