6 Year Experience of Treatment by Imatinib in CML CP Patientsin 6 Million Population Region of Russia(Saint-Petersburg and Leningrad region)with Impact On Time and Kind of Pretreatment.

There are 335 pts with CML in databases in Saint-Petersburg and Leningrad region. Most of them (283/335-84,5%) are ever treated with IM. Disease phases at the time of the start of IM therapy by ELN (from 268/283 evaluable pts) and MDACC (from 256/283 evaluable pts) criteria were: CP – 232 and 215, AP – 28 and 33, BP - 8 and 8 respectively. All 232 pts in CML CP (by ELN criteria) treated since 2001 by IM were included in the study. Before IM 91/232(39%), 114/232(49%) and 17/232 (7,3%) pts were pretreated by hydroxyurea, interferon-alfa with or without hydroxyurea and busulfan. 12/335(4%) pts were undergone alloSCT(6 alive, 6 dead due to progression or TRM)

There were 134/232(58%) pts in early (duration before Im ≤ 12 mos) and 98/232(42%) pts in late CP (> 12 mos). In early and late CP, there were 49/123 and 50/89, 40/123 and 23/89, 34/123 and 16/89 evaluable pts with low, intermediate and high Socal score respectively. The predominance of low Sokal score in late CP pts could to be related to survival benefit before imatinib.. The median time before Im for the whole group, for early and late CP pts were 7,4 mos(from 7 days to 132 mons), 1,8 mons (form 7 days to 12 mons) and 39 mons (from 12,1 mos to 132 mos) respectively. Median time of Im therapy was 33 mos (1 - 75 mos) in whole group, 24mons (1 - 73mos) in early and 34mos(2 - 75mos) in late CP pts respectivel

Estimated overall survival by 6 years was 94,2% in whole group, 97% and 87% in early and late CP pts resp. Only 14/228(6,1%) of evaluable patients died due to CML: 4/130(3%) in early and 10/98(10,2%) in late CP group. 4 pts, resistant to IM, were transplanted: 1 in early CP and 3 in BP. Deathes were due to TRM or disease progression.

CHR was achieved by 3 mons in most cases: 82/110(74,5%) and 36/64(56%) pt, in early and late CP, resp. Patients (39 in hole group, 12 in early and 27 in late CP) with CHR before IM were excluded from these analyses.

The probability of CCyR by 6 years was 98% in early CP and 82% in late CP (p=0.002). The rate of CCyR was 75% 80/107) vs 31% (14/75) in patients with or without CHR by 3 mons (p=0.00). The same differences were found in early and late CP. CCyR in patients with CHR before IM was the same as in patients with newly obtained CHR by 3 mons on IM.

Thereafter we have divided group of pts with late CP according to its duration before IM (very early -<6mons, early late - 6-60 mons and very late ≥60 mons) and compared CCyR in early CP with different subgroups of late CP.

Achievement of CCyR was higher in pts in very early(69.1%) and early –late(68.2%) than in very late group(34.6%)(p=0.09) Further subdivisions of the period of 6-60 mos did not reveal any differences. Moreover, when we deleted the patients pretreated with busulfan, the differences were found only between early and early-late phases. We have separately analyzed very late group, it appeared that pretreatment with busulfan severely decreases CCyR (22% vs 81% in with (12 pts) or without (7 pts) busulfan pretreatment, p=0,002. Probably, patients in very late CP is a specific group of patients with preformed very good prognosis.

Clonal evolution before treatment (8 pts in early CP and 7 in late CP) did not influence CCyR achievement.

The probability of progression to AP/BP was slightly higher in late (6%) than in early CP (3%) (p=0.05). The appearance of clonal evolution was higher in late than in early CP (p=0,0002). Progression to AP/BP was 1% vs 11% in pts with or without CHR by 3 mos resp. (p=0.003).

Imatinib is efficacious drug in general hematological practice with very high probability of overall survival, CCyR and low risk of progression to AP/BP. CHR is an early and very important predictor for further successful treatment. Achievement of CCyR strongly depends on CHR by 3 mons. Patients with CHR before imatinib have similar CCyR in patients with CHR by 3 mons on imatinib. Pretreatment period predispose patients to clonal evolution on imatinib treatment. Busulfan pretreatment severely decreases probability of CCyR.

No relevant conflicts of interest to declare.