The mSHOX2 is capable of assessing the therapeutic effect and predicting the prognosis of stage IV lung cancer

Abstract

Background: Instant monitoring of the therapeutic effect of systematic therapy in late-stage lung cancer is crucial for response assessment and strategy adjustment. Previous study found that specific plasma methylation markers may be applied to therapeutic effect assessment. In order to investigate the performance of plasma mSHOX2 in assessing the therapeutic effect and predicting the prognosis of stage IV lung cancer, we performed the study focusing on patients underwent chemotherapy or tyrosine kinase inhibitor (TKI)-based targeted therapy.

Methods: Blood samples from 163 subjects, including 30 stage I, 29 stage II, 26 stage III and 68 stage IV lung cancer patients, were recruited in this study. Quantitative relationship between primary tumor size and the plasma mSHOX2 level was established. Blood samples before therapy and two cycles after therapy were obtained from 68 stage IV patients, and the mSHOX2 level was quantified as ΔΔCt.

Results: Sharp decrease of plasma mSHOX2 level was seen in patients with partial response (PR) while not in those with stable disease (SD). The plasma mSHOX2 level change reflected the degree of response and correlated with the maximal diameter of primary tumors in linear relationship. The mSHOX2 levels before and two cycles after therapy were predictors of the overall survival, while the mSHOX2 level change or the tumor size change were not predictors of the overall survival. Furthermore, univariable and multivariable Cox regression revealed that mSHOX2 level before therapy was the only independent predictor of the overall survival with a hazard ratio of 1.414.

Conclusions: mSHOX2 is effective for therapeutic effect assessment and prognosis prediction of stage IV lung cancer patients underwent systematic therapy.

Keywords: SHOX2; circulating tumor DNA (ctDNA); lung cancer; mSHOX2; methylation; prognosis; therapy.

Figure 1

The relationship between tumor diameter and plasma mSHOX2 methylation level (ΔΔCt). Box and Whisker plots show the diameter (A) and the ΔΔCt values (B) from stage I to stage IV lung cancer. The linear relationship between the mean values of diameter and the ΔΔCt was shown in (C) and the linear relationship between the medians of diameter and the ΔΔCt was shown in (D).

Figure 2

The mSHOX2 levels before and two cycles after therapy for stage IV lung cancer patients. The before-after plot is shown in (A), and data from the same patient is connected by dashed line to show the mSHOX2 level change. The scatter plot is shown in (B), and bars represent mean values with 95% CI. The paired mSHOX2 levels before and two cycles after therapy were shown in (C) in descending order of the pre-therapeutic mSHOX2 level. Solid dots and blank dots represent mSHOX2 level before and two cycles after therapy, respectively.

Figure 3

The mSHOX2 levels before and two cycles after therapy for stage IV lung cancer patients with partial response (PR) or stable disease (SD). The before-after plot is shown in (A) and (C) for patients with PR and SD, respectively, and data from the same patient is connected by dashed line to show the mSHOX2 level change. The scatter plot is shown in (B) and (D) for patients with PR and SD, respectively, and bars represent mean values with 95% CI.

Figure 4

The therapeutic response and the corresponding mSHOX2 level change (ΔΔCt change) for stage IV lung cancer patients. (A) The therapeutic response of all involved stage IV lung cancer patients in ascending order of the response. 30% threshold was used for distinguishing patients with PR from those with SD. (B) The ΔΔCt change of the corresponding patients in descending order. Positive numbers indicate ΔΔCt increase and negative numbers indicate ΔΔCt decrease. Solid bars represent the ΔΔCt change values for patients with PR and blank bars represent ΔΔCt change values for patients with SD. −3.0 (arrow) was the median value of the dataset, which was used in Figure 5 for patient dichotomization.

Figure 6

Linear relationship between the therapeutic response and mSHOX2 level change (ΔΔCt change) for all stage IV patients involved in this study. r²=0.57 for the linear regression.

Figure 5

Kaplan-Meier survival analysis of risk factors in stage IV lung cancer patients involved in this study. (A) the overall survival analysis based on pre-therapeutic mSHOX2 level with stratifying threshold at the ΔΔCt median of −1.62; (B) the overall survival analysis based on two cycles post-therapeutic mSHOX2 level with stratifying threshold at the ΔΔCt median of −4.0; (C) the overall survival analysis based on mSHOX2 level change (ΔΔCt change) with stratifying threshold at the median of −2.72; (D) the overall survival analysis based on targeted tumor maximal diameter change with stratifying threshold at the median of 31.6%.

Figure S1

Test of normality using the histogram analysis and the P-P plot methods for three datasets used in this study. LC, lung cancer; P-P, probability-probability.