Long term follow up study and prevention of ATL occurrence among HTLV-1 carriers : a nationwide cohort study

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There are still 1.0 million HTLV-1 carriers in Japan. Definitive risk factors for ATL development from carrier status remain unclear. To investigate viral- and host-specific determinants of the development of ATL among HTLV-1 carriers. A nationwide cohort study for HTLV-1 carriers named the Joint Study on Predisposing Factors of ATL Development (JSPFAD) comprising of 41 institutions. Participants were HTLV-1 carriers who provided written informed consent. HTLV-1 proviral load (VL) and sIL-2R were measured annually. Demographic characteristics and clinical data were also collected annually. We evaluated 1218 HTLV-1 carriers (426 males and 792 females) who were enrolled during 2002-2008. VL at enrollment was significantly higher in males than females (median, 2.10 vs 1.39 copies/100PBMC), in those aged 40-49 and 50-59 yrs than that of those aged &lt ; 40 yrs (P=0.02 and 0.007, respectively), and in those with a family history of ATL than those without the history (median, 2.32 vs 1.33 copies/100PBMC) (P=0.005). During follow-up as of September 2009, 14 participants progressed to overt ATL. Their baseline VL was high (range, 4. 17-28.58 copies/100PBMC). None developed ATL among those with a baseline VL lower than &lt ; 4 copies/100PBMC. Multivariate Cox analyses indicated that not only a higher VL but also advanced age, family history of ATL, and first opportunity for HTLV-1 testing during treatment for other diseases were independent risk factors for progression of ATL from carrier status