This study investigated the impact of timeliness of care from the diagnosis of cancer to the receipt of first surgical treatment on five-year mortality in lung cancer patients with diabetes, hypertension, or dyslipidemia using nationwide data. The findings revealed that mortality risk was higher among individuals who received their first treatment for lung cancer more than 30 days after diagnosis, which is significant because cancer patients with chronic diseases are often more susceptible to mortality and may require extensive monitoring and management. Furthermore, the impact of time-to-treatment on five-year mortality was particularly magnified in individuals of lower economic status and in those with a higher level of comorbidity. The findings suggest the potential importance of avoiding delays in cancer treatment in lung cancer patients with diabetes, hypertension, or dyslipidemia, which are highly prevalent chronic diseases.
A large variability in time-to-treatment for lung cancer has previously been reported. Some studies found that shorter time-to-treatment was associated with improved prognosis, while others found the opposite or concluded that no significant relationship exists between waiting times and cancer prognosis [16, 17]. Such inconsistencies may be attributable to the waiting time bias, in which the most urgent patients are more likely to receive care most rapidly following diagnosis, in addition to variability in the sociodemographic or clinical characteristics of the study participants and the utilization of different cut-off values for classifying delays in treatment [18, 19]. Nevertheless, time-to-treatment has been cited as an important predictor of mortality in patients with lung cancer and prolonged time-to-treatment has been related to worse survival in many studies [20, 21]. Maximum time intervals regarding the diagnosis and treatment of lung cancer are also included in the clinical practice guidelines of several international organizations, such as the British Thoracic Society and the RAND Corporation of the United States of America [22].
The results of this study support the existing body of literature that delayed treatment is associated with an escalated risk of mortality in lung cancer patients with chronic diseases, namely diabetes, hypertension, and dyslipidemia. The findings emphasize the importance of providing timely treatment to cancer patients with chronic diseases. Chronic diseases can influence the progression and outcomes of lung cancer and although results on the impact of diabetes, hypertension, or dyslipidemia on mortality in cancer patients have been conflicting, many studies have demonstrated a positive association between these diseases and increased mortality [9, 23]. The specific mechanism behind such tendencies requires further investigation but in the case of diabetes, hyperinsulinemia, hyperglycemia, or chronic inflammation has been suggested to enhance cancer progression, in addition to the pre-existing disease itself exerting an impact on patients’ response to treatment [13, 24, 25]. Diabetes has also been related to a higher risk of cardiovascular diseases, post-surgery complications, and infection [26-28]. Under such circumstances, the association revealed underscores the importance of time-to-treatment in the treatment of lung cancer patients with common chronic diseases as they may be susceptible to a higher risk of mortality.
The differences in mortality according to time-to-treatment in cancer patients with diabetes, hypertension, or dyslipidemia were more pronounced in those with higher CCI scores and lower income. Comorbidity has been linked to higher perioperative mortality in lung cancer patients undergoing surgery [29]. In fact, comorbidity has been established as a significant predictor of poor prognosis in cancer, with studies presenting an association between severity of comorbidity and lung cancer mortality [30]. Although provision of optimal care for lung cancer patients with comorbid diseases may be comparatively challenging because such individuals generally require multimodal treatment by several healthcare professionals, the findings stress the importance of providing timely care to lung cancer patients with diabetes, hypertension, or dyslipidemia who also have a high level of comorbidities [31]. Apart from comorbidity, the impact of time-to-treatment on patient`s outcome was stronger in lower income patients, which may have resulted because these individuals are reported to have fewer resources for diagnosis and medical treatment [32]. Lung cancer patients with lower socioeconomic status may also be subject to lower health literacy and be less aware of the different treatment choices available [33]. Considering that the healthcare system of Korea provides relatively wide coverage for cancer treatment and has little barriers in accessing general or tertiary general hospitals, the findings imply the importance of monitoring and stressing timely treatment to more vulnerable populations.
This study has some limitations. First, the stage of cancer diagnosis could not be considered due to limitations in the data. However, this study only included individuals who underwent surgery as the primary treatment for cancer and excluded those who died within three months of diagnosis to ensure homogeneity of the study population. Second, although this study accounted for many different covariates, the possibility of residual confounding cannot be excluded. For instance, variables on individual`s lifestyle, such as smoking and heavy alcoholic drinking, were unavailable in the data used. Third, identification of diabetes, hypertension, and dyslipidemia were solely based on diagnosis codes as clinical information, such as blood glucose levels or blood pressure, were absent. Despite the limitations stated above, this study offers important insights because it is the first to reveal the impact of treatment delays on five-year mortality in lung cancer patients with chronic diseases using large, nationwide data in Korea.