1 Introduction

Sarcomas, rare but highly aggressive tumors, encompass a heterogeneous group of mesenchymal neoplasms traditionally divided into two main groups: soft tissue sarcomas and bone sarcomas [1,2,3]. Currently, the response of anti-cancer therapy in sarcomas are primarily evaluated by imaging without specific and reliable biomarkers. However, it should be borne in mind that repeated imaging examinations appears to bedetrimental to the body, expensive, and inconvenient. Thus, it is essential to find useful biological markers that can identify which patients with sarcoma acquire better response to anti-cancer therapy and guide the optimal timing for imaging evaluation.

An increasing body of evidence suggests that vitamin D deficiency might increase the incidence and mortality risk for many kinds of cancer, including colorectal, prostate, breast, and lung cancer [4,5,6,7,8,9]. The active hormonal form of vitamin D is 1,25-dihydroxyvitamin D (1,25(OH)2D3), also known as calcitriol, which has been reported to regulate gene expression and play an essential role in cell differentiation and growth [10]. Current evidence suggests that the half-lives of vitamin D and 1,25(OH)2D3 are 24 h and 4 h respectively, which indicates that 1,25(OH)2D3 may represent the actual functional level of vitamin D, for the reason that 1,25(OH)2D3 have shorter half-lives and are the active hormonal form of vitamin D. 1,25(OH)2D3 is a kind of hormone with anti-cancer and anti-inflammatory activity [11]. However, the status of 1,25(OH)2D3 in patients with sarcoma has been largely underinvestigated, warranting further research.

During clinical practice, decreased serum 1,25(OH)2D3 level is commonly observed in many patients with sarcoma. However, whether the change of 1,25(OH)2D3 is related to the disease development of patients with sarcoma has not been reported. Therefore, this study analyzed the expression of 1,25(OH)2D3 in sarcoma patients at our hospital and further explored whether the change in serum 1,25(OH)2D3 level could predict sarcoma prognosis.

2 Materials and methods

2.1 Study design and patients

This retrospective study included sarcoma patients treated between January 2021 and November 2022. This study protocol was approved by the Ethics Committee (Approval No. B2020-338). Given that this real-world study involved retrospectively collected data, the requirement for individual consent was waived by the Ethics Committee of Zhongshan Hospital of Fudan University. All data were anonymized before data processing.

Inclusion criteria: (1) sarcoma confirmed by histology; (2) blood test results are available, including serum 1,25(OH)2D3, parathyroid hormone (PTH), calcium, and calcitonin; (3) no synchronous or metachronous cancer; (4) no severe liver and kidney insufficiency.

2.2 Data collection

Data were collected on various demographic and clinical parameters, including gender, age, stage, pathology, sarcoma location, and treatment phase. Serum 1,25(OH)2D3, PTH, calcium, and calcitonin were further collected and analyzed before and after disease evaluation. The disease assessment was executed by the Response Evaluation Criteria in Solid Tumors version 1.1. The normal concentration range for 1,25(OH)2D3 was > 50 nmol/L [12]. The normal concentration range for calcium was between 2.15 to 2.55 mmol/L. The normal concentration range for PTH was 15 to 65 pg/ml, while for calcitonin, it was 0 to 6.4 pg/ml.

2.3 Statistical analysis

Categorical data were displayed in numbers and further examined by the chi-square test. The values of continuous variables were presented as means ± SEM (standard error of the mean). The results were compared using unpaired t-tests and ordinary one-way ANOVA tests.

3 Results

3.1 Characteristics of the patients

From January 2021 to November 2022, 331 patients with a mean age of 46 (14 to 83 years) met the inclusion criteria, exhibiting female predominance (n = 183, 55.3%). A comprehensive data collection was conducted for all patients (Table 1). Most sarcoma patients were in the 40 to 60 years old group. The pathological types of sarcomas mainly include leiomyosarcoma (LMS), liposarcoma (LPS), and undifferentiated pleomorphic sarcoma (UPS), etc. LMS was the most common pathological type. More than 70% of patients (n = 242) with sarcoma presented with stage IV disease. Among the patients, 56.19% (n = 186) were undergoing first-line treatment, while 15.41% (n = 51) were receiving second-line treatment, and 14.80% (n = 49) were receiving adjuvant treatment. Interestingly, the abdomen and limbs were the most commonly affected sites, accounting for 40.18% and 22.05%, respectively. Notably, among patients with abdominal involvement, the retroperitoneum accounted for the majority of those cases (n = 96, 29%).

Table 1 The characteristics of patients with sarcoma
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3.2 Relationship between 1,25(OH)2D3 status and clinical outcomes

The mean serum 1,25(OH)2D3 level in these patients with sarcoma was 45.68 ± 1.06 nmol/L, lower than the standard normal level (> 50 nmol/L). However, the median serum PTH, calcium, and calcitonin were all within the normal range. The mean serum level of 1,25(OH)2D3 was 50.65 ± 1.68 and 41.67 ± 1.28 nmol/L for male and female sarcoma patients, respectively. The concentration of 1,25(OH)2D3 in females was significantly lower than in males (P < 0.01, Table 2). The concentration of PTH in females was slightly higher than in males (43.14 vs. 37.66 pg/ml), with a significant difference (P = 0.024). Furthermore, there were slight variations in 1,25(OH)2D3 levels based on age in sarcoma patients. Patients below 60 years old exhibited lower levels of 1,25(OH)2D3, which were below the normal range. However, among patients above 60 years old, the levels of 1,25(OH)2D3 were within the normal range. In this respect, among patients younger than 20 years old age, the serum concentration of 1,25(OH)2D3 was the lowest, with a mean value of approximately 33.80 ± 2.18 nmol/L.

Table 2 Serum level of 1,25(OH)2D3 and PTH in patients with sarcoma
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During subgroup analysis according to pathological type and tumor clinical stage, 1,25(OH)2D3 serum concentration was not significantly different. Although the serum concentration of 1,25(OH)2D3 was higher in the patients with adjuvant therapy (48.84 ± 2.69 nmol/L), the difference was not significant. Besides, there was no correlation between the level of 1,25(OH)2D3 and tumor sites (Table 2). The serum concentration of PTH was slightly different after stratification according to gender, tumor stages, and tumor treatment phase but remained within the normal range (Table 2). We also analyzed calcium and calcitonin in sarcoma patients (Table 3). The concentrations of calcium and calcitonin were both within the normal range. Further stratification according to gender revealed that calcium and calcitonin were significantly different, indicating calcium and calcitonin levels were higher in male patients. Additionally, the concentration of calcitonin was slightly different based on the sarcoma treatment phase, and calcitonin levels were different based on tumor sites, but all values remained within the normal range.

Table 3 Serum calcium and calcitonin concentration in patients with sarcoma
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3.3 Characteristics of patients stratified according to 1,25(OH)2D3

To further analyze the potential value of 1,25(OH)2D3 in sarcoma patients, we stratified sarcoma patients according to 1,25(OH)2D3 serum concentration and divided them into normal-level (> 50 nmol/L) and low-level (≤ 50 nmol/L) groups. The results showed that 1,25(OH)2D3 expression was lower than normal in 208 (62.8%) patients with sarcoma and remained within the normal range in 123 (37.2%) patients (Supplementary Table 1). The average 1,25(OH)2D3 concentration was 66.25 nmol/L in the normal-level group and 33.52 nmol/L in the low-level group (Table 4). The serum concentration of 1,25(OH)2D3 was correlated with sex in both normal-level and low-level groups (P < 0.05). The reduction of 1,25(OH)2D3 was more likely in female patients (n = 128) than in male patients (n = 80). The levels of 1,25(OH)2D3 were higher in male patients with sarcoma than in female patients in both normal-level and low-level groups. In the normal-level group, 1,25(OH)2D3 was also upregulated with increased age (P < 0.05). However, there was no correlation between 1,25(OH)2D3 and age in the low-level group. After stratification by serum levels of 1,25(OH)2D3, we analyzed the correlation between 1,25(OH)2D3 and the pathological characteristics, clinical stage, disease progression stage, and location of sarcoma. However, there was no significant correlation between them.

Table 4 Serum level of 1,25(OH)2D3 in patients with sarcoma cut-off by 50 nmol/L
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Next, we analyzed the differences in PTH, calcium, and calcitonin between the normal-level and low-level groups (Supplementary Table 2). PTH was slightly higher in the 1,25(OH)2D3 low-level group than in the high-level group (42.81 vs. 37.10 nmol/L, Supplementary Table 2). PTH exhibited differences with age and treatment phase in the 1,25(OH)2D3 normal-level group. However, there was no difference in PTH with age in the 1,25(OH)2D3 low-level group. Calcitonin was also lower in the 1,25(OH)2D3 low-level group, but there was no statistical difference (Supplementary Table 3). Calcitonin was highly expressed in male patients with sarcoma in both low-level and normal-level groups. Calcium concentration was also lower in the 1,25(OH)2D3 low-level group (Supplementary Table 4). Calcium was associated with age and treatment phase in the 1,25(OH)2D3 low-level group. However, it is worth noting that the mean values of PTH, calcitonin, and calcium in all sarcoma patients were within the normal range, irrespective of grouping.

3.4 1,25(OH)2D3 and survival analysis

Among the 331 patients with sarcoma, 213 underwent baseline and post-treatment imaging assessments and the serum data of 1,25(OH)2D3, calcium, calcitonin, and PTH. The disease assessment was executed by the Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1). 90 patients had progressive disease (PD), while 123 were classified with non-progressive disease (non-PD, including complete remission, partial remission, and disease stabilization).

Further analysis showed that the serum level of 1,25(OH)2D3 decreased by 7.08 nmol/L in the PD group, while it increased by 1.11 nmol/L in the non-PD group, compared with baseline in sarcoma patients (P < 0.01). 1,25(OH)2D3 was decreased by 13.74% in the PD group, while it increased by 6.98% in the non-PD group (P < 0.01). The serum concentration of PTH increased in both non-PD and PD groups. Although the increase in PTH levels was higher in the PD group compared to the non-PD group, there was no significant difference. Furthermore, there were no significant differences in calcium and calcitonin levels between the non-PD and PD groups (Table 5).

Table 5 Comparation of variables in patients with sarcoma with tumor evaluation
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4 Discussion

Sarcomas comprise several heterogeneous subtypes of mesenchymal tumors, posing challenges in their assessment due to reliance on imaging tests and a lack of specific tumor biomarkers. In clinical practice, abnormal 1,25(OH)2D3 levels have been observed in patients with a wide range of sarcoma. However, few studies have been conducted on the correlation between 1,25(OH)2D3 level and the progonosis and clinical features of sarcoma, especially on the potential value of 1,25(OH)2D3 as a prognostic marker in patients with sarcoma. In this study, we comprehensively analyzed the clinical characteristics of sarcoma patients in our hospital and uncovered that LMS and LPS were the most common types. These sickness have the special age distribution. Data were collected from 331 Chinese patitents with a mean age of 46 years old at baseline and an age range from 40 to 60 years. In addition, the most common site of sarcoma in our present study is abdomen, especially the retroperitoneum, which is slightly inconsistent with the published research [2].

A past study has documented that 1,25(OH)2D3 deficiency was discovered in 28% of patients with sarcoma [12]. However, our study found that 1,25(OH)2D3 level was decreased in more than 60% of patients with sarcoma. Our study found that 1,25(OH)2D3 level was lower in females with sarcoma than males with sarcoma. However, the reference [12] showed the results that the mean 1,25(OH)2D3 concentration was 101.6 ± 8.7 nmol/l for females with sarcoma than 82.4 ± 5.9 males with sarcoma, which has no significant value. We noted the sample number of that study was very small, which only 15 males and 10 females. And there was a significant difference of age between female sarcoma patients and male sarcoma patients. So we conduct the difference in sample size and age may be one of the reasons for the different results. Extensive studies during the past few decades revealed that 1,25(OH)2D3 is the major regulator of calcium homeostasis and protects the organism from calcium deficiency via effects on the intestine, kidney, parathyroid gland, and bone [13]. Therefore, patients with renal insufficiency and thyroid dysfunction were excluded from our data. Vitamin D has a complicated role in bone, which stimulates matrix formation and bone maturation, enhances osteoclast activity, and may affect the cell differentiation of osteocyte precursors [14]. During stratification according to pathological types, we also analyzed patients with osteosarcoma and chondrosarcoma. However, we found there is no correlation between 1,25(OH)2D3 and pathological types in sarcomas, which suggests that the difference in pathological types was not responsible for the abnormal changes in 1,25(OH)2D3 level. Next, we analyed the relationship between 1,25(OH)2D3 and sarcoma patients’ clinical features and found that serum concentration of 1,25(OH)2D3 was not associated with clinical features, such as tumor stage, site, and treatment phase. However, serum 1,25(OH)2D3 level correlated with patient gender and age, suggesting that systemic factors were the main factor influencing the serum 1,25(OH)2D3 level.

It has been established that multiple factors influence 1,25(OH)2D3 metabolism. The production of 1,25(OH)2D3 is tightly regulated by serum PTH, calcium, and calcitonin [15]. Thus, to clarify the abnormal expression of 1,25(OH)2D3 in sarcoma, we also analyzed serum PTH, calcium, and calcitonin levels. PTH levels were within the normal range (15–65 pg/ml) for 85% of sarcoma patients. The calcium and calcitonin levels of more than 90% sarcoma patients were in the normal region. Taken together, these data revealed no significant alterations in PTH, calcium, or calcitonin among patients with sarcoma, which indicates that 1,25(OH)2D3 variation in patients with sarcoma might be independent of PTH, calcium, and calcitonin. Compared to PTH, calcium, and calcitonin, 1,25(OH)2D3 was more closely associated with disease development in patients with sarcoma.

We found that serum 1,25(OH)2D3 level was downregulated in more than half of patients with sarcoma. To further understand the clinical characteristics of sarcoma patients based on their 1,25(OH)2D3 levels, we divided them into a low-level group and a normal-level group. Our results revealed that female patients and younger patients were more likely to have a lower concentration of 1,25(OH)2D3. However, there was no significant difference in 1,25(OH)2D3 levels after stratification according to pathological types, tumor stage, treatment phase, or tumor site.

A meta-analysis of observational studies revealed that women with the highest blood levels of 1,25(OH)2D3 experienced a significantly reduced risk of breast cancer [16]. Recent reports suggested that maintaining vitamin D levels within the normal range during anti-PD-1 inhibitor therapy in patients with advanced melanoma may improve clinical outcomes [17]. Vitamin D deficiency was found in Kaposi sarcoma patients but was not associated with tumor response and survival time [18]. However, it remains unclear whether the variation in serum concentration of 1,25(OH)2D3 was associated with the survival of sarcoma patients. Therefore, we then employed the value of serum 1,25(OH)2D3 level before and after treatment in sarcoma patients that underwent imaging evaluation. After further analysis, we found that the variation in serum 1,25(OH)2D3 level was consistent with the outcome of the imaging evaluation. Accordingly, decreased 1,25(OH)2D3 indicated tumor progression, and increased 1,25(OH)2D3 indicated tumor stability. Emerging evidence suggests that lower vitamin D level is associated with a higher cancer incidence [19, 20]. Interestingly, vitamin D supplementation may improve the supportive hazard ratio of metastatic colorectal cancer patitents,- and contributes to longer two months of progression-free survival [21]. Our findings suggest that an increased 1,25(OH)2D3 serum level may predict a better treatment effect. However, whether exogenous 1,25(OH)2D3 supplementation can prolong the survival of sarcoma patients remains to be further investigated.

1,25(OH)2D3 has been reported to be important in regulating cancer cell proliferation, apoptosis, and angiogenesis [22, 23]. A recent studies have unraveled that 1,25(OH)2D3 induced autophagosome formation, increased autophagy-related protein light chain (LC)3II/LC3I levels, and decreased ubiquitin-binding protein P62 expression [24]. The supplementation of optimal levels of 1,25(OH)2D3 may have the ability to reduce cancer risk [25]. Treatment with 1,25(OH)2D3 combined with active anticancer agents may prevent the onset of cancer and delay its progression [26]. Nonetheless, the mechanism underlying the association between 1,25(OH)2D3 and the prediction of sarcoma patient survival requires further investigation.

5 Conclusion

This study uncovered the clinical and biological significance of the potent regulator 1,25(OH)2D3 and suggested that the serum level of 1,25(OH)2D3 may serve as a potential prognostic marker for sarcoma patients. The observed decrease of 1,25(OH)2D3 in the majority of sarcoma patients indicated its potential role in disease progression. Accordingly, monitoring the variation in this biological marker could assist in predicting the development and outcomes of sarcoma.