Low T3 syndrome is a strong prognostic predictor in diffuse large B cell lymphoma.

The aim of this study was to evaluate the prognostic effect of low triiodothyronine (T3) syndrome on patients with diffuse large B cell lymphoma (DLBCL). A hundred and eighty-eight patients with detailed thyroid hormone levels at diagnosis of DLBCL were enrolled. Low T3 syndrome was defined as a low serum free T3 (FT3) level with low or normal serum free tetraiodothyronine (FT4) and thyroid stimulating hormone levels. Multivariate Cox regression analysis was used to screen prognostic factors associated with progression-free survival (PFS) and overall survival (OS). Receiver-operator characteristic curves and the corresponding areas under the curve were calculated to assess the predictive accuracy of International Prognostic Index (IPI) and low T3 syndrome. Twenty-four patients were diagnosed with low T3 syndrome, which was associated with worse PFS and OS in the rituximab era. It was an independent prognostic factor for PFS and OS, especially for those with IPI 0-2, extranodal sites ≤1 and stage III-IV. Synchronously low FT3 and FT4 had poorer survival outcome compared to only low FT3 and adding criterion of low T3 syndrome improved the prognostic capacity of IPI for predicting PFS and OS in DLBCL. Low T3 syndrome was found to be a strong prognostic predictor in DLBCL.