Neoadjuvant Therapy for Locally Advanced Rectal Cancer: Recent Advances and Ongoing Challenges

Abstract

Locally advanced rectal cancer has a rising global incidence. Over the last 4 decades, advances first in surgery and later in radiotherapy and chemoradiotherapy have improved outcomes, particularly with regard to local recurrence. Unfortunately, distant metastases remain a significant problem. In clinical trials of patients with stage II and III disease, distant relapse occurs in 25% to 30% of patients regardless of the treatment approach. Recent phase 3 trials have therefore focused on intensification of systemic therapy for localized disease, with an aim of reducing the distant relapse rate. Early results of trials of total neoadjuvant therapy with combination systemic therapy provided in the neoadjuvant setting are promising; for the first time, a significant improvement in the rate of distant relapse has been noted. Longer-term follow-up is eagerly awaited. On the other hand, trimodal therapy with chemotherapy, radiotherapy, and surgery is toxic. Several trials are currently assessing the feasibility of a watch-and-wait approach, omitting surgery in those with complete response to neoadjuvant treatment, in an attempt to reduce the burden of treatment on patients. The future for rectal cancer patients is likely to be highly personalized, with more intense approaches for high-risk patients and omission of unnecessary therapy for those whose disease responds well to initial treatment. Biomarkers such as circulating tumor DNA will help to more accurately stratify patients into risk groups. Improvements in survival and quality of life are expected as the results of ongoing research become available throughout the next decade.

Keywords: Chemoradiation; Chemotherapy; Radiotherapy; Total neoadjuvant therapy; Toxicity.