Efficacy and safety of tolvaptan in patients with malignant ascites: a phase 2, multicenter, open-label,...

This phase 2 study examined the efficacy and safety of tolvaptan, an aquaretic drug, in the treatment of ascites associated with cancer.

In the dose-escalation phase, oral tolvaptan was initiated at a dose of 3.75 mg/day, and the dose was increased daily to 7.5, 15 and 30 mg/day. Dose escalation was terminated once the increase from baseline in the daily urine volume reached 500 ml, at which point the patient proceeded to the maintenance phase of 5-7 days. Improvement of ascites was determined primarily by reduction in body weight and ascitic fluid volume.

The mean change from baseline in body weight was maintained below 0 kg throughout the study. The mean change (±standard deviation) from baseline in ascitic fluid volume at the end of treatment (EOT) was 237.45 ± 868.14 ml in 33 evaluable patients. Although an increase from baseline in ascitic fluid volume at the EOT was observed in 23 of 33 patients (maximum: 1589.3 ml, minimum: 3.83 ml), a reduction in ascitic fluid volume was observed in the remaining 10 patients (maximum: -2304.3 ml, minimum: -27.5 ml). The common treatment-emergent adverse events included vomiting (5 of 43 patients, 11.6%), abdominal distension, constipation, thirst, blood osmolarity increased and renal impairment (3 of 43 patients, 7.0% each).

Tolvaptan seemed to have no definitive effect on reducing ascites; however, it might be effective in at least some cancer patients. No new safety concerns were identified at doses of 3.75-30 mg/day.