Iris Kanera

5 111 Lifestyle-related effects of the Kanker Nazorg Wijzer Ajzen, 2010; Kanera et al., 2016a). Consequently, behavior change interventions need to be tailored to the specific behavior, individual determinants, and motivational phases (Kanera et al., 2016a; Noar et al., 2007). During the development of the KNW, these aspects were taken into account by tailoring the provided information to relevant determinants. Only few theory-based studies have been conducted which have investigated the effect of web-based interventions aimed at lifestyle outcomes in cancer survivors (Goode et al., 2015; Kuijpers et al., 2013). Increases in PA and mixed results in diet change have been reported in web-based interventions for cancer survivors using behavior change strategies such as action planning, problem solving, decision making, and tailoring (Bantum et al., 2014; Lee et al., 2014). Moreover, a usability study revealed that a web-based computer tailored intervention for breast cancer survivors based on the Theory of Planned Behavior and the Transtheoretical Model was well accepted and perceived as interesting, attractive, comprehensible and credible (De Cocker et al., 2015). Besides that, a web-based smoking cessation intervention among cancer survivors, based on social cognitive theories and tailored to stage of readiness, yielded equivalent levels of success compared to an intervention delivered by telephone (Emmons et al., 2013). Thus, current evidence is limited but promising concerning the effects of theory grounded, web-based, computer tailored interventions on (multiple) lifestyle behaviors for cancer survivors. In the present study, we assessed the effects of the KNW on lifestyle outcomes (PA, diet, and smoking) six months after getting access to the intervention, among cancer survivors who recently completed primary cancer treatment. First, we assessed whether having access to the KNW may improve PA, diet behavior (fruit, vegetable, whole grain bread and fish consumption), and can lead to a higher rate of quitters among smokers in comparison to a usual care control group. Second, we explored the effects of following the module Diet on diet outcomes specifically, and the effects of following the module PA on PA outcomes. METHODS Trial design A randomized controlled trial was conducted to reveal effects betweenparticipants assigned to the intervention condition (IC), or the usual care control condition (UC). Randomized allocation (ratio of 1:1) was automatically performed by means of a digital randomizer after centralized registration of participants (OverNite Sofware Europe). Ethical approval for this trial (Dutch Trial Register NTR3375) was obtained from the Medical Research Ethics Committee (MERC) Z (NL41445.096.12, 12-T-115). After approval, the MERC’s and the board of directors of each hospital endorsed the execution of the study.