Background & objective: Although intracavitary irradiation (ICI) is usually applied to enhance dose in radiotherapy for early stage nasopharyngeal carcinoma (NPC), its use in parapharyngeal enhancing dose is limited because of dislocation and poor repetition of conventional catheterization. This study was to evaluate the application of a new technique, interstitial brachytherapy via parapharynx involvement transnasal approach, to enhance dose in radiotherapy for NPC.
Methods: Twenty-three naive and recurrent NPC patients with tumor residue of more than 1 cm under nasopharyngeal mucosa or restricted tumor residue in the parapharyngeal space received interstitial brachytherapy between Sep. 2005 and Aug. 2006 via parapharynx involvement transnasal approach under the guidance of sinus endoscopy. The 3-dimensional (3D) planning system was used to delineate target volume, optimize dose distribution, and perform interstitial brachytherapy after CT scan. The depths of catheters under mucosa on the moment of inserting and pulling out were measured. The efficacy and complications were assessed.
Results: All catheters were intubated into tumors successfully; the veracity of catheter location was 100%. The submucosa depths of catheters were (9.59+/-2.72) mm when inserted and (9.43+/-2.30) mm when pulled out, without significant difference (t = 0.23,P > 0.05); the shift length was (0.75+/-0.75) mm. The patients were followed up from 3 to 15 months (median, 6 months), and no one dropt out. Three cases of irradiation-associated turbinate adhesion occurred and were cured after lysis; no infection, serious bleeding, palatal perforation, nasopharyngeal necrosis, and other serious complications occurred. All tumors disappeared in 3 months after treatment. No local recurrence and distant metastasis occurred.
Conclusions: The nasopharyngeal and parapharyngeal catheterization with sinus endoscopy guidance is accurate, steady, safe, and feasible. Interstitial brachytherapy is effective for tumor residue in the nasopharynx or parapharyngeal space of NPC patients after radiotherapy without serious complications.