This study established and validated a nomogram based on 1,623 elderly Stage I SCLC patients from the SEER database. The nomogram was used to predict the 1-, 3- and 5-year CSS rates of elderly patients with early-stage SCLC according to four significant factors: age at diagnosis, histologic type, AJCC stage, and tumor size. The nomogram is a reliable and straightforward predictive tool to estimate prognosis and make appropriate therapy recommendations.
As the population is aging and lung cancer affects many older people, efforts should be made, and additional resources should be given to choosing optimal treatments for this patient population. The current model contains only essential, clinically available variables. These variables are cheaper than molecular tests, a more economical and practical option. The C-index implied that the model is satisfactory, and the internal calibration curves show good consistency between the actual observation and nomogram prediction. Hence, the reliability and repeatability of the nomogram could be ensured.[15] The predictive ability of our nomogram is consistent compared to the previous study (C-index, 0.68 vs. C-index, 0.68).[16] The predictive tool could identify high-risk patients, achieve more precise patient survival predictions, and prescribe the best treatment options.
A total of 30% of SCLC are defined as a limited-stage disease (characterized as disease confined to one hemithorax that can be compassed in a tolerable radiation field) or stage I-III based on the TNM classification.[17] Compared to extensive-stage disease (defined as disease beyond that included in the limited-stage disease), the 5-year survival rate of limited-stage I SCLC is much higher (1.6% vs. 12.1%).[18, 19] Combs et al. indicated that the 5-year overall survival (OS) for stage I of resectable SCLC patients treated with surgery and chemotherapy even reached 49%.[20] Both the American College of Chest Physicians (ACCP) and NCCN recommend surgery with adjuvant chemotherapy for stage I disease.[21, 22] Li and his colleagues recently constructed a nomogram for predicting CSS in patients diagnosed with stage I SCLC. Their results show that surgery, chemotherapy, and radiotherapy could improve the one-year survival rate. Surgery effectively reduces cancer-specific mortality, with the one-year cumulative incidence drops from 34.5% to 11.2%.[10]
Overall, in clinical practice, the use of surgery and optimal treatment with chemotherapy in the elderly population remains low, leading to under-treatment and undesirable survival rates.[23, 24] Most elderly stage I SCLC patients are concerned about whether to undergo surgery, chemotherapy, and thoracic radiation, knowing the unwanted risk and side effects of these treatment options. Therefore, there is an urgent need to build a scoring system to guide patients. Besides, our study was aimed to assess the prognosis at the onset of diagnosis in the elderly SCLC patients. The nomogram helps select appropriate candidates for surgery, optimize the allocation of medical resources, and establish effective communication between patients and physicians.
By performing a comparison among four age cohorts (65-70 years, 70-75 years, 75-80 years, and > 80 years), we found that the 5-year CSS of the >80-years group was the lowest (29.3% compared with 36.6%, 44.3%, 48.8%). Similar to previous studies, the current analysis confirms that age is an independent prognostic factor.[25-27] Similarly, a study of 1,303 patients enrolled in 11 trials show that older subjects, compared with younger subjects, have worse progression-free survival (PFS) and OS, increased comorbidity score, poor performance, and difficulty in tolerating and completing therapy. All these factors probably contribute to lower survival.[28] Older age is directly linked with an unfavorable prognosis, and this variable is recommended to be considered in selecting treatment strategies.[29]
The different histological types of SCLC are significantly associated with biological characteristics and prognosis. As shown in the nomogram, the histological type is an important predictive factor of CSS. From the data on the cumulative incidence of death, the combined SCLC has a smaller percentage of dying than other types of SCLC. Since 1981, the World Health Organization divided SCLC into three subtypes: oat cell, intermediate cell, and combined cell. Combined cell indicates combinations of malignant squamous and glandular elements.[30] Several retrospective studies have reported that combined SCLC has notable characteristic clinical features, frequently presenting with early-stage disease and potentially curable. This explains the possible benefit of multimodality therapies, including surgery, in patients with combined SCLC.[31, 32]
Growing studies reveal that tumor size is an independent prognostic factor of survival in many cancers, including SCLC.[33-35] According to our research, tumor size exerts a significant effect on the survival rate. In patients with tumor size > 2 cm, CSS is significantly higher than in patients with a tumor size ≤ 2cm. Published research shows that tumor size is positively associated with the deficiency of patient’s immune ability, which is related with cancer survival.[36, 37] Therefore, the positive relationship between immunity deficiency and tumor size might be why tumor size is a prognostic factor in SCLC.
Our study has the following limitations: 1) potential inevitable bias due to the nature of retrospective data collection, 2) the SEER program lacks data on therapy and comorbidity, which may influence the prognosis, 3) the predictive nomogram was constructed according to data derived from the SEER database, which does not reflect the global population. Further, multi-center, large-sample studies are necessary to externally validate the nomogram to verify whether these results are generally applicable. Despite these limitations, the nomogram is constructed based on enormous population data collected in the SEER database leading to unique opportunities to forecast CSS for patients with Stage I SCLC.