We read with great interest the recent review article in ESMO Gastrointestinal Oncology by T. E. Kroese et al., which presents an update on the recommendations in oligometastatic disease in esophagogastric cancer as defined by the Oligometastatic Esophagogastric Cancer (OMEC) project. As the biology of esophagogastric cancers becomes better known, identifying patients with oligometastases from esophagogastric cancer who may benefit from more invasive therapies is an urgent and unmet need. The efforts to propose a uniform classification of oligometastatic disease is noteworthy and will certainly aid in designing further clinical trials and pave the way for improved survival outcomes for patients. However, we believe that esophagogastric cancers are not all the same disease: esophageal squamous cell carcinoma, esophageal adenocarcinoma and gastric adenocarcinoma all represent different distinct diseases with differing biology, prognosis, sites of metastases and different optimal treatment strategies.1Siewert J.R. Ott K. Are squamous and adenocarcinomas of the esophagus the same disease?.Semin Radiat Oncol. 2007; 17: 38-44Crossref PubMed Scopus (262) Google Scholar,2Obermannová R. Alsina M. Cervantes A. et al.Oesophageal cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up.ESMO Ann Oncol. 2022; 33: 992-1004Abstract Full Text Full Text PDF PubMed Scopus (110) Google Scholar Hence, considering these different entities together as a whole may confound results, causing key outcomes to be difficult to interpret. In addition, the peritoneum is one of the commonest sites of metastases for gastric adenocarcinoma and gastroesophageal junction (GEJ) adenocarcinoma, presenting in up to 12.9%-26.5% of patients with gastric cancer.3Riihimäki M. Hemminki A. Sundquist K. Sundquist J. Hemminki K. Metastatic spread in patients with gastric cancer.Oncotarget. 2016; 7: 52307-52316Crossref PubMed Scopus (246) Google Scholar, 4Verstegen M.H. Harker M. van de Water C. et al.Metastatic pattern in esophageal and gastric cancer: influenced by site and histology.World J Gastroenterol. 2020; 26: 6037-6046Crossref PubMed Scopus (24) Google Scholar, 5Gwee Y.X. Chia D.K.A. So J. et al.Integration of genomic biology into therapeutic strategies of gastric cancer peritoneal metastasis.J Clin Oncol. 2022; 40: 2830Crossref PubMed Scopus (18) Google Scholar The potential role for conversion surgery in patients with good response to chemotherapy is also emerging.6Ishigami H. Fujiwara Y. Fukushima R. et al.Phase III trial comparing intraperitoneal and intravenous paclitaxel plus S-1 versus cisplatin plus S-1 in patients with gastric cancer with peritoneal metastasis: PHOENIX-GC trial.J Clin Oncol. 2018; 36: 1922-1929Crossref PubMed Scopus (221) Google Scholar,7Chia D.K.A. Sundar R. Kim G. et al.Outcomes of a phase II study of intraperitoneal paclitaxel plus systemic capecitabine and oxaliplatin (XELOX) for gastric cancer with peritoneal metastases.Ann Surg Oncol. 2022; 29: 8597-8605Crossref PubMed Scopus (12) Google Scholar Hence, the inclusion of peritoneal metastases in the definition of oligometastatic disease in OMEC is imperative, given its clinical significance. Finally, the standardization of an imaging modality for baseline and follow-up staging and evaluation of oligometastatic disease is commendable. However, 18[F]2-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG PET) scans are reported to have a low sensitivity rate of 21%-33% for metastases in patients with GEJ and gastric adenocarcinomas.8Fencl P. Belohlavek O. Harustiak T. Zemanova M. FDG-PET/CT lymph node staging after neoadjuvant chemotherapy in patients with adenocarcinoma of the esophageal-gastric junction.Abdom Radiol. 2016; 41: 2089-2094Crossref PubMed Scopus (7) Google Scholar,9Smyth E. Schöder H. Strong V.E. et al.A prospective evaluation of the utility of 2-deoxy-2-[(18) F]fluoro-D-glucose positron emission tomography and computed tomography in staging locally advanced gastric cancer.Cancer. 2012; 118: 5481-5488Crossref PubMed Scopus (116) Google Scholar In addition, only a minority of diffuse-type gastric adenocarcinomas are FDG-avid despite this histological subtype comprising 30% of gastric cancers.10Ooki A. Yamaguchi K. The dawn of precision medicine in diffuse-type gastric cancer.Ther Adv Med Oncol. 2022; 1417588359221083049Crossref PubMed Scopus (15) Google Scholar, 11Kaneko Y. Murray W.K. Link E. Hicks R.J. Duong C. Improving patient selection for 18F-FDG PET scanning in the staging of gastric cancer.J Nucl Med. 2015; 56: 523-529Crossref PubMed Scopus (31) Google Scholar, 12Youn S.H. Seo K.W. Lee S.H. Shin Y.M. Yoon K.Y. 18F-2-deoxy-2-fluoro-D-glucose positron emission tomography: computed tomography for preoperative staging in gastric cancer patients.J Gastric Cancer. 2012; 12: 179-186Crossref PubMed Scopus (13) Google Scholar This suggests that the use of 18F-FDG PET scans as the sole staging modality for oligometastatic disease may be insufficient. Multi-slice computed tomography scan and staging laparoscopy are still useful especially for peritoneal metastases.13Gertsen E.C. Brenkman H.J.F. van Hillegersberg R. et al.18F-fludeoxyglucose-positron emission tomography/computed tomography and laparoscopy for staging of locally advanced gastric cancer.JAMA Surgery. 2021; 156e215340Crossref PubMed Scopus (24) Google Scholar The recent introduction of fibroblast activation protein inhibitor (FAPI) PET scans have also shown to be superior to the conventional 18F-FDG PET in the detection of primary tumor and metastatic lesions, especially for peritoneal metastases.14Arçay Öztürk A. Flamen P. FAP-targeted PET imaging in gastrointestinal malignancies: a comprehensive review.Cancer Imaging. 2023; 23: 79Crossref PubMed Scopus (0) Google Scholar,15Qin C. Shao F. Gai Y. et al.68Ga-DOTA-FAPI-04 PET/MR in the evaluation of gastric carcinomas: comparison with 18F-FDG PET/CT.J Nucl Med. 2022; 63: 81-88Crossref PubMed Scopus (60) Google Scholar In conclusion, the work of OMEC is valuable and important to improving care for patients with oligometastatic esophagogastric cancer. We propose that incorporating peritoneal metastases and reconsidering the sole use of 18F-FDG PET for staging in all esophagogastric cancers may help to provide a more robust classification in diagnosing and defining oligometastatic disease. Taking into account the distinct disease processes of the different cancer subtypes among patients is also vital to determine accurate recommendations for treatment. We eagerly look forward to further updates that will improve patient care in this exciting field. None declared.
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