Background: Alterations in retinoid signaling appear to be involved in the pathogenesis of small cell lung cancer (SCLC). Fenretinide [N-(4-hydroxyphenyl)retinamide], a synthetic retinoid, inhibits the growth of SCLC cells in vitro via the induction of apoptosis. Since these data suggested that SCLC is the adult solid tumor that is most susceptible to fenretinide, a trial to evaluate the clinical activity of fenretinide in patients with SCLC was considered the definitive test of its clinical potential in adult oncology.
Methods: Patients with progressive SCLC after one or two prior chemotherapy regimens and a performance status of 0-2 were eligible for the study. Patients with stable, treated brain metastases were eligible. Fenretinide 900 mg/m(2) twice daily was administered orally on days 1-7 of each 21-day cycle. Blood and saliva were collected pre-treatment and on day 7 of cycle 1 to measure fenretinide and retinol levels by high-pressure liquid chromatography (HPLC).
Results: Nineteen patients were enrolled. Fifteen patients had one prior chemotherapy regimen and four patients had two prior regimens. The median time from diagnosis to enrollment was 10 months. A median of two cycles of fenretinide was administered. There were no objective responses, but four of 17 evaluable patients (24%) had stable disease after 2-17 cycles. The median time to treatment failure was 5.7 weeks overall, while the four patients with stable disease demonstrated treatment failure at 11, 13, 19, and 52 weeks. Median survival was 25 weeks, with one patient alive 22 months after the start of treatment. The 1-year survival rate was 29%. Toxicity included mild, reversible visual changes (haziness, altered night vision), grade 1-3 nausea/vomiting, and grade 1-2 diarrhea. The mean day 7 plasma fenretinide level was 2.90 +/- 1.66 μg/ml (7.40 +/- 4.25 muM; n = 14). The mean pre-treatment and day 7 plasma retinol levels were 0.47 +/- 0.16 μg/ml and 0.05 +/- 0.07 μg/ml (n = 8), respectively. The mean day 7 salivary fenretinide level was 0.08 +/- 0.18 μg/ml, with no correlation between salivary and plasma drug levels.
Conclusions: Fenretinide is well tolerated in patients with SCLC and stabilization of disease was noted in 24% of patients with this aggressive disease. However, after the first stage of enrollment, the response rate did not meet criteria to proceed with full trial accrual. Plasma concentrations of fenretinide that induce cytotoxicity in vitro in SCLC cell lines are clinically achievable, but there were no objective responses. Non-invasive drug monitoring using saliva underestimates systemic exposure.