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Overrepresentation of patients from HTLV ‐1 endemic countries among T cell Non‐Hodgkin lymphomas in the Netherlands: an indication of under‐diagnosis of Adult T cell leukaemia/lymphoma

2018; Wiley; Volume: 184; Issue: 4 Linguagem: Inglês

10.1111/bjh.15160

1365-2141

Carla van Tienen, Otto Visser, Pieternella J. Lugtenburg, Graham P. Taylor, Lucy Cook,

Vector-Borne Animal Diseases

Human T cell Lymphotropic Virus type 1 (HTLV-1) is a retrovirus that is found worldwide, with an estimated 10 million people infected. In 5% of infected persons, HTLV-1 causes Adult T cell Leukaemia/Lymphoma (ATL) and in 3% it leads to HTLV-1-associated myelopathy (Verdonck et al, 2007). The diagnosis of ATL can be challenging, especially in areas where it is a less known entity. It is important to distinguish ATL from other T cell lymphomas (T-NHL) as the prognosis for ATL is very poor (4-year overall survival, 5%) (Takasaki et al, 2010) and requires different treatment [allogeneic stem cell transplantation (SCT) for ATL; autologous SCT for peripheral T-NHL] (Phillips et al, 2016). The Netherlands has a large immigrant population from Surinam and the former Netherlands Antilles, where HTLV-1 is endemic. According to the Central Bureau of Statistics (https://www.cbs.nl), approximately 500 000 people live in the Netherlands whose country of birth (or whose parents' country of birth) is Surinam or the former Netherlands Antilles. The HTLV-1 prevalence in these regions is thought to be 2%, and therefore, we estimate that at least 10 000 (500 000 × 0·02) persons living in the Netherlands are HTLV-1 infected (Alberga et al, 1996; Kamphuis et al, 1998). Hence, 7 cases per annum of ATL would be expected in a lifetime (500/70). However, this is not reflected in the Netherlands Cancer Registry (NCR) to which 52 ATL cases were reported between 1994 and 2015, and not the expected 147 cases (7 cases per year for the 21-year observation period). Of these reported ATL cases, 9 were born in the Netherlands and 32 in Surinam. Using the age-specific (15-year age groups) incidence rates of ATL for the population born in the Netherlands and the number of person years per 15-year age group of the population born in Surinam, we calculated a risk ratio (RR) of 328 (95% confidence interval 224–463) for the population born in Surinam. As it is difficult to distinguish between ATL and T-NHL on pathological and immunological grounds, ATL might be under-diagnosed in the Netherlands (Ishitsuka & Tamura, 2014). We thus hypothesized that the incidence of T-NHL is higher among Dutch residents born in HTLV-1 endemic areas than among patients born in the Netherlands. A query was performed on the NCR database for the period 1994–2015 and, using the same method as for ATL, we calculated the expected number of T-NHL diagnoses among the different countries of origin (using the population born in the Netherlands as a reference) and compared this to the observed number (Table 1). For residents born in countries where HTLV-1 is highly endemic or known to circulate, the RR for T-NHL was 1·7–3·2, despite exclusion of ATL cases (European Centre for Disease Prevention and Control 2015). As a control, this analysis was also performed for Hodgkin lymphoma and B cell non-Hodgkin lymphoma, which did not show an increased RR for people born outside the Netherlands (including all countries listed in Table 1). From Table 1, an additional 81 potential cases of ATL might have been identified; adding these to the 52 registered ATL cases, 133 potential ATL cases might have been detected in the 21-year observation period. This number is closer to the expected number of 147 ATL cases. We conclude that persons born in high HTLV-1 endemic countries (Surinam, Netherlands Antilles, Ghana) and countries where HTLV-1 is present are overrepresented among patients diagnosed with T-NHL in The Netherlands, suggesting under-diagnosis of ATL. Further analyses of stored biopsies of these patients are planned to confirm this. This straightforward analysis can easily be applied in other countries and prove helpful in raising awareness for this rare and preventable malignancy.