Epidemiology of adult T-cell leukemia/lymphoma (ATL) in people living with HTLV-1: A 30-year study in Peru

Background Adult T-cell Leukemia/Lymphoma (ATL) is caused by human T-leukemia virus type 1 (HTLV-1). Over 10 million people are infected worldwide, but only up to 5% develop ATL. HTLV-1 infection is endemic in Peru; however, there are currently no reports focusing on the epidemiological characteristics of Peruvian individuals with ATL. Methods Data from the HTLV-1 Unit registry covering the period from June 1992 to November 2023 were retrospectively analyzed. Clinical report forms and histopathology records from national referral cancer centers were reviewed. Descriptive statistics were used to characterize patients, and Kaplan-Meier methods assessed survival by ATL subtype. Findings A total of 116 confirmed ATL cases were identified. There was a slight female predominance, with 52.6% women (n = 61) and 47.4% men (n = 55). The median age at diagnosis was 54 years (IQR 42–61), with 42.2% of patients diagnosed before age 50. Only 13.8% of patients (n = 16) were diagnosed with HTLV-1 infection before ATL development, and only 8 of those were diagnosed through routine screening. The most common ATL subtype was lymphomatous (65.5%), followed by smoldering/chronic (24.1%), and acute ATL (9.5%). With a median follow-up of 15.9 months, median survival times were 6.5, 12.5, and 89.6 months for acute, lymphomatous, and smoldering/chronic subtypes, respectively. One-year survival rates ranged from 37.5% in acute ATL to 84.6% in smoldering/chronic ATL. Comorbid HTLV-1-associated diseases included infective dermatitis (15.5%), HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) (8.6%), and Strongyloides stercoralis hyperinfection (6.9%). Interpretation This is the first study to describe ATL epidemiology in Peru from an infectious disease perspective. Most patients were unaware of their HTLV-1 status before developing ATL, highlighting missed opportunities for earlier detection. Routine HTLV-1 testing should be considered in the evaluation of T-cell malignancies in endemic countries. In addition, screening high-risk populations could support earlier diagnosis and reduce transmission. Improving access to diagnostic tools, along with stronger collaboration between infectious diseases and oncology services could improve patient outcomes in endemic regions.