The goal of this observational, no-profit, spontaneous, retrospective, monocentric study is to compare surgical and oncologic outcomes in patients affected by gastric cancer before and after the institution of the Tumor Board, a multidisciplinary weekly case discussion. The main question it aims to answer is whether the Textbook Outcome (TO) and Textbook Oncological Outcome (TOO) of patients with non-early, non-metastatic gastric cancer undergoing surgical treatment with curative intent have improved before (from January 2018 to November 2019) and after (from December 2019 onwards) the establishment of the Multidisciplinary Tumor Board (MTB) at Fondazione Policlinico Gemelli (FPG).

Background. Textbook Outcome (TO) is a composite parameter for quality in surgical oncology proposed by the Dutch Upper Gastrointestinal Cancer Audit (DUCA) group, directly related to survival [1]. A Polish group proposed an integration to the TO, adding the item perioperative chemotherapy administration compliance (POC), for a comprehensive assessment of multimodal treatment in gastric cancer (GaC) patients' management, named Textbook Oncological Outcome (TOO) [2]. This has been subsequently validated in the European GASTRODATA database [3], showing a correlation with lower 90-day mortality rates. The latter study acknowledges a TO of 68.5%, higher than previous experiences reported from the Western world, while reporting a TOO of only 22.8%, pointing out the need to improve multimodal treatment of GC patients.

To evaluate any influence of systematic Multidisciplinary Tumor Board (MTB) on patient outcomes, we aim to assess TO, TOO, Time from first diagnosis To first Therapy (TTT), the appropriateness of Patient to Treatment Allocation (PTA), and MTB hospital Adherence (TBA) as indicators of Tumor Board Performance (TBP) before and after its institution. At Policlinico Universitario Agostino Gemelli, the MTB for GaC was established in November 2019. We will collect data from 2018 to date in order to minimize bias due to different perioperative regimens.

Hypothesis. We hypothesize a global improvement in GaC patients' TO and TOO following the institution of the MTB.

Objectives. The study's primary objective is to evaluate the Textbook Outcome (TO) and Textbook Oncological Outcome (TOO) of patients with gastric cancer undergoing surgical treatment with curative intent before (from January 2018 to November 2019) and after (from December 2019 onwards) the establishment of the Multidisciplinary Tumor Board (MTB) at Fondazione Policlinico Gemelli (FPG) (primary endpoint: percentage of patients achieving TO and TOO out of the total number of patients who underwent surgery with curative intent for gastric cancer at FPG before and after the MTB institution). Secondary objectives include assessing Tumor Board Performance (TBP) by measuring: - Time from diagnosis To Treatment, the interval between diagnosis and beginning of the first oncological treatment (TTT; endpoint: delay in days/weeks from diagnosis to treatment before and after MTB institution), - Patient to Treatment Allocation (PTA; endpoint: percentage of upfront surgery candidates who do not receive adjuvant chemotherapy before and after MTB institution) and - Tumor Board Adherence (TBA; endpoint: percentage of patients operated on at FPG who were previously discussed at the MTB out of the total number of patients who underwent surgery with curative intent for gastric cancer at FPG).

Methods. We will review clinical, pathological, surgical and oncological data of patients affected by Gastric Cancer candidated for surgical intervention -either upfront, either post neoadjuvant treatment, either in conversion surgery- with curative intent for primary and secondary outcomes.

Expected results. This study aims to demonstrate an improvement in Gastric Cancer patients' outcomes, such as Textbook Outcome (TO) and Textbook Oncological Outcome (TOO), following the establishment of the MTB. Additionally, we anticipate enhanced Tumor Board Performance over time, thanks to the improvements of Time from Diagnosis to Treatment (TTT), Tumor Board Adherence (TBA), and Patient to Treatment Allocation (PTA), attributable to a learning effect.

Inclusion Criteria:

• pathology-confirmed diagnosis of gastric adenocarcinoma
• age 18 years or older
• surgical candidates with curative intent

Exclusion Criteria:

• Endoscopic Mucosal Resection (EMR) or Endoscopic Submucosal Dissection (ESD)
• previous EMR or ESD (salvage surgery)
• histologies other than adenocarcinoma (no squamous cell carcinomas, GISTs, sarcomas, lymphomas, etc)
• unsufficient staging (unclear clinical stage at diagnosis)
• emergency presentation (obstrucetd, significantly bleeding, perforated gastric cancer)
• synchronous tumors affecting survival
• pregnant patients
• age <18years

All subsequent patients aged 18 years or older, surgical candidates with curative intent, with a pathology-confirmed diagnosis of gastric adenocarcinoma, treated at Fondazione Policlinico Universitario Agostino Gemelli IRCCS of Rome from 2018 to date.