The present study assessed the QoL of a unique Dutch population of RB survivors using the SF-36 questionnaire and a semi-structured interview focusing on early adaptation to the diagnosis and the perceived burden of their illness in relation to educational achievement and social functioning. To our knowledge, this is the first study to examine long-term QoL in adult RB survivors.
Our results show no significant differences between the adult RB survivors compared to the healthy reference group in the QoL measures, except for the mental health scale. RB survivors learn to live with many of the consequences of their disease, but reported more problems with regard to their mental health compared with the reference group. This result is clinically significant, because the mean MH score in the RB group was 18.1 points (3 standard deviations (SD), p < 0.001) lower than that of the Dutch reference group. A difference of 18.1 points on a scale from 0–100, means almost 20% difference between the RB survivors and the Dutch reference group on the MH scale. In particular, anxiety, feelings of depression and loss of control seem to have a negative impact on their lives. These unfavorable mood states might be caused by their feelings of being different from others. According to our survivor's reactions during the interview, this often originates from having been bullied about their facial appearance or prosthesis, and/or their visual impairment or blindness. Besides that, loss of control may lead to feelings of depression. In particular, realization about their loss of control appears to be connected to the emotion of shame [24
], and experiencing shame in childhood can be a forerunner of depression [25
]. In the present study, our group of RB survivors are more anxious and worried compared with the reference group. They grew up with uncertainty about their facial appearance and the feeling of being different; this can lead to feelings of shame, which may influence their perception and experiences during general development and may eventually result in depression. This finding is consistent with results from other diseases with atypical visible facial characteristics, such as strabismus and patients with a cleft. Strabismus patients experience more social anxiety [26
], and have more difficulties with self-image and interpersonal relationships [27
] in comparison with the reference group. Persons with visible facial characteristics (like a cleft), expressed greater dissatisfaction with their appearance [28
]. Further research should be conducted to identify the specific psychological factors that lead to problems in mental health in this population.
The second aim of this study was to compare the QoL of hereditary RB survivors with that of non-hereditary RB survivors. The general health perception of hereditary RB survivors was significantly impaired compared with non-hereditary RB survivors. This probably reflects a realistic view of their situation. Hereditary RB survivors often experience more physical problems than the non-hereditary group: i.e. they are often subjected to more treatments [12
], are bilaterally affected, have a greater chance of visual impairment, and are at greater risk of developing second primary tumors. It is remarkable, however, that despite these additional problems they do not report to be affected in other QoL areas.
Another striking result is that non-hereditary RB survivors also experience anxiety concerning second primary tumors, even though they are at less risk for this compared with hereditary RB survivors. Nowadays, clinicians can estimate the probability of survivors passing on the disease to their offspring or the probability of developing second primary tumors. However, for patients with a rare disease, the impact of hearing that there is a 'low probability' of something occurring might be received differently from how clinicians may expect. From a healthy person's perspective, a low probability generally means a minor or no chance of having/passing on a certain disease. For a person with a rare disease, however, a low probability might logically mean the same but their own reality of having a rare disease may have proven otherwise. The discrepancy between theory and their own reality might introduce fear (or at least some existential thoughts) about why they could not escape from developing a rare disease. This might explain the fears also experienced by non-hereditary RB survivors. Therefore, clinicians should be aware that RB survivors (including non-hereditary RB) might interpret these probabilities differently from what may be expected. A similar tendency was also found among women at risk for breast cancer [29
The third aim of the study was to gain insight into the predictors of QoL. Bullying in childhood and impairment appeared to be the major predictors of QoL of our RB survivors. According to the interview results, the reasons for bullying were in most cases related to the appearance of the eye or to the survivor's facial appearance. This was also found in another study on children with RB in which parents reported that their child had experienced bullying related to either facial appearance or the ocular prosthesis [11
]. The association between bullying and QoL has also been reported in other types of childhood cancer [30
Most of the impairments mentioned by survivors were associated with a wide range of activities related to their visual acuity. Lamoureux et al. (2004) [31
] concluded that the areas of greatest restriction in people with impaired vision were associated with reading, outdoor mobility, participation in leisure activities and shopping. It is understandable that a serious restriction in these activities is negatively related to the experience of health and vitality.
This study focused on the QoL of a diverse and rare population of RB survivors and provides information on a population-based RB group. Nevertheless, a number of study limitations should be considered when interpreting the results. First, since the possibilities of treatment have improved over time, our results may no longer apply to survivors who have been treated more recently. On the other hand, some form of treatment will always be necessary and the current RB treatments still do not leave the appearance of the RB survivor totally unaffected; further research is therefore desirable.
Second, it is conceivable that some of the RB survivors who did not participate in the present study experienced a poorer QoL than those who did participate. Indeed, several non-participants refused participation because they did not want to be confronted with their disease again; if this subgroup consists of those who do not accept their disease as well as the other subgroups, then the overall QoL of RB survivors might be worse than reported here.
Third, we are aware of the fact that some SF-36 subscales show ceiling effects [22
]. Therefore, it can be that the effects we found were underestimated. Estimates of the coefficients and their standard errors are robust to the non-normal distributions. Although the tests confidence intervals originate from normal distributions the consequences of violating this assumption are minor with sufficient sample size.