Cognitive decline is common among patients with PHPT, which is characterized by elevated PTH and serum calcium. Several reports have identified that patients with PHPT appear to have an increased incidence of cognitive dysfunction.40–42 According to a current systematic review, cognitive impairment in PHPT is more likely to be associated with elevated PTH levels rather than hypercalcemia.13 However, the mechanism for inducing the impairment of cognition remains to be studied. The details of these relationships between cognitive impairment and serum biomarkers, such as PTH and serum calcium, merit further investigation. Despite the conclusion of the current 5th International Workshop that cognitive evaluation for patients with PHPT is not a necessary test.43 The cognitive function assessment in patients with parathyroid cancer, who may have cancer-related cognitive impairment, may offer new ideas to distinguish benign parathyroid disease from parathyroid cancer.
High-level PTH may play a role in cognitive dysfunction and cerebrovascular diseases by way of PTH2 receptors (PTHrP) scattered throughout the arteries of the cerebral cortex. PTH2 receptor expression is dominated in limbic, hypothalamic, and sensory areas, particularly hypothalamic periventricular neurons and median eminence nerve terminals.13,41,44−46 The cerebral area responsible for these functions is the same as the area where PTH receptors are distributed. Therefore, it seems reasonable to speculate that the cognitive decline in patients with PHPT might be proportionally interrelated with PTH level. Bjorkman found that elevated levels of PTH was associated with MMSE in a five-year follow-up in a general-aged population.44. Unlike these previous reports41,45−47, only a weak link between cognition deficit and elevated PTH level was observed in MMSE (Spearman correlation = -0.172 p = 0.048 < 0.05) based on our data, while MOCA failed to show a correlation with PTH level (p = 0.474 > 0.05). The reasons for this inconsistency may be as follows. One reason is that we excluded the influence of age, education, depression, and anxiety on cognitive performance by comparing the PC group to the matched control group, which has been neglected in previous research. Another may be that the effect of peripheral cancer on cognitive impairment could not be excluded in parathyroid cancer because patients often experience significant neurocognitive decline, as has been observed in other cancers.14 Based on the physiological perspective, cognitive decline may be associated with the distribution of PTH2 receptors in different pathological states, which requires to be proved by subsequent experiments. The modification of PTH secretion by serum calcium is changed in patients with PHPT. In accordance with previous studies13,17, we found no link between calcium levels and neurocognitive function. (MMSE: p = 0.106 > 0.05; MOCA: p = 0.506 > 0.05). Additionally, lacking vitamin D could lead to cognitive decline in the older adult.48 Though the mean concentrations of vitamin D with patients both in PC and BP are lower than normal, we didn’t observe a link between decrease vitamin D and impaired cognition both in MMSE and MOCA. (MMSE: p = 0.716 > 0.5; MOCA: p = 0.834 > 0.5) Further, it needs more mechanistic experiments to determine whether these effects are related to neurocognitive aspects of PC.
By self-report neurocognitive symptoms (presenting difficult concentration and memory problems), Daniel Repplinger reported that neurocognitive dysfunction may be used as a predictor of parathyroid hyperplasia.49 In our study, we proposed the pre-surgery cognitive function as a potential indicator for PC and both MMSE and MOCA could be used as robust tools for assessing the cognition of patients with PC (p < 0.05). In addition, MMSE was superior to detect cognition in distinguishing patients with PC from PHPT. This is more likely due to MMSE stability of no influence on sex and good internal consistency in measuring the severity of cognitive problems.50–52 Those deteriorations of cognitive function in patients with PC are primarily characterized by impaired attention, diminished calculative accuracy, difficulties in extracting acquired information from memory, and scathed visual constructive abilities. (Table 5. attention and calculation p = 0.003; recall p = 0.007; language and visual construction p = 0.03). Notably, a similar phenomenon was reported by Janelsins et al, who found that patients with stage I-IIIC breast cancer have significant cognitive impairment before treatment, particularly in the areas of memory, attention, and executive function.53 Whether a similar phenomenon is observed in other cancer needs further investigation.
Table 5
Distribution of the scores of the MMSE between PC and BP.
Factors
|
BP group
(n = 101)
|
PC group
(n = 32)
|
P
|
AUC
|
Orientation to time and place
(0–10)
|
10(10,10)
|
10(10,10)
|
0.301
|
0.551
|
Registration
(0–3)
|
3(3,3)
|
3(3,3)
|
0.072
|
0.524
|
Attention and Calculation
(0–5)
|
5(3,5)
|
3(1,5)
|
0.003*
|
0.677
|
Recall
(0–3)
|
2(1,3)
|
1(0,2)
|
0.007*
|
0.71
|
Language and Visual Construction
(0–9)
|
9(8,9)
|
8(7,9)
|
0.03*
|
0.66
|
Based on the above perspective and the study data, we developed three prediction models for PC on the XGBoost algorithm, LASSO regression and logistic regression by preoperatively taking scores of MMSE and clinical features into account (in Table 4). As far as we are aware, this is the first time that the use of XGBoost and LASSO regression in the prediction of PC has been presented. The sensitivities of the three models were 0.773,0.727 and 0.682, and their specificities were 0.817,0.789 and 0.887, respectively. In comparison to the traditional statistical approach, the XGBoost model could learn complex nonlinear decision boundaries through boosting, whereas linear models such as logistic regression may ignore interactive relationships of the multiple indicators in non-linear and perform the suboptimal outcome54–56. In our study, the predictive performance of the XGBoost model, with a lowest false negative rate, was superior to that of the logistic model and LASSO regression model. With a low percentage of underdiagnosis, it would be sensitive to forecast the likelihood of cancer in PHPT avoiding the second surgery. This research offers a reasonably accurate tool for predicting PC.
Our study has serval limitations. First, this is considered a preliminary study due to a single-center study with an inevitably small sample size which may affect the generalizability of the findings. Future studies with a larger number of participants in multi-center are required. Second, the model was developed based on our internal verification in Chinses population, consequently unknowing in other populations. Furthermore, multiple populations need to be used to validate the prediction models developed by XGBoost.
In conclusion, our research demonstrated that the pre-surgery cognitive function might be a potential predictor for PC in patients with PHPT. MMSE is superior to MOCA in evaluating cognition function in PHPT patients and differing PC from BP. Preoperative cognitive assessment of MMSE is necessary for patients with PHPT suspected of PC. The XGBoost model, which had a better performance than the LASSO and logistic model, could predict PC based on pre-surgery cognitive function and clinical features. The performance of the prediction model for PC based on the XGBoost model needs to be further verified in larger populations of PHPT patients.