The objective of the study is to determine the efficacy of a 12-week mobile chat-based exercise counselling intervention (ChatEx) for increasing exercise behaviour (operationalized as self-reported aerobic MVPA) at 3-month (primary analysis, post-intervention) and 6-month (3-month post-intervention) among older cancer survivors. This will be a randomized controlled, assessor-blind trial conforming to the CONSORT guidelines. A total of 196 cancer survivors aged over 60 who have completed curative treatment and screened as having an ECOG performance status of 0 or 1 will be recruited and randomized into intervention and control groups. It is expected that upon intervention completion, the intervention group will exhibit increased and sustained exercise behaviors compared to the control group. Study instruments will be Physical Activity Scale for the Elderly, 6-minute walk test, grip strength, Edmonton Frail Scale, European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire, M-PAC constructs, and a background questionnaire. The intervention comprises of 12 weeks of messages aimed at promoting physical activity structured with the multi-process action control framework complemented with two face-to-face exercise instructional sessions at week 1 and week 6. The control group participants will receive a one-page written information sheet on the recommended exercise guidelines and exercise safety precautions in cancer survivors. Also, they will receive 3-4 messages via IM monthly on non-exercise-related self-management tips of cancer survivorship. They can receive the ChatEx intervention upon completion of the study. Intention-to-treat analysis will be performed.

Older adults account for more than half of cancer diagnoses. With advances in detection and treatment, older adults constitute the fastest-growing segment in the cancer population. A history of cancer has been found to increase the odds of and accelerate functional decline, suggesting that cancer and/or its treatment alters aging trajectories. Therapeutic interventions are therefore needed to mitigate the consequences of cancer and aging. Robust evidence indicates that exercise attenuates the major hallmarks of aging. Meanwhile, exercise is recommended by multiple best practice guidelines to alleviate the adverse sequelae of cancer. Well-documented benefits include improvements in physical functioning and quality of life (QoL), reduction of cancer-related symptoms (e.g., fatigue, insomnia, depression), and decreasing risk of recurrence, secondary cancers, and mortality.

Exercise counseling, which involves advice and discussions to promote exercise, is a less intensive and more scalable approach than supervised exercise sessions. Instant messaging (IM) offers a promising platform for delivering exercise counseling due to its accessibility, customizability, and widespread use. This study utilizes the Multi-Process Action Control (M-PAC) framework, which emphasizes reflective, regulatory, and reflexive processes to overcome barriers to exercise adherence. The study hypothesizes that ChatEx, an IM-based exercise counseling intervention grounded in the M-PAC framework, will be effective in increasing and maintaining exercise behavior among older cancer survivors.

This study aims to evaluate the efficacy of a 12-week mobile chat-based exercise counseling intervention (ChatEx) for increasing exercise behavior in older cancer survivors. The primary objective is to determine if ChatEx can increase exercise behavior at both 3-month (post-intervention) and 6-month (3-month post-intervention) time points. Secondary aims include examining the intervention's impact on other exercise parameters, exercise capacity, grip strength, frailty, and quality of life, as well as exploring the mediating roles of Multi-Process Action Control (M-PAC) constructs and participant engagement in changing exercise behavior.

Inclusion Criteria:

1. aged ≥60
2. diagnosed with stage I-III non-metastatic cancer (rationale: exercise levels and interests in receiving exercise interventions are similar across cancer types in post-treatment survivors
3. completed primary treatment with curative intent (rationale: post-cancer treatment period imposes less exercise barriers related to treatment schedule and side-effects, and is most desired by cancer patients to start/resume exercising
4. can communicate in Cantonese or Mandarin
5. have an ECOG performance status of 0 or 1
6. own a smartphone and proficient in using IM

Exclusion Criteria:

1. contraindications to unsupervised exercise (e.g., dementia, recent myocardial infarction or stroke, chronic obstructive pulmonary disease, walker or wheelchair use)
2. already performing ≥150 minutes of moderate or 75 minutes of vigorous aerobic exercise and two sessions of resistance exercise per week (already meeting recommended exercise guidelines).

Data will be available on reasonable request as decided by the principal investigator.

Data will be available for 3 years after the manuscript on main findings is published.

An independent randomizer will prepare a computer-generated list of random assignments in sealed, sequentially numbered opaque envelopes. Permuted blocks of different sizes will be used to aid allocation concealment. A secure copy of the randomization list will be kept by independent personnel, serving as a central allocation centre. The outcome assessors and statistician performing data analysis will be blinded.