Colorectal cancer (CRC) is one of the most common cancers worldwide. Stage II/III patients undergo curative-intent surgery yet still face the recurrence risk. Detecting recurrences early provides the best opportunity for optimal treatment. We aimed to develop a microsimulation model to evaluate CRC management-associated outcomes based on current guidelines, including the performance of guideline-recommended surveillance in detecting recurrences.

Two separate individual-level state transition (microsimulation) models for colon and rectal cancer were built with a lifetime horizon using monthly cycles. The models integrated treatment and surveillance strategies per current guidelines.

The currently recommended surveillance modalities by National Comprehensive Cancer Network guidelines for surveilling patients with CRC after curative-intent surgery.

65-year-old patients with stage II and stage III CRC who underwent curative-intent surgery in the USA.

Cumulative recurrences, detected recurrences, detection rate, overall survival and recurrence-free survival in a 5-year horizon, as well as average life expectancy, were the outcome measures used.

Over 5 years, disease recurrence was observed in 9.5% of patients with stage II–III colon cancer and in 38.0% of patients with stage II–III rectal cancer. Of these, 82.5% and 85.5% were detected via surveillance, respectively, within 5 years. The predicted 5-year overall survival was 86.0% for colon cancer and 69.3% for rectal cancer, with corresponding recurrence-free survival rates of 78.9% and 53.8%. Based on current guidelines-recommended surveillance, detecting one colon cancer recurrence requires 148 carcinoembryonic antigen (CEA) tests, 37 CT scans and 21 colonoscopies. In contrast, detecting one rectal cancer recurrence requires 31 CEA tests, 8 CT scans and 4 colonoscopies.

Our validated model suggests that relative to an optimal benchmark in which all recurrences are detected, recurrence detection under current guidelines may be suboptimal, indicating room for improvement. As new tests emerge, this model could be a valuable tool for evaluating existing clinical practices and the potential of new tests to enhance patient outcomes.

There is high interest in long-acting injectable antiretroviral therapy (LAI-ART) among people with HIV (PWH), with many conveniences for uptake and persistence. However, both patients and clinicians have expressed important barriers to effective implementation, including concerns about frequent clinic visits and strain on clinic resources. Administration of LAI-ART by a trained layperson injector (such as family, friend or partner of the patient) can help mitigate some of these patient-identified and clinician-identified barriers. Alternative LAI-ART delivery methods have the potential to increase the PWH and layperson injector’s confidence, empowerment, convenience, privacy and self-management skills and ultimately facilitate LAI-ART uptake and persistence.

INVITE-Home (innovative administration of long-acting injectables for HIV treatment enhancement at home) will support the expansion of LAI-ART in non-clinical settings by developing, implementing and evaluating a comprehensive, theory-informed training to support the administration of LAI-ART by a trained layperson injector. First, INVITE-Home will design and develop an innovative, theory-based layperson injector training to improve acceptability and uptake of LAI-ART in home-based settings, grounded in qualitative evaluation of training barriers and needs of PWH, layperson injectors and clinicians to develop the training. In Aim 2, INVITE-Home will enhance understanding of home-based LAI-ART using the training, by examining implementation and effectiveness of home-based LAI-ART injections.

This study and its protocols have been approved by the University of California, San Francisco (UCSF) Institutional Review Board and the scientific staff of HIV Research Branch, Division of HIV Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, at the Centers for Disease Control and Prevention. Study staff will disseminate findings locally (eg, to partnering clinics, via the UCSF Center for AIDS Prevention Studies’ Community Engagement Core), statewide (eg, the California Department of Public Health’s Office of AIDS) and nationally at conferences related to HIV.

NCT06488846.