High doses regimes of HDR brachytherapy at squamous cell carcinoma of the lip

Introduction. Despite the large number of recommendations the applicator insertion during HDR brachytherapy, a lot of questions regarding the choice and placement of the applicators, normalization and dose selection are still under discussion. Randomized trial comparing standard fractionation modes with other modes are not available. There are recommendations for the applicator types: they can be flexible or rigid, placed parallel to (French school) or "hand free". Data taking into account are the follows: the volume of the tumor, histology and data from diagnostic tests. If the absence of invasion to regional lymph node are confirmed by different diagnostic tests we deliver monobrachytherapy. The aim of the study was to evaluate the efficacy of high local doses using HDR brachytherapy for lip squamous cell cancer. Materials and methods. 27 patients with histologically confirmed squamous cell carcinoma of the lower lip were treated in the department of radiation therapy from 2012 to 2016. According to US or CT data, regional lymph nodes were not invaded by the tumor. All patients underwent interstitial HDR brachytherapy with MicroSelectron (source 192Ir). Metal needles were inserted "hand free" under local anesthesia and were removed after each fraction. The geometry of needle spacing and the direction was dictated by the necessity to deliver maximal dose to the tumor. The number of needles varied from 2 to 7 depending on the tumor volume. The mandible was considered as a critical organ. A single dose was 8 Gy. Irradiation was carried out 2 times per week, total of 4 fractions. Irradiated volume ranged between 10 to 28 ccm. Treatment planning was carried out based on the 3D CT and with Oncentra treatment planning system. Graphical optimization was used. An example of a dose distribution is shown. Patients were examined every month during the first half off a year and every 3 month later. If necessary, the frequency of examination was increased. Results. Treated patients felt comfortable between the factions since the needles were extracted after each irradiation session. This reduces the risk of infection, which is often observed after insertion of flexible applicators. Short bleeding could happen just after the needles extraction but in few minutes it stopped. Swelling after the insertion of the needles usually disappeared in the evening of the same day of treatment. Radiation reactions lasted one month on average. New young tissue was formed under the crusts. No recurrence during period of observation was noted in all patients. Severe complications were also not noticed. Conclusion. 8 Gy per fraction, 4 fractions total, 2 times per week irradiation scheme for squamous cell carcinoma of the lower lip seems to be tolerant method of HDR brachytherapy allowing good local tumor control with reduced chance of infection. It significantly improves the patient's well-being between the fractions. Radiation complications were not observed in this fractionation regime. (author)