Increased prostacyclin biosynthesis in patients with osteoid osteoma.

Osteoid osteoma is a benign osteoid-forming tumor of the bone characterized by pain which is relieved by nonsteroidal anti-inflammatory drugs. Very high levels of prostaglandins have been found in the lesion. In nine patients with osteoid osteoma, prostaglandin E2 (PGE2) and prostacyclin (PGI2) synthesis in explants from the nidus incubated in vitro yielded 947.3 +/- 482.6 (mean +/- SD) and 340.2 +/- 178.1 pg/mg of wet tissue respectively, values 32 and 49 times higher than in fragments of normal bone. In eight patients the excretion rate of the major urinary metabolite of PGI2, i.e. 2,3-dinor-6-keto-PGF1 alpha, was nearly double the control value (499 +/- 93 vs 257 +/- 117 pg/mg of creatinine; mean +/- SD). In six of them, from whom urine was collected 1 month after surgery, urinary 2,3-dinor-6-keto-PGF1 alpha decreased significantly (P less than 0.01) from 487 +/- 100 to 229 +/- 52 pg/mg creatinine. Urinary 6-keto-PGF1 alpha, largely a reflection of intrarenal PGI2 synthesis, was comparable to the control group (4.6 +/- 0.9 vs 4.5 +/- 1.0 ng/h, respectively) and remained unchanged after operation. These results suggest an enhanced PGI2 biosynthesis in vivo in patients with osteoid osteoma. This abnormality of arachidonate metabolism is consistent with enhanced biosynthetic capacity of the tumor in vitro, and is reversible upon its removal.