Recently, there is an increasing tendency of colorectal cancer in Korea, probably due to changes of diet pattern to western style. In rectal cancer, as the local recurrence is a common and major problem despite of radical resection, it is recommended to use 5-fluorouracil(5-FU)- based chemotherapy in combination with pelvic radiation after radical operation in MAC B,-C, cancers. But until now, there are many controversies about the effective chemotherapeutic agent, radiation dose, route, and chemoradiation schedule. There is increasing evidence that genes involved in normal cell growth and differentiation(oncogenes) or genes that encode for growth factor are important in determining the development and biologic aggressiveness of various cancers. Among many oncogenes thought to be related with cancer, c-erbB-2 is a relatively well known protein to be associated with cancers, especially in breast and colorectal cancers. In addition to c-erbB-2 and Epidermal Growth Factor Receptor(EGFR), c-erbB-3 belongs to Type -I Growth Factor Receptor Family(EGFR-related Family) and is the most recently identified protein in EGFR-related Family. There have been a few reports about the prognostic value of c-erbB-3 in breast and prostate cancers. In this study we performed immunohistochemical staining of 114 surgically resected specimens of rectal cancers to investigate the expression rate and clinical relevance of c-erbB-3 as a prognostic factor and drug selection marker. c-erbB-3 expression rate was 46% in 114 rectal cancers and there were significant differences in recurrence rate and survival rate between c- erbB-3 positive and negative group. Twenty-one cases(40%) recurred in 52 c-erbB-3 positive cases and 10 cases(16%) recurred in 62 c-erbB-3 negative cases(p=0.004). The difference in recurrence rate between c-erbB-3 positive and negative group was significant exclusively in MAC stage C(p=0.0126), but not in MAC stage B(p=0.4357). In c-erbB-3 positive and negative group, 2-year disease free survival rate was 66% and 87%, respectively(p=0.0052), and 2-year overall survival rate was 84% and 95%, respectively(p=0.005). Again, the difference in 2-year disease free survival rate between the two groups was significant only in MAC stage C(p=0. 0137), not in stage B(p=0.4182). There were no significant differences in recurrence rate and 2- year disease free survival rate in chemo-radiation group regardless of c-erbB-3 expression and stage. But in adjuvant radiotherapy alone group, increased recurrence rate and decreased survival rate were found in c-erbB-3 positive group. This finding suggested c-erbB-3 as a possible relative radioresistance marker, in whom a higher radiotherapy dose is needed. In conclusion, c-erbB-3 may be regared as a prognostic marker and as a possible indicator of radioresistance in the treatment of rectal cancer.
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