High circulating tumor cell concentrations in a specific subtype of gastric cancer with diffuse bone metastasis at diagnosis

AIM: To clarify the biological feature contributing to gastric cancer with diffuse bone metastases at diagnosis.METHODS: The participants visited the Department of Clinical Oncology, Akita University Hospital, from January 2014 to August 2015. The selection criterion for gastric cancer with diffuse bone metastases at diagnosis includes over 29 hot spots of bone scintigraphy. Circulating tumor cell were collected from 20 m L of peripheral venous blood drawn using a Cell Search kit and a Cell Tracks Auto Prep system by SRL, a clinical laboratory. The endpoints of this study were correlations between circulating tumor cells(CTC) count and therapeutic outcomes. RESULTS: Among 39 patients with gastric cancer, 5 patients met the criterion. The incidence of this subtype was 12.8%. CTC counts ranged from 235 to 6440 cells/7.5 m L of peripheral blood(median of 1724). These values were much higher than common gastric cancers(2 cells). In chemo-sensitive cases, CTC counts decreased within 14 d(median) from 275, 235 and 1724 to 2, 7 and 66, respectively. On the other hand, CTC counts increased after treatment failure or insensitive case from 2, 7 and 6440 to 787, 513 and 7885, respectively. The correlation between CTC count and survival time showed a trend, but did not reach significance(Y = 234.6- 0.03 X, P = 0.085).CONCLUSION: High CTC count is a biological hallmark of this subtype, and can be used as a direct and definitive indicator of therapeutic outcome.