Small-cell lung cancer (SCLC), accounting for about 15% of all lung cancers, is a subtype of lung cancer with poor prognosis. It has a 5-year survival rate of 7% and kills an estimated 250,000 people worldwide annually. Although many studies have estimated the prognosis of SCLC, most of them were conducted without considering competing risks. This study aimed to evaluate the probability of cause-specific death for patients with stage I small cell lung cancer (SCLC) with a competing risk analysis.
We identified patients with stage I SCLC between 2004 and 2010 in the Surveillance Epidemiology, and End Results (SEER) database. We calculated the cumulative incidence function (CIF) for all the SCLC patients, and the differences in CIF between subgroups were estimated by Gray’s test. Proportional subdistribution hazard model was constructed to predict cancer-specific death for patients with stage I SCLC. We also built a competing risk nomogram based on Fine and Gray’s model to predict the 3-year, the 5-year prognosis of SCLC patients. We evaluated the model performance by the c-index and calibration plot using a bootstrap cross-validation method with 200 resamples. All statistical analyses and visualization were performed on R statistical software version 3.4.4 (Institute for Statistics and Mathematics, Vienna, Austria). Statistical significance was set as a 2-sided p < 0.05.
We identified 864 stage I SCLC patients. The 5-year cumulative incidence of cause-specific death for stage I SCLC was 56.2% and 13.7% for other causes of death. Predictive factors for the prognosis of stage I SCLC included age, surgery, chemotherapy, and radiotherapy (Table). Fine and Gray competing risk regression model indicated that age at diagnosis, surgery treatment, and radiotherapy could be independent predictive factors of SCLC cause-specific death. Those who were diagnosed with SCLC at an older age were more like to die of lung cancer, with a subdistribution hazard ratios (sdHR) of 1.02 (95% CI, 1.012-1.03). Patients without treatment were at an elevated risk of SCLC cause-specific death except for chemotherapy, with an sdHR of 2.85 (95% CI, 2.29-3.54) and 1.89 (95% CI, 1.53-2.33) for patients without surgery and radiotherapy, respectively. No statistical significance was detected between chemotherapy and SCLC cause-specific death. The competing risk nomogram based on the Fine and Gray’s model was established to predict the 3-year and 5-year cause-specific death. The c-index for SCLC cause-specific mortality model was 0.66, and the calibration curves suggested that the nomogram was well-calibrated.
In the study, we performed a competing risk analysis in patients with stage I SCLC based on the SEER database. We discovered independent predictive factors of death due to SCLC and built a nomogram to calculate the 3- and 5-year cause-specific mortality. The competing risk nomogram might be a convenient tool to evaluate crude mortalities of stage I SCLC, and help clinicians to choose appropriate treatment strategies.
Clinical trial identification
Legal entity responsible for the study
National Key R&D Program of China (2016YFC0905500).
All authors have declared no conflicts of interest.
Five-year cumulative incidences of death among patients with stage I SCLC
|Characteristics||N (%)||Event (%)||Cause-specific death||Death from other causes|
|5 year (%) (95% CI)||p||5 year (%) (95% CI)||p|
|Total||864||680||56.2 (52.9-59.5)||13.7 (11.5-16.1)|
|<65||257 (29.7)||178 (26.2)||48.5 (42.2-54.4)||12.5 (8.8-16.9)|
|65+||607 (70.3)||502 (42.9)||59.5 (55.5-63.3)||14.2 (11.6-17.1)|
|Male||407 (47.1)||332 (52.9)||59.2 (54.2-63.8)||15.4 (12.0-19.1)|
|Female||457 (52.9)||348 (40.8)||53.6 (48.9-58.1)||12.3 (9.5-15.5)|
|White||772 (89.4)||609 (89.6)||55.8 (52.2-59.2)||14.4 (12.0-17.0)|
|Black||68 (7.9)||49 (7.2)||58.2 (45.3-69.0)||6.0 (1.9-13.5)|
|Others/Unknown||24 (2.8)||22 (3.2)||65.2 (41.0-81.5)||13.0 (3.0-30.6)|
|Yes||305 (35.3)||187 (27.5)||39.2 (33.7-44.6)||11.5 (8.2-15.4)|
|No||559 (64.7)||493 (72.5)||65.6 (61.5-69.3)||14.9 (12.1-18.0)|
|Yes||567 (65.6)||433 (63.7)||53.1 (48.9-57.1)||13.1 (10.4-16.0)|
|No||297 (34.4)||247 (36.3)||62.3 (56.5-67.5)||15.0 (11.1-19.3)|
|Yes||399 (46.2)||313 (46.0)||52.2 (47.1-56.9)||15.1 (11.8-18.8)|
|No||465 (53.8)||367 (54.0)||59.8 (55.1-64.1)||12.6 (9.7-15.8)|
SCLC: Small cell lung cancer; CI: confidence interval