In our study, we established an individualized nomogram to predict the prognosis of “driver-gene-negative” LUAD based on age, TNM stage and CTCs count. The nomogram showed promising prediction efficacy, with a C-index of 0.785 (95% CI, 0.753-0.817). We further explored the biological basis of the nomogram as being linked to cell cycle and transcriptional processes. The pathways suggested the biological basis for the role of the predictive model may be due to changes in cell proliferation, metabolism and neurological disease. The easy-to-use nomogram and the enriched pathways can help clinical decision-making, guide follow-up planning, and develop new therapeutic targets.
Clinical nomogram has gained a lot of attention for its more convenient and advanced prognosis ability[18]. It had already showed promising prognostic capability in different kinds of cancers including lung cancer[10, 19], gastric cancer[20, 21]], colorectal cancer[22], liver cancer[23], melanoma[24], etc. For resected NSCLC (stage I-IIIa)[19], a clinical nomogram built on sex, age, histology, sampled lymph nodes, T and N stage achieved higher C-index than that of the seventh edition American Joint Committee on Cancer TNM staging system for predicting OS (primary cohort, 0.71 v 0.68, respectively; P .01; validation cohort, 0.67 v 0.64, respectively; P .06). Another study devised an effective clinical nomogram for assessing the survival of patients with stage I NSCLC receiving complete resection[25]. The nomogram built on age, sex, tumor size, and visceral pleural invasion had C-indices of 0.694 (95% CI 0.651–0.737) for predicting OS and 0.653 (95% CI 0.61–0.696) for DFS. Despite these promising findings, gene mutation status was unknown in these studies which may lead to variance prognosis when targeted treatment was applied. Science “driver-gene-negative” LUAD have fewer treatment options and poor prognosis, studies focused on this genetically unique subset of patients are imminent. In this study, the clinical prognosis nomogram built on pre-treatment clinical data displayed promising prediction efficacy and the suggested pathways can provides a feasible way to explore new therapeutic drugs for this genetic subgroup of patients.
CTCs count is an independent prognostic indicator for NSCLC[26], especially advanced staged NSCLC[27]. However, there are few studies on “driver-gene-negative” LUAD and CTCs. In our study, we confirmed the prognostic role of CTCs in “driver-gene-negative” LUAD patients. It can not only predict prognosis prior to treatment, but also can help to monitor the dynamic treatment response[28] and the change of survival probability during the course of the disease. In this study, we also studied the prognostic value of PD-L1 expression, unfortunately, it was not an independent risk factor of prognosis for “driver-gene-negative” LUAD. It is reported that PD-L1 expression is related to the prognosis of patients with untreated NSCLC[29, 30], and many studies have shown that the greater the PD-L1 expression, the worse the prognosis of patients with NSCLC. The discrepancy of this finding between ours and the reported may be due to the difference in patient enrollment and the potential bias caused by retrospective detection of the tissue sample.
We also do initial genomic association study to explore the biological basis of the Nomogram predict models. The result shows five pathways including Parkinsons disease, oxidative phosphorylation, Huntingtons disease, cell cycle and Alzheimers disease are the most different in the low and high OS score group. Previous studies shown that cell-cycle and oxidative phosphorylation pathway is involved in poor prognosis of NSCLC[31-33], and drugs targeting them have also achieved good results[34, 35]. Notably, three of this five pathways are neuropathy-related, which suggests that the above neurological disease pathways are closely related to lung cancer prognosis. This result is consistent with previous findings[36-39]. Currently, drugs targeting neuropathy-related pathways have also been reported to have anticancer effects. Albanol B, a drug against Alzheimer's disease, has been shown to inhibit the growth of lung cancer cells and tumors[40]. Pimavanserin, a drug for Parkinson's disease, also has some efficacy against pancreatic cancer[41]. These findings suggest that the neuropathy-related pathways enriched in this study have the potential to be therapeutic targets for lung cancer.
This study has several limitations. First, there may be potential selection bias due to the retrospective nature of this study. Second, our study focused on LUAD and did not address other histologic subtypes. Third, our findings deserve further study with expanded samples and extra external validation. Fourth, PD-L1 expressions of some cases were detected retrospectively, so the accuracy of the detection results may have potential bias. The prognostic value of PD-L1 expressions in “driver-gene-negative” LUAD deserves further study.
In conclusion, the individualized nomogram based on age, TNM stage and CTCs count showed promising prediction efficacy and is expected to predict the prognosis of “driver-gene-negative” LUAD. Furthermore, we evaluated the biological basis of the proposed biomarker as being linked to cell cycle and transcriptional processes, and found to be correlated with cell proliferation, metabolism and neurological potential. The easy-to-use nomogram and the enriched pathways can help clinical decision-making, guide follow-up planning, and develop new therapeutic targets.