Carcinoembryonic antigen for monitoring patients with small cell carcinoma of the lung during treatment.

Carcinoembryonic antigen (CEA) was measured at specific intervals in the plasma of 56 patients with small cell carcinoma of the lung. Of these patients, 47 had serial analyses for varying periods during their illness, 42 had pretreatment CEA levels, and 17 of the latter patients had determinations throughout the entire course of their disease. Pretreatment CEA levels were elevated above 2.5 ng/ml for 74% of the 42 patients and above 5.0 ng/ml for 48%. Although exceptions were noted, in general, a direct relationship was found between pretreatment CEA levels and extent of disease or tumor burden. Initial stage of disease, however, was more predictive of survival than was the pretreatment CEA level. With response to therapy, a corresponding decrease in CEA levels occurred for patients with an elevated pretreatment level. For those patients with a pretreatment CEA level below 5.0 ng/ml, an immediate slight increase in level was often seen associated with response and followed by a subsequent fall after one month. A rising CEA level was usually found with recurrence or progression of disease after initial response and occurred frequently prior to clinical evidence of progression. In combination with careful clinical evaluation, serial CEA measurements can aid in assessing tumor changes associated with treatment in patients with small cell carcinoma of the lung particularly at the times of recurrence or disease progression following a partial or complete response.