Soft-Tissue Sarcomas in Adults in Ecuador in the Period 2010–2020

Background Soft-tissue sarcomas (STSs) are rare tumors; they represent 1% of all tumors in adults. There are new diagnostic techniques to differentiate tumor types, and surgery continues to be the most important treatment for STS. Methods This cross-sectional study analyzed the morbidity and mortality caused by STS in adults between 2010 and 2020 using national databases. Results A total of 8,393 patients hospitalized due to STS were reported. The total number of deaths in Ecuador due to STS was 7,088 over the last decade, the provinces of Pichincha and Guayas registered the highest number of cases, and the mortality rate was 1.2 to 2.0 per 100,000 people. It is noteworthy that the lowest point of registered cases was in 2012. Conclusion Soft-tissue sarcomas are rare tumors in Ecuador. The morbidity and mortality caused by these tumors have not changed in the last decade. National studies are needed to determine the prevalence of this illness and study intervention to lower mortality.


Background
Soft-tissue sarcomas (STSs) are rare and heterogeneous tumors derived from the mesenchyme and represent about 1% of all malignancies in adults [1][2][3]. Tere are several subtypes of STS, and they can arise from cartilage, muscle, blood vessels, nerves, and fat [4].
STSs occur in 2-4 people per 100,000. Te annual incidence of STS is approximately between 1.8 and 5.0 cases per 100,000 people per year [5]. Te most common locations of these tumors are the lower limbs [6]. Genetic studies improve the diagnostic accuracy of STSs since they are often difcult to diagnose through morphological studies [7].
Surgery remains the primary treatment modality; however, chemotherapy and radiotherapy can be adjuvant treatments in certain STS [6]. Determining the clinical stage is essential to establish the best treatment option. Small, localized, and low-grade tumors have a good prognosis when treated with surgery. Large, wide, extended, and high-grade tumors that may not be suitable for surgery can be treated with adjunctive chemotherapy and radiotherapy [8]. Recurrences are common, and they are associated with the tumor size, histological grade and localization of the tumors [9].
Te epidemiology of STS in adults is established by ICD-10 (International Statistical Classifcation of Diseases and Related Health Problems, 10th Revision) codes that are used to identify cases. Tis study aims to describe the current situation of patients who were hospitalized and the mortality due to STS in the period of 2010-2020 in Ecuador.

Study Setting and Design.
Tis cross-sectional study analyzed the morbidity and mortality caused by STS in adults between 2010 and 2020 in Ecuador using national databases.

Data Sources.
We analyzed the data available from the National Registry of Hospital Discharges and Deaths. Tis registry is of mandatory use in the National Health System of Ecuador, and the National Institute of Statistics and Census (INEC) is responsible for the validation of the information. Tese databases provide information from public and private health establishments.

Study Population.
Tis study included adult patients over 18 years of age registered with ICD-10 codes related to STS (2020 WHO Classifcation of Tumors of Soft Tissue) between 2010 and 2020. Te ICD-10 codes considered for the analysis were C47, C48, C49, C85.0, and C92.3 (Table 1). Te variables included in the descriptive analysis were age, sex, place of residence, type of health establishment, length of hospital stay, and year of diagnosis.

Statistical Analysis.
We performed a descriptive analysis of qualitative and quantitative variables related to morbidity and mortality. Results are presented through frequency distributions, proportions, rates, and measures of central tendency and dispersion. Te statistical software used for the analysis was Stata Version 14.

3.1.
Morbidity. 8393 cases of STS were reported to have been hospitalized during the period of the study.
General characteristics of the sample are displayed in Table 2. Distribution by gender was almost even between groups, 51% males versus 49% females. Te most frequent diagnosis code reported for hospitalization was due to "malignant neoplasm of other connective and soft tissues" (C49) in 69.75% of the cases, followed by cases of malignant neoplasms of the retroperitoneum and peritoneum (C48) in 23.72% of the cases ( Table 2).
Te average length of hospital stay for all neoplasms was 6.2 days, ranging from 1 to 362 days.
Te reported cases are evenly distributed among regions if we consider the population density. Te provinces with more reported cases of STS were Guayas and Pichincha ( Figure 1).
As shown in Table 3, the most common type of neoplasm registered was unspecifed malignant neoplasm of connective and soft tissue (41.6%), followed by malignant neoplasms of the retroperitoneum and malignant neoplasms of connective and soft tissue of lower limbs, including hip (10%). Information of neoplasms by anatomical localization is depicted in Table 3, and Figure 2 shows a scheme of the anatomical location of the tumors reported in this study.
Between 2010 and 2020, there was a slight increase in tumors coded as C49. Te rest of the neoplasms showed changes over the years but without a relevant increase over time ( Figure 3).

Mortality.
Te total number of deaths in Ecuador due to soft-tissue sarcomas was 2904 over the last decade, in which 50.48% of deaths were in females and 49.52% of deaths were in males.

Number of Deaths per
Year. Te total number of deaths per year due to STS was relatively constant during the period of the study with an average of 264 cases per year, with the lowest number of cases reported in 2012 and the highest in 2018 (Table 4 and Figure 4).
Te mortality rate per 100,000 people ranged from 1.2 to 2.0, with the lowest occurring in 2012 (Table 5).

Discussion
Tis is a large study of soft-tissue sarcomas in adults in Ecuador, with data from the National Registry of Hospital Discharges and Deaths in a 10-year cohort. Te published data on the epidemiology of soft-tissue sarcomas are scarce; they represent less than 1% of malignant tumors, and little is known about their epidemiology or incidence patterns [10].
Te data reported in several studies do not show a gender distribution; however, our results show an almost uniform distribution between genders, with a slight majority of patients being male (50.61%) and living in the highlands, results that are similar to those published by Bozzo et al. in Canada [11] in a fve-year cohort study. However, these data are in contrast with those reported in Brazil in a sixteen-year cohort study where soft-tissue sarcomas were reported to be slightly higher in females [12]. Te results of this study in this sense resemble those of a ten-year retrospective cohort study in Germany that reported an even distribution between genders [13]. We found that in the highland and coastal regions, there were more cases of soft-tissue sarcomas registered. Tis can be explained by the fact that the hospitals specializing in these pathologies are in these regions, where principal cities are located, and the population is more dense.

Sarcoma
In contrast to other studies, we used information according to ICD-10. Soft-tissue sarcomas are relatively rare, but they can occur in almost any anatomic site [10]; however, we found that malignant neoplasm of unspecifed connective and soft tissue sites was the most reported, in about 41% cases; this may be due to the manner of coding by the specialist. Nevertheless, although the literature shows that retroperitoneal soft-tissue sarcoma (STS) is relatively uncommon [14], we found that it was the second most reported diagnosis, accounting for 15% of cases. Tis contrasts markedly with the data reported by Saltus et al. [13], where the retroperitoneal location of these tumors was reported in only 6%, consistent with data reported by Toro et al. in the United States, including 26,758 cases between 1978 and 2001 [15]. Both studies reported that the most frequent anatomical locations of these tumors are the lower extremities, around 20%, which is in contrast with our fndings in which this location was lower than retroperitoneal one, with 13.5% and 23.6%, respectively, if we consider all ICD-10 codes.
A local study [16] that included 71 patients with a diagnosis of soft-tissue sarcomas in a single site, specialized hospital in Ecuador, reported that 67.6% of tumors were in the extremities. Tis fnding is distinct from our study in which only 13.6% were in the extremities; nevertheless, the report of many cases as "unspecifed" site could correspond to the location in the extremities.
During the 2010-2020 period, there was a slight increase in diagnoses of STS coded with ICD-C49 (connective, subcutaneous, and other soft tissues). It is comparable with the study by Alorjani et al. published in 2021 [17], which showed that 58% of the cases were ICD-C49. Yang et al. [18] also found that the most frequent diagnosis was ICD-C49 in 22.61% cases.
We encountered a mortality rate of 1.2 to 2.0 per 100,000 habitants due to STS in Ecuador. A similar mortality rate was reported by Saltus et al. in 2018 [13], with an average annual mortality rate of 2.31 per 100,000 habitants. Our report also is comparable with the data from the United States National Cancer Institute with a mortality rate of 1.3 per 100,000 per year in 2021 [19].

Conclusion
Tis study has analyzed the most recent data on hospital discharges and mortality from soft-tissue sarcomas in the Ecuadorian population. Hospital discharges and mortality rates due to soft-tissue tumors have not seen major changes in Ecuador in the last decade.

Data Availability
Data for this study were obtained from the National Registry of Hospital Discharges and Deaths published as open access from INEC (National Institute of Statistics and Census). Tese data could be accessed from https://www. ecuadorencifras.gob.ec/estadisticas/.

Ethical Approval
All the information came from secondary data. In Ecuador, the use of public databases with secondary data does not require approval by any ethics committee. Te database is properly anonymized before its use.

Conflicts of Interest
Te authors declare that they have no conficts of interest.