To our knowledge, this is the largest population based study establishing a novel nomogram prognostic model predicting lung cancer related death rate, other cancer related death rate, and non–cancer related death rate for NSCLC patients who received surgery in SEER database.
Recent studies showed that several factors include tumor size, lymph node metastasis, clinical stage, age, etc were associated with long time survival for lung cancer patients with surgery. However, the results were heterogeneous for the reason that most studies evaluating the prognosis of NSCLC had relative short follow-up with limited sample size. Therefore larger sample data with more validated and rigorous statistical methods were required. Besides, the population-based SEER database could be used with the ability to assess this issue on a larger sample with long follow-up, which can effectively avoid biases. In this study, was collected a large population of 44,880 resected NSCLC patients in SEER database.
Moreover, to make the bias minimized, we used a novel and validated prognositc model. Nomogram has been considered as a trustworthy method to generate more accurate prediction of prognosis[16–18]. The performance of the nomogram may also have discrimination, thus calibration should be conducted using a validation data set. Our study showed, the unadjusted C-index was 0.73 (95% CI, 0.72–0.74), 0.71 (95% CI, 0.66–0.75) and 0.69 (95% CI, 0.68–0.70) for lung cancer related death, other cancer related death and non-cancer related death in the validation cohort. This indicates that the models are convincingly precise. Besides, our study showed good coincidence between predicted and actual outcomes because the points are close to the 45-degree line
Our study showed 5- and 10-year lung cancer related death probability increased with age, stage, tumor size, tumor extent, lymph node involvement, positive lymph node numbers which were consistent with previous studies[3–6]. In our study, male patients had higher lung cancer-related death rate compared with female patients. Several studies have demonstrated that epidermal growth factor receptor (EGFR) - tyrosine kinase inhibitors (TKIs) could noticeably improve survival of EGFR positive mutation advanced NSCLC patients[19–22]. EGFR mutation is the most common gene mutation in Asian female lung adenocarcinoma patients, therefore the prognosis of female lung cancer patients might be better. Our study showed patients with radiotherapy were associated with a significantly higher lung cancer related death rate. Radiotherapy were always performed to patients with more aggressive stage or, mediastinal lymph node metastasis and these patients may originally have poor prognosis. However, the appropriate opportunity and indication of radiotherapy still need further investment.
Previous studies mainly focus on investigating lung cancer related survival for NSCLC patients, studies with concern of other causes of death are limited. In SEER database, death resulting from other cancer and non-cancer were also recorded. We divided cause of death into lung cancer related, other cancer related and non-cancer related. In our study, the most frequent non-cancer deaths were resulted from diseases of heart, chronic obstructive pulmonary disease and associated conditions and cerebrovascular diseases. Therefore the complications of heart and respiratory system during treatment procedures require closer monitoring.
There were also some limitations in this study. First, some variables are not recorded in SEER database, such as disease progression time, specific chemotherapy regimens, etc. Besides, we did not use the 7th AJCC staging for the reason that 7th AJCC staging system has been widely used after 2010, and stage information from 2004 to 2010 could not be accessed when using 7th AJCC staging system.