T-cell lymphoblastic leukaemia: The Johannesburg state-sector experience

Background: T-cell lymphoblastic leukaemia (T-ALL) is a malignancy of immature T-cells which is reported to comprise 7% – 23% of cases of lymphoblastic leukaemia (ALL), making up a larger proportion of adult ALL than childhood cases. It is characterised by an increased risk for early relapse but reportedly has superior outcomes as compared to B-cell ALL amongst adult patients. The frequency and clinical behaviour of T-ALL in Africa are unknown.Aim: This study aimed to assess the prevalence and selected clinicopathological features of T-ALL in Johannesburg, South Africa (SA).Setting: The Johannesburg state sector.Methods: All cases of ALL diagnosed by flow cytometry in the state-sector hospitals of Johannesburg over 42 months between 2016 and 2019 were identified and pertinent data recorded from the laboratory information system.Results: One hundred and eighty-one cases of ALL were identified, of which 59 (32.6%) were of T-cell lineage. The proportion of adult and paediatric ALL made up by T-ALL was similar (19/54 [35.2%] vs 40/127 [31.5%] respectively). Crude survival rates were very poor, with 80.0% having demised at the time of data collection. The mortality rate was overall significantly poorer amongst patients with T-ALL (80.0%) as compared to those with B-ALL (53.8%; p = 0.005) but was similarly poor in adults with B-ALL (83.3%) vs T-ALL (86.7%) (p = 0.53). The mortality rate did not differ between those with low-risk versus high-risk clinical features (77.8% vs 80.6%; p = 1.00).Conclusion: T-cell lymphoblastic leukaemia makes up a larger proportion of ALL in Johannesburg than is reported elsewhere, and it is a high-risk disease that is not well stratified by conventional risk factors.