Controversies and progress in adjuvant chemotherapy for patients with locally advanced rectal cancer receiving neoadjuvant chemoradiotherapy

Colorectal cancer is one of the most common malignant tumors worldwide. Surgical resection is the most important and decisive method in the treatment of rectal cancer. Total mesorectal excision (TME) has greatly reduced the local recurrence rate of middle and low rectal cancer. However, local recurrence and distant metastasis remain the leading cause of death in patients with rectal cancer. 5-fluorouracil (5-FU)-based neoadjuvant chemoradiotherapy has been widely accepted in locally advanced rectal cancer and was recommended by various clinical practice guidelines as the standard treatment option. Tumors often achieve satisfactory reduced stage after neoadjuvant radiotherapy, and some patients even achieve pathological complete regression, which brings much controversies to the choice of adjuvant chemotherapy. This article intends to introduce evidence-based evidences for adjuvant chemotherapy for rectal cancer, impact of current neoadjuvant models on choice of adjuvant chemotherapy strategies, controversies and considerations for adjuvant chemotherapy in the context of neoadjuvant radiotherapy. Key words: Rectal neoplasms, locally advanced; Neoadjuvant chemoradiotherapy; Adjuvant chemotherapy