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Calcitonin elevation in small cell lung cancer without ectopic production
M J Kelley1, K L Becker, J M Rushin
1NCI-Navy Medical Oncology Branch, National Cancer Institute, National Naval Medical Center, Bethesda, MD 20889-5105.
American Journal of Respiratory and Critical Care Medicine
|January 1, 1994
Summary
In patients with small cell lung cancer (SCLC), elevated calcitonin (CT) levels may not always originate from the tumor itself. Some patients show high CT despite undetectable tumor CT, suggesting non-ectopic sources.
Area of Science:
- Endocrinology
- Oncology
- Biochemistry
Background:
- Small cell lung cancer (SCLC) is associated with elevated calcitonin (CT) levels.
- The origin of this elevated CT (ectopic tumor production vs. other sources) in SCLC patients requires clarification.
Purpose of the Study:
- To investigate the contribution of ectopic calcitonin production by SCLC tumors versus non-ectopic secretion.
- To correlate serum and urine immunoreactive CT (iCT) levels with tumor CT mRNA expression and CT production in SCLC patients.
Main Methods:
- Radioimmunoassay (RIA) was used to measure serum and urine immunoreactive CT (iCT) in 86 subjects (49 SCLC patients, 17 smokers, 20 nonsmokers).
- CT mRNA expression in SCLC tumor cell lines was assessed using RNase protection assay (RPA).
- Immunohistochemical staining was performed on tumor samples to detect iCT.
Main Results:
- Serum and urine iCT levels were significantly higher in SCLC patients compared to smokers and nonsmokers (p < 0.0003).
- In 16 SCLC patients with available tumor cell lines, CT mRNA was detected in 9 and iCT in 8.
- Five SCLC patients with undetectable tumor CT mRNA and iCT still exhibited elevated serum or urine iCT levels, exceeding those in smokers.
Conclusions:
- Elevated iCT values in some SCLC patients are likely due to non-tumor sources.
- The study highlights the complexity of CT secretion in SCLC and the potential for extrapulmonary sources of CT.