A shared understanding of a patient’s status between physicians, the patient, and caregivers is important in shared decision-making. Not only can it reduce the discrepancy in expectations regarding treatment objectives, it can also enable more appropriate decision-making for patients [1]. Precise awareness of disease status, i.e., shared understanding of cancer stages between cancer patients and their caregivers, is essential for shared decision-making.

Discrimination between advanced and terminal cancer is important because the treatment goals are different. In cases of advanced cancer, which is not curable but responds to treatment, disease-directed therapy is still very important because it prolongs life. However, for terminal cancer, therapy cannot prolong survival significantly due to the progressive nature of the disease [2-5]. Therefore, palliative care that provides psychosocial support and controls symptoms is the main treatment option for patients with terminal cancer [6,7]. Accurate prognostic understanding may affect decision-making towards more appropriate care [8]. However, studies suggest that patients and their families often misperceive the patient’s cancer stage and prognosis [9-11], leading to unrealistic expectations regarding the treatment effect and inappropriate treatment decisions [9,12-14].

In addition, many end-of-life care studies are based on the assumption that there is a shared definition of language regarding the cancer stage among patients, caregivers, the general population, and physicians [15]. For example, Yun et al. [16,17] assessed patients’ awareness of terminal illness soon after they were considered terminal by their doctor with the following question: “Do you know your disease stage?” Response options included, “I don’t know,” “early stage,” “advanced stage,” “terminal stage,” and “other.” The authors regarded “terminal stage” as the correct awareness of the terminal nature of the illness [16,17]. Without a shared understanding regarding the definition of terminal stage cancer of physicians and respondents, the validity of such research could be compromised.

Therefore, the lack of a common understanding of words used in cancer care is a critical problem in communication within the clinical practice and the research environment [18]. However, few studies evaluating public awareness regarding the definition of cancer stages have been reported. In a study conducted in Korea, Lee et al. [19] surveyed participants regarding the correct definition of terminal cancer. Five choices were given and “6-month life expectancy” and “treatment refractoriness” were regarded as the correct answers. In that study, 29.4% of the participants from the general population misunderstood locally advanced cancer and metastatic/recurrent disease as terminal stage disease. However, this study was limited in that the response options were not mutually exclusive, and the authors asked for a conceptual definition rather than using an actual situation [19].

In this study, a survey was conducted to evaluate the understanding of the definition of advanced versus terminal cancer in the general population and determined associated socio-demographic factors.

To the best of our knowledge, this is the first study assessing the understanding of the definition of advanced versus terminal cancer in the general population using a hypothetical vignette about a case of advanced cancer. We found that a large proportion (74.5%) of the general population misunderstood the medical definition of terminal cancer, and could not discriminate terminal cancer from advanced cancer with metastasis.

The proportion of inadequate responses was as high as 80%, even higher than that reported in previous survey results (one-third of participants answered incorrectly) on the public perception of the definition of terminal cancer in South Korea. Although there are several exceptions, many patients with advanced stage cancers cannot expect to be cured, and have a poor long-term prognosis. Despite the availability of life-prolonging treatment, most patients will eventually die because of their cancers. The results of our survey suggest that most members of the general population seem to not be familiar with the concept of ”treatment refractoriness” and “life expectancy less than 6 months,” and may regard advanced stage cancer as terminal cancer [19]. Differences in the correct response rates across different studies can be explained by differences in study design. In a previous study, in which five response options for the definition of terminal cancer were provided to a conceptual question, many respondents could have chosen the correct option by chance or by avoiding extreme options (“a cancer still resectable and curable” or “a cancer with a prognosis of death within a few days or weeks”). Therefore, a continuous effort is required in order to establish common and shared definitions of cancer staging and to increase awareness across the general population [18].

The results of this study have several important clinical and research implications. First, members of the general population can become cancer patients themselves or caregivers of cancer patients in the future. Misunderstanding about the accurate cancer stage can lead to discrepancies in expectation regarding the treatment effect between patients, caregivers, and physicians [20]. Although doctors inform patients of their exact cancer stages, patients and caregivers might not understand the prognostic meaning of the cancer stage. Providing patients and their families with a full understanding of the disease status is very difficult for physicians [21], and physicians rarely check their patient’s understanding of the diagnosis [22]. Therefore, for informed decision-making or shared understanding, it is not sufficient to simply provided information on the stage of the cancer as early, advanced, or terminal. For patients, the perception of terminal cancer can influence decision-making regarding the treatment plan [23]. This misunderstanding can lead to an undesirable scenario, in which patients forgo treatment when diagnosed with advanced cancer that could prolong survival. For patients with terminal cancers, this misunderstanding may lead to precious time being occupied with futile disease-directed treatment options [24]. When shared understanding about the stage of the cancer is lacking, the decision-making process cannot guarantee an appropriate outcome. Therefore, for informed decision-making, it is essential for physicians to not only provide information on the exact cancer stage, but to also explain the meaning of that stage and to confirm the patient’s understanding [25].

Second, there was no consistent and strong predictor as to which respondents would answer correctly, as defined in terms of medical context. However, some factors were partially associated with the choices. Interestingly, the educational status of the participants was not significantly associated with choosing the correct answer. In addition, personal experience with relatives or acquaintances diagnosed with cancer also did not improve the understanding of cancer staging, and even increased the frequency with which respondents chose the response option of “terminal cancer.“ The experience of cancer in close relationships could affect the perceived knowledge of the general population, resulting in a more sensitive reaction than those who had no relatives or acquaintances with cancer. Thus, they chose “terminal stage” more frequently in this study. Although no significant difference in sex was observed between the response groups “advanced stage” and “terminal stage,” female tended to choose “early stage” more frequently. As the hypothetical case in our vignette was a breast cancer patient, females might react with more emotion. However the result is limited to those who chose “early stage” (n=13). In addition, marital status and respondents’ income were not consistently associated with their choices. These results suggest that physicians should verify the understanding of cancer stages during communication with cancer patients and their caregivers regardless of their socio-demographic characteristics and personal experiences.

Finally, many studies based on survey data of the general population regarding terminal disease relied on the correct perception of “terminal cancer.” Some of the surveys did not inform participants of the exact definition of terminal disease, which would be sufficient to ensure that patients have the same understanding as the researchers [15]. However, considering the high proportion of the general population lacking accurate knowledge of the medical definition of terminal cancer, the reliability and validity of those surveys might be compromised. For example, in surveys on topics such as the recently issued legalization of euthanasia, accurate understanding of terminal disease is required for the response to be valid. Therefore, our study suggests that more care should be taken to ensure that respondents of such surveys have a shared understanding of the exact definition of advanced or terminal disease.

The strengths of this study include systematic sampling methods and the large sample size, ensuring the generalizability of these findings across the Korean population. Another advantage of this study is the use of a clinical vignette. Clinical vignettes do not require in-depth knowledge of the study topics. Therefore, the practical understanding of the respondents can be better assessed using clinical vignettes based on a hypothetical case than by using questions based on conceptual knowledge.

There are some limitations in our study.

One notable limitation is that it included only members of the general population. Many of the respondents had not experienced advanced or terminal cancer, and these participants may have less knowledge about cancer than those affected by cancer. However, the proportions of the correct answer between the general population and patients or family caregivers were not significantly different in a previous study [19]. In addition, personal experiences with cancer did not significantly affect the response rate in our study, suggesting that a potential bias would not be significant. Moreover members of the general population can become patients themselves and their close caregivers or friends may influence medical decisions. Therefore, understanding of cancer staging of the general population is relevant from a clinical and research perspective. Development of a communication strategy for end-of-life discussions would also be important.

Second, the staging terms for cancer are defined based on the viewpoint of medicine. Thus, most of the general population might not perceive the exact definitions of the terms for cancer staging. However, as mentioned above, clinical vignettes do not require in-depth knowledge of the study topics. Therefore the results of our study might reflect the understanding of the definition of cancer stages in the naive general population. However, if we asked about the possibility of complete cure, necessity for aggressive chemotherapy for life prolongation, or expected survival time of the hypothetical patient in the vignette, more of the general population might have answered correctly, as defined in terms of medical context. Also, a well-designed study comparing before and after adequate education using patient decision aids regarding the definition of the cancer stages may be needed for more sensitive evaluation of the knowledge in the general population.

In conclusion, we found that a large proportion of the general population could not differentiate advanced cancer from terminal cancer, as defined in terms of medical context. Continuous effort is required in order to establish common and shared definitions of cancer stages and to increase the shared understanding of cancer staging for patients, caregivers, and the general population. In addition, a detailed explanation concerning the stage of the cancer and its clinical meaning is essential for shared understanding and informed decision-making between cancer patients and their families and physicians. Researchers need to ensure that respondents to surveys and studies have a shared understanding of the definition of advanced or terminal disease.