Answers to Frequently Asked Questions
What
is HAMA?
Why use CEA-Scan if the CEA blood level is not yet drastically elevated?
Over 95% of colorectal cancers, as well as more than 80% of other solid tumors express CEA. Clinical experience has shown that CEA-Scan does localize CEA-expressing tumors in patients with "normal" blood CEA levels. Many patients with known tumor and normal blood CEA levels have tumors that simply don't shed enough CEA to be detected with today's blood tests ... but there is enough CEA at the cell membrane to be localized with CEA Scan.
Murine monoclonal antibodies (mMab) can sensitize the immune system and induce human anti-mouse antibodies (HAMA). The presence of HAMA in patients can cause false-positive or false-negative results with tests for the determination of blood CEA levels. HAMA may also change the biodistribution of mMab-based diagnostic agents such as CEA-Scan and increase the risk of an adverse reaction. Common adverse reactions to mMab include nausea, rash, generalized itching, headache, upset stomach and fever. Anaphylactic type reactions are rare, but possible; therefore, CEA-Scan should not be administered to patients who are hypersensitive to murine-derived products. A prudent practice is to monitor patients’ vital signs for about 20 minutes following the injection of any protein derived product.
Patients who have previously received CEA-Scan have a greater chance of developing HAMA, which increases the risk of allergic reactions, and altered biodistribution of CEA-Scan . The presence of HAMA may also interfere with two-site mMab based immunoassays, such as for CEA or CA-125. If HAMA is suspected, the clinical laboratory should be notified that interference may occur. Adverse reactions observed with CEA-Scan include: Transient eosinophilia, nausea, bursitis, urticaria, generalized itching, headache, upset stomach and fever. There has been one report of a grand mal epileptic seizure in a severely hypertensive patient that may have been possibly related to CEA-Scan infusion.
The fragment technology used with CEA-Scan yields a product to which less than 1% of patients develop HAMA after a single injection. Even though CEA-Scan is currently only indicated for single use in the U.S. and Canada, clinical studies involving re-administration of CEA-Scan in a small population of patients have yielded similar HAMA rates as with patients who only had one injection.
If an adverse reaction or altered biodistribution of CEA-Scan is suspected of being related to HAMA, telephone Immunomedics, Inc. in the U.S. at (800)327-7211 between 8:30 a. m. and 5:00 p.m. eastern time for information on procedures to submit a patient serum sample for assessment of HAMA against mMab fragments.