Tumor Flare Reaction

**Semantic type:** Finding

**Definition:** A side effect of cancer treatment. It has been described in patients with chronic lymphocytic leukemia treated with lenalidomide, breast cancer patients during the initial phase of hormonal treatment, and in prostate cancer patients treated with luteinizing hormone-releasing hormone agonists. Symptoms include a sudden and painful increase in the tumor size, rash, low grade fever, bone pain, hypercalcemia, and an increase in the tumor markers levels.

**Synonyms:** - TFR