# Clinical Complete Response and Organ Preservation Strategies in Rectal Cancer: A Real-World Single-Center Experience Clinical Complete Response and Organ Preservation in Rectal Cancer

## TL;DR

This study shows that some rectal cancer patients can avoid surgery if they fully respond to preoperative treatment, especially those with small tumors.

## Contribution

The study provides real-world evidence supporting organ preservation strategies based on tumor size and stage in rectal cancer patients.

## Key findings

- Clinical complete response was observed in 37.8% of evaluable rectal cancer patients.
- Tumors smaller than 4 cm showed particularly high response rates regardless of neoadjuvant regimen.
- A watch-and-wait approach was implemented in 28.4% of patients, with five recurrences observed over 26 months of follow-up.

## Abstract

Rectal cancer treatment is increasingly tailored according to how well tumors respond to preoperative therapy. In selected patients who achieve a clinical complete response after neoadjuvant treatment, surgery may be safely avoided using a “watch-and-wait” strategy, thereby preserving the rectum and reducing long-term functional impairment. However, most available evidence comes from clinical trials, and data from routine clinical practice remain limited. In this real-world single-center study, we evaluated treatment response and the implementation of organ-preservation strategies in 148 patients with rectal cancer. Clinical complete response was observed in 37.8% of evaluable patients, and a watch-and-wait approach was adopted in 28.4%. Baseline tumor size and clinical stage were the main determinants of response. Tumors smaller than 4 cm showed particularly high response rates, regardless of the neoadjuvant regimen used. These findings support individualized, response-adapted treatment strategies and highlight the importance of tumor burden in selecting candidates for non-operative management in everyday clinical practice.

Background: The management of rectal cancer has evolved toward response-adapted strategies, including organ preservation in selected patients achieving a clinical complete response (cCR) after neoadjuvant treatment. However, most available evidence derives from clinical trials, and data from real-world clinical practice remain limited. Methods: We conducted a retrospective observational cohort study including consecutive patients with rectal adenocarcinoma treated at a tertiary referral center between January 2021 and December 2025. Baseline clinical, tumor-related, and treatment characteristics were collected. Tumor response was assessed using clinical, endoscopic, and radiological criteria. The primary endpoint was the rate of clinical complete response and the implementation of watch-and-wait strategies. Secondary endpoints included recurrence patterns and exploratory oncologic outcomes according to baseline tumor characteristics. Results: A total of 229 patients were identified, of whom 148 were evaluable for treatment response. Clinical complete response was documented in 56 patients (37.8%), and a watch-and-wait strategy was implemented in 42 patients (28.4%). Higher cCR rates were observed in patients with stage I–II disease and in tumors measuring < 4 cm on baseline magnetic resonance imaging, with cCR rates exceeding 55% in this subgroup. Tumors ≥ 4 cm showed substantially lower response rates. Clinical complete responses were observed across both short-course radiotherapy plus chemotherapy and long-course chemoradiotherapy regimens in patients with small tumors and early-stage disease. Tumor distance from the anal verge was not consistently associated with response. With a median follow-up of 26 months in the watch-and-wait group, five recurrences were observed, including three local recurrences. Conclusions: In this real-world cohort, baseline tumor size and clinical stage were the main determinants of clinical complete response and eligibility for organ-preservation strategies in rectal cancer. Small tumors (<4 cm) showed high response rates regardless of neoadjuvant regimen. These findings support response-adapted, individualized treatment strategies and highlight the importance of tumor burden in selecting candidates for non-operative management in routine clinical practice.