A New Test for Recurrent Colon Cancer

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The summary below is from the full report titled "Guanylyl Cyclase C Messenger RNA Is a Biomarker for Recurrent Stage II Colorectal Cancer." It is in the 7 December 1999 issue of Annals of Internal Medicine (volume 131, pages 805-812). The authors are B. Cagir, A. Gelmann, J. Park, T. Fava, A. Tankelevitch, E.W. Bittner, E.J. Weaver, J.P. Palazzo, D. Weinberg, R.D. Fry, and S.A. Waldman.

What is the problem and what is known about it so far?

In less advanced stages (stages I and II), cancer of the colon (large intestine) does not extend outside of the large intestine, and cancer cells are not seen under the microscope in the lymph nodes that lie near the large intestine. Surgery alone is used to treat these early stage cancers; chemotherapy is reserved for cancers at more advanced stages. Despite the fact that cancer cells cannot be found with ordinary testing of the lymph nodes in early stage colon cancers, the cancer recurs after initial surgery in up to half of the patients with stage II cancer. This suggests that some cancer cells are actually hidden in the lymph nodes but are just not detected by the tests available. Researchers have looked for other ways to detect these hidden cells, but none of these have proven reliable so far.

Why did the researchers do this particular study?

They wanted to see if testing lymph nodes from patients with early (stage II) cancers for a substance known as guanylyl cyclase C (GCC) would provide a clue as to which patients had cancer cells hidden in those nodes. GCC is ordinarily found only in intestinal cells—both normal cells and cells from intestinal polyps and cancers—but not in lymph nodes.

Who was studied?

Stored specimens of lymph nodes from 21 patients treated at least 6 years previously for stage II colon cancer were obtained from the pathology laboratory. Eleven of these 21 patients were still free of the cancer 6 years or more after the initial surgery; the cancer had come back within 3 years of surgery in the other 10 patients.

How was the study done?

The researchers looked for GCC in lymph nodes using special, highly sensitive tests.

What did the researchers find?

GCC was present in the lymph nodes of all 11 patients who later developed recurrent cancer but in none of the 10 patients who remained free of cancer.

What were the limitations of the study?

The study was very small, included only patients with stage II cancer, and used specimens of lymph node tissue that had been stored for a long time. The test for GCC is still experimental and is not widely available. Also, the study did not try to see whether more intensive therapy for patients with GCC in their lymph nodes would actually prevent cancer from returning.

What are the implications of the study?

These results suggest that testing for GCC in lymph nodes of patients with early stage colon cancer could eventually be useful in predicting which patients are likely to have their cancer return after early surgical treatment.