As mentioned above, adult renal sarcomas are an extremely rare group of tumors, accounting for only 0.8% of primary renal tumors(3). The SEER stage grading system was used by urologists to evaluate the progression of renal sarcomas. Sarcomas are classified into different grades based on the location and the extent to which it invades organs, blood vessels, and lymph nodes, including localized, regional, distant, and unstaged. However, due to the influence of individual differences, such as sex, age, race, marital status, radiation, chemotherapy, surgery, etc., it is not comprehensive enough to use the extent of tumor invasion alone to evaluate the prognosis for adult RS patients.
The nomogram is a graphical representation of a clinical prediction model that calculates a total score based on the values of individual predictor variables, and then predicts the risk of an event or the probability of survival based on the total score(15). It is a novel prediction model that is gradually sought after by clinicians. In recent years, predictions for the prognosis of various urinary cancer with nomograms have been reported more and more. For instance, Wu et al. employed a genomic-clinicopathologic nomogram to predict preoperative lymph node metastasis in bladder cancer(16); A nomogram was conducted by Mao et al. to predict prognosis in patients with lung metastatic renal cell carcinoma(17). Zhang et al. established a radiomics nomogram to predict bone metastasis in newly diagnosed prostate cancer patients(18). The nomogram and Aggtrmmns scoring system were utilized by Zhou et al. for predicting overall survival and cancer-specific survival of kidney cancer patients(19).
As it is known that compared with the SEER stage, nomogram has the following advantages:1. By combining various independent risk factors according to the patient's condition, it allows for a more intuitive assessment and individualization of the patient’s prognosis (20). 2. It quantifies the possibility of OS and CSS in patients, permitting a more precise prognostic evaluation (21). Therefore, for the first time, the prognostic nomograms were developed for adult RS patients to obtain personalized and accurate prognostic predictions in this study.
We extracted data from the SEER database for adult RS patients and used COX univariate and subsequent multivariate regression analysis to conclude that histological type, SEER stage, surgery were independent risk factors for OS and CSS. Based on the multivariate regression analysis, the OS and CSS nomograms were constructed, respectively. Subsequently, we validated the nomograms. The area under the ROC curves for 3-,5- OS were 0.775 and 0.829, respectively, and 0.807 and 0.855 for 3-, 5- CSS, respectively, which depicted that the nomograms accurately predict the probability of 3- and 5- OS and CSS for adult RS patients. The calibration curves showed high consistencies between the predicted and actual survival rates.
From the nomograms, it was suggested that RS patients without surgery, with distant SEER stage grade, and histological type of fibrosarcoma had the poorest prognosis. Depending on histological type, the prognosis from good to the poor was liposarcoma, leiomyosarcoma, carcinosarcoma, rhabdomyosarcoma, clear cell sarcoma, and fibrosarcoma. According to the Kaplan-Meier overall and disease-specific survival analysis of patients with RS established by Nazemi et al. (1), liposarcoma had the greatest prognosis, followed by leiomyosarcoma and clear cell sarcoma, while carcinosarcoma had the worst prognosis. Regardless of carcinosarcoma, its prognostic ranking was consistent with ours. However, it was shown that carcinosarcoma had the worst prognosis, which was inconsistent with our analysis. The reason for this may be that rhabdomyosarcoma and fibrosarcoma were not included in the Kaplan-Meier analysis due to the small sample size in their study, thus leading to biased results.
In addition, our study demonstrated that surgical treatment for adult RS patients may effectively reduce the risk of death. This is in line with the findings of Moreira DM et al. (22) and Öztürk H (23). Moreover, it is also found that chemotherapy may also improve the prognosis of adult RS patients. Chemotherapy has now been applied clinically to treat advanced or recurrent renal sarcoma, although not standardized(24), and the latest research of Yakirevich E et al. suggested that comprehensive genomic analysis of adult RS patients may provide new opportunities for targeted therapy(25).
To our surprise, our data suggested radiotherapy was not an independent prognostic factor for the adult patient with renal sarcoma, which was in accordance with the findings of Li et al. (26). However, Gamboa et al. reported that preoperative radiotherapy may improve the prognosis by making some tumors easier to resect(27). Thus, the prognostic impact of radiotherapy on patients with renal sarcomas should be further explored. The clinical outcome of primary adult renal sarcoma is extremely poor and the optimal treatment remains to be debated. Further studies are needed to verify whether it is surgery or combination therapy that works best. Furthermore, our data also suggested that female patients had a better prognosis than male patients, which could be attributed to differences in female anatomy or hormone levels.
We appraised the prognosis of adult RS patients with nomograms for the first time, which adds a new dimension to our research. Simultaneously, using the SEER database excluded the influencing factors of single-center. Even so, there are still a few flaws in our study: 1. Because of the rarity of renal sarcoma, limited sample size is inevitable and therefore our findings may not be representative; 2. As our study is retrospective, there is a lack of multicenter data for external validation. 3. Due to the lack of data in the SEER database, genetic factors, laboratory findings, and medication history were not included in our study.