Background: The purpose of this study was to assess the learning curve (LC) for inguinal hernia repair with robotic transabdominal preperitoneal (R-TAPP) approach. Methods: Between April 2016 and October 2019, patients who underwent R-TAPP were retrieved. Patient demographics, operative variables and postoperative outcomes were assessed. The moving average method and cumulative sum of operation times (OT) were used to evaluate the LC. The surgeon (BB) in this study had completed his laparoscopic (Lap) TAPP experience. Results: There were 50 (two females) consecutive patients (mean age was 51.7 � 16.9 years). The first phase (learning phase) included initial 35 operations. The second phase included the next 15 operations. It was observed that, with increasing experience, a statistically significant shortening in the average OT by about 25 min was achieved (p ¼ 0.041). Conclusion: The LC phase for R-TAPP, for surgeon with previous experience in Lap TAPP, seems to be very quick without compromising the operative morbidity.

Aims: Esophageal atresia is the most common congenital malformation of the esophagus. It can be diagnosed in the prenatal period, during the delivery or at the neonatal intensive care unit. With the operation, the respiratory system and digestive tract are being corrected to the anatomic position. In this case, we wanted to emphasize that patients with esophageal atresia may continue to have functional problems even after successful surgical treatment. Case Report: After preterm delivery, a female patient was consulted to Trakya University Department of Pediatric Surgery, at one day of age with the symptom of regurgitation of saliva. There were no abnormalities on physical examination. Due to the inability to pass an orogastric tube to the stomach, esophageal atresia was suspected. Thus, radiocontrast x-ray study was performed: the proximal esophageal pouch was identified, and malformation was diagnosed. After the diagnosis, tracheoesophageal fistula has been ligated. The patient received physical therapy after the operation, and she was followed-up for 10 months. A full recovery was observed, and the patient was able to swallow food. Conclusion: Esophageal atresia with distal tracheoesophageal fistula is not an uncommon malformation. The patients can have problems with swallowing in their infancy even they are treated surgically in the neonatal period.

202 Background: The optimal treatment for metastatic colorectal cancer (mCRC) after the second line is still controversial. Regorafenib (Reg) revealed promising results by improving overall survival compared to best supportive care. However, in real-world practice rechallenge chemotherapy (CTr) is often preferred even though supporting evidence is not enough. We aim to compare the efficacy of regorafenib and 5-fluorouracil-based (5-FU) rechallenge treatment in the third line setting of mCRC. Methods: In this retrospective multi-institutional trial, mCRC patients from 21 centers in Turkey progressing after 2 lines of chemotherapy between 2012-2020 were analyzed. Patients who were treated with Reg or rechallenge therapy in the third-line setting were eligible. Rechallenge chemotherapy was identified as the re-use of the 5-FU based regimen which was administered in one of the previous treatment lines. Overall survival (OS), objective response rate (ORR), progression free survival (PFS) and toxicity were analyzed. Chi-square, Kaplan-Meier method and Cox regression analysis were used for analysis. Results: The clinical data of 441 mCRC patients were analyzed. Of these, 284 received regorafenib while 156 received rechallenge chemotherapy. The mean age was 57 and 56% was male. Median OS since the diagnosis was better with CTr than with Reg (48 months (95% CI, 43.4–52.6) vs. 39 months (95% CI, 35.4–42.5), p<0.001). Median OS after the third-line treatment was 12.0 (95% CI, 9.9–14) and 9.0 months (95% CI, 7.5–10.4) for CTr and Reg groups, respectively (p<0.001). PFS was 6 months for patients receiving CTr and 4 months for those treated with Reg (p = 0.139). ORR was significantly higher in CTr group than Reg (p<0.001). BRAF status, MSI status and treatment type (CTr vs. Reg) are factors found associated with OS in Cox regression analysis (p<0.001, p=0.021 and p<0.001, respectively). Adverse effects were seen in 82% and 68.2% of patients receiving Reg and CTr, respectively. Discontinuation of treatment due to adverse effects was higher in patients treated with Reg (10% vs. 2.5%). Conclusions: Our analysis revealed that rechallenge is an appreciated option, in both efficacy and toxicity, when the limited treatment options for mCRC is considered. Although regorafenib treatment contributes to survival, CTr shows better disease control. Our study has the highest number of patients in the literature. Still, prospective studies are mandatory for validation of CTr in the third-line treatment of mCRC.

Aims: This study aims to evaluate medical students' knowledge, thoughts, and awareness of the COVID-19 pandemic. Methods: A questionnaire consisting of 31 questions was prepared for this descriptive study. In the questionnaire, medical students' knowledge, attitudes and behaviors during the COVID-19 pandemic were investigated. Categorical variables are demonstrated as numbers and percentages, whereas continuous variables are presented as minimum, maximum, and mean values. Results: A total of 575 participants completed the questionnaire. The mean participant age was 21.7 years. Fifty-two percent of participants knew about the coronaviridae family before the outbreak and 38.8% were informed about COVID-19 in their medical schools. Of the students, 99.7% stated that the first case's origin was in China. Eighty percent of the participants stated that droplet spread is the transmission route of COVID-19. The most common opinion about the incubation period of the SARS CoV-2 was two to twelve days. Being older than 65 years old, having a comorbidity, being immunosuppressed, or working in the healthcare sector were the most particular risk factors to get infected. The majority of the participants follow the vaccine developments from social media, radio and television. According to 75.83% of the participants, all people should wear a mask in daily life for protection. Conclusion:The epidemiology and diagnostic factors of COVID-19 are well known by medical students. To minimize information pollution and raise awareness, medical students should be educated about pandemic and management of it. Further evaluation with various methods and more participants may help to better understand the awareness of the COVID-19 pandemic in medical students.

e15516 Background: The invasion of extramural veins is an independent predictor of poor outcome in colorectal cancer whereas the significance of intramural component of venous as well as lymphatic and perineural invasion is less clear. We aimed to search the prognostic impact of these invasion patterns and their association with various clinicopathological variables. Methods: All patients undergone surgery for colon cancer between December 2014 and December 2020 were analyzed retrospectively and patients with stage II and III disease were enrolled. The patients were divided into four categories as no invasion, intramural invasion only, extramural invasion only or both (intramural and extramural) for vascular invasion (VI), lymphatic invasion (LI) and perineural invasion (PNI). 5-year disease-free (DFS) and overall-survival (OS) were the primary outcomes. Results: 626 patients were included (47.1% stage II patients). There was no significant difference between the presence of ‘intramural only’ venous (DFS, 87.2 vs 88.4% p = 0.84; OS, 88.3 vs 90.7% p = 0.90), lymphatic (DFS, 89.5 vs 85.1%, p = 0.13; OS, 89.5 vs 89.4%, p = 0.9) and perineural invasion (DFS, 89.1 vs 80.9%, p = 0.26; OS, 90.6 vs 84.8%, p = 0.12) compared to ‘no invasion’ in terms of DFS and OS. Invasion of both intramural and extramural compartments for each of these parameters demonstrated poor survival. Presence of exclusively extramural venous and perineural invasion without intramural invasion had adverse effect on DFS (87.2 vs 78.7%, p = 0.036, 89.1 vs 80.9%, p = 0.044, respectively) but not OS (88.3 vs 89.3%, p = 0.78, 90.6 vs 83.8%, p = 0.215, respectively). Tumor sidedness did not have impact on the depth and rate of lymphatic invasion however right-sided and dMMR tumors exhibited less venous and perineural invasion (24.7 vs 33.9% p = 0.007; 34.5 vs 41.5% p = 0.034 and 13.5 vs 33.5% p < 0.001; 25 vs 41.4% p = 0.004, respectively). The ratio of stage III patients with venous, lymphatic and perineural invasion was consistently higher when compared with stage II patients (for LI 69.8 vs 39.7% vs p < 0.001; for VI 36.9 vs 22.7% p < 0.001; for PNI 51.4 vs 24.4% p < 0.001). Low grade tumors exhibited less LI and PNI when compared with high grade tumors (for LI 53.2 vs. 71.3% p = 0.004, for PNI 37.1 vs. 48.3% p = 0.031) however there was no significant difference for venous invasion rates among two groups. Conclusions: Presence of merely intramural component of invasion may not be considered a synonym for lymphovascular invasion which is supposed to be a high-risk factor for systemic recurrence.

Aims: This study aims to investigate the main effects of physical exercise on lower back pain with the Short Form-36 Health Survey and Oswestry Disability Index scores. Methods: University students between 18-25 years old who suffer from low back pain were enrolled in the study. Short Form-36 Health Survey and Oswestry Disability Index were used as the reference scales of lower back pain and quality of life, respectively. There are some questions in the questionnaire to scale the average comfort of the place they sleep and sit during the day, which is the result of the Personal Comfort Score. The Mann-Whitney U test was used for non-normal distributed variables. Correlation and Linear Regression were used to analyze data. SPSS 25.0 was used for all statistical analysis. Results: A total of 139 university students (94 females, 45 males) were included in the study. The median age was 20 years (IQR=2) for female students and 20 years (IQR=1) for male students. Oswestry Disability Index scores of female students were higher, while Short Form-36 scores were lower than the male students. Male students' physical functioning scores were higher than female students. Each one-unit increase in Personal Comfort Score is associated with an increase in the rate between the energy/fatigue (3.34 units). Body Mass Index considerably affected the pain and Oswestry Disability Score, an increase in one unit of baseline BMI upsurged the Short Form-36 pain score to 0.13, and Oswestry disability score to 0.55. Conclusion: In our study, Body Mass Index is found to be associated with Oswestry Disability Index and Short Form-36 score, which are used for the severity of low back pain and defining the life quality and of patients. PCS had a positive correlation between energy/fatigue. In addition, There was a positive correlation between physical exercise and general health score.

e15590 Background: Total neoadjuvant therapy (TNT) integrates whole planned systemic chemotherapy within standard neoadjuvant protocols either before or after radiotherapy for locally advanced rectal cancer (LARC). Preference of neoadjuvant treatment type may vary among the medical oncologists. This study aimed to evaluate impact of professional seniority on TNT approach for LARC. Methods: A 20-item questionnaire was presented to medical oncologists as a cross-sectional survey during a national oncology congress via tablets. The evaluation was stratified by position; early-career oncologists (ECOs) and seniors. 2 questions were about experience regarding rectal cancer treatment. 5 questions were about physicians’ choice of screening and treatment in LARC and the factors affecting their treatment choices. 13 questions were about TNT approach (the sequencing of treatment, denominators of sequencing, chemotherapy choice, treatment response evaluation, operation preferences, adjuvant treatment and its denominators). Results: 189 medical oncologists were included (62.4% (n = 118) ECOs). An endorectal ultrasound was significantly preferred by the seniors (p = 0.039) in addition to conventional staging tools. 65.6% (n = 124) of the participants preferred long-course chemoradiation as their favorite neoadjuvant treatment approach. External sphincter invasion, threatened circumferential resection margin (CRM) and clinical stage were the most common denominators of TNT regardless of experience. ECOs favored short-course RT (p = 0.009) while the seniors chose long-course chemoradiotherapy (p = 0.041) as the index step of TNT. 57% (n = 108) of the physicians preferred to monitor treatment response for TNT at 8-weeks periods. Almost half of the participants (47.1%) reported pathological complete response (pCR) rates between 25-50% with TNT in their clinical practice. The physicians who prefer to give adjuvant treatment after completion of TNT make individualized decisions when surgical pathology reveals non-pCR, CRM and lymph node involvement. There was a significant difference between the ECOs and seniors (63.6 vs 45.1%, p = 0.013) in terms of choosing the adjuvant chemotherapy based on CRM positivity. Majority of the senior medical oncologists (88%) and ECOs (76.3%) agree that TNT should be the standardized neoadjuvant treatment approach for LARC. The preferred adjuvant chemotherapy after TNT was capecitabine-oxaliplatin (51.1%) or capecitabine alone (46%). Conclusions: TNT for LARC is well accepted among the medical oncologists and the professional seniority seems to affect its clinical application.

Background: Extramural venous invasion is an independent predictor of poor outcome in colorectal cancer, whereas the significance of the intramural component of venous and lymphatic and perineural invasion is unclear. Aims: To evaluate the prognostic impact of intramural components for venous, lymphatic, and perineural invasions and the relation of these invasion patterns with clinicopathological features in patients with colon cancer. Study Design: A retrospective cross-sectional study. Methods: The analysis included 626 patients with colon cancer in stages II and III. All patients were divided into four categories (no invasion, intramural invasion only, extramural invasion only, or both intramural and extramural invasions) for vascular invasion, lymphatic invasion and perineural invasion. The primary outcomes were 5-year disease-free and overall survival. Results: Right-sided (for vascular invasion, 24.7% vs. 33.9%, p = 0.007; for perineural invasion, 34.5% vs. 41.5%, p = 0.034) and dMMR tumors (for vascular invasion, 13.5% vs. 33.5, p < 0.001; for perineural invasion, 25% vs. 41.4%, p = 0.004) exhibited less venous and perineural invasion. Compared with no invasion, presence of intramural invasion only, did not exert any effect on disease-free or overall survival for vascular invasion, lymphatic invasion, and perineural invasion. Multivariate analyses revealed that the presence of both intramural and extramural invasion was independently associated with poor disease-free and overall survival for venous (hazard ratios: 2.39, p = 0.001; hazard ratios: 2.46, p = 0.001), lymphatic (hazard ratios: 2.456, p < 0.001; hazard ratios: 2.13, p = 0.02) and perineural invasion (hazard ratios: 2.99, p < 0.001; hazard ratios: 2.68, p < 0.001), respectively. Conclusion: Our data strongly advocates the importance of reporting intramural and extramural components of invasion since the presence of intramural invasion alone may not be considered as a high-risk factor for systemic recurrence.