Iris Kanera

5 129 Lifestyle-related effects of the Kanker Nazorg Wijzer that participants had Internet access and sufficient computer skills. These intervention characteristics can also explain the overrepresentation of middle-aged participants. Present results might have been influenced by the selective dropout. However, the dropout rate was very low, analyses were corrected for the corresponding variables, and intention- to-treat analyses revealed comparable results to complete cases analyses. Besides this, health behaviors were measured using self-report questionnaires, thus allowing over- and underestimations to occur due to social desirability or recall bias (van Assema, Brug, Ronda, Steenhuis, & Oenema, 2002). Although the self-administrated questionnaires were validated, easy to apply, inexpensive, and have often been used in large-scale studies, wemay presume that overestimation occurred in PA (van den Brink, 2005; Campbell et al., 2015; de Hollander et al., 2012; Helmerhorst, Brage, Warren, Besson, & Ekelund, 2012; Mudde et al., 2006; Te Poel et al., 2009; Wendel-Vos et al., 2003). The proportion of smoking cessation might be slightly underestimated, due to accounting smokers at baseline as smokers in intention-to-treat- analyses if their smoking behavior could not be measured after six months. Prior to the baseline assessment, the participants knew about their group-assignment, which might have influenced the responses on the baseline questionnaire. We assume, however, that the baseline differences in dietary behavior occurred merely by chance, given the comparable response of participants in both intervention conditions at baseline. There were also no differences in PA and smoking behavior at baseline. In addition, in this RCT, the intervention was compared to a usual-care control group, who possibly participated in other aftercare interventions. Multilevel linear regression analysis was applied for addressing possible differences in (after-) care between the different hospitals, and all analyses were corrected for aftercare-use. CONCLUSIONS Having access to the KNW and following the KNW modules do affect lifestyle behaviors, although to a limited extent. Meaningful increases in moderate PA were detected in the IC, and the effect size of the increase in vegetable consumption was higher than in comparable studies. Moreover, the outcomes point in the direction that following the module Diet could affect fruit and fish consumption. Non-significant results after accounting for multiple testing in moderate PA, vegetable, fruit and fish consumption might be due to the high number of outcomes and the low numbers of module users who set a goal on the specific outcome behavior. No significant intervention effect was found on smoking behavior due to the low number of smokers. An exploration of the use of this complex KNW intervention is recommended to get further insights into underlying mechanisms, and to improve the intervention effectiveness. Overall, results provide preliminary indications that this theory- based, broad-scoped, computer tailored web-based cancer aftercare intervention can provide valuable support in usual cancer aftercare.