The Spectrum of FIP1L1-PDGFRA-Associated Chronic Eosinophilic Leukemia

Fanny Legrand, Aline Renneville, Elizabeth MacIntyre, Samuel Mastrilli, Felix Ackermann, Jean Michel Cayuela, Philippe Rousselot, Aline Schmidt-Tanguy, Olivier Fain, Marc Michel, Jean-Pierre de Jaureguiberry, Pierre-Yves Hatron, Pascale Cony-Makhoul, Didier Lefranc, Damien Sène, Vincent Cottin, Mohamed Hamidou, Olivier Lidove, André Baruchel, Sylvain Dubucquoi, Olivier Bletry, Claude Preudhomme, Monique Capron, Lionel Prin, Jean Emmanuel Kahn

Imatinib is the treatment of choice for FIP1L1/PDGFRA (F/P)-associated chronic eosinophilic leukemia (F/P CEL), but its optimal dosing, duration, and possibility of discontinuation are still a matter of debate. A retrospective multicenter study was conducted with 44 F/P CEL patients identified in the French Eosinophil Network and treated with imatinib. The most frequently involved systems were skin (57%), spleen (52%), and lung (45%), and eosinophilic heart disease was observed in 15 patients (34%). Complete hematologic response (CHR) was obtained in all patients, and complete molecular response (CMR) in 95% of patients (average initial imatinib dose, 165 mg/d). For 29 patients the imatinib dose was tapered with a maintenance dose of 58 mg/d (±34 mg/d), allowing sustained CHR and CMR. None of the patients developed resistance during a median follow-up of 52.3 months (range, 1.4-97.4 mo). Imatinib was stopped in 11 patients; 6 of the patients subsequently relapsed, but 5 remained in persistent CHR or CMR (range, 9-88 mo). These results confirm that an initial low-dose regimen of imatinib (100 mg/d) followed by a lower maintenance dose can be efficient for obtaining long-term CHR and CMR. Our data also suggest that imatinib can be stopped in some patients without molecular relapse.