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International audience; BACKGROUND Ampullary adenocarcinoma (AAC) is a rare neoplasm that accounts for only 0.2% of all gastrointestinal cancers. Its incidence rate is lower than 6 cases per million people. Different prognostic factors have been described for AAC and are associated with a wide range of survival rates. However, these studies have been exclusively conducted in patients originating from Asian, European, and North American countries. AIM To evaluate the histopathologic predictors of overall survival (OS) in South American patients with AAC treated with curative pancreaticoduodenectomy (PD). METHODS We analyzed retrospective data from 83 AAC patients who underwent curative (R0) PD at the National Cancer Institute of Peru between January 2010 and October 2020 to identify histopathologic predictors of OS. RESULTS Sixty-nine percent of patients had developed intestinal-type AAC (69%), 23% had pancreatobiliary-type AAC, and 8% had other subtypes. Forty-one percent of patients were classified as Stage I, according to the AJCC 8th Edition. Recurrence occurred primarily in the liver (n = 8), peritoneum (n = 4), and lung (n = 4). Statistical analyses indicated that T3 tumour stage [hazard ratio (HR) of 6.4, 95% confidence interval (CI) of 2.5-16.3, P < 0.001], lymph node metastasis (HR: 4.5, 95%CI: 1.8-11.3, P = 0.001), and pancreatobiliary type (HR: 2.7, 95%CI: 1.2-6.2, P = 0.025) were independent predictors of OS. CONCLUSION Extended tumour stage (T3), pancreatobiliary type, and positive lymph node metastasis represent independent predictors of a lower OS rate in South American AAC patients who underwent curative PD.

To assess whether extended time intervals (8-12, 13-20 and20 weeks) between the end of neoadjuvant chemoradiotherapy and surgery affect overall survival, disease-free survival.Retrospective study in 120 patients with rectal adenocarcinoma without evidence of metastasis (T1-4/N0-2/M0) at the time of diagnosis that underwent surgery with curative intent after neoadjuvant chemoradiotherapy with capecitabine and obtained R0 or R1 resection between January 2010 to December 2014 at the National Cancer Institute of Peru. Dates were evaluated by Kaplan-Meier method, log- rank test and Cox regression analysis.Of the 120 patients, 70 were women (58%). The median age was 63(26-85) years. All received neoadjuvant chemoradiotherapy. No significant difference was found between the association of the median radial (0.6, 0.7 and 0.8 cm; p=0.826) and distal edge (3.0, 3.5 and 4.0 cm; p=0.606) with time interval groups and similarly the mean resected (18.8, 19.1 and 16.0; p=0.239) and infiltrated nodules (1.05, 1.29 and 0.41); p=0.585). The median follow-up time of overall survival and desease free survival was 40 and 37 months, respectively. No significant differences were observed in overall survival (79.0%, 74.6% and 71.1%; p=0.66) and disease-free survival (73.7%, 68.1% and 73.6%; p=0.922) according to the three groups studied at the 3-year of follow-up.We found that widening the time intervals between the end of neoadjuvant chemoradiotherapy and surgery at 24 weeks does not affect the overall survival, disease-free survival and pathological outcomes. It allows to extend the intervals of time for future studies that finally will define the best time interval for the surgery.

e15158 Background: The literature reports that longer interval between the end of neoadjuvantchemoradiotherapy (CRT) and surgery is associated with a better rate of pathologic complete response (pCR) in rectal cáncer. Optimal interval remains to be defined. The effects of the extended time intervals on the prognosis are not clear. The objective was to assess whether extended time intervals ( < 8, 8-12, > 12-20 and > 20 weeks) between the end of neoadjuvant CRT and surgery improve overall survival (OS), disease-free survival (DFS) and pathological outcomes Methods: Aretrospective study was conducted for 124 patients with rectal adenocarcinoma without evidence of metástasis (T1-4/N0-2/M0) at the time of diagnosis that underwent surgery with curative intent after neoadjuvant CRT with capecitabine and obtained R0 or R1 resection between January 2010 to December 2014 at National Cancer Institute of Peru. Patients undergoing emergency surgery and R2 resection have been excluded. Survival curves were calculated according to Kaplan-Meier method and compared with log-rank test Results: Of the 124 patients, 72 were women (58.1%). The average age was 59.5 years. All received neoadjuvant CRT. Rates of pCR in the four groups were 25.0%, 10.3%, 7.7% and 17.2%, respectively. No significant difference was found between the association of the radial (P = 0.418) and distal edge (P = 0.487), with time interval groups and similarly with resected (P = 0.308) and compromised nodules (p = 0.783). The median OS follow-up time was 39.5 months and for DFS was 34 months. No significant differences were observed in OS (p = 0.739) and DFS (p = 0.902) according to the four groups studied. Conclusions: We found that amplifying the time interval at 31.9 weeks did not change the mean radial and distal edge. It does not affect the mean of resected and compromised nodules and does not improve overall survival and disease-free survival. The present study is the only one that reports these results at these time intervals. It allows to extend the intervals of time for future studies that finally will define the best time interval for the surgery.