Clinical significance of plasma vascular endothelial growth factor in gastrointestinal cancer

Circulating vascular endothelial growth factor (VEGF) was measured in gastric and colorectal cancer patients using an enzyme-linked immunosorbent assay (ELISA). Firstly, serum and plasma samples were collected from 20 normal controls to compare the values of VEGF and to determine which specimen type was most suitable for detecting circulating VEGF. Seventeen of 20 normal controls had plasma VEGF levels under the limit of detection (15 pg/ml) and the levels of the remaining three controls were 21, 22 and 38 pg/ml. In contrast, all serum samples indicated high levels of VEGF (mean 238 pg/ml), ranging from 44 to 450 pg/ml. In a time-course test of two normal controls serum VEGF values increased markedly between 30 and 60 min and remained high, whilst plasma VEGF values were low up to 480 min. Thus, plasma samples are more suitable for the measurement of circulating VEGF. Next, plasma VEGF levels were examined in 44 patients with gastric cancer (8 early, 7 advanced without remote metastasis and 29 metastatic), 13 with colorectal adenoma (2 with focal cancer) and 26 with colorectal carcinoma (8 advanced without metastasis and 18 metastatic) before treatment. An extremely high plasma concentration of VEGF was seen in some cancer patients with metastasis. To discriminate these patients, a cut-off level was determined, considering both the distribution of the sample concentration and the upper limit of 95% confidence area of VEGF in the cancer patients without metastasis. The cut-off value was 108 pg/ml and most cancer patients without metastases had VEGF levels below the cut-off value. In 11 of 29 metastatic gastric cancer patients (38%) and 9 of 18 metastatic colorectal cancer patients (50%), plasma VEGF levels were higher than the cut-off value. Survival was also analysed in the patients with metastasis. It was significantly longer in the patients with low VEGF levels (below the cut-off) than in those with high VEGF levels (logrank test, P = 0.042). 34 patients with metastasis (19 gastric cancer and 15 colorectal cancer) were treated with systemic chemotherapy, and their pretreatment levels of plasma VEGF and conventional tumour markers (CEA and CA19-9) were evaluated in relation to response. The response to chemotherapy was significantly higher in patients with low VEGF levels (< or = 108 pg/ml) than in those with high VEGF levels (P = 0.047). Such a difference was not observed with CEA/CA19-9. In conclusion, plasma VEGF is a useful marker for tumour metastasis and patient survival, and a possible predictive factor for the response of patients with gastrointestinal cancer to chemotherapy.