Abstract Book

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ESTRO 37

contralateral lymph nodes and OS in patients with locally advanced cancer of the oral cavity.

analysis. There is a need for widely acceptable and reproducible cutoffs and methods of tissue processing and IHC interpretations especially for CD44. This work was financially supported by the Czech Ministry of Health, grant no. 15-31627A, project MZ CR – RVO (MOU, 00209805), by the Ministry of Education, Youth and Sports of the Czech Republic under the project CEITEC 2020 (LQ1601). EP-2293 Base of tongue SCC should be treated with primary radiotherapy. Radiobiological background. A. Gevorkov 1 , A. Boyko 1 , N. Volchenko 2 , L. Zavalishina 3 , E. Nosova 4 1 Moscow Research Gerzen Oncology Institut, Radiation Oncology, Moscow, Russian Federation 2 Moscow Research Gerzen Oncology Institut, Pathology, Moscow, Russian Federation 3 Russian Medical Academy of of Postgraduate Education, Pathology, Moscow, Russian Federation 4 Central Research Institute of Health Organization and Informatization, Informatization, Moscow, Russian Federation Purpose or Objective The optimal treatment for patients with base of tongue (BOT) squamous cell carcinoma remains controversial and depends on various factors. Nonsurgical therapy is of great interest because of the better quality of survival when complete response observed. The aim of the study was to identify biological potential predictors of radiation therapy effectiveness in patients with BOT cancer. Material and Methods Study included 49 patients with histologically proven squamous cell BOT cancer, diagnosed and treated at Moscow Herzen Research Institute, Russia, between 2003 and 2015. Patients had locally advanced III-IV stage in 92% (n=45) with regional metastatic disease in 69% (n=34). Nonresectable tumor was diagnosed in 39% (n=19). All patients underwent concurrent chemoradiotherapy with photon external beam altered fractionation as a primary treatment. Due to aggressive surgical tactics operation as a part of combined treatment modality was performed in 39% (n=19). Organ- sparing surgery was possible only in 7 cases. Complete morphological response in surgically removed tissues was obtained in 47% (n=9). We assessed tumors for potential biologic predictors of treatment effectiveness (HPV DNA, p53, COX-2, VEGF, Ki67, E-cadherin , p21 , Bcl-2, Ki67 expression, EGFR gene mutations and amplification, KRAS gene mutation). Multivariate analyses were used to adjust all tumor, patient and treatment parameters. Results Multivariate analysis revealed (p <0,05) a positive correlation of the treatment effectiveness with the HPV DNA positivity, high expression of E-cadherin, p21, Bcl-2. Negative relationship was found with expression of p53, COX-2, VEGF, Ki67. Conclusion Patients with BOT squamous cell cancer has a good prognosis for conservative treatment effectiveness because of radiosensitivity associated with various factors, including often HPV association, high expression level of E-cadherin, p 21, Bcl-2 proteins. Beside that thay have less chances for organ-sparing surgery. This type of cancer is an aggressive and often diagnosed at a late stage, but may be effectively treated by nonsurgical modality with preservation of swallowing and speech functions.

EP-2292 CD44, EGFR and p16 expressions in oropharyngeal squamous cell cancer patients treated by IMRT. M. Slavik 1 , T. Shatokhina 2 , J. Sana 3 , P. Ahmad 3 , M. Hermanova 2 , T. Kazda 1 , P. Slampa 1 , O. Slaby 3 1 Masaryk Memorial Cancer Institute and Faculty of Medicine- Masaryk University, Radiation Oncology, Brno, Czech Republic 2 St. Anne´s University Hospital and Faculty of Medicine- Masaryk University, 1st Department of Pathological Anatomy, Brno, Czech Republic 3 CEITEC- Masaryk University, Molecular oncology, Brno, Czech Republic Purpose or Objective The aim of this study was to analyse the expression of epidermal growth factor receptor (EGFR), cluster of differentiation- 44 (CD44) and p16 in patients with oropharyngeal squamous cell carcinoma (OSCC) and correlate the expression profiles with radiation We retrospectively analyzed 77 OSCC patients, of those 70 patients had stage 4 of disease according to AJCC classification. There were only 5 and 2 patients with stage 3 and 2 respectively. All patients underwent definitive intensity – modulated radiation therapy with curative intent as a main treatment modality. Concomitant platinum based chemotherapy or targeted therapy with cetuximab was administered in 28 (36%) and 25 (33%) patients respectively. Expressions of CD44, EGFR, and p16 were immunohistochemically examined in primary tumor biopsy specimens of all patients and correlated with treatment outcomes. Cut-offs f diffuse and intensive nuclear and cytoplasmic immunostaining in at least 70 % tumour cells (TC) or p16 and ≥90 % of TC for CD44, EGFR staining was evaluated semiquantitatively using the scoring system analogous to HER2, score 2+/3+ concluded as positive. Results The positive tumor expression rates of p16, EGFR, and CD44 were 37 %, 48%, and 16 %, respectively. With median follow-up of 39 months, correlation were found between expression of all three proteins and both locoregional control (LRC) and overall survival (OS ) as follows. Median LRC (months) P16+/ p16- not reached/40,75; p=0.06, (HR 0,49 95% CI 0,23-1,05), CD 44+/CD44- 14.59/not reached, p=0,0419, HR 2,25 (95%CI 1.01-4.98), EGFR+/EGFR- 19.75 /not reached p=0.0035, HR 2.88 (95% CI 1.37-6.06) and median OS (months) p16+/p16- not reached/36.5, p=0.003, HR 0,34 (95% CI 0.16-0.72) ,CD44+/CD44- 32.67/ 59.2, p= 0.0034, HR 2.13 (95% CI 1.04-4.36) and EGFR+ /EGFR- 33.18/not reached, p= 0.0019, HR 2.71 (95%CI 1.41-5.21). Univariable analysis confirmed CD44, p16, EGFR, performance status defined by Karnofsky index and age being predictive for OS and CD44, EGFR and age for LRC , while multivariate analysis showed only a statistical trend for OS being associated with p16 (p=0.063) and LRC with EGFR (p=0,052) Conclusion Immunohistochemically detected molecular profiles combining CD44, p16, and EGFR expressions seem to be efficient in prediction of prognosis and treatment outcomes in patients with OSCC, Surprisingly, CD44 was not associated with neither OS nor LRC in multivariable treatment outcomes. Material and Methods