Short-term outcomes from the 'Watch and Wait' (WoW) study: prospective cohort study.

Background: Despite absence of level 1 evidence on the long-term oncological safety of non-operative management for rectal cancer (watch and wait), increased implementation has occurred globally over the past decades. In Sweden, a pan-national prospective non-randomized study was initiated in 2017 to assess its implementation.

Method: Patients with biopsy-proven rectal cancer receiving neoadjuvant therapy according to national guidelines in whom a clinical complete response was detected at reassessment were eligible for inclusion following informed consent. Only patients with an opportunistic watch-and-wait approach were included. Inclusion and follow-up, according to the study protocol, was managed at the participating study centres. The primary outcome measure of the study is 3-year disease-free survival. Here, the secondary short-term outcomes local regrowth rate, distant metastasis rate and outcomes after surgery for regrowth, at 6 months follow-up, are reported.

Results: Between January 2017 and February 2023, 211 patients with a clinical complete response were included in the study. Thirty-three (16%) patients developed suspicious regrowth within 6 months of inclusion. Thirty-two of 33 patients had abdominal resectional surgery for regrowth. The curative intention rate was 94% for patients with regrowth. Three patients (1.4%) developed distant metastases within 6 months of inclusion.

Conclusion: This Swedish national study on watch and wait reports regrowth rates after 6 months are in line with previous reports in the literature. Nearly all patients with early regrowth could be treated with salvage surgery and curative intent.