title: Postoperative chemoradiotherapy vs. preoperative chemoradiotherapy for locally advanced (operable) gastric cancer: clarifying the role and technique of radiotherapy.
abstract: BACKGROUND
  Worldwide, almost one million new cases of stomach cancer were diagnosed in 2012, making it the fifth most common cancer, and the third leading cause of cancer deaths. The current tumor node metastasis (TNM) staging system represents a consensus between the East and the West, and will serve as a strong foundation upon which to build future evidence. In this review article, we first discuss the definition and optimal surgery for locally advanced gastric cancer, followed by the general principles when considering a pre vs. postoperative radiotherapy (RT) strategy. We then provide a synthesis of the existing randomized trial evidence in an attempt clarify the role of pre and postoperative RT in the management of locally advanced gastric cancer.
  
  
  METHODS
  A Medline search 1966-Jun 2014 was undertaken. Randomized trials including patients with locally advanced gastric cancer (using established definitions), comparing RT [with or without chemotherapy (CT)], with surgery alone or other treatment modalities were included. Systematic reviews and evidence based practice guidelines that include this body of primary studies were preferentially discussed. Medline, Cochrane Library, Clinicaltrial.gov, Guidelines Clearinghouse were searched.
  
  
  RESULTS
  Sixteen randomized trials, three systematic reviews and one practice guideline were included as the evidence base. In this group of studies, two reports compared postoperative chemoradiotherapy (CRT) with surgery alone. Driven predominantly by INT0116, they established the role of postoperative CRT to provide a survival benefit in a patient group that underwent surgery with predominantly D0-1 dissections. Preoperative RT (four studies) showed promise for survival benefit but the risks of bias in these trials were high. Postoperative CRT compared with CT alone (eight trials) showed no survival benefit with the addition of radiation although some evidence of activity can be observed with improved local regional control.
  
  
  CONCLUSIONS
  Technical expertise to enable the delivery of high quality RT to complex target volumes as is required in gastric cancer, and surgical standards to ensure the delivery of high quality surgery, have matured in recent years. Six trials with large sample sizes are currently ongoing to better define the role of preoperative CRT (two studies) and postoperative CRT (four studies), when used in conjunction with high quality surgery and RT, and contemporary CT regimens. The moderate likelihood of locoregional recurrences and the favorable therapeutic ratio with using RT preoperatively in other settings, provide optimism that preoperative CRT would have a pivotal role to play in locally advanced gastric cancer. Active accrual into ongoing trials is strongly encouraged.
authors: 1 Radiation Medicine Program, 2 Medical Oncology, 3 Thoracic Oncology, Princess Margaret Cancer Center, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors: Rebecca K S
authors: RK
authors: Wong
authors: 1 Radiation Medicine Program, 2 Medical Oncology, 3 Thoracic Oncology, Princess Margaret Cancer Center, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors: Raymond
authors: R
authors: Jang
authors: 1 Radiation Medicine Program, 2 Medical Oncology, 3 Thoracic Oncology, Princess Margaret Cancer Center, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors: Gail
authors: G
authors: Darling
keywords: Gastric cancer; locally advanced cancer; multimodality; radiotherapy (RT)
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