Purpose: Sinusoidal obstruction syndrome (SOS), also known as veno-occlusive disease, has been described following treatment of acute lymphoblastic leukemia (ALL) with the anti-metabolite 6-thioguanine (6-TG). Previous studies incorporating daily 6-TG into maintenance chemotherapy demonstrated a high incidence of SOS, typically presenting after prolonged exposures to 6-TG. 6-TG continues to be used as a single, 14-day burst during intensification; however, SOS associated with brief courses of 6-TG is poorly described. We aim to describe this rare though clinically significant phenomenon.
Methods: Children with 6-TG-related SOS were retrospectively identified from 680 de novo patients with ALL at Texas Children's Cancer Center over 8 years. Clinical characteristics and outcomes are described.
Results: Ten (1.5%) patients were identified with SOS. No predominant sex, ethnicity, or race was noted. SOS was diagnosed 16.5 (6-42) days from starting 6-TG. Isolated thrombocytopenia (IT) was noted in 9/10 patients and presented a median of 5 days prior to SOS. Refractoriness to platelet transfusions was noted in 8/10 patients, presenting a median of 2 days prior to SOS. Most patients were otherwise clinically stable outpatients upon presenting with IT or transfusion refractoriness. Fever was noted in 7/10 patients at diagnosis and 6/10 had documented or suspected infection within 14 days of SOS. Two patients died, while eight fully recovered. Intermediate thiopurine methyltransferase genotype was noted in 5/8 patients with data available.
Conclusion: SOS following short courses of 6-TG in DI is clinically distinct from SOS following prolonged courses of 6-TG in maintenance, particularly in its early presentation and outcomes.
Keywords: 6-MP; 6-TG; ADR; ALL; SOS; VOD.