Extranodal stage I DLBCL have worse outcome than nodal stage I DLBCL
PET at the end of immunochemotherapy may help select extranodal patients for RT consolidation
This retrospective study aimed to better define the characteristics and outcomes of extranodal stage I DLBCL in the rituximab era. Patients diagnosed with stage I DLBCL from 2001-2015 treated with rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP) or R-CHOP-like regimens with or without radiation (RT) were included. We identified 1955 patients with newly diagnosed DLBCL, of whom 341 had stage I and were eligible for this analysis. Extranodal presentation was observed in 224 (66%) patients, while 117 (34%) had nodal involvement. The most common extranodal sites were bone 21%; stomach 19%; testis 9%; intestine 8%; breast 8%. Overall, 69% extranodal and 68% nodal patients received RT. Median follow-up was 5.5 years (interquartile range 4.3-8.2). 10-year overall survival (OS) and disease-free survival were 77% (95% CI 67%, 83%) and 77% (95% CI 68%, 85%). In the multivariable analyses, extranodal involvement was associated with worse OS (HR 3.44, 95% CI 1.05, 11.30) and progression-free survival (PFS) (HR 3.25, 95% CI 1.08, 9.72) compared to nodal. Consolidation RT was associated with better OS (HR, 0.26, 95% CI 0.12, 0.49) and PFS (HR, 0.35, 95% CI 0.18, 0.69) in the extranodal population; however, the benefit was no longer observed in patients with PET negative at the end of immunochemotherapy. Relapses occurred usually late (median 37 months) and the most common sites were the lymph nodes (31%) and the central nervous system (27%). Extranodal stage I DLBCL had a worse outcome than nodal. End of immunochemotherapy PET results may help select extranodal patients for consolidation RT.