Symptom trajectories of postoperative low anterior resection syndrome: a scoping review based on multi-time-point follow-up

1.Registration title Symptom trajectories of postoperative low anterior resection syndrome: a scoping review based on multi-time-point follow-up 2. Background and rationale Colorectal cancer is one of the most common malignant tumors of the digestive system worldwide and represents a substantial public health burden. According to the GLOBOCAN 2022 statistics released by the International Agency for Research on Cancer (IARC), approximately 1.93 million new cases of colorectal cancer are diagnosed globally each year, with about 904,000 deaths attributed to this disease. Colorectal cancer ranks as the third most commonly diagnosed cancer and the second leading cause of cancer-related mortality worldwide. In recent years, advances in sphincter-preserving surgical techniques and the widespread adoption of multidisciplinary team (MDT) approaches have led to continuous improvements in sphincter preservation rates and 5-year survival outcomes among patients with colorectal cancer. However, a considerable proportion of patients continue to experience long-term functional complications after surgery, among which low anterior resection syndrome (LARS) is particularly prevalent. Previous studies have reported that approximately 62.3%–82.6% of patients undergoing sphincter-preserving surgery for rectal cancer develop LARS. This syndrome is characterized by a spectrum of bowel dysfunction symptoms, including increased stool frequency, a sensation of incomplete evacuation, urgency, and fecal incontinence, all of which can severely impair patients’ quality of life. Most existing studies have assessed symptom severity using the LARS score; however, the majority have relied on cross-sectional analyses conducted at a single postoperative time point. Longitudinal evidence describing how LARS symptoms evolve over time remains relatively limited. Moreover, existing longitudinal studies exhibit substantial heterogeneity with respect to follow-up schedules, study design, and surgical techniques, leading to inconsistent conclusions regarding symptom improvement trajectories and temporal patterns. Given the diversity of evidence types, the complexity of time-related dimensions, and the heterogeneity of outcome reporting in this research field, and considering that the primary aim of the present study is to comprehensively map the evolution of LARS symptoms rather than to pool effect sizes or compare intervention effects, a scoping review methodology is considered the most appropriate approach. This scoping review aims to systematically map the available evidence on the temporal evolution of LARS symptoms following colorectal cancer surgery, synthesize symptom change patterns across different postoperative time frames, summarize key time windows for symptom improvement and potential stabilization phases, and identify methodological and reporting gaps in the current literature. 3. Objectives and review questions The overall objective of this scoping review is to systematically synthesize longitudinal evidence on the evolution of low anterior resection syndrome (LARS) symptoms in patients after colorectal cancer surgery, and to identify key time points at which symptoms improve or stabilize, thereby providing evidence to inform clinical management and follow-up strategies. Guided by the Population–Concept–Context (PCC) framework, this scoping review seeks to address the following questions: • Population: Adult patients with colorectal cancer who have undergone sphincter-preserving anterior resection and whose postoperative bowel function has been assessed using the LARS score; • Concept: The temporal trajectories, improvement patterns, and stabilization phases of LARS symptoms over time; • Context: Postoperative follow-up studies conducted across different countries and healthcare systems. The specific review questions are as follows: 1. How are follow-up time points and follow-up durations for LARS symptom assessment distributed across existing studies? 2. What typical temporal trajectories of LARS symptoms are reported following surgery? 3. How are key time windows for symptom improvement and relative stabilization defined across studies? 4. What evidence gaps exist in terms of study design and reporting in the current literature? 4. Eligibility criteria The eligibility criteria for this scoping review are developed in accordance with the PCC framework. Participants:Eligible participants are adult patients (≥18 years) with colorectal cancer who have undergone sphincter-preserving anterior resection and whose postoperative bowel function has been assessed using the low anterior resection syndrome (LARS) score. Only studies including patients without a stoma at the time of LARS assessment, or those who had undergone reversal of a temporary diverting stoma, will be included. Studies involving patients who underwent abdominoperineal excision (APE), Hartmann’s procedure, or those with a permanent stoma will be excluded. Concept:This review focuses on the temporal evolution or trajectories of LARS symptoms. Eligible studies must report LARS outcomes at two or more postoperative follow-up time points within the same patient cohort, using a validated LARS scoring instrument, thereby allowing assessment of longitudinal changes in symptom severity. Studies reporting only a single postoperative time point, not using the LARS score, or focusing solely on intervention effects without describing symptom evolution over time will be excluded. Context:Studies conducted in any country or healthcare setting will be considered, with no restrictions on language. Eligible study designs include longitudinal observational studies (such as prospective or retrospective cohort studies and registry-based studies), as well as randomized controlled trials that include follow-up data from control groups not receiving standardized LARS-specific interventions. Time and language restrictions:the LARS score was first developed and validated in 2012, and its Chinese version was subsequently translated and validated in 2013, English-language publications published in or before 2011 and Chinese-language publications published in or before 2012 will be excluded； Exclusion of publication types:Case reports, study protocols, editorials, clinical guidelines, expert opinions, policy documents, duplicate publications, and studies for which full texts are unavailable will be excluded. 5. Information sources The following databases will be systematically searched: • PubMed • Web of Science • China National Knowledge Infrastructure (CNKI) • Wanfang Data • VIP Database In addition, reference lists of included studies will be manually screened to identify potentially relevant publications. The search period will cover from database inception to November 2025. 6. Search strategy A combination of controlled vocabulary terms and free-text keywords will be used. English search terms will include, but are not limited to: low anterior resection syndrome, low-anterior resection syndrome, LARS, LARS score, bowel dysfunction, defecation disorder, evolution, natural history, longitudinal, time course, trajectory, follow-up, change over time. Chinese search terms will include: 低位前切除术, 低位前切除综合征, LARS, 轨迹, 趋势, 变化趋势, 演变, 随访, 纵向, 严重程度. Search strategies will be adapted to the syntax and requirements of each database. 7. Selection of sources of evidence All retrieved records will first undergo title screening by one reviewer to exclude clearly irrelevant studies. Titles and abstracts of the remaining records will then be independently screened for eligibility by one reviewer. Any disagreements will be resolved through discussion, with a third reviewer consulted if necessary. Subsequently, two reviewers will independently assess the full texts of potentially eligible studies. The study selection process will be reported using a PRISMA-ScR flow diagram. 8. Data charting process Data extraction will be independently conducted by two reviewers using a predefined data charting form. Any discrepancies will be resolved through discussion. The extracted information will include: • Author(s) and year of publication • Country or region • Study design and evidence type • Participant characteristics and sample size • Follow-up time points and duration • Surgical procedures • Patterns of LARS symptom change and key findings 9. Synthesis of results Results will be presented in tabular form and narrative summaries to illustrate temporal patterns of LARS symptoms, trajectories of symptom improvement, and potential stabilization phases and synthesized in a stratified manner according to surgical approach and the mode of reporting LARS outcomes (e.g., categorical vs. continuous measures).No methodological quality assessment or meta-analysis will be performed in this scoping review. 10. Amendments Any significant amendments to this protocol made during the course of the review will be documented and updated on the Open Science Framework (OSF) platform, with reasons for the changes clearly stated. 11. Funding and conflicts of interest Funding: None. Conflicts of interest: The authors declare no conflicts of interest. 12. Data and materials sharing plan Upon completion of the review, the following materials will be made publicly available via the Open Science Framework (OSF) or as supplementary materials in a peer-reviewed journal: • Detailed search strategies • Records of the study selection process • Data extraction forms