Am. J. Respir. Crit. Care Med., Vol 149, No. 1, 01 1994, 183-190.
Calcitonin elevation in small cell lung cancer without ectopic production
MJ Kelley, KL Becker, JM Rushin, D Venzon, R Phelps, DC Ihde, DP Bliss Jr, K Melby, RH Snider and BE Johnson
NCI-Navy Medical Oncology Branch, National Cancer Institute, National Naval Medical Center, Bethesda, MD 20889-5105.
To determine the relative contribution of ectopic calcitonin (CT)
production versus nonectopic secretion of CT in patients with small cell
lung cancer (SCLC), serum and urine immunoreactive CT (iCT) levels of 86
different subjects were measured by radioimmunoassay (RIA) using two
polyclonal antisera (Ab3b and Ab4). The subjects included 49 previously
untreated patients with SCLC, 17 smokers, and 20 nonsmokers. Serum and
urine iCT values were highest in the patients with SCLC, intermediate in
the smokers, and lowest in the nonsmokers (p < 0.0003). Sixteen of the
49 patients with SCLC had tumor cell lines available for determination of
CT mRNA expression by RNase protection assay (RPA) and iCT production by
RIA. CT mRNA was detected in nine of 16 subjects and iCT in eight of 16.
The tumor cell lines of seven patients had undetectable CT by both RPA and
RIA, and of these, five had elevated urine or serum iCT values compared
with those of nonsmokers, and two had levels above all values in the smoker
group. Immunohistochemical staining of formalin-fixed, paraffin-embedded
tumor samples detected iCT in two of four tumors from patients whose tumor
cell lines had CT mRNA by RPA and iCT by RIA, but in none of six whose
tumor cell lines had undetectable CT mRNA. Thus, increased iCT values in
some patients with SCLC are likely due to sources other than CT production
by tumor cells.
