Purpose: The aim of this study was to determine the value of DCC (deleted in colorectal cancer) protein for predicting metachronous distant metastases after curative surgery for rectal cancer. The DCC protein--for which a gene has been located on chromosome 18q--has recently been reported to have a prognostic value in colorectal cancer. This finding might have implications for treatment of International Union Against Cancer Stage II rectal carcinoma, in which distant metastases will develop in 14 percent of patients despite optimal surgery.
Methods: Paraffin-embedded tissues from 85 patients who developed distant metastases, but no local recurrence, after curative surgery for rectal cancer were matched with 85 samples from patients who remained disease-free. Matching criteria were tumor stage, age, gender, and date of surgery. Expression of DCC protein was assessed using immunohistochemistry. End points of follow-up were recurrence of disease and death. Mean follow-up was 9.6 years. No patient received either local or systemic adjuvant therapy.
Results: The DCC protein was found to be expressed in 64.9 percent of tumor samples. Nonexpression of DCC protein had an negative influence on survival (P = 0.03). For all tumor stages together, sensitivity of the test for subsequent occurrence of distant metastases was 42 percent and specificity was 71 percent. In Stage II cancers, the positive predictive value was 19 percent, and the negative predictive value was 88 percent.
Conclusions: Our results confirm that DCC protein is a useful prognostic marker in patients with rectal carcinomas, but the positive predictive value of DCC protein for occurrence of metachronous metastases does not appear to be sufficient to justify adjuvant therapeutic measures in Stage II rectal cancer.