Effect of pilocarpine during radiation therapy: Results of RTOG 97-09, a phase III randomized study in head and neck cancer patients

Radiation therapy is an important curative modality in the treatment of patients with head and neck cancer. However, radiation-induced changes in the oral cavity, such as xerostomia and mucositis, are among the most debilitating treatment sequelae experienced by patients undergoing radiation therapy, and attempts at ameliorating these side effects have been poor at best. Pilocarpine has been approved for post-radiation xerostomia, and the effect of its use during radiation therapy on salivary flow, xerostomia, mucositis, and quality of life (QOL) was assessed in a phase III study conducted by the Radiation Therapy Oncology Group (RTOG 97-09). In total, 245 evaluable patients were randomized to pilocarpine or placebo. Selected patients were required to have ≥ 50% of the volume of the major salivary glands receive ≥ 50Gy; to agree to provide stimulated and unstimulated samples of saliva (measured in g) before treatment, at the end of treatment, and 3 and 6 months after completion of radiation therapy; and to complete the University of Washington Head and Neck Symptom Scale. Following the completion of radiation therapy, the average unstimulated salivary flow was statistically greater in the pilocarpine group, whereas no difference was noted following parotid stimulation. There was no effect on the amelioration of mucositis. The results of the QOL scales did not reveal any significant difference between the pilocarpine and placebo groups with regard to xerostomia and mucositis. The significant difference in unstimulated salivary flow supports the concomitant use of oral pilocarpine to decrease radiation-associated xerostomia. However, the absent correlation between improved salivary flow and QOL scores is of some concern (though not a new finding) and may be related to the existence of comorbidities and the lack of effect on mucositis.