Preliminary results of a pilot study using WR-2721 before fractionated irradiation of the head and neck to reduce salivary gland dysfunction.

Abstract

Based on in vivo evidence of radioprotection of the salivary glands using WR-2721, a pilot study was undertaken to determine the feasibility, toxicity, and salivary function of patients receiving WR-2721, while undergoing radiation therapy to the head and neck. Patients undergoing radiation therapy for cancer of the head and neck were eligible if the major salivary glands received more than 45 Gy. WR-2721 was administered over 6 min IV, 10-15 min prior to each dose of radiation five times per week. Saliva was collected and measured prior to radiation therapy, weekly during radiation therapy, 1 month postradiation therapy, and every 3 months thereafter. Flow rates of unstimulated whole saliva, stimulated whole saliva, and stimulated parotid saliva were measured using standard techniques. 99mTc salivary scintiscans were performed prior to radiation therapy, 1 month postradiation therapy and every 3 months thereafter. Nine patients are presently enrolled on the first dose level (100 mg/m2) of this study. Eight completed per protocol, two with minor decreases of total WR-2721 doses. Two patients progressed with distant metastases soon after completion of therapy. All available data are included in the analysis. Median follow-up for all patients is 18 months. Flow rates of unstimulated whole saliva decreased significantly during radiation therapy reaching 5.6% of baseline at 9 months postradiation therapy, subsequently recovering to 20% of baseline, then remaining stable over time. Stimulated whole salivary flow rate similarly decreased during radiation therapy and reached its nadir (11% of baseline) at 3 months postradiation therapy, improving to 27% of baseline by 2 years. The stimulated parotid flow rate decreased during radiation therapy to 1.4% of pretreatment levels. Significant recovery took place 6 months postradiation therapy and by 18 months values had recovered to 54% of baseline. 99mTc salivary scintiscans confirmed this rebound of parotid function postradiation therapy. Toxicity was minimal with the exception of one patient who received only 27% of the planned total drug dose due to grade 3 hypotension after the eighth treatment. No recovery of salivary function has been seen in this patient; flow rates remain zero in all three areas tested 21 months after radiation. Administration of WR-2721 prior to each dose of radiation was feasible and without significant toxicity at 100 mg/m2. Salivary gland function improved over time after completion of radiation, particularly the parotid. Future directions include escalation of WR-2721 dose to 200 mg/m2 and then 300 mg/m2, and a Phase III randomized trial will be undertaken once the optimal dose is established.