Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
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        Breast Carcinoma Associated Antigen Test, Blood
      
Serum or plasma testing for CA27.29
This agent is one of several "tumor marker" antigens which can be detected in a patient's blood. Being manufactured for different test systems or by different test manufacturers may lead to different names for the same (or nearly the same) test...the "name" tending to indicate the specific antibody. CA27.29 is a one-epitope antibody (automated testing on the Chiron ACS system) generated against a particular antigen epitope on a mucinous glycoprotein in the MUC1 family (there are 6-7 MUC families). The histology IHC marker, EMA, roughly corresponds to the membrane location of MUC1 .  This test is a breast cancer test, and it is best used as a serial test wherein doctors are looking for increases or decreases from whatever the baseline level was at the starting point. It is essential for patients to keep in mind that the "normal range" for most lab tests is + or - 2 standard deviations from the "mean" of values found in a group of normal people (rule of thumb: "normal" includes about the 85% of normals closest to the mean). CA15.3 is roughly the same test but performed on the Abbott IMx system (and, on the same test sample, elevations likely not proportional...so, need to serial test by the same method) .

Key Uses
  • post-biopsy imaging detection of questionable small liver, lung, etc. possible mets (especially if too small for PET scan): normal/negative is meaningless; clearly elevated supports likelihood of mets[LMC-02-4883]
  • monitor breast cancer treatment...see if high levels drop with treatment; but, serum changes lag so slowly that changes in imaging status (size and number of liver mets) are the most timely indicator of therapeutic response
  • monitor for recurrence from a state of cure/remission...see if levels start rising.
  • as a clue to the origin of a cancer "of unknown primary"...high levels mean "look for breast".
  • in presurgical chemo case (systemic mets at time of initial diagnosis) that comes to mastectomy and has positive ALNs with significant extranodal spread, significantly elevated marker level would be grounds not to radiate axilla [LMC-01-4378]

Causes of Decreased Values/Levels:
  • normal range is down to zero
  • one hopes to see decreases (or at least a halt in rising levels) during cancer treatment (see above)

Causes of INCREASED (>30U/mL) Values/Levels:
  • high breast-cancer-caused elevations: value tends to correlate with tumor burden1
  • 2% of normals run a mildly elevated value [ warning] (less so with CA27.29 than CA 15.3)3
  • rare (3 of 253 cases) patients develop an elevation which remains steady...a test-system artifact/discordance (can't be confirmed by Western Blot test)
  • breast cancer recurrence elevations more likely with metastases to lung, liver, or bone (so, in general, test is only 77% good that an isolated elevation means a recurrence has taken place).
  • may not elevate early with breast cancer recurrence elsewhere (so, in general, test is only 90% good that an isolated "normal value" means no recurrence)
  • other adenocarcinomas: pancreatic, lung, ovarian, and colorectal3
  • some benign breast diseases2,4
  • cysts or benign tumors of ovary (even common follicular cysts)4
  • cases with uterine fibroids (leiomyomata)
  • intestinal/colonic problems: from irritable bowel syndrome, to enteritis, to colitis.
  • medications: Paxil
  • hypothyroidism4 or anything slowing down liver metabolism of the antigen4
  • chronic hepatitis and/or cirrhosis of the liver2,3,4
  • sarcoidosis3,4
  • tuberculosis3,4
  • systemic lupus erythematosus (SLE)3,4

Test Synonyms:

Other names for this exact or approximate agent are: breast carcinoma associated antigen; MAM6; milk mucin antigen; CA 15.3 (a two-epitope test automated on the Abbott IMx system); MCA; CA549; CA M26; and CA M29. CA27.29 antigen is detected by an antibody to an epitope in the protein core of this MUC1 protein. 

References:

  1. Clinical Chemistry, May 1999, page 630 (technical info.)
  2. Interpretation of Diagnostic Tests, Wallach, 2000, 7th Ed., pages 904-905.
  3. The Handbook of Clinical Pathology [text], McKenna & Keffer, 2nd Ed., 2000, p. 268.
  4. Aguiar-Bujanda D, et. al., "False Elevations...", letter, The Breast J. 10(4):375-6, July/August 2004
 
(posted 23 Dec. 2000; latest addition, 27 October 2004)
 
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