The Alberta’s Tomorrow Project (ATP) prospective cohort study was established in 2000 to investigate the causes of cancer and chronic disease. The cohort consists of almost 55 000 participants aged 35–69 years at the time of recruitment. From 2020 to 2022, ATP conducted a longitudinal substudy, the COVID-19 Antibody Testing (CAT) study, nested in this existing cohort, to understand the spread and impact of the SARS-CoV-2. In this cohort profile, we describe the CAT study design, recruitment and initial findings.

In this prospective cohort substudy, ~4000 participants completed online surveys and provided blood samples at a study centre every 4 months for 1 year, across four cities in Alberta, Canada. The study was launched on a rolling basis beginning in September 2020 and data collection was completed in May 2022. The surveys collected information on health and lifestyle factors, COVID-19 (testing, symptoms, vaccination, public health recommendations) and impacts of the pandemic (including economic, health services, mental health). Blood samples were tested for antinucleocapsid and antispike protein SARS-CoV-2 antibodies.

A total of 4102 participants consented and attended a study centre at baseline, and almost 90% of these completed the study. Overall, participants were aged 61±10 years, 60% female, 12% came from rural areas, 45% had at least a bachelor’s degree, 24% reported a household income 4 weeks). By the end of the study, 96% of participants had received at least one COVID-19 vaccine dose. Through investigating other outcomes, it was observed that participants under 50 years of age were more likely to be assessed to have mild or moderate-to-severe anxiety and depressive symptoms compared with older participants. In addition, approximately 15% of participants reported a moderate to major impact on their ability to meet financial obligations.

Serology results, together with health, lifestyle and sociodemographic data, and the continued follow-up of these participants as part of the broader ATP cohort study (planned through 2065), will provide opportunities to investigate the long-term sequelae of COVID-19 infection as well as the broader impacts of the pandemic on physical, mental and emotional health. Data are available to researchers on request through the ATP access process.

Randomised controlled trials have aimed to assess the effectiveness of stereotactic ablative radiotherapy (SABR) with curative intent versus surgical resection for individuals diagnosed with early-stage non-small cell lung cancer (NSCLC) but have failed to recruit sufficient numbers of patients. Non-randomised studies for early-stage NSCLC have reported mixed outcomes following curative SABR versus surgical resection, but did not fully address confounding by indication. The Surgery Or RadioTherapy for early-stage cancer study (SORT) will assess the comparative effectiveness of SABR with curative intent versus surgical resection for NSCLC with a target trial emulation approach, as this can reduce biases in observational studies that aim to estimate the causal effect of interventions.

The SORT study will use the National Cancer Registry for individuals diagnosed with early-stage NSCLC in England during 2015–2020 (inclusive) who received SABR with curative intent or surgical resection. These data will be linked to Hospital Episode Statistics, National Radiotherapy Data Set and the Systemic Anti-Cancer Therapy dataset to obtain information on clinical and sociodemographic characteristics and the treatment received. This target trial emulation will define study population eligibility criteria and regimens for SABR with curative intent and surgical resection. We will reduce the risk of residual confounding with instrumental variable analyses that will exploit geographical variation across the National Health Service in England in the use of SABR with curative intent versus surgical resection for early-stage NSCLC. The primary outcome will be 3-year all-cause mortality after treatment initiation. Secondary outcomes will include 3-month, 6-month, 12-month and 24-month all-cause and lung-cancer mortality, time to death, numbers of hospitalisations, incremental costs and incremental cost-effectiveness.

Ethical approval was obtained from the London School of Hygiene and Tropical Medicine Research Ethics Committee (reference number 29 717–1). Results will be disseminated to clinicians, patients, policy-makers and researchers.