Resection margin adequacy plays a critical role in the local control of sarcomas. Fluorescence-guided surgery has increased complete resection rates and local recurrence-free survival in several oncological disciplines. The purpose of this study was to determine whether sarcomas exhibit sufficient tumor fluorescence (photodynamic diagnosis (PDD)) after administration of 5-aminolevulinic acid (5-ALA) and whether photodynamic therapy (PDT) has an impact on tumor vitality in vivo. Sixteen primary cell cultures were derived from patient samples of 12 different sarcoma subtypes and transplanted onto the chorio-allantoic membrane (CAM) of chick embryos to generate 3-dimensional cell-derived xenografts (CDXs). After treatment with 5-ALA, the CDXs were incubated for another 4 h. Subsequently accumulated protoporphyrin IX (PPIX) was excited by blue light and the intensity of tumor fluorescence was analyzed. A subset of CDXs was exposed to red light and morphological changes of both CAMs and tumors were documented. Twenty-four hours after PDT, the tumors were excised and examined histologically. High rates of cell-derived engraftments on the CAM were achieved in all sarcoma subtypes and an intense PPIX fluorescence was observed. PDT of CDXs resulted in a disruption of tumor-feeding vessels and 52.4% of CDXs presented as regressive after PDT treatment, whereas control CDXs remained vital in all cases. Therefore, 5-ALA mediated PDD and PDT appear to be promising tools in defining sarcoma resection margins (PDD) and adjuvant treatment of the tumor bed (PDT).

Ewing sarcoma (EwS) is the second most common bone and soft tissue tumor, affecting primarily adolescents and young adults. Patients with secondary EwS are excluded from risk stratification in several studies and therefore do not benefit from new therapies. More knowledge about patients with EwS as secondary malignant neoplasms (SMN) is needed to identify at-risk patients and adapt follow-up strategies. Epidemiology, clinical characteristics, and survival analyses of EwS as SMN were analyzed in 3844 patients treated in the last three consecutive international EwS trials, EICESS 92, Euro-E.W.I.N.G. 99, and EWING 2008. Forty-two cases of EwS as SMN (approximately 1.1% of all patients) were reported, preceded by a heterogeneous group of malignancies, mainly acute lymphoblastic leukemias (n = 7) and lymphomas (n = 7). Three cases of EwS as SMN occurred in the presumed radiation field of the primary tumor. The median age at diagnosis of EwS as SMN was 19.4 years (range, 5.9–72) compared with 10.8 years (range, 0.9–51.2) for primary EwS. The median interval between first malignancy and EwS diagnosis was 7.4 years. The 3-year overall survival (OS)/event-free survival (EFS) was 0.69 (SE = 0.09)/0.53 (SE = 0.10) for localized patients and 0.36 (SE = 0.13)/0.29 (SE = 0.12) for metastatic patients (OS: p = 0.02; EFS: p = 0.03). Survival in patients with EwS as SMN did not differ between hematologic or solid primary malignancies. EwS as SMN is rare; however, survival is similar to that of primary EwS, and its risk-adjusted treatment should be curative, especially in localized patients.

Studies of the genomic stability of Ewing sarcoma (EwS) have produced contradictory findings. While they are generally characterized by low mutation rates of individual genes, several cases exhibit genomic alterations that manifest as chromosomal gains and losses. Taken together, these alterations represent independent biomarkers for EwS, such as loss of heterozygosity (LOH) or an altered genome. Patients with primary EwS tumors with fewer than three copy number alterations (CNAs) have a better prognosis than those with more CNAs. The functional mechanisms underlying this chromosomal instability are not yet clear. However, there are indications that this may be directly caused by the EWSR1::ETS translocations that are characteristic of EwS. The transcriptional behavior of the chimeric transcription factor EWSR1-FLI1 leads to the formation of R-loop DNA–RNA hybrids that form when RNA binds back to DNA during transcription and increased replication stress, which may result in structural chromosomal changes. Additionally, the formation of EWSR1 fusion genes in EwS results in the loss of one or both wild-type EWSR1 alleles in sarcoma cells. As chromosome segregation has been observed under loss of wild-type EWSR1, EWSR1 loss has been proposed as a potential source of LOH. So, it is highly probable that a chromosomal translocation and the subsequent formation of the EWSR1-ETS fusion protein cause the genomic alterations in EwS. This indicates that targeted therapy should be directed against the CNA and LOH biology caused by the fusion protein.