Background/aims: Chemo-radiation therapy (CRT) has been used to improve local control and survival in patients with advanced rectal carcinoma. However, a significant proportion of patients shows poor response to adjuvant CRT. We thus investigated the usefulness of RAD51 expressions as a predictive maker of the CRT response.
Methodology: Forty two patients who suffered from lower rectal cancer were investigated. All patients received preoperative CRT consisting of TS-1, concurrent with 40Gy of pelvic irradiation before having curative radical resection. The relationship between pathological responses of the tumors after therapy and expression of RAD51 was evaluated by immunostaining of resected specimen.
Results: Positive expression of RAD51 was observed in 24 of 42 patients (57.1%). RAD51 positively expressed in 68.2% (15 of 22 cases) of SD and 42.2% (9 of 20 cases) of PR and CR. There is a tendency of reverse correlation between clinical response and expression of RAD51. Regarding the correlation between pathological response and RAD51 expression, positive expression of RAD51 was recognized in 75.0% (15 of 20 cases) of Grade 1, 47.1% (8 of 17 cases) of Grade 2 and 20.0% (1 of 5 cases) of Grade 3. A significant reverse correlation was recognized between RAD51 expression and pathological responses.
Conclusions: RAD51 expression could be one of the most important predictive factors of preoperative CRT for advanced lower rectal cancer.