Predictors of peritoneal metastasis of gastric origin.

Background: Gastric adenocarcinoma is one of the most aggressive forms of cancer. Despite marked advancements in radiological techniques, peritoneal deposits are still only discovered during laparotomies in a significant number of cases. The role of surgery in the management of metastatic gastric cancer is very limited, reducing the value of conducting laparotomies. In addition, conducting laparoscopies for the purposes of properly staging every case of gastric cancer is difficult, especially in healthcare systems with limited resources. It is thus crucial to investigate all possible predictors of peritoneal metastasis of gastric cancer, with the aim of reserving the use of laparoscopies to cases known to have high incidences of peritoneal metastasis despite negative radiological results.

Patients and methods: This is a case control study that included all cases of gastric adenocarcinoma that had presented to the National Cancer Institute-Cairo University between January 2018 and December 2019. The 'cases' group encompassed all gastric adenocarcinoma patients who were found to have peritoneal metastasis, whilst the 'control' group included those patients who were apparently metastasis-free. Comparisons were made between the two groups in terms of demographics, tumor characteristics, and results of laboratory tumor marker investigations.

Results: Patients with peritoneal metastasis were statistically significantly younger than those who had no apparent metastasis (mean ± SD 51.4 ± 12.5 and 56.2 ± 12.6 respectively; P = 0.020). Significant associations were found between a finding of peritoneal metastasis and (i) a middle tumor site (P = 0.002); (ii) tumor thickening morphology (P < 0.001); (iii) undifferentiated histopathology (P = 0.040); (iv) tumor grade III (P < 0.001); (v) lower lymphocyte counts of < 1.9/ml (P = 0.030); and (vi) high levels of CA 19-9 of > 37 units/ml (P = 0.032).

Conclusion: Tumor pathological criteria, including tumor site, degree of differentiation, shape, and grading, as well as laboratory findings of low lymphocytic counts and high levels of CA 19-9 appear to be reliable predictors of the presence of peritoneal metastasis from a gastric adenocarcinoma.