Intraperitoneal radioimmunotherapy of refractory ovarian carcinoma utilizing iodine-131-labeled monoclonal antibody OC125.

Refractory epithelial ovarian cancer is generally confined to the peritoneal cavity and is thus amenable to intraperitoneal (ip) therapy. Radiolabeled monoclonal antibodies raised to tumor-associated antigens offer the promise of selective tumor irradiation while reducing toxicity to normal tissues. We have conducted a phase I therapeutic trial to examine the feasibility of ip radioimmunotherapy utilizing escalating doses of 131I-labeled OC125 F(ab')2. Twenty-nine patients were each treated with a single dose of radiolabeled antibody. Twenty-eight patients were evaluable for dose-related toxicity. The toxicities most frequently observed were hematologic and gastrointestinal. Hematologic toxicity was noted in 5/14 (36%) patients receiving 18-87 mCi and in 12/14 (71%) receiving 100-144 mCi (P = 0.018). The median white blood cell nadir of 2-3K/microliters (range, 1.4-3.5K/microliters occurred at a median of 4.5 weeks and the median platelet nadir of 41K/microliters (range, 20-78K/microliters) at a median of 6.5 weeks. Mild gastrointestinal toxicity was observed in 4/14 patients (28%) at doses less than 100 mCi whereas at doses greater than or equal to 100 mCi, 11/14 (79%) patients developed nausea, vomiting, or chronic ileus (P = 0.021). This toxicity occurred most frequently in patients with protracted urinary 131I excretion. We conclude that 131I-labeled OC125 can be safely administered ip. Hematologic and gastrointestinal toxicity is predictable and related to the dose and rate of clearance of isotope.