ESTRO 2021 Abstract Book

S1226

ESTRO 2021

(DKTK), Partner site Munich, Radiation Oncology, Munich, Germany

Purpose or Objective Ablative stereotactic body radiation therapy (SBRT) is a frequently used treatment strategy especially for oligometastatic cancer (OC) patients (pat). The spine is a common site for metastases, yet a complex site for SBRT, given the proximity to the spinal cord and the relevant risk of vertebral compression fracture (VCF). The purpose of this evaluation was to determine the toxicity and efficacy of SBRT to spine metastases (sm) using a simultaneous integrated boost concept to the macroscopic tumor (SIB-SBRT) in OC pat. Materials and Methods 35 pat with 39 sm with OC (max. 5 metastases) treated with SIB-SBRT between 2010 and 2020 in our institution were included in this retrospective analysis. Side effects during SBRT, acute (AT, < 90 days, available for 33 pat with 36 sm) and late (LT, ≥ 90 days, available for 26 pat with 29) toxicities were assessed according to CTCAE, with a particular interest in VCF (new endplate fracture or collapse deformity). Clinical factors possibly associated with VCF development were assessed and tested for significance. For effectivity analysis, local control (LC) and overall survival (OS, Kaplan-Meier) were calculated. Results Sm from different primaries (prostate 60%, breast 11.5%, melanoma 8.5%, lung 8.5%, sarcoma 8.5%, pheochromocytoma 3%) were treated in 5 fractions (median, R 5-6) with a median PTV and SIB dose of 25 (R 20-30) and 40 Gy (R 35-48), respectively. Median time from initial diagnosis to sm development was 3 yrs (R 0- 17). Median FU, if available, was 20.5 months (R 4-96). De-novo-VCF rate was 8.3% (3 cases, one requiring surgery) with events at 152, 338 and 498 days after SIB-SBRT. 1-year-VCF-free probability was 94%. There was one case of pre-SBRT-VCF and we observed a fracture progression shortly after SIB-SBRT. Other than VCF, no III° toxicities were recorded. During SIB-SBRT, 20% of pat reported pain, 17% fatigue, 9% diarrhoea, 3% dysphagia and 3% radiodermatitis. Pain (21%), nausea (9%), fatigue (6%), and hyperpigmentation, radiodermatitis and dysphagia (3%) were observed as AT. LT were pain (19%) and hyperpigmentation and fatigue (4%). Pain newly developed under SIB-SBRT was transient in 50%. Radiographic signs of myelopathy were observed in two pat (5%) without clinical symptoms at 11 and 33 months after SIB-SBRT. Local failure was not observed. Analysis of potential VCF-risk factors revealed that the only common features of de-novo- VCF pat were a mixed or lytic lesion (p=0.031) and localization in the lumbar spine (p=0.14). Mean OS after SIB-SBRT was 66.11 months (95% CI 50.37-81.85). Conclusion SIB-SBRT of sm has been demonstrated to be excellent in terms of LC, even for radioresistant tumors. De- novo-VCF rate is comparably low with an 8.3% occurrence rate and a 1-year-VCF-free probability of 94%. The rate and intensity of further side effects is reasonably low. A lytic component of the sm was shown to be a significant predictor of VCF. Risk factor assessment must be taken with caution due to the low number of pat, events and FU time. PO-1496 Superficial X-Ray Therapy in Keloids after surgery: our experience M. Cerrolaza 1 , P. Sanagustin 2 , R. Ibañez 2 , A. Campos 1 , S. Flamarique 1 , C. Garcia 1 , C. Escuin 1 , V. Navarro 1 , A. Lanuza 1 1 University Hospital Miguel Servet, Radiation Oncology, Zaragoza, Spain; 2 University Hospital Miguel Servet , Radiation Oncology, Zaragoza, Spain Purpose or Objective Keloids are benign tumors formed by skin hyperplasia due to excessive fibrin, collagen, and fibroblasts. They could develop after surgical incision, scars or burns. The highest incidence occurs in patients between 10 and 30 years old, increasing the prevalence in Dark-skinned people and in patients with a family history of keloids. Multiple therapeutic options have been studied such as corticosteroid injection, laser or cryotherapy. In cases of refractory lesions, surgery followed by radiotherapy has been observed to be a treatment option that has shown to be more effective than surgery alone. Exclusive surgery is followed by recurrence in 50% to 80% of the cases and adding adjuvant radiotherapy increase control rates up to 85% in some literature series. Our objective was to know the characteristics of the patients and keloid lesions treated in our center and the response to adjuvant radiotherapy after surgical excision. Materials and Methods Patients treated in our service with a diagnosis of keloids between 2010 and 2019 were retrospectively collected. Adjuvant radiotherapy was administered on the day of surgery after leaving the operating theatre and on the following two days. Treatments were performed with the Therapax X-ray machine using cylinders adapted to the size of the lesion from 1 to 15 cm and filters of 80, 100 and 120 Kv. Results 26 patients were treated with a mean age of 35.86 years. 54% were male and 46% female. Considering the ethnics differences among patients, 31% were African, 12% from Latin America and 58% European. A total of 30 treatments were performed as 4 patients received 2.The main location was the ear earlob (72%), followed by the back 14%, thorax (7%), abdomen 3% and inguinal region 3%, with a mean size of 4.9 cm. The most used fractionation schemes were 16.5 Gy in 3 fractions of 5.5 Gy in 59% and 15 Gy in 3 fractions of 5 Gy in 34%. The filters used were 80 Kv 21%, 100 Kv 76% and 120 Kv 120%. Follow-up data were obtained for 84% of patients. 72% presented complete response after 3 years of follow- up, only one patient presented partial response as best response (4%) and 2 patients relapsed during the same period (8%). No toxicities were observed. Conclusion Adjuvant radiotherapy after surgery is an effective treatment that reduces keloid tumour recurrence. For its treatment we must consider previous treatments, age, sex, and ethnicity as well as the characteristics of the X-ray machine, filters, cylinders, and dose fractionations.