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

## TL;DR

This study examines the 30-year epidemiology of adult T-cell leukemia/lymphoma in Peru, revealing that most patients were unaware of their HTLV-1 infection until developing cancer.

## Contribution

The first detailed epidemiological study of ATL in Peru, emphasizing missed opportunities for early HTLV-1 detection and the need for routine testing in endemic regions.

## Key findings

- Most patients were unaware of their HTLV-1 status before developing ATL.
- Lymphomatous subtype was the most common, with smoldering/chronic subtype having the highest survival rate.
- Comorbid HTLV-1-associated diseases included infective dermatitis, HAM/TSP, and Strongyloides stercoralis hyperinfection.

## Abstract

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.

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.

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%).

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.

Human T-leukemia virus type 1 (HTLV-1) is a virus that infects immune cells and causes a lifelong infection. Discovered more than 40 years ago, it is common in several regions of the world, including parts of South America, the Caribbean, Africa, and Japan. HTLV-1 can be transmitted from person to person through breastfeeding, sexual contact, and blood transfusion. Most people living with HTLV-1 do not experience symptoms or complications. However, a minority develops serious conditions. The most strongly associated diseases include HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a chronic and debilitating neurological disorder that causes progressive weakness in the lower limbs; and adult T-cell leukemia/lymphoma (ATL), an aggressive cancer with a very poor prognosis. There is currently no cure for HTLV-1 infection and no effective treatment for its complications beyond supportive care. Despite its clinical impact, HTLV-1 continues to receive limited public health attention. Here, we describe the epidemiological characteristics of patients diagnosed with ATL over 30 years at the main HTLV-1 referral center in Peru, a country with high HTLV-1 endemicity. We found that most patients did not know they were infected with HTLV-1 until they developed ATL. This highlights the urgent need to raise awareness and expand access to HTLV-1 testing, particularly in endemic settings.