Objective: Cis-platinum and 13-cis-retinoic acid have received much attention in the treatment of head and neck squamous cell cancer. Even though they have different mechanisms of action, little information is available on their interaction. This paper reviews experimental evidence for retinoic acid-cis-platinum synergy and presents toxicity data from patients with stage IV head and neck squamous cell cancer participating in a phase I trial combining 13-cis-retinoic acid and cis-platinum.
Methods: Patients were given 13-cis-retinoic acid orally daily for 7 days before and daily during high-dose (150 mg/m2 per week for 4 weeks) intraarterial cis-platinum treatment with concurrent radiation. Toxicity was scored with use of the cancer and leukemia group B scale.
Results: In the phase I clinical trial, 15 patients were treated to determine a maximum tolerated dosage for 13-cis-retinoic acid of 20 mg/day. Grade 4 hematologic toxicity was dose limiting in 3 of 8 patients treated with 40 mg/day and in 1 patient treated with 60 mg/day. There were no deaths caused by toxicity; 12 of the 15 patients received all four weekly doses and the remaining 3 received three doses. Of 10 patients with fully evaluable data, all achieved a complete response at the primary site and 9 had a complete response in the neck. One patient had persistent neck disease after chemoradiation, and this tumor was removed with neck dissection.
Conclusions: 13-Cis-retinoic acid and cis-platinum are strongly synergistic against head and neck squamous cell cancer in vitro. Pretreatment with retinoic acid results in stronger synergy than concurrent drug exposure alone. Preliminary clinical experience with combined retinoic acid and cis-platinum in a design that parallels the in vitro study indicates that toxicity is acceptable with 13-cis-retinoic acid dosages of 20 mg/day in a high-dose-intensity intraarterial chemoradiation regimen.