[Aggressive tumor progression during immunosuppressive therapy with abatacept]. / Une progression tumorale fulgurante sous abatacept.

INTRODUCTION: Co-stimulatory molecule cytotoxic T-lymphocyte antigen-4 (CTLA-4) inhibits T-cell activation. Clinically, CTLA-4 has been targeted in opposite ways: its blockade enhances antitumor immunity in the field of oncology, whereas CTLA-4 agonists such as abatacept are used for the treatment of immuno-inflammatory diseases as rheumatoid arthritis (RA). OBSERVATION: We herein report the case of a 69-year-old man with a history of severe RA successfully treated with abatacept, who showed unusually rapid progression of undifferentiated multi-metastatic carcinoma. DISCUSSION: Although no significant increase in malignancy has been reported in abatacept-treated patients, several case reports have documented the possible association with the acceleration of the progression of malignancy. Here, abatacept may have altered immune surveillance and hence allowed tumor growth.