Cohorts of 3-6 patients receive escalating doses of celecoxib until the maximum tolerated dose (MTD) and biologically active dose (BAD) are determined. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience dose-limiting toxicity (DLT). The BAD is defined as the maximum decrease in the level of PGE_2 where no DLT occurs.