ESTRO 2021 Abstract Book

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ESTRO 2021

Results The trial was approved by the ethics committee and registered with ClinicalTrials.gov number NCT02992886. Sixty-eight fit patients were enrolled. Sixty-four patients (94.1%) finished radiotherapy without dose reduction. Fifty-four (79.3%) patients finished the prescribed Raltitrexed therapy as planned. A serious toxicity (Grade 3 or above) was observed in twenty-four patients (35.3%), and only fourteen pati ents (20.6%) experienced non-hematological side effects. Forty-eight patients underwent surgery (R0 resection for 95.8%, R1 resection for 4.2%, respectively), within 34.2 months follow-up time, one local-recurrence and seven metastasis events were observed among these patients, and the 2-year DFS was 83.9% (95%CI: 72.9-94.9) for them. Conclusion This Phase II trial met the primary endpoint, which showed that preCRT was safe and efficient in older patients with rectal cancer who were evaluated as fit based on CGA. PD-0841 Definitive therapy for anal cancer with synchronous metastases K. Wind 1 , L. Riber 2 , B. Mayland Havelund 2 , E. Serup-Hansen 3 , C. Kronborg 4 , A. Jakobsen 2 , K. Garm Spindler 5 1 Aarhus University Hospital, Department of Experimental Clinical Oncology , Aarhus, Denmark; 2 Vejle Hospital, University Hospital of Southern Denmark, Department of Oncology, Vejle, Denmark; 3 Herlev Hospital, Department of Oncology, Herlev, Denmark; 4 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark; 5 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark Purpose or Objective Synchronous metastatic squamous cell carcinoma of the anus (mSCCA) is a rare presentation of an already rare malignancy, and very little evidence exists on potential curative treatment options. Long-term disease control is reported after curative treatment strategies in oligometastatic colorectal cancer, but there is an obvious gap of knowledge in mSCCA. The purpose of this study was to evaluate outcome after induction chemotherapy (ICT) and curative intended treatment for synchronous mSCCA in a nation-wide cohort. Materials and Methods Patients with synchronous mSCCA treated with ICT between 2000 and 2018 were identified through hospital registers from the three National Centres. Pre-treatment characteristics, treatment information, and outcome data were retrospectively collected from medical records. Survival analyses were done using the Kaplan-Meier method. Cox-regression analyses were used for calculating hazard ratios (HRs) to compare differences in survival functions by metastatic site (organ metastases versus lymph node metastases). Results A total of 19 patients were identified. Location of metastases were liver (n=5), lung (n=1), bone (n=1), skin (n=3), retroperitoneal lymph nodes (n=4), and para aortic-/common iliac lymph nodes (n=5). Patients were treated with ICT consisting of cisplatin, 5-flourouracil, leucovorin and ifosfamide (n=18) or cisplatin and 5- flouruoracil (n=1) followed by either radiotherapy (n=14) or chemoradiotherapy (n=5) delivered with 3D conformal technique (n=8) or IMRT (n=11). Prescribed radiotherapy doses to tumour and pathological lymph nodes were 50.4-64 Gy in 28-32 fractions and prescribed doses to the elective clinical target volume were 49.9-51.2 Gy. Four patients underwent further local treatment for metastases (surgery, RFA and/or SBRT). Response evaluation after ICT was available in 16 patients. Overall objective local tumour response was 88% (n=14) with 31% (n=5) achieving complete local tumour response on ICT alone. The median follow-up time was 4.5 years (range 0.9-.17). In brief, three patients (16%) had primary treatment failure after completing curative treatment and eight patients (42%) experienced later recurrence. Overall survival at three and five years was 72% and 55%, respectively, and three- and five-year disease-free survival (DFS) was 47% and 42%, respectively. Comparison of organ metastases versus lymph node metastases showed a significant better DFS in patients with organ metastases (HR 3.47, p=0.0457). Conclusion Selected patients with synchronous mSCCA could be treated with a definitive curative strategy hereby shifting patients from a palliative to a curative treatment intent. Prospective trials are needed to investigate this approach further. PD-0842 Prophylactic cranial irradiation in patients with small cell lung cancer in the Netherlands M. Tomassen 1 1 University Medical Center Utrecht, Radiation Oncology , Utrecht, The Netherlands Purpose or Objective An important basis for prophylactic cranial irradiation (PCI) in limited-stage small cell lung cancer (LS-SCLC) is provided by the meta-analysis by Aupérin in 1999. The phase III randomized controlled (RCT) trial of the EORTC by Slotman in 2007 supported the use of PCI in extensive-stage (ES-)SCLC. Controversy has arisen regarding the benefit of PCI in patients with SCLC since the 2017 Takahashi RCT that supported MRI surveillance as alternative in ES-SCLC. The primary aim of this study was to assess trends and determinants in PCI use over the years 2010-2018. A secondary aim was to determine contemporary practice considerations among radiation oncologists (ROs) in 2020. Materials and Methods A nationwide population-based cohort study was conducted using the Netherlands Cancer Registry data on all newly diagnosed SCLC patients (2010-2018). The change in PCI frequency over the years and determinants for PCI were analyzed using logistic regression models. Second, an online survey was performed among Dutch lung cancer ROs in 2020. Poster discussions: Poster discussion 20: Lung 1