Abstract 5084: Investigation of expression of RAD51 in biopsied specimen as a predictive factor of chemo-radiation therapy for advanced rectal cancer

Abstract

Abstract 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 show poor response to adjuvant CRT. We thus investigated the usefulness of RAD51 expressions as a predictive maker of the CRT response. METHODOLOGY: Twenty three biopsied specimens among forty two patients who were suffered from lower rectal cancer were investigated. All patients received preoperative CRT consisting of TS-1, concurrent with 40 Gy 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 biopsied and resected specimen, and evaluated the expression of RAD51 as a predictive factor of CRT. RESULTS: Positive expression of RAD51 was observed in 14 of 23 biopsied specimens (61%), and 24 of 42 patients (57.1%) in resected specimen. All RAD51 positive case which expressed in biopsied specimen expressed RAD51 positive in resected specimen. In biopsied specimen, RAD 51 positively expressed in 62.8% (10 of 14 cases) of SD, 44.4% (4 of 9 cases) of PR, and 0% (0 of 0 case) of CR, whereas in resected specimen, RAD 51 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 in biopsied specimen, positive expression of RAD51 was recognized in 90% (9 of 10 cases) of Grade 1, 50% (5 of 10 cases) of Grade 2, and 0% (0 of 3 cases) of Grade 3, and in resected specimen, 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 both in biopsied and resected specimen.CONCLUSIONS: RAD51 expression could be one of the most important predictive factors of preoperative CRT for advanced lower rectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5084. doi:10.1158/1538-7445.AM2011-5084