Carcinoma of the floor of the mouth: a case treated with precisely controlled external beam radiotherapy.

A new external radiotherapy system has been developed for head and neck cancer and a case with T2 oral floor carcinoma treated with this system is presented in this report. The system consists of real-time tumor-tracking equipment and a gold-marker implanted mouthpiece. Accuracy of the order of 2 mm was achieved during the entire course of fractionated radiotherapy (a total of 52.5 Gy in 15 fractions). Planning target volume became smaller compared to the conventional parallel-opposed technique. Dose-volume histogram analysis demonstrated a significant reduction in the dose to the mandible bone compared to the conventional technique. A confluent fibrinous mucositis developed in the oral floor mucosa that corresponded to 90% dose area. Mucositis in the lower gum was minimal and analgesics were not required. The patient is currently free from both tumor and complication during a follow-up period of 48 months. External radiotherapy can be an option as a curative treatment for early stage carcinoma of the floor of the mouth provided that patient set-up is rigid and reproducible.