ESTRO 2020 Abstract Book

S644 ESTRO 2020

mean dose for BCC was 47.11Gy and for SCC was 53.05Gy. 29 (5.22%) recurrences were observed: 17.2% in OV, 37.9% in EB and 44.8% in HDR (p 0.197). 62.1% of them were SCC. Four patients died due to the NMSC (2.7%), all of them were SCC histology. Complete response was mostly appreciated in all groups. Only 0.5% BCC and 4.2% SCC had partial response, and in 2.4% BCC and 2.1% SCC the disease persisted. Acute toxicity was greater in the OV (57.3% G3) than in EB (47.7% G2) and HDR (42.8% G2) (p 0.0001). Despite most patients did not present chronic toxicity, 7.3% G4 was detected in EB (p=0.0001). There were excellent cosmetic results reported in the patients clinical histories. Conclusion 1. We don’t observe outcome differences between radiotherapy techniques in our retrospective review. PO-1223 Superficial radiotherapy in epithelial skin cancer S. Blanco Parajon 1 , M.Á. De la Rúa Calderón 1 , C. Prada García 1 , M. Balagué Montes 1 , P. Sánchez Galiano 2 , G. Juan Rijo 1 1 Hospital Universitario Central de Asturias, Radiation Oncology, Oviedo, Spain ; 2 Hospital Universitario Central de Asturias, Radiological Physics, Oviedo, Spain Purpose or Objective To retrospectively review epithelial skin cancer treated with superficial radiation therapy (SRT) in our institution. Material and Methods We analyzed 249 patients with a total of 272 lesions, treated with SRT between February 2005 and November 2018. Results Mean age was 79.57 years (77.18 in BCC and 83.32 in SCC). 51% were women. Histologically, 62.1% were BCC and 37.5% SCC. 70.6% were primary tumors, 28.3% recurrences after surgery and 1.1% recurrences after topic treatment. By location 9.2% were in area L, 36.4% in area M and 54.4% in area H. Staging was 4.8% in situ, 58.8% T1, 25.4% T2, 9.9% T3 and 1.1% T4. Positive perineural invasion was present in 2.6% and not known in 71%. Immunosuppression in 28.1%. Definitive primary SRT was performed in 59.9%, after surgery R0 in 1.1%, after surgery R1 in 29%, after surgery R2 in 3.3% and palliative treatment in 6.6%. The most common radiation dose was 54 Gy in 20 fractions delivered in 74.3% of lesions. Median follow up was 45 months (0.1-168). Globally recurrence free survival (RFS) was 91.2%, being 91.7% for primary tumors and 90% for recurrences. In lesions treated after surgery, primary lesions and palliative treatments, RFS was 87.9%, 92.6% and 94.4% respectively. Recurrences were 8.8% (58.3% BCC, 41.6% SCC), with 66.7% in-field, 16.7% out-field and 16.7% regional recurrences. RFS at 11.5 years was 75.3±7.7% in BCC and 54.2±22.8% in SCC. Multivariate Cox regression analyses showed increased risk of recurrence in SCC ( P =0.042) and T3 stage ( P =0.026). 2. OV technique presents major acute toxicity with statistical significance compared with HDR and EB, however, EB present major chronic toxicity and poor cosmetics results.

Conclusion SRT is a good treatment for epithelial skin cancer with an excellent local control. There is a high risk of recurrence in SCC and T3 stage in our patients. PO-1224 Clinical outcomes of malignant melanoma treated with immune checkpoint blocker in Korean patients J. Lee 1 , J.S. Chang 2 , M.R. Roh 3 , B.H. Oh 3 , K.Y. Chung 3 , W.S. Koom 4 , S.J. Shin 5 1 Inha University Hospital, Radiation Oncology, Incheon, Korea Republic of ; 2 Yonsei University College of Medicine, Radiation Oncology-, Seoul, Korea Republic of ; 3 Yonsei University College of Medicine, Dermatology, Seoul, Korea Republic of ; 4 Yonsei University College of Medicine, Radiation Oncology, Seoul, Korea Republic of ; 5 Yonsei University College of Medicine, Medical Oncology, Seoul, Korea Republic of Purpose or Objective Early clinical trials established the efficacy of immune checkpoint blocker (ICB) in advanced malignant melanoma. Because there is considerable discrepancy in clinical subtypes of melanoma between different races and populations, its efficacy remains to be elucidated in Asian populations. Material and Methods We retrospectively reviewed 127 patients with metastatic or advanced melanoma treated with ICB between 2014 to 2018. Clinical subtypes of melanoma were classified by extent of solar elastosis around tumor and anatomical site, as follows: chronically sun-damaged (CSD) and non-CSD melanomas (acral lentiginous, mucosal and uveal types). Primary endpoint was objective response rates (ORR) included complete and partial response rate. We attempted to seek links between a close temporal relationship of palliative RT and ICB and increased ORR. Results The iRECIST ORR was 15% (95% CI 9.3-22.4), with 11 complete and 8 partial responses. The ORR was 50% for CSD type, 16.5% for acral or mucosal type, and 0% for uveal type ( P = .009). Aside from clinical subtypes, stage at treatment (M1a/unresectable vs. M1b/c/d; 36.1% vs. 6.6%), total tumor burden based on the sum of the longest diameters of target lesions (< 4 mL vs. ≥ 4 mL; 37.1% vs. 6.5%), and types of ICB (anti-PD-1 vs. anti-CTLA-4; 18.8% vs. 3.2%) were significantly associated with ORR. Administration of palliative RT seems likely to increase the ORR, only when there is close temporal relation between ICB and RT (< 2 weeks vs. ≥ 2 weeks, 22.2% vs. 11%, P =.089). Clinical responders to ICB had significantly improved progression-free and overall survivals than non- responders (61.2% vs 8.7% at 1-year, P < .001 and 100% vs 71.2% at 1-year, P = .015, respectively).