The incidence of radioepidermitis and the dose-response relationship in parotid gland cancer patients treated with 125I seed brachytherapy: incidence of radioepidermitis and the dose-response relationship.

BACKGROUND: We studied the incidence and dose-response relationship of radioepidermitis in parotid gland carcinoma patients treated with [(125)I] seed brachytherapy in the hopes of designing an optimized pre-implant treatment plan that would reduce the incidence and severity of radioepidermitis in patients receiving this therapy. PATIENTS AND METHODS: Between January 2007 and May 2010, 100 parotid gland cancer patients were treated postoperatively with [(125)I] seed brachytherapy. The matched peripheral dose (MPD) was 80-140 Gy, and [(125)I] seed activity was 0.7-0.8 mCi. The mean dose delivered to the skin was calculated in the post-implant CT on day 0 following implantation. Grades of acute and late dermatitis were evaluated at 2, 6, 12, and 18 months post-implantation.
RESULTS: Most patients experienced grade 0-2 acute and late skin side effects (86 and 97%, respectively), though a small subset developed severe complications. Most grade 1-3 effects resolved within 6 months of implantation, though some grade 1-3 effects and all grade 4 effects remained unchanged throughout the 18-month follow-up period. Grade 3 and 4 effects were most prominent (75 and 25%, respectively) with doses of 110-140 Gy; doses higher than 140 Gy produced only grade 4 effects.
CONCLUSION: [(125)I] seed brachytherapy produced acceptable levels of acute and late radioepidermitis with a good clinical outcome. A mean dose under 100 Gy delivered to the skin was safe, though doses of 110-140 Gy should be given with caution and extra monitoring; doses greater than 140 Gy are dangerous and likely to produce grade 4-5 effects.