Low-Dose Dasatinib as Front-Line Therapy for Elderly (> 60 Years) Patients with CML

Dasatinib is a tyrosine kinase inhibitor that has 325-fold greater in vitro activity against native BCR-ABL (breakpoint cluster region-Abelson leukemia virus) compared with imatinib and can overcome primary (intrinsic) and secondary (acquired) imatinib resistance. A phase III dose optimization study showed that in patients with chronic phase (CP) chronic myeloid leukaemia (CML), dasatinib at 100 mg once daily improved the safety profile while maintaining efficacy compared with the previously recommended dose of 70 mg twice-daily. Few data exist on the efficacy and safety of dasatinib in elderly CML patients.

The aim of the study was to evaluate the impact of dose reduction on dasatinib efficacy.

We revised 129 unselected pts with CP CML aged >60 yrs treated in 21 Italian haematological Institution, who received dasatinib after being resistant/intolerant to imatinib. Among this group 70 pts were given dasatinib at adjusted-dosage below the standard recommended dose of 100 mg daily for > 6 months. In relation to the dose modulation, patients were divide in 2 groups: group-a (21/70, 30%) received a starting dose of 20 mg daily dose excalated to the maximum tolerated dose of 70 mg daily; group-b (49/70=70%) received a starting dose of 100 mg daily, successively adhusted according to tolerance. Sokal score was evaluable for 59/70 patients (low for 16, intermediate for 28, high for 15). All patients were analyzed for haematological, cytogenetic and molecular response.

All patients were fully evaluable for response at a median FU time of 25 mos (range 0,7- 56,3 mos). Eight pts (11.4%) discontinued treatment due to intolerance. Response rates were 25,7% (18pts), 24.3% (17 pts), 15.7% (11 pts), 10% (7 pts), 12.8% (9 pts) for complete haematologic response (RHC), complete cytogenetic response (RCyC), major molecular response (RMolM), complete molecular response (RMolC), partial cytogenetic response (RCyP), respectively. Median Cumulative event free survival (EFS) and overall survival (OS) were 21.3 and 27.3 mos respectively. We did not observe any significative difference in term of response between group A and B receiving different doses. Interestingly, 3/9 patients in group A who had a transient loss of molecular response achieved major molecular response after dose escalation to 50 mg.

Dasatinib given at a lower dose than currently recommended is still effective in elderly CML patients. However, more close molecular monitoring is advised when lower doses are prescribed. Studies in larger series are warranted to better define optimal dose and schedule of dasatinib in this frail patient population.

Rosti: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol Myers Squibb: Honoraria, Speakers Bureau; Roche: Speakers Bureau.