Background: The outcome of gastric cancer patients with peritoneal metastasis remains poor. We treated these patients with intraperitoneal and intravenous paclitaxel plus oral S-1 (tegafur/gimeracil/oteracil), followed by gastrectomy in responders. We evaluated the clinical significance of peritoneal lavage carcinoembryonic antigen (CEA) messenger RNA (mRNA) levels as a biomarker for indication of conversion gastrectomy.
Methods: The peritoneal lavage of 68 patients who received the above regimen as induction chemotherapy was repeatedly collected via intraperitoneal access ports. Gastrectomy was considered when improvement of peritoneal metastasis was confirmed by a second laparoscopic examination with negative peritoneal cytology. CEA and porphobilinogen deaminase mRNAs were chronologically quantified using the transcription reverse-transcription concerted reaction method. The CEA mRNA index (CmRI) was calculated as CEA mRNA/porphobilinogen deaminase mRNA × 10,000.
Results: Thirty-nine patients underwent gastrectomy and 29 patients did not (median survival time, 27.8 vs. 10.7 months, respectively; P < 0.001). In gastrectomy-positive patients, the outcome largely differed according to CmRI values immediately prior to surgery. Patients with a preoperative CmRI value <100 (n = 20) were associated with a significantly longer survival than those with a preoperative CmRI value >100 (n = 19) (41.8 vs. 20.1 months, respectively; P < 0.001). A preoperative CmRI value <100 was confirmed as an independent predictor of survival for gastrectomy-positive patients in the multivariate analysis.
Conclusions: The CmRI reflects the response of peritoneal metastases to induction intraperitoneal chemotherapy. It may be a useful biomarker for indicating gastrectomy in gastric cancer patients with peritoneal metastasis.