SCARLET - Italian proSpeCtionAl obseRvationaL multicEntre Study on Treatment for recTal pT1 Cancer

Background To date, the therapeutic management of patients with pathological T1 (pT1) rectal cancer after local surgical or endoscopic excision remains a subject of ongoing debate. Although traditional radical surgery has demonstrated proven advantages, discussion persists regarding the adequacy of less invasive techniques for specific subgroups of patients, particularly those with a low risk of disease progression. In these cases, local excision options through endoscopic or surgical interventions, including Endoscopic Submucosal Dissection (ESD), Transanal Minimally Invasive Surgery (TAMIS), and Transanal Endoscopic Microsurgery (TEM), may represent a valid curative approach. These techniques, which generally carry a low risk of lymph node metastasis, offer important advantages in terms of organ preservation and reduction of postoperative complications, including anorectal, urinary, and sexual dysfunction, which may significantly impair quality of life.

Rationale The choice of a conservative approach must be carefully evaluated, especially when post-excision histopathological analysis reveals high-risk features. These include deep submucosal invasion greater than 1 mm, poor tumor differentiation, tumor budding, lymphovascular invasion, or positive or close resection margins. In these situations, radical surgery with Total Mesorectal Excision (TME) is considered the standard treatment strategy for reducing the risk of local and nodal recurrence, although available evidence is largely derived from retrospective studies. Because TME may substantially affect quality of life and functional outcomes, treatment decisions should be discussed within a multidisciplinary team. National and international guidelines suggest that patients with pT1 rectal cancer who present high-risk features and are either unwilling or unsuitable to undergo radical surgery may be considered for alternative organ-preserving strategies, including adjuvant radiotherapy or chemoradiotherapy.

Study Objective This prospective, observational, multicenter study aims to evaluate the impact of adjuvant radiotherapy or chemoradiotherapy on Disease-Free Survival (DFS) in patients with pT1 rectal cancer presenting at least one high-risk histopathological feature who have undergone local excision and declined treatment with TME. The study will also assess long-term oncologic outcomes, organ preservation, and quality of life in this patient population.