An 84-year-old woman presented with the chief complaint of melena. Colonoscopy revealed a type 2 tumor that circumferentially occupied the lumen of the lower rectum about 6 cm from the anal verge. A biopsy specimen was obtained from the tumor and the patient was diagnosed with moderately differentiated adenocarcinoma. Computed tomography revealed that the rectal cancer had invaded the marginal fatty tissue, accompanied by several regional lymph node metastases with no distant metastasis. On the basis of this evidence, the tumor was staged as cT4a, cN2b, cM0 according to the TNM Classification of Malignant Tumors (7th Edition, UICC). Preoperative radiotherapy combined with an oral chemopreventive agent (RT 1.8 Gy × 25 frames; total 45 Gy, S-1 80 mg/day) was administered with trivial adverse effects. Laparoscopy-assisted low anterior resection with Japanese D3 dissection was performed successfully. The patient is doing well without recurrence after 14 months of surgery. Histological examination revealed that both the primary lesion and regional lymph nodes had no residual cancer; that is, the histological effect of the preoperative chemoradiotherapy was a pathologically complete response (pCR).