Phase I Trial of All-Trans Retinoic Acid in Patients with Treated Head and Neck Squamous Carcinoma

Although retinoids show promise for prevention of second primary upper aerodigestive tract tumors, the optimum retinoid, dose, and schedule are unknown. All- trans retinoic acid (ATRA) has greater affinity for retinoic acid receptors and may be more active than other retinoids but has a shorter plasma half life and may up-regulate its own metabolism. We defined the maximum long-term tolerable dose, dosing frequency, pharmacokinetics, and toxicity of ATRA in patients with treated squamous cell carcinoma of the head and neck (SCCHN). Twenty-one patients were randomized to 45, 90, or 150 mg/m 2 ATRA either once daily, or as divided doses every 8 h, for 1 year. Pharmacokinetics were assessed periodically. Fourteen men and seven women with previous SCCHN of initial stage I–IV were treated. Grade≥ 3 toxicities (reversible) included headache and hypertri-glyceridemia in 5 and 6 patients each, mucositis in 2 patients, and hyperbilirubinemia, elevated alkaline phosphatase, colitis, lipasemia, xerostomia, eczema, and arthritis in 1 patient each. The 150-mg/m 2 dose was not tolerable. Doses were reduced for grade ≥3 toxicity in seven of eight patients at 90 mg/m 2 daily. Three of nine patients at 45 mg/m 2 /day required dose reduction, two at the once-daily dose. Day 1 ATRA area under the plasma concentration versus time curve (AUC) increased with dose, and after 1–2 months of continued dosing, the AUC declined in 7 of 13 patients (54%) studied. ATRA AUC did not correlate with toxicity severity or frequency. Fifteen mg/m 2 /day every 8 h is a tolerable dose for 1 year in patients with treated SCCHN. ATRA pharmacokinetics did not correlate with toxicity.