ESTRO 36 Abstract Book

S293 ESTRO 36 _______________________________________________________________________________________________

stereotactic body radiotherapy (SBRT) and intensity- modulated radiation therapy (IMRT) boost techniques have comparable overall survival (OS) with brachytherapy boosts for patients with cervical cancer when adjusted for known prognostic factors. Material and Methods We used the National Cancer Data Base to study women who received radiation between 2004 and 2013 diagnosed with squamous cell carcinoma, adenocarcinoma or adenosquamous carcinoma of the cervix. Biological effective doses (BED) were calculated for both SBRT and IMRT treatments. A logistic regression model was built to identify factors associated with the receipt of SBRT and IMRT. Correlates of OS were determined using Kaplan- Meier and propensity score matching. Results

Conclusion BED was significantly higher in patients who received SBRT compared with IMRT. Patients who receive non- brachytherapy boosts tend to have factors correlated with poor prognosis. In a propensity matched analysis, those who received SBRT had equal OS in compared with brachytherapy, but those who received IMRT had worse OS than patients who received brachytherapy boost. Prospective studies are needed to validate the use of SBRT as boost technique in selected patients who are not candidates for brachytherapy. PV-0550 Combined high dose radiation and tyrosine kinase inhibitors in renal cell carcinoma: a phase I trial K. De Wolf 1 , S. Rottey 2 , K. Vermaelen 3 , K. Decaestecker 4 , N. Sundahl 5 , G. De Meerleer 6 , N. Lumen 4 , V. Fonteyne 1 , D. De Maeseneer 2 , P. Ost 5 1 University Hospital Ghent, radiotherapy and oncology, Gent, Belgium 2 University Hospital Ghent, medical oncology, Ghent, Belgium 3 University Hospital Ghent, laboratory of immunoregulation and mucosal immunology, Gent, Belgium 4 University Hospital Ghent, urology, Gent, Belgium 5 University Hospital Ghent, radiotherapy and oncology, Ghent, Belgium 6 University Hospital Leuven, radiotherapy and oncology, Leuven, Belgium Purpose or Objective Tyrosine kinase inhibitors (TKIs) targeti ng vascular endothelial growth factor are currently standard of care for patients with metastatic renal cell carcinoma (RCC) in first and second line. Nevertheless, durable responses are rare and most patients eventually develop progressive disease. New therapeutic approaches are needed to improve durable disease control. We studied a combination of high-dose radiotherapy and TKIs because of the immunomodulatory properties of both therapies. The primary endpoint was to determine the maximum tolerated radiotherapy doses. Secondary endpoints were local control and tumour response in non-irradiated lesions as per RECIST 1.1 or as per MD Anderson (MDA) criteria for bone lesions next to progression-free survival. Material and Methods Treatment-naïve patients with clear cell metastatic RCC, who had undergone cytoreductive treatment of their RCC at least 6 weeks prior to inclusion, were treated with a first line TKI, pazopanib, during a 1-week run-in period. Stereotactic body radiotherapy (SBRT) was delivered to the largest metastatic lesion concurrently with pazopanib administration at day 8. SBRT doses were escalated in 3

Of all 15,905 patients, 14,394 (90.5%) received brachytherapy, 42 (0.8%) received SBRT, and 1468 (9.2%) received IMRT. A multivariable binary logistic regression model identified the following factors associated with receipt of SBRT: advancing age, higher income status, Asian ethnicity, and FIGO Stage III cervical cancer. The following factors were associated with receipt of IMRT: advancing age, treatment at an academic/research program, treatment at an integrated network cancer program, private insurance, lower income status, FIGO Stage III, IVA, and IVB cervical cancer, positive nodal status, metastatic disease, and not receiving chemotherapy as part of the first course of treatment. Median BED was 63.7 Gy for patients treated with IMRT and 75.5 Gy for SBRT (p < 0.001). The median follow-up was 4.8 years. Median survival was 99.1 months (95% CI: 94.4 – 103.8 months), 30.6 months (95% CI: 20.5 – 40.6. months), and 29.8 months (95% CI: 26.0 – 34.7 months) for patients who received brachytherapy, SBRT, and IMRT boost, respectively. Using propensity score matching, there was no significant difference in OS for patients who received SBRT boost vs. brachytherapy boost (HR 1.477; 95% CI 0.746 – 2.926; p = 0.263). IMRT boost patients were also matched and did significantly worse than those who received brachytherapy boost (HR 1.455, 95% CI 1.300 - 1.628; p <0.001).