Clinical characteristics of methotrexate-associated lymphoproliferative disorders: relationship between absolute lymphocyte count recovery and spontaneous regression

Several reports have shown that patients with rheumatoid arthritis (RA) are at increased risk of developing lymphoproliferative disorders (LPD). Methotrexate (MTX) has been recognized as a major cause of LPD. Sometimes spontaneous regression (SR) occurs after withdrawal of MTX. Recent studies suggest that the early recovery of the absolute lymphocyte count (ALC) after withdrawal of MTX is associated with the spontaneous regression of MTX–LPD. We retrospectively analyzed 26 patients with MTX–LPD to identify predictive factors for spontaneous regression. The spontaneous regression after withdrawal of MTX occurred in 13 of 26 (50%) cases. We assessed the ALC at the time of MTX cessation and 1 month after cessation in 23 evaluable cases. The spontaneous regression was observed in 3 of 11 in the ALC recovery group (27%) and in 8 of the 12 in the ALC non-recovery group (67%). Thus, we could not detect any relationship between the recovery of ALC after withdrawal of MTX and the spontaneous regression. The patients in the ALC recovery group had a poorer prognosis than those in the ALC non-recovery group (2-year overall survival: 65.6 vs. 100%, p = 0.05). According to these results, the recovery of the ALC might not be useful as a predictor of the spontaneous regression. Furthermore, the existence of extranodal sites and advanced-stage were associated with non-SR. It is suspected that MTX–LPD patients with high disease activity at the time of their diagnosis might have little hope of spontaneous regression. This result indicated the importance of the early detection of MTX–LPD.