Serum beta 2-microglobulin in patients with bronchial carcinoma and controls.

We measured serum levels of beta 2-microglobulin in 467 patients mainly with suspected pulmonary malignancy. By applying serum concentrations of 3.0 mg/liter as the normal upper limit, we found elevated levels in 21% of the patients with verified bronchial carcinoma (n = 230) and in 11% of the patients with lung diseases of infectious, inflammatory, or other origins but without proven malignancy. A rise in serum beta 2-microglobulin levels with advancing age was demonstrated in cancer patients and controls. No significant differences in serum concentrations were seen between cancer patients subgrouped according to the WHO clssification. Serial measurements on cancer patients generally revealed increasing serum-beta 2-microglobulin with time. The most striking elevations during tumor growth were observed in patients with small cell anaplastic or epidermoid carcinoma. After surgical removal of the lung tumor, no decrease of beta 2-microglobulin was found. Patients who at admission had low circulating levels of beta 2-microglobulin (less than 1.5 mg/liter) had a better prognosis than those with serum beta 2-microglobulin greater than 3.0 mg/liter. The mechanism behind elevated beta 2-microglobulin in bronchial carcinoma and the variation of this protein during progression of the cancer disease is unknown. One possible interpretation is that levels increase as a consequence of an increased cell turnover in tumor tissue in combination with an enhanced immune response secondary to the malignant process.