SEER program of NCI has been used to analyze a variety of malignancies. Bladder rhabdomyosarcoma, as a rare malignant genitourinary neoplasm, is relatively lack of precious large-scale epidemiological study. In our research, we compared the epidemiology characteristics in each age group and explored the prognostic factors affecting the 5-year OS by utilizing an open access population-based public database.
As expected, most of the cases occur in 0–2 age group (49 cases) and about two-thirds of cases were diagnosed in children younger than 10 years old as Perez et al had reported. But unlike the former study results said that ERMS had a bimodal peak in early adolescence, there were only 11 cases between 11–24 years old in our research. We divided patients as pediatric and adult in principle and further divide pediatric group into infant (0–2 years) and children (3–16 years) according the WHO classification. The adult group was made up of adult (17–60 years) and the elder (> 60 years). Cox regression results showed that age was a significant risk factor, the hazard ratio for elder group can be 15.553 to infant group.
The total ratio of male and female is about 2:1. It remains relatively stable in different age groups, which is not consistent with former research (about 75% arise in male) as they focused on the whole genitourinary RMS and the prostate RMS increased the proportion of male patients. We confirmed that the gender was not associated with different survival time and was not a risk factor, As all SEER data were collected in the United States, this study was lack of global representation of race proportions. The number of cases increased significantly over every ten years, however when we considered the whole SEER database, the percentage of bladder RMS was quite stable (3.37%, 3.36%, 2.17%, 2.21%).
Embryonal RMS is the most common pathological type in pediatric bladder RMS and ERMS always indicates a better prognostic than non-embryonal RMS. This well-known phenomenon has been reported many times and was also validated in our study, only the percentage of ERMS (71.58%) is lower than former studies (about 90%).
Summary stage system is used by SEER program based on the theory of cancer growth: localized, regional and distant. We converted the Summary Stage into TNM system according the regional nodes examination results, tumor size and metastasis situation. Both of the stage systems were brought into analysis. The stage distribution among age groups demonstrated no differences. As staging increases, patient survival rates gradually decline.
Regarding the surgical treatment of bladder RMS, lymph node dissection(LND) plays an critical role as the bladder is a rich blood supply organ. Due to lack of the majority of the regional nodes examination results, survival analysis and cox regression results can be affected and cannot achieve satisfactory goal. Meanwhile, the LND template and positive lymph node location have not been included in SEER data, that make it difficult to analysis the association of LND with prognostic.
Currently, radiotherapy, multi-agent chemotherapy and surgery are all important invention choices, the problem is the treatment timing and sequences of these therapy for suitable subgroup patients. In this research, radiotherapy improved the prognostic significantly no matter before surgery or after surgery than surgery alone, so as the chemotherapy. Although we cannot get the chemotherapy regimens and radiotherapy dose data, we believe the core function of radiotherapy and chemotherapy in RMS treatment are beyond doubt.
In 2000, the Intergroup Rhabdomyosarcoma Study Group (IRSG) and other 3 groups came together to merge COG. During IRSG studies and COG period, they have published 6 protocols for RMS[12, 19–23]. The 5-year overall survival rates had increased from 55% in IRS-I to 71% in IRS-IV, this trend was also noticed in our research: from 33% (1975–1984) to 70% (2005–2016). This can be attributed to the improvement of technology development in this years.
In former other studies, M. Fisch et al evaluated different treatment modalities include conservative surgery, radical surgery and irradiation therapy in 22 urogenital tract rhabdomyosarcoma and they recommended radical operative intervention with multiple biopsies after chemotherapy to for the long-term benefit. In their updated study, they still confirmed the previous conclusion. Sherbiny et al reported a one single-centre experience of 30 cases low urinary tract tumor and 11 cases of them is bladder rhabdomyosarcoma. They stratify patients into two risk-groups according their response to the chemotherapy and for the low risk group patients, their bladders could be salvaged. Kathleen Kieranc and Margarett Shnorhavorian systematically summarized the epidemiology and treatment status of bladder/prostate rhabdomyosarcoma.
As far as we know, this is the largest samples retrospective study based on the data of SEER program for bladder RMS under the conditions of relatively comprehensive information and the long follow-up time. The limitations of this study are mainly the inherent defects of the SEER program: it is impossible to compare different chemotherapy regimens, to discuss the influence of positive surgical margins, to know the related immunohistochemistry results, to examine the fusion genes (PAX3/7-FOX1) exist. All of these elements can promote the accuracy judgement of treatment and prognosis research. Moreover, as urologists, while concerning about the tumor control, we also focused on the urination control situation for the patient quality of life. Therefore, we look forward further studies to provide more clinical evidences for us to explore and treat bladder RMS better.