ESTRO 2021 Abstract Book

S1159

ESTRO 2021

Fig.2: LDH vs. tumor burden (Pearson’s r=0.4 (0.24-0.53)).

Conclusion The combination of image-based and blood-based biomarkers outperforms iRECIST or blood-only models for the prediction of patient survival in metastatic melanoma treated with immune checkpoint inhibition. Furthermore, although LDH is often considered a direct proxy for TB, our analysis shows only a weak correlation between LDH and TB. This finding underlines the importance of considering LDH levels and image- based TB as complementary factors in survival analysis of melanoma patients. PO-1410 Hypofractionated radiotherapy in elderly patients with non-melanoma skin cancer: preliminary results B. Floreno 1 , C. Greco 2 , E. Ippolito 3 , M. Fiore 3 , S. Silipigni 3 , G. D'Ercole 4 , S. Ramella 3 1 University Campus Bio-Medico , Radiotherapy, Rome, Italy; 2 Univeristy Campus Bio-Medico, Radiotherapy, Rome, Italy; 3 University Campus Bio-Medico, Radiotherapy, Rome, Italy; 4 University Campus Bio-Medico, Rome, Rome, Italy Purpose or Objective Radiation therapy can often cure skin cancers and can delay the growth of more advanced cancer. In elderly patients, often of poor performance status, extended daily treatment may be logistically difficult to deliver or are even considered inappropriate. The objective of this study was to assess the rate of tumour response and toxicity of a hyfrofractionated radiation therapy (RT) regimen (8 Gy/fraction on days 0, 7, 14) for elderly patients with non-melanoma skin cancer (NMSC). Materials and Methods Patients included in this study were deemed unsuitable by the multidisciplinary team for radical surgery for patient factors (age, performance status, cognitive impairment) and/or tumour factors (size, depth of invasion, location). 17 patients with histological confirmation of NMSC and no previous RT to that site were treated with RT from April 2017 to April 2020. Radiotherapy was delivered using electrons with energies of 6- 9-18 MeV. A bolus was used to ensure the full dose was delivered to the skin surface. Elective nodal radiation was not carried out. The dose prescribed was 24 Gy in three fractions, delivered on days 0, 7, and 14. The response to treatment was based on the Response Evaluation Criteria in Solid Tumors Group (RECIST). CTC vers. 4.02 scale was used to grade toxicity. Results Six patients were affected by basal cell carcinoma and eleven patients of squamous cell carcinoma of the skin. Median age was 85.1 years (range 80-96). All patients completed the treatment and no severe acute and late toxicities were seen. 4 patients had incomplete follow-up data. At the time of last follow-up (median 4.8 months), 84,6% of patients had a complete response (11/13 pts) and 15,4% a partial response (2/13 pts). Conclusion This regimen (8 Gy/fraction on days 0, 7, 14) offers impressive response rates and good toxicity profile for elderly patients with NMSC. PO-1411 Electronic skin cancer brachytherapy: our experience and first outcomes M. Cerrolaza 1 , P. Sanagustin 2 , M. Lanzuela 3 , R. Ibañez 2 , A. Campos 2 , S. Flamarique 3 , C. Garcia 3 , C. Escuin 3 , V. Navarro 3 , A. Lanuza 2 1 Universitary Hospital Miguel Servet, Radiation Oncology, Zaragoza, Spain; 2 University Hospital Miguel Servet, Radiation Oncology, Zaragoza, Spain; 3 University Hospital Miguel Servet , Radiation Oncology, Zaragoza, Spain Purpose or Objective The use of surface radiation therapy and surface brachytherapy is a treatment option for patients who are not surgical candidates or who are found to have risk factors such as close margins, infiltrative tumors, perineural