Clinical complete regression after local radiotherapy combined with chemotherapy for stage IV rectal cancer: A case report.

Colorectal cancer is the fourth most common type of cancer worldwide with about 0.8 million new cases annually. Improving patient survival remains a challenge for clinicians. Observation waiting method provides improved quality of life compared with direct surgery. This case report suggested that colorectal cancer patients could choose active observation waiting method for treatment. A 59-year-old male patient, with rectal bleeding and an Eastern Cooperative Oncology Group (ECOG) performance status score of 0, was admitted to the hospital due to increased fecal blood volume. The electronic colonoscopy revealed multiple polyps in colon and rectum, whereas the pathological biopsy indicated poorly differentiated rectal adenocarcinoma. The clinical stage was defined as T3N2M1a according to the TNM classification of the American Joint Committee on Cancer (AJCC) staging manual (version 8). In addition, positron emission tomography/computed tomography (PET/CT) examination showed non-regional lymph node metastasis (subclavian). Subsequently, the expression of PD-L1 (-), NRAS (-), KRAS (-), HRAS (-), BRAF (-) (-, negative) and the microsatellite stability (MSS) were detected in the rectal cancer lesion using molecular pathological examination. Patients with primary rectal cancer and pelvic lymph node metastasis were treated with three-dimensional conformal radiotherapy (3D-CRT; dose, 60 Gy/30 Fr) and XELOX chemotherapy (200 mg oxaliplatin at day 1 plus 1.5 g capecitabine twice a day from day 1-14 for a total of 5 cycles). PET/CT scan revealed that the metabolism levels of the lesion returned to normal. In addition, the routine re-examination showed progressive improvement of tumor lesions. Until recently, the carcinoembryonic antigen (CEA) level of the male patient has been within normal range. The observation waiting method rather than the direct sequential surgical resection of the primary lesion in patients with advanced rectal cancer who achieved complete clinical remission (CCR) may provide a novel treatment method for rectal cancer. Thus, overall survival (OS) and quality of survival (QoS) differences between the two strategies need to be further verified by multicenter clinical trials.