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Combining Imatinib-Following-Nilotinib Treatment in First Line Therapy for Chronic Phase Chronic Myeloid Leukemia. Update from the PhilosoPhi34 Study at 24 Months of Follow-up


 Background Chronic Myeloid Leukemia (CML) is a clonal myeloproliferative disorder which molecular base is represented by the bcr-abl fusion gene, encoding for the constitutionally activated BCR-ABL tirosine-kinase. Three Tirosin-Kinase Inhibitors (TKI) are approved for first line treatment: Imatinib (IM) and the second generation (2G) TKI Nilotinib (NIL) and Dasatinib. 2G TKI are known to provide faster and deeper molecular responses (MR) compared to Imatinib, but serious toxicities may hamper long term treatment with these molecules. Furthermore, 2G TKI were usually employed as second line after IM failure, while the inverse sequence from second to first generation TKI (like an induction-maintenance model) has not been explored yet.
 We used this schedule in a small group of patients in the PhilosoPhi34 study (EudraCT: 2012-005062-34), a clinical trial designed by the REL (Rete Ematologica Lombarda) cooperative group. This study was composed by three consecutive phases: a Recruitment Phase, a Core Phase (CP) in which patients received NIL 300 mg BID for 12 month (mos), and an Observational Phase (OP), restricted for patients who obtained at least complete cytogenetic response at the end of the CP. During OP, treatment choice was up to the physician and any TKI approved for first line treatment could be used, including IM.
 In 2017 we presented preliminary data showing that a 12-mos-NIL treatment followed by IM appears as a safe and effective choice for first line therapy in chronic phase CML.
 Fluctuations in BCR/ABL ratio were similar between IM and NIL treated pts, and the probability of loss of MR4 or MR3 was the same in the two groups; furthermore, despite fluctuations, MR was maintained or improved over time in IM subgroup. Our purpose is to verify these data after 24 mos follow up (FU) at the end of OP.
 Methods We analyze PhilosoPhi34 database; MR is reported at 3, 6 and 12 mos during the CP and every 6 mos during the OP. The last pt completed the 24 mos of OP in June 2018. Database is still open, evaluations ongoing, and some data can be missing yet: our preliminary observations concern pts with available data of 24 mos OP.
 Results Seventy-nine pts started the OP. Fourteen pts switched to IM during the OP (Table 1) due to high cardiovascular risk or grade 1-2 chronic AEs . Only 11 pts started IM since the beginning of OP, and we consider these pts in our analysis. Sokal score was high in 2 pts (18%), intermediate in 5 (45.5%), low in 4 (36.5%). At the beginning of OP, 6 pts had a MR ≥ 4 (54.5%), 5 had MR3 (45.5%). At 12 mos of the OP, 7 had MR ≥ 4, 3 had MR3 and 1 had lost MR3 with PCR 0.192%IS (1/5, 20%). At 24 mos of the OP, 9 had MR ≥ 4 (81,8%), and 2 had MR3. Notably, none of pts lost MMR; 2/3 pts(66%) improved response from MR 3 to MR 4 and the pt who transiently lost MMR at 12 mos, recovered it at 24. Sixty-four pts maintained 2G TKI: 62 NIL, 2 other TKI (not considered for analysis). Of them, 4 were lost during this phase: 2 within the first year of OP, other 2 within 12 and 24 mos of OP.
 In the NIL group, Sokal score was high in 10 pts (16.6%), intermediate in 19 (31.6%) and low in 31 (51.6%). At the beginning of OP, 32 pts had MR ≥ 4 (51.6%), 21 had MR3 (33.8%) and 9 less than MR 3 (14.5%). Responses were improved over time: at 12 mos, 36 pts had MR ≥ 4 (60%), 20 had MR3 (33%) and 4 less than MR3 (6%). At 24 mos 46 pts had MR ≥ 4 (78%), 8 MR3 (13.5%) and 4 less than MR3 (8,5%), Among them, 1 pt experienced disease progression due to a mutation.
 In particular, during the second year of OP, 11 pts improved response from MR3 to MR ≥ 4(11/20, 55%).
 Discussion Our data show progressive MR improvement in both IM and NIL group. In particular, risk of loss of MMR is not increased in IM group. More data, more balanced groups and a longer FU are necessary to further confirmations, but after three years of FU, we consider this combination of NIL-followed-by-IM a possible strategy for first line treatment in chronic phase CML, in particular for pts with cardiovascular risk factors.
 
 
 
 Rossi: Janssen: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees; Teva: Membership on an entity's Board of Directors or advisory committees; Mundipharma: Honoraria; BMS: Honoraria; Sandoz: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees.
