Abstract
BACKGROUND: According to the latest report, colorectal cancer is still one of the most prevalent cancers, with the third highest incidence and mortality worldwide. Treatment of advanced rectal cancer with distant metastases is usually unsatisfactory, especially for mismatch repair proficient (pMMR) rectal cancer, which leads to poor prognosis and recurrence. CASE SUMMARY: We report a case of a pMMR rectal adenocarcinoma with metastases of multiple lymph nodes, including the left supraclavicular lymph node, before treatment in a 70-year-old man. He received full courses of chemoradiotherapy (CRT) followed by 4 cycles of programmed death 1 inhibitor Tislelizumab, and a pathologic complete response (pCR) was achieved, and the lesion of the left supraclavicular lymph node also disappeared. CONCLUSION: pMMR advanced rectal cancer with preserved intact distant metastatic lymph nodes may benefit from full-course CRT combined with immunotherapy.