The purpose of the present study was to conduct a meta-analysis of empirical literatures on association of positive psychological resources with quality of life among cancer patients. Five positive psychological variables and cancer patients’ quality of life were organized in the current study. The meta-analysis showed that cancer patients’ quality of life was positively and significantly associated with hope (r = 0.50), resilience (r = 0.52), self-efficacy (r = 0.54), self-esteem (r = 0.45) and optimism (r = 0.32), which were consistent with previous theory [10, 66–69].
Self-efficacy and quality of life among cancer patients
The meta-analysis presented that highly efficacious cancer patients tended to live a better quality of life throughout the course of suffering cancer. The result was consistent with previous study, for instance in a recent meta-analytic review by Andrea et al involving 3162 cancer patients, there was a large significant overall effect size of r = 0.73 for the association of self-efficacy with quality of life . The reason could be highly efficacious cancer patients characterized by sense of agency or control may perceive some causal relationship between coping behaviors executed and certain desired outcomes, including level of type of quality of life . Future research may benefit from addressing the question of how self-efficacy interacts with other factors to affect quality of life in cancer patients. For example, a study found that self-efficacy for coping moderated the effect of distress on quality of life among breast cancer patients .
Resilience and quality of life in patients with cancer
Results from the meta-analysis indicated that highly resilient cancer patients could remain the better life quality, compared to low resilient individuals. Evidence suggests that high-resilient people strategically elicit positive emotions through the use of humor, relaxation techniques, and optimistic thinking in order to proactively cultivate their positive emotionality . Then, positive emotionality emerges as the crucial element of resilience. It was found that resilience had indirect impact on cancer patients’ quality of life by influencing social support, in addition to direct impact . Besides, resilience was found to be associated with lower psychological distress and fatigue among patients and survivors with cancer .
Subgroup analysis indicated that the relationship between resilience and quality of life among cancer patients was affected by age. Correlation of adolescent or children sample was significantly larger compared to adult sample, and the correlation of both groups was significant. Risks of loneliness and psychological distress rise with age for the elderly owing to the self-neglect and physical degradation, while resilience can effectively cope with these symptoms and enhance the quality of life, which was a crucial factor for successful aging [74, 75]. However, it was inconsistent with previous study . The result of adolescent or children sample might be overweight or inaccurate due to the small number of this group (k = 2). Thereby, future research may benefit from examining the effect of age on the association of resilience with quality of life.
Hope and quality of life in patients with cancer
The present meta-analysis indicated that cancer patients high in hope tended to show better health outcomes, such as quality of life. According to the theory of Snyder, hope is conceptualized as a positive motivational state based on interactively derived sense of successful agency (goal-directed energy) and pathways (planning to meet goals) [10, 11]. Rousseau  found that hope could be developed by learning to control one’s symptoms, exploring one’s faith, and strengthening interpersonal relationships. It was also found in another study that individuals full of hope reported significantly higher levels of personal adjustment and global life satisfaction, and less psychological distress . Subgroup analysis indicated that the effect of hope varied with the change of patients’ age. The impact of hope on quality of life was more significant on studies based in children and adolescent with cancer than adult suffering cancer. Furthermore, few studies aimed to explore the effect of hope on quality of life in children and adolescent with cancer. Therefore, future studies may benefit from efforts to increase or develop patients’ levels of hope through psychological treatment, and focus on investigating the impact on children and adolescent with cancer.
Optimism and quality of life in patients with cancer
The meta-analysis reported that optimistic patients lived a better quality of life among cancer patients. The optimistic attitude plays a crucial role in effectively coping with disease diagnosis, treatment and prognosis, as well as in enhancing quality of life . Furthermore, comparing with pessimists, optimistic cancer patients reported greater survival rates a year after diagnosis . Most of studies investigated the effect of optimism on quality of life in adult patients with cancer, but few studies examined the association among children and adolescent patients. Hence, future studies can benefit from examining the impact of optimism on quality of life in children and adolescent.
Self-esteem and quality of life in cancer patients
Results of the current meta-analysis showed that the more self-esteem experience by cancer patients, the higher quality of life. many studies have indicated that patients with cancer had the low to moderate level of self-esteem [80–82]. Low self-esteem patients mean self-contempt, self-disappointment, self-rejection and lack self-respect for themselves. Based on the theory of Rosenberg , high level of self-esteem implies that they have high self-respect for who they are within limits, and do not assume that they are more superior in any way than anyone else. Cancer diagnosis has the tendency of affecting the patients’ body image, which negatively results in changes in self-esteem. Even the easiest daily routine may be disrupted and patients need to be aware of these long-term consequences negatively influencing their level of self-esteem. The results of subgroup analysis reported that the differences of age in the relationship between self-esteem and quality of life among cancer patients was non-existent, which was not similar to prior study . The result might be overweight or inaccurate due to the small number of this group. Thus, further research should focus on the effect of age on the association of self-esteem with quality of life in cancer patients.
The present meta-analysis has some limitations. Firstly, a dearth of longitudinal study exists on positive psychological resources and quality of life among cancer patients. Although cross-sectional study is easier to perform, longitudinal study is more valuable in terms of answering questions concerning the long-term relations between positive psychological resources and quality of life in patients with cancer. Secondly, the subgroup analysis of the children or adolescent group and the adult group could not be performed for every meta-analysis in the present study with limitations of number of studies concerning the association of self-efficacy and optimism with quality of life among cancer patients. Hence, there is a need for additional research on the impact of self-efficacy and optimism on quality in children or adolescent with cancer. Besides, although our study has investigated each positive psychological resource individually, it is significant to recognize that some positive psychological variables may covary. For instance, individuals relatively full of hope tend to effectively buffer the impact of stressful and negative life events, and successfully their goals could be achieved so that they possess more resilience . Thus, hope might trump the effects of resilience on quality of life. Moreover, the optimistic attitude inherent in hopeful individuals plays a crucial role in improving health-related quality of life. Therefore, further research may examine their covariation and unique and interactive relation with quality of life among cancer patients. Finally, most studies were written by English in the current study, which may lead to language bias. However, Thornton and Lee thought that there was similar bias in all meta-analysis that not review all studies. Therefore, despite of the limitations, our study’s outcomes are reliable and warranted.
Although these five variables are defined in different models, they may affect mental health and quality of life among cancer patients by different mechanisms, they have two significant points in common. Namely, these constructs are positive coping styles or protective factors to fight cancers, and they are dynamic and developmental resources. Therefore, these variables could be increased though intervention in order to better improve quality of life in cancer patients. Furthermore, increasingly research have found that interventions based on positive psychological resources could cope with mental problems and enhance quality of life in cancer patients. For example, in randomized and controlled trail, Promoting Resilience in Stress Management (PRISM), a psychosocial intervention for adolescents and young adults with cancer, enhances resilience resources via four skills-based training sessions, compared to usual care (UC) may improve health-related quality of life, especially in psychosocial domains of wellbeing . Hope is a positive psychological variable related to better quality of life that focuses on goal-oriented thinking. Carla et al  developed and tested Achieving Wellness After Kancer in Early life (AWAKE), a scalable 8-week app-based program consisting of educational videos, mood/activity tracking, and telephone-based coaching to promote hope and quality of life in young adult cancer survivors, which evidences that the AWAKE supports patients cope with cancer-related sequelae and reestablish goals across life domains after experiencing cancer. Evidence suggests that nurse-administered self-efficacy intervention given on five monthly occasions and designed to enhance patients' self-care self-efficacy have significantly higher scores on quality of life and self-care self-efficacy than the control group and significantly less symptom distress . Besides, beauty care intervention  and Framed Portrait Experience intervention  are similar to enhance self-esteem and self-efficacy among cancer patients. Therefore, interventions based on positive psychology constructs should be emphasized and developed in the field of oncology psychology in order to treat psychological disorders and enhance quality of life.