Interstitial Brachytherapy for Lip Cancer: Technical Aspects to Individualize Treatment Approach and Optimize Outcomes.

Primary radiotherapy using interstitial brachytherapy (IBT) provides excellent local tumor control for early-stage squamous cell carcinoma (SCC) of the lip. Technical aspects of treatment are important to optimize outcomes. In this report, we discuss patient selection criteria, procedural details, and dosimetric considerations for performing IBT for cancers of the lip. Catheters are inserted across the length of tumor entering and exiting approximately 5 mm beyond the palpable tumor extent. A custom mouthpiece is fabricated to facilitate normal tissue sparing. Patients undergo CT imaging, the gross tumor volume (GTV) is contoured based on physical exam and CT findings, and an individualized BT plan is generated with goals of achieving GTV D90% ≥ 90% and minimizing V150%. Ten patients with primary (n=8) or recurrent (n=2) cancers of the lip who received high dose rate (HDR) lip IBT using 2.0-2.5 week treatment regimens are described (median prescription: 47.6 Gy in 14 fractions of 3.4 Gy). Local tumor control was 100%. There were no cases of acute grade ≥4 or late grade ≥2 toxicity, and cosmesis scores were graded as good-excellent in all patients. IBT represents an excellent treatment option for patients with lip SCC. With careful attention to technical considerations furthered described in the current report, high rates of tumor control, low rates of toxicity, and favorable aesthetic and functional outcomes can be achieved with IBT for lip cancer.