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92 Background: Gastric cancer is the leading cause of cancer death in Chile, with mortality rate of 26.7/100.000 in men, placing the country among the highest mortality rates worldwide. For locally advanced gastric cancer, a multimodality treatment is recommended, but in Chile, the treatment covered by the public health insurance, which assists more than 70% of the patients, is surgery alone. We conducted an observational study to assess efficacy and toxicity of perioperative chemotherapy (CT) in public hospitals in Chile (NCT01633203). Methods: Patients with locally advanced, operable gastric carcinoma, defined as presence of invasion of serosa or beyond (cT > 3 AJCC 2002) and/or lymph node metastasis (cN+) without distant metastasis (M0), were offered to receive preoperative CT with Epirubicin+Cisplatin+Capecitabine (ECX) regimen for 3 cycles followed by curative surgery with D2 lymphadenectomy. Staging abdominal CT scan was mandatory, laparoscopy was recommended. Patients with gastric retention, severe dysphagia or contraindications for CT were excluded. All patients signed the IRB approved informed consent form prior to enrolment. Data were collected using the OpenClinica platform. Results: Between August 2010 and March 2013, 110 patients were screened and 61 enrolled. Median age was 62 years (23-76 years) and most patients had good performance status at baseline (ECOG 0: 42, ECOG 1: 19). Tumor site was proximal in 24 (39%), medial in 16 (26%) and distal in 10 patients (16%). All but 4 patients (n = 57, 93%) completed three cycles of preoperative CT as planned. Fifty-five patients were operated and 54 (89%) had curative R0 resection. Of these, 36 (67%) had pT0-2, and 15 (28%) had pN0 tumors. A complete pathological response was found in 2 patients. Two patients were not operated for other reasons (one patient refused surgery and one patient presented a cerebrovascular accident during preoperative CT and died), and 5 patients (8%) progressed. As of September 1, 2015, 32 patients died. Three-year survival rate was 49%. Conclusions: Perioperative CT is feasible in public hospitals in Chile and should be offered as an alternative to primary surgery for patients with locally advanced gastric cancer.

101 Background: Gastric cancer (GC) is one of the leading causes of cancer death. Perioperative chemotherapy (CT) for locally advanced GC improves curative resection rates and survival compared to surgery alone. Response assessment is challenging and no tumor markers have been validated for this purpose. We conducted a pilot study to investigate the role of methylated Reprimo (RPRM) cell-free DNA (cfDNA) as tumor marker for assessment of response to preoperative CT in patients enrolled in the study GOCCHI 2009-01 (NCT01633203). Methods: Patients with locally advanced GC referred to receive preoperative CT with Epirubicin + Cisplatin + Capecitabine for 3 cycles were offered to enter the study. Patients had to have operable GC, with baseline CT showing a transmural tumor and/or regional lymphnode metastasis with no distant spread assessed by a multidisciplinary tumor board. After the approval of the amendment of the protocol to allow blood sampling for tumor marker measurement and only if informed consent had been given, blood samples were taken at day one of each cycle of preoperative CT. The status of methylated RPRM cfDNA was assessed by Methylight and the number of copies per mL was determined. Patients with at least 2 samples were analyzed. Results: Thirteen patients signed the informed consent form for this substudy, and 11 patients had blood samples available for analysis. Of these, 8 patients had detectable methylated RPRM cfDNA on Day 1 of the first cycle (i.e. baseline). Five patients showed decrease in methylated RPRM cfDNA, while 5 patients had increased levels of the tumor marker in subsequent measurements. In one patient, methylated RPRM cfDNA was not detected in either of two assessments. One patient with a marked increase in methylated RPRM cfDNA after two cycles of CT had metastatic disease at laparotomy. Correlation between pathological findings and changes in methylated RPRM cfDNA will be presented. Conclusions: Our findings suggest that methylated RPRM cfDNA could serve as a novel tumor marker to assess response in locally advanced GC treated with preoperative chemotherapy. Further validation of these preliminary results is warranted.

319 Background: Gallbladder cancer (GBC) is the leading cause of cancer death in women in Chile. Even after curative surgery, prognosis is grim. To evaluate acute and late toxicity and efficacy in terms of overall survival of adjuvant chemoradiation (CR) after curative resection of GBC. Methods: We retrospectively analyzed the cohort of patients with curatively resected GBC diagnosed between January 1999 and April 2009, treated with adjuvant CR at the Instituto Nacional del Cáncer, Santiago de Chile. Treatment protocol considered external beam radiation therapy (RT) (45–54 Gy) to tumor bed and regional lymphnodes with concurrent 5-fluorouracil (5-FU) (500 mg/m2/day by 120-h continuous infusion on days 1-5 and 29-33). Data was obtained from medical records, mortality from death certificates. NCI CTC v 3.0 was used for toxicity grading, and 6th Edition of AJCC Cancer Staging Manual for staging. Survival was estimated by Kaplan- Meier curves. Results: 45 patients with curatively resected GBC received adjuvant CR. Mean age was 56 years (range 33-75), 38 patients were female. All patients had PS 0 or 1 at baseline. After diagnosis a second surgery was performed in 41 patients. Cholecystectomy with hepatic segmentectomy and lymphadenectomy was the curative surgery in 40 patients. For tumor and staging details see the Table. All patients received RT with a planned dose of 45 Gy in 25 fractions. 9 patients received a boost to the tumor bed up to 54 Gy. Three patients stopped RT early. 33 patients had concurrent 5-FU, 31 completed treatment as planned. Therapy was well tolerated, only 4 grade 3 toxicities were observed (1 neutropenia, 1 thrombocytopenia, 2 elevated alkaline phosphatase). No grade 4 or 5 toxicity was observed. No grade >2 late toxicity was observed. Twenty two patients have died. Median survival was 26 months, with 3- and 5-year overall survival of 64% and 46% respectively. Conclusions: Adjuvant chemoradiation with 5-FU is well tolerated and might impact favorably on survival in patients with curatively resected GBC. [Table: see text] No significant financial relationships to disclose.