Chronic Myeloid Leukemia in Adolescents and Young Adults Treated with Generic Form of Imatinib in Resource Limited Setting: A Single Center Experience from Myanmar

Chronic myeloid leukemia (CML) is an acquired myelo-proliferative disorder characterized by the presence of BCR-ABL1 fusion transcript with deregulated tyrosine kinase activity. Leukemias are one of the leading causes of cancer related deaths in adolescents and young adults (AYA) particularly in resource limited countries. Recent democratic government in Myanmar holds supportive policies for treatment of cancers in younger population and subsidizes some therapies including imatinib mesylate, a selective BCR-ABL 1 tyrosine kinase inhibitor, although there is still limitation for cytogenetic and molecular monitoring of therapy. This study on response to imatinib in newly diagnosed chronic phase CML was carried out during January 2016 to February 2018 at the North Okkalapa General and Teaching Hospital of Yangon, Myanmar where molecularly confirmed new CML in chronic phase were treated with generic form of imatinib bought by hospital tender system, Unitinib (United Biotech (P) ltd. India) followed by cytogenetic analysis of bone marrow and molecular detection of BCR-ABL1 transcript from peripheral blood by in house real time PCR machine at one year. They are divided into AYA (aged 15-39 years) and adult age groups (40 years and older) and clinical parameters and response to treatment with imatinib 400mg per day were compared. Among 56 cases (median age of 39.5 years, male to female ratio of 1.5:1), half were AYA (28 of 56) with median age of 28.5 years compared to 50 years in adult group with higher male to female ratio of 3.6:1 in AYA group. Patients in AYA had larger spleen size (11 vs 5.5 cm) and higher median white cell count compared to adults (366 x 10⁹/l vs 224 x 10⁹/l) although initial platelet count, peripheral blood eosinophil, basophil and blast percent and Sokal score were comparable. Additional chromosomal abnormalities were detected in 2 AYA and 3 adults with CML. There was no difference in complete haematologic response at 3 and 12 months between AYA and adults (96.4% vs 96.4% and 92.9% vs 89.3% respectively). At 12 months, complete cytogenetic response of AYA at 67.9% was less than 75.0% of adults, it was statistically not significant. Using in house molecular method although not standardized, 14.3% of AYA and 32.1% of adults were molecularly undetectable at one year. The response of AYA to imatinib in this study was comparable to adults despite having adverse prognostic features and receiving only generic forms of treatment in resource limited setting and it would further help support from authorities for leukemia in younger population.