Serum lactic dehydrogenase. Serum LDH levels are sometimes elevated in extensive carcinomatosis, often without any obvious reason. This is especially true in lymphoma, where it may be abnormal in up to 50% cases. However, LDH levels can be elevated in many conditions, which considerably lessens its usefulness in cancer diagnosis.

Carcinoma antigen 19-9. CA 19-9 is a carbohydrate antigen segment of a glycoprotein that appears to be a sialylated derivative of the Lewis A blood group. It is detected by monoclonal antibody immunoassay and is reasonably (but not highly) specific for GI tract origin (Table 33-14).

CA 19-9 in various conditions

Table 33-14 CA 19-9 in various conditions

Currently, although there is considerable research activity, CA 19-9 assay is not being widely used. Although it has reasonably good sensitivity in pancreatic carcinoma, it does not detect these tumors early enough to improve their current dismal prognosis, and it is not specific for pancreatic neoplasms. It might be useful in the workup of patients when pancreatic or gastric carcinoma is a possibility and more informative diagnostic procedures (e.g., ultrasound or CT) are not available or do not provide a definite answer. A definitely elevated CA 19-9 level result would favor carcinoma of GI or GI accessory organs. The specimen has to be sent to a reference laboratory in most cases, and the results would not be available for several days. The CA 19-9 assay could be used to follow pancreatic carcinomas after surgical resection to detect recurrence, but the question then arises as to what could be done if it does recur. Finally, CA 19-9 has been used in addition to CEA in order to detect recurrence of colon cancer. In some cases, CA 19-9 values become elevated before CEA, and the combination of the two tests is said to be more reliable than either test alone. However, at present CA 19-9 is not widely used for this purpose. As noted in Table 33-14, CA 19-9 may be elevated in some persons who do not have cancer. Also, 5%–10% of the population is Lewis A (blood group) negative and will not react with CA 19-9, even if they have cancer.

Centocor CA 15-3 and Hybritech CA 549. CA 15-3 detects membrane antigens against human milk globules. It is said to be elevated in 57% of preoperative breast cancer patients, 75% (68%–80%) of patients with breast cancer with metastases, 3%–9% of patients with benign breast tumors, 4.5%–10.5% of patients with various nonmalignant conditions, and 1% of clinically normal persons. It is said to correlate with the clinical course of about 75% of patients with metastatic breast cancer, more frequently correlating with tumor progression than tumor regression. CA 549 detects any antigen present both in milk fat globule membranes and also in tumor cytoplasm. CA 549 is reported to be abnormal in 53%–90% of patients with metastatic breast cancer and 1%–13% of patients with benign breast disease. Certain other metastatic tumors are also detected.

Flow cytometry test for bladder cancer. One study reports that standard urine cytology detected 58% of high-grade bladder carcinomas and 33% of low-grade bladder carcinomas. Flow cytometry methods detected 76% of low-grade tumors and 100% of high-grade tumors. However, one study suggests that the technique is not reliable when intravesical chemotherapy is given (which is also the problem with standard urine cytology).