Epidemiology, Clinical Features, and Outcome of HTLV-1-Related Adult T-Cell Leukemia/Lymphoma in Latin America: A Study from the Latin American Group of Lymphoproliferative Disorders (GELL)

INTRODUCTION: Adult T-cell leukemia/lymphoma (ATLL) is a mature peripheral T-cell neoplasm caused by the Human T-cell Leukemia Virus Type 1 (HTLV-1). HTLV-1 infects up to 10 million people worldwide and is most endemic in Southwestern Japan, the Caribbean basin, South America, and Western Africa. In Latin America (LA), Peru and Brazil have the highest prevalence of HTLV-1-related diseases, however, data on ATLL in other LA countries is scarce. ATLL carries a dismal prognosis and is essentially incurable by conventional drugs. We describe the epidemiology, clinical features, treatment, and disease outcome of ATLL encountered in 11 countries in LA.

METHODS: We retrospectively analyzed patients (pts) diagnosed with ATLL between January 1995 and December 2019. ATLL cases were classified according to the Shimoyama criteria into acute (A), lymphomatous (L), chronic (C) and smoldering (S). Treatment approaches used as first-line therapy were: 1) chemotherapy alone; 2) combined chemotherapy with zidovudine/interferon-alpha (AZT-IFN); and 3) AZT-IFN alone, as previously done with Miami cohort (Malpica and Ramos et al. Blood Advances 2018). Treatment response was assessed according to Tsukasaki et al. (JCO 2009) criteria. To be classified as complete response (CR), partial response and stable disease, these had to persist for a period of at least 4 weeks. Survival curves were estimated using the Kaplan-Meier method and Log rank test.

RESULTS: A total of 253 pts with ATLL were identified. Two hundred twenty six pts (L=122, A=73, C=26, S=5) had sufficient data for analysis. Demographic and clinical features are shown in Figure 1 and Table 1. Median age at diagnosis was 57 years, with a female predominance in A (58%) and S (100%) types. Most ATLL pts were from Peru (n=159, 63%) followed by Chile (n=44, 17%), Argentina (n=20, 8%) and Colombia (n=17, 7%). B symptoms were high present in A, L and C types (73%, 72%, 58% vs. 8% S type, respectively, p=0.011). Hypercalcemia was highly associated with A type (57% vs. L 27%, p=0.014). The PIT score yielded to a more aggressive risk classification compared to the IPI score (high-risk: 55% vs. 29%, respectively, p<0.001). Strongyloidiasis (n=5) and pneumocystis jirovecii pneumonia (n=5) were the most commonly observed co-infections at diagnosis. Commonly affected extranodal sites other than bone marrow in all subtypes were skin 25% (n=63) and liver 9% (n=24). The therapy approach used during the first 2 therapy evaluations are summarized in Table 2. The median survival (MS) times were 4.3 months, 7.9 months, 21.1 months, and not reached for A, L, C and S form, with 4-year survival of 8%, 22%, 40% and 80%, respectively (Figure 2). First-line AZT-IFN resulted in overall response (OR) rate of 63% (CR 24%) for A (n=8) and 75% (CR 50%) for L (n=8), respectively (Table 3). The OR rates after first-line multi-agent chemotherapy alone for A vs. L were 21% (CR 8%) and 41% (CR 29%), respectively (Table 3). The most commonly used regimens were CHOP/CHOP-like (n=117, 59%) and CHOEP (n=40, 20%) regimens with OR rates of 29% (CR 12%) and 60% (CR 42%), respectively (Table 3). Progression-free survival (PFS) rates in pts with aggressive ATLL who achieved CR after chemotherapy vs. AZT-IFN (alone or in combination with chemotherapy) were 2.8 months vs. 30.4 months for A (n=8) type and 67.1 months vs. 17.7 months for L (n=30) type, respectively (Figure 3). Only 2 pts with L type underwent allogeneic hematopoietic stem cell transplant (allo-HSCT) with PFS of 12 and 17 months (Table 4).

CONCLUSION: ATLL continues to carry a dismal outcome with conventional therapies thus urging the development of novel approaches. Our study found that Latin American ATLL variant presents at a younger age, has a female predominance, high incidence of L type, low incidence of indolent types and lower survival rates, suggesting that Latin American ATLL variant presents earlier and more aggressively than in Japanese pts. AZT-IFN produced durable responses in A type patients who achieved CR as compared to chemotherapy alone. Chemotherapy responses were more durable in L types who achieved CR as compared to A type. In conclusion, in the management of aggressive ATLL, chemotherapy remains the preferred choice for L type (with consideration of allo-HSCT upfront), while AZT-IFN is a good option to attempt for A type upfront.