We investigated the usefulness of serum
pro-gastrin-releasing
peptide (Pro-GRP) as a
tumor marker for diagnosis, treatment monitoring and the prediction of relapse and prognosis in patients with
small-cell lung cancer (SCLC). Serum samples were obtained from 127 patients with primary
lung cancer (48 patients with
small-cell carcinoma, 31 with
adenocarcinoma, 36 with
squamous cell carcinoma and 11 with
large-cell carcinoma). The cutoff levels of serum Pro-GRP and
neuron-specific enolase (NSE) were set at 46 pg/ml and 10 ng/ml, respectively. The specificity of Pro-GRP was significantly higher than that of NSE (Pro-GRP: 93.7%, NSE: 65.8%, p < 0.01). According to the histological type of
lung cancer, the positive rates of Pro-GRP were 75% (36/48) in the
small-cell carcinomas, 9.7% (3/31) in the
adenocarcinomas, 5.6% (2/36) in the
squamous cell carcinomas and 0% (0/10) in the
large cell carcinomas. The median levels of Pro-GRP in limited disease (LD) and extensive disease (ED) patients were 199 and 295.5 pg/ml, whereas those of NSE were 14.8 and 29.3 ng/ml, respectively. The positive rates of Pro-GRP in LD and ED patients were 80.0% (16/20) and 71.4% (20/28), whereas those of NSE were 70.0% (14/20) and 89.3% (25/28), respectively. The positive rate of NSE tended to elevate with the progression of disease, whereas that of Pro-GRP was already high at an early stage. Among the 29 patients with SCLC who could be followed, the serum Pro-GRP levels of 18 responders were significantly decreased
after treatment (p < 0.01), whereas those of the 11 nonresponders were not significantly different between before and
after treatment (p = 0.72). In the 9 patients with SCLC who relapsed, the serum Pro-GRP levels were again elevated at the time of relapse. Seventeen patients whose ratio of the Pro-GRP level
after treatment to the level before treatment was below 50% (taking the levels before treatment as 100%) survived significantly longer than did the patients whose ratio was over 50% (p < 0.01). The results of the present study suggest that serum Pro-GRP has high specificity and could be a useful marker of SCLC for treatment monitoring and prognosis.