By Frances Bishopp

Working under a reclassification the FDA approved in September 1996, Centocor Inc. received clearance from the agency to market its CA 15-3 serum tumor marker radioimmunoassay for monitoring patients with breast cancer.

Already on the market in Europe and Japan, CA 15-3 will now be available in the U.S. through a distribution agreement with Fisher Scientific, of Houston. As part of this agreement, Centocor, of Malvern, Pa., is providing four technical marketing specialists to support Fisher sales efforts.

Tumor markers are in vitro diagnostic blood tests used by physicians in the management of cancer patients, William Newbould, manager of investor relations with Centocor, explained. CA 15-3 is used to detect disease in patients with Stage II and Stage III breast cancer.

CA 15-3 joins a line-up of other Centocor tumor markers already on the market, such as: CA 125 for ovarian cancer monitoring (marketed in the U.S., Europe and Japan), CA 19-9 for pancreatic cancer monitoring (marketed in Europe and Japan), CA 72-4 for gastrointestinal cancer monitoring (marketed in Europe and Japan) and CYFRA 21-1 for non-small cell lung cancer monitoring (marketed in Europe and Japan).

Centocor estimates the U.S. market for CA 15-3 to be approximately $15 million.

In September 1996, Centocor successfully petitioned the FDA for reclassification of serum tumor markers, an action that reclassified tumor-associated antigen immunoassay systems from Class III to Class II. The products are now subject to 510(k) premarket notification rather than premarket approval regulations, which require costly and time-consuming clinical trials.

The affected in vitro diagnostic (IVD) systems are used to identify specific tumor antigens and are designed for use with other diagnostic tools for monitoring disease progression, response to therapy and recurrent and residual disease. The reclassification covers use of reagents used to measure, by immunological techniques, tumor-associated antigens in body fluids.

Not included in the reclassification ruling are systems designed to screen for early detection of cancer in the general population and high-risk groups. Also not included are tissue receptor assays, immunohistochemical stains and direct tests for oncogenes and other genetic markers. They will continue to require premarket approval as Class III devices.

Tumor markers allow clinicians to assess treatment success and monitor for cancer remission or recurrence. Traditionally, the assessment procedure consists of a clinical exam, blood tests, radiographs and other expensive diagnostic procedures.

CA 15-3, Newbould said, will cost between $40 and $50 per test.

Centocor, as of March 31, 1997, had $163.8 million in cash. Centocor stock (NASDAQ: CNTO) closed Monday at $33.125, down $1.375. *