Abstract
Dose volume histograms of the high dose rate brachytherapy for 30 patients with tongue cancer and 6 patients with cancer of the mouth floor were calculated by means of PLATO. All patients were treated with HDR brachytherapy of 6Gy per day. 20 patients with tongue cancer and 4 patients with mouthe floor cancer were treated with 60Gy/10 fractions of HDR brachytherapy alone. Other 12 patients were treated with 20-41Gy of external radiation and 42-60Gy of HDR brachytherapy. V100% was defined as the volume of 6Gy per fraction.
For tongue cancer, V100% of patients treated with single plane, single plane plus one tube, double plane and volume implant were 14cm3, 29cm3, 18cm3 and 64cm3, respectively. The corresponding figures of V200% were 3cm3, 8cm3, 3cm3 and 10cm3. V100% and V200% of mouth floor cancer were 10cm3 and 3cm3.
For patients treated with HDR brachytherapy alone, local recurrence occurred in 2 patients with small treatment volume (V100%: 9.7cm3, 11.0cm3) and soft tissue ulcer occurred in 2 patients with large treatment volume (V100%: 25.6cm3, 31.8cm3). Treatment volumes of mouth floor cancer were small compared with tongue cancer patients. There were no soft tissue ulcer in 6 patients.
For 10 tongue cancer patients treated with combination of external radiation and HDR brachytherapy, 6 patients were treated with single plane implant and 4 patients with volume implant. For single plane implant, V100% and V200% were 13-19cm3 and 2.3-4.3cm3, respectively. There were no local recurrence and no soft tissue ulcer. For volume implant, V100% and V200% were extremely high compared with other treatment. Ulcer occurred in the patient without local recurrence. It is difficult to treat these bulky tumor without late complication.
Treatment volume is an important factor for both local control and late complication.
