In this study, we successfully established a novel prognostic Lasso regression model based on clinical features and blood-biomarkers for individualized prediction of the OS for NPC patient. The novel prognostic model showed better predictive accuracy and discrimination compared with the traditional AJCC TNM staging system, clinical treatment, and EBV DNA, which successfully split NPC patients into high-risk and low-risk groups, and the two groups of patients exhibited significant differences in the OS.
The present prognostic model consisting of 13 prognostic variables: age, BMI, HGB, PLT, LMR, CRP, CAR, GLOB, AGR, LDH, Cys-C, ALI, and PNI. All the prognosis variables had been reported to be associated with survival in NPC patients except ALI[24–30], these were credible evidence supporting our analysis results. The ALI was devised to assess the degree of systemic inflammation in patients with advanced non-small cell lung cancer patients[31]. Subsequently, ALI had also been demonstrated to be a prognostic factor of survival in some cancers[32–34]. The difference between the ALI and other inflammatory markers was that the ALI contained not only indices related to inflammation but also the body mass index (BMI), which was reported to correlate with the sarcopenic status[33]. So, this was the first study to indicate ALI as a prognostic marker in NPC patients.
Subsequently, we compared the predictive accuracy and discrimination of the novel prognostic model with TNM staging, clinical treatment and EBV DNA using C-index, tdROC and DCA. The results all showed the prognostic model had good predictive accuracy and discriminatory power than TNM staging, clinical treatment and EBV DNA in training cohort. Above similar results were observed in the validation cohort except EBV DNA. The C-index of the prognostic model was slightly lower than EBV DNA, but there was no statistical difference. The most likely explanation was that this was a retrospective analysis, and there may have some potential patient selection bias. Then the nomogram consisting of the prognostic model, TNM staging, clinical treatment and EBV DNA shown some superior net benefit. Finally, according to the model risk score, we split the patients into two subgroups: low-risk and high-risk, and there were significant differences in OS between the two subgroups of patients. These results indicated the novel prognostic model had good predictive accuracy and discrimination for estimating OS in NPC patients.
Although previous studies had established some models for predicting NPC survival, this study still had several merits compared to other studies: 1. The prognostic model only included basic clinical and routine laboratory data, which did not include some not routinely available markers, such as EBV DNA[35], and circulating tumor cells (CTC)[36–37]. and this model was low-cost, non-invasive, no risk of radiation exposure, and convenient. So, this model could widely and safely used in clinical practice, especially in primary hospitals. 2. The prognostic model was constructed by using the newly algorithm LASSO model, as a statistical method for screening variables to establish the prognostic model, which enabled to adjust for model's over fitting and avoid extreme predictions. So, the predictive accuracy could be improved significantly, and this approach had been applied in many study[18, 38–39]. 3. Many previous models usual integrated with TNM staging and/or clinical treatment to improve the predictive accuracy for clinical outcome[27, 40–45], which made them not applicable to the patients with uncertain clinical TNM staging. This model can be used for patients with TNM staging remained unclear because of it was not include TNM staging.
There also had several drawbacks of this study. First, this was a retrospective analysis and selection bias might exist. Second, the treatment effect heterogeneity for metachronous metastasis patients might bring confounding effects. Third, the endpoint of this study was OS, and the effect of the model for predicting disease-free survival (DFS), distant metastasis free survival (DMFS) and locoregional relapse-free survival (LRFS) in NPC patients were not assessed[46]. It was better clinical application that the endpoint combined OS with DFS and DMFS. Finally, it was a single-institutional study with a relatively small sample size. Thus, a large-scale and multicenter validation of the model will be needed in the future