Pro-gastrin-releasing peptide(31-98) is a specific tumor marker in patients with small cell lung carcinoma.

Gastrin-releasing peptide (GRP) is a specific and an actively secreted product of small cell lung carcinoma (SCLC) cells. Based on this observation, we attempted to develop a new approach for early detection of SCLC and for monitoring therapeutic response in SCLC patients. Recombinant human ProGRP(31-98), a region common to three types of human ProGRP molecules, was synthesized, and a convenient radioimmunoassay system was developed; in this assay, the minimum detectable amount in serum was 10 pM when 0.1 ml of unextracted serum was used. Serum levels of immunoreactive ProGRP(31-98) were measured in 247 normal subjects, 180 patients with nonmalignant pulmonary diseases, 231 patients with non-SCLC, and 140 patients with SCLC. The percentages of subjects with the level greater than 10 pM in normal subjects and patients with nonmalignant pulmonary diseases and with non-SCLC were 1.2, 2.2, and 3.0%, respectively. In contrast, 76% of patients with SCLC had elevated levels; the positive rates in SCLC patients with limited and extensive diseases were 73 and 79%, respectively, indicating that the serum Pro-GRP(31-98) level could serve as a reliable tumor marker in SCLC patients, even at a relatively early stage of this disease. Moreover, changes in the serum ProGRP(31-98) showed excellent correlation with the therapeutic responses in SCLC patients. These results indicate that the determination of serum ProGRP(31-98) levels plays an important role in the diagnosis and treatment of SCLC patients.