Permanent iodine-125 (I-125) boost implants after external radiation therapy in nasopharyngeal cancer

Higher doses of external irradiation in patients with nasopharyngeal cancer have resulted in improved control of the primary tumor, but can result in significant late toxicity. Tumor control in locally advanced nasopharyngeal cancer remains suboptimal due to the technical difficulties associated with delivering high doses of radiation to the tumor while shielding the brainstem, spinal cord, optic chiasm, etc. We report the use of I-125 boost implants following moderate dose external radiation therapy in nasopharyngeal cancer, in an attempt at improving the local tumor control without increasing toxicity.

Twenty consecutive patients with nasopharyngeal cancer were treated with external beam irradiation (median dose 60 Gy over 6 weeks) to the primary site and the neck followed by I-125 implant to the primary site.

With a median follow-up of 2 years (range 1-5 years) there has been no instance of necrosis or other complications related to the implant. So far, in no patient has the tumor recurred at the primary site, although 6 of the 20 patients (30%) have developed metastases.

These data indicate that elective I-125 implantation could be performed safely after external irradiation in nasopharyngeal cancer, and has yielded an encouraging level of primary tumor control, to date.