ESTRO 38 Abstract book

S860 ESTRO 38

RT combined with IMT improved local tumor control compared to RT alone. Combination treatment with RT and IMT can be an effective treatment option in patients with mucosal melanoma. EP-1594 Two years’ experience of electronic brachytherapy for basal cell carcinomas in selected patients H. Westenberg 1 , R. Keus 1 , M. Van Hezewijk 1 , B. Oosterveld 2 1 Radiotherapiegroep, radiotherapy, Arnhem, The Netherlands ; 2 Radiotherapiegroep, medical physics, Arnhem, The Netherlands Purpose or Objective In 2016 electronic brachytherapy (EB) by low kilovoltage energy (69,5 kV Esteya®/Elekta, Sweden) was introduced in our department as addition to our radiation facilities for treating basal cell skin cancer. Due to the maximum applicator diameter of 3 cm, only small lesions are eligible. Maximum depth for dose prescription is 4 mm. After 2 years we evaluated toxicity, outcome and patient comfort. Material and Methods Patients with basal cell carcinoma referred for radiotherapy with curative intent were selected for EB. From March 2016 to September 2018 56 patients with 66 lesions were treated with electronic brachytherapy. All lesions received 6 fractions, twice a week, of 7 Gy prescribed to a depth of 3 mm (in 92% of the lesions) from the skin surface. In 2 patients the dose was prescribed to a depth of 4 mm, because of the tumour thickness, and in 3 patients to 2 mm because of superficial growth of the tumour. Before the first fraction the lesion (gross tumour volume GTV) and the treatment margin (GTV was expanded by 5- 10 mm to clinical target volume CTV, depending on size and histology) was delineated on the skin by the radiation oncologist. Dermatoscopy was used for precise GTV delineation. Photographs were routinely taken before the 1 st , 4 th and 6 th fraction and during follow- up. Results One patient, in poor medical condition, was treated with palliative intent and one patient discontinued treatment because of a pneumonia. The remaining 54 patients with 64 lesions were evaluated. All lesions were ≤ 20 mm and 90% were histologically confirmed basal cell carcinoma, either of solid (67%), morpheaform (17%) or superficial growing (5%) type. Mean age was 75.7 years and despite high age and comorbidities, the treatment was well tolerated. Most lesions were localised in the head and neck area, with the majority on the nose (in 65% of the patients). The most common acute toxicity was a mild erythema and nasal mucositis, both self-limiting. In one patient, with a lesion on the tibia, delayed wound healing for several months occurred. Follow-up ranges from 0.5- 26 months with an average FU of 5 months. There were 2 recurrences, one in and therefore a true recurrence, and one recurrence close to the radiation field. Conclusion In our two years’ experience electronic brachytherapy offers an effective, comfortable and simple method for the curative treatment of small basal cell skin cancers in elderly patients with lesions in areas where surgery is complicated or mutilating. Our preliminary results are comparable to the published results with EB. EP-1595 In unoperable SSCC, radiotherapy schedules could be chosen using dermoscopic features? F. Pastore 1 , A. Rese 1 , G. Panelli 1 , A. Pepe 1 , D. Toledo 1 , V. Iorio 1 1 Emicenter, Radiation Oncology, Casavatore, Italy

Overall survival was 21.8m (3-149m)

Conclusion These data suggest that consolidative radiotherapy after loco-regional relapse is feasible and could contribute to the long-term control in up to half of the treatments, with acceptable toxicity rates.

Electronic Poster: Clinical track: Skin cancer / malignant melanoma

EP-1593 The impact of Radiotherapy combined with immunotherapy on local control in mucosal melanoma patients H.J. Kim 1 , S.J. Shin 2 , K. Woong Sub 3 1 Gil Medical Hospital, Department of Radiation Oncology, Incheon, Korea Republic of ; 2 Yonsei Cancer Center, Division of Medical Oncology- Department of Internal Medicine, Seoul, Korea Republic of ; 3 Yonsei Cancer Center, Department of Radiation Oncology, Seoul, Korea Republic of Purpose or Objective Mucosal melanoma is an aggressive malignancy with a poor response to conventional therapies. The efficacy of immunotherapy (IMT), especially combined with radiotherapy (RT), has not been reported in this rare subtype. We investigated the impact of RT combined with IMT in mucosal melanoma patients. Material and Methods Forty-two patients with mucosal melanoma who were treated with RT at Yonsei Cancer Center between Jul 2008 and Feb 2017 were identified from our database. Patients who received postoperative RT, had no response evaluation, and expired during RT were excluded. A total of 18 patients with 22 lesions were included in this analysis. All patients received RT for primary or metastatic gross tumor mass. The median dose of radiation was 45 Gy (range, 20-69 Gy) with a median fractional dose of 3 Gy (range, 1.8-7.5 Gy). Eleven patients with 14 lesions were treated with RT alone, while 7 patients with 8 lesions were administered IMT sequentially or concurrently; pembrolizumab in 6 patients and nivolumab in 1. The local control (LC) rate, infield failure-free survival (IFFS), and outfield failure-free survival (OFFS) were compared between two groups (no- IMT vs. IMT group). IFFS and OFFS was determined from the date of RT finish, while overall survival (OS) was calculated from the date of diagnosis. Results Common anatomic sites of primary tumors were the head and neck (59%), anorectal region (31.8%), and female genital tract (9.1%). Patient characteristics including sex, age, primary site, tumor stage, BRAF mutation, adjuvant interferon, and RT site (primary vs. metastatic mass) were not significantly different between two groups. The median OS was 50.2 months with a median follow-up of 39.7 months (range, 7.3-102.1 months) for all patients. The LC rate was 59.1% for 22 lesions and the median time to local progression was 4.8 months (range, 0.5-20.3 months). Although RT dose was not significantly different between two groups, the LC rate was better in the IMT group than no-IMT group. (57.1% versus 12.5%; P = 0.074). The outfield failure rate was 87.5% in IMT group and 100% in no-IMT group (P = 0.364). Dividing lesions according to RT dose in terms of EQD2 (α/β=10), higher dose group ( ＞ 45 Gy) showed better tumor control; the LC rates were 53.8% vs. 22.2% and the median IFFSs were 20.3 vs. 7.3 months for ＞ 45 Gy vs. ≤45 Gy group, respectively. The OFFS was not significantly different between the IMT and no-IMT group. Conclusion

Purpose or Objective