An Eastern Cooperative Oncology Group Phase I trial of all-trans-retinoic acid and interferon-alpha: E2Y92

The Eastern Cooperative Oncology Group conducted a Phase I trial to determine the maximally tolerated doses of combination therapy with alpha interferon (IFN-α) and all-trans-retinoic acid (tRA). Fifty patients with incurable malignancies received IFN-α administered subcutaneously three times weekly, and tRA administered by mouth at bedtime. Doses were escalated between patient groups, starting at tRA dose level of 45 mg/m² and 3 million units of IFN-α. Major, dose-limiting toxicities were attributable to either the tRA (rash, chelitis) or IFN (constitutional symptoms), and were observed only at tRA dose levels of 224 mg/m² and 291 mg/m², or 6 million units of IFN-α. The maximally tolerated dose level of 172.5 mg/m² of tRA and 3 million units of IFN-α was well-tolerated, with no grade 3 or 4 toxicities attributable to therapy. One patient at the third dose level (75 mg/m² of tRA and 3 million units of IFN-α) developed acute hepatic and renal failure and a metabolic encephalopathy of unclear etiology. We conclude that tRA and IFN-α may be safely administered together at the maximally tolerated dose of tRA as a single agent without unexpected side effects. The recommended doses of IFN-α and tRA for Phase II trials are 3 million units of IFN-α and 172.5 mg/m² of tRA.