A nomogram to predict the cumulative risk for brain metastases in patients with limited-stage small cell lung cancer without prophylactic cranial irradiation

Patients with small cell lung cancer (SCLC) have a high risk of developing brain metastases (BM). Prophylactic cranial irradiation (PCI) is a standard therapy for limited-stage SCLC (LS-SCLC) patients who achieved complete or partial response after thoracic chemoradiotherapy (Chemo-RT). Recent studies have indicated that a subgroup of patients with a lower risk of BM can avoid PCI, and the present study therefore tries to construct a nomogram to predict the cumulative risk of development of BM in LS-SCLC patients without PCI. After screening of 2298 SCLC patients who were treated at the Zhejiang Cancer Hospital from December 2009 to April 2016, a total of 167 consecutive patients with LS-SCLC who received thoracic Chemo-RT without PCI were retrospectively analyzed. The paper analyzed clinical and laboratory factors that may be correlated with BM, such as response to treatment, pretreatment serum neuron-specific enolase (NSE) and lactate dehydrogenase (LDH) levels, and TNM stage. Thereafter, a nomogram was constructed to predict 3- and 5-year intracranial progression-free survival (IPFS). Of 167 patients with LS-SCLC, 50 developed subsequent BM. Univariate analysis showed that pretreatment LDH (pre-LDH) ≥ 200 IU/L, an incomplete response to initial chemoradiation, and UICC stage III were positively correlated to a higher risk of BM (p < 0.05). Multivariate analysis identified pretreatment LDH level (hazard ratio [HR] 1.90, 95% confidence interval [CI] 1.08-3.34, p = 0.026), response to chemoradiation (HR 1.87, 95% CI 1.04-3.34, p = 0.035), and UICC stage (HR 6.67, 95% CI 1.03-49.15, p = 0.043) as independent predictors for the development of BM. A nomogram model was then established, and areas under the curve of 3-year and 5-year IPFS were 0.72 and 0.67, respectively. The present study has developed an innovative tool that is able to predict the individual cumulative risk for development of BM in LS-SCLC patients without PCI, which is beneficial for providing personalized risk estimates and facilitating the decision to perform PCI.