In this report, we present one of the largest series of patients with DSRCT. Consistent with previously published data, DSRCT tends to occur in younger males. Most patients presented with abdominal or pelvic tumours and many have evidence of metastases, the majority being in the lungs and liver.
Multimodality treatment of DSRCT and prognostic factors
The reported MS of DSRCT is in the region of 17 to 25 months [
6]. Given the poor outcome of the disease and the significant morbidities and mortality associated with its treatment, prognostic indicators are very important. Two retrospective studies performed at the Memorial Sloan-Kettering Cancer Center (MSKCC) have both found that aggressive surgical debulking of DSRCT is of prognostic significance [
7,
8]. An analysis of 32 patients by Schwarz
et al. demonstrated that improved survival was found to be associated with the following: more than 90% surgical debulking either before or after chemotherapy, complete or very good partial response (PR) to multimodality treatment, and use of the P6 protocol (see below) [
7]. In a report of 66 patients by Lal
et al., treatment with chemotherapy, surgery and radiotherapy conferred a 3-year survival of 55% compared to 27% for those who did not receive all three treatments [
8]. In addition, gross tumour resection was also associated with prolonged survival (3-year survival of 58% compared to 0% in the non-resected patients). Naturally such an analysis performed retrospectively cannot adequately control for the fact that patients with radically resectable disease are likely to have less bulky and more localised tumours.
There is no general consensus on the best therapeutic approach, as strong evidence is lacking given the rarity of the disease, although multimodality treatment with chemotherapy, surgery and radiotherapy appears to represent optimal management. The MS of patients diagnosed with DSRCT was 16 months in this study, which is slightly lower than those reported previously [
6]. Comparatively, it is clear that the management in our centres took a more conservative approach than others, as evident by the less frequent use of radiotherapy, surgery and myeloablative chemotherapy with stem cell transplantation. In a review by Hassan
et al. of 12 patients with intra-abdominal DSRCT (all of whom had received multi-agent chemotherapy), those who underwent surgical resection had a longer MS of 34 months compared to 14 months for those who had biopsy alone [
9]. In our study, the MS observed for patients who had resection for their abdominal or pelvic tumours was 47 months, compared to 16 months for those who did not. Moreover, for patients with metastatic intra-abdominal DSRCT, palliative radiotherapy for locoregional disease control appeared to confer a survival advantage (MS of 47 vs 14 months in those who did not have radiotherapy). Although patients with localised abdominal or pelvic disease who underwent surgery appear to have similar MS (i.e. 47 months) compared to those with metastatic disease who received palliative radiotherapy, they are by no means comparable and surgery is still indicated in resectable DSRCT. In our series, the only patient with abdominal disease who has been cured (disease-free 10 years from diagnosis) has had chemotherapy and surgical resection. Hence, a more aggressive multimodality treatment approach would seem to be indicated in order to prolong survival, although larger prospective trials with quality-of-life measures would be necessary to confirm this. This is difficult to perform in such a rare disease.
Subbiah
et al. presented the largest series of patients diagnosed with DSRCT at the 2012 American Society of Clinical Oncology meeting [
10]. This was a retrospective review of 197 patients treated at the MD Anderson Cancer Center (MDACC) and MSKCC. In that series, 87% were males with a mean age of presentation of 25 years. In total, 139 (71%) patients underwent surgery, 38 (19%) had debulking surgery, 30 (15%) received radiotherapy, 27 (14%) had intraperitoneal chemotherapy after debulking, and 11 (5%) had stem cell transplant. They found that radiotherapy, surgery, intraperitoneal chemotherapy, removal of primary mass and metastases, age <30 years and patients treated after 2003 were associated with improved survival. In contrast, our study did not show a difference in survival with regards to age of presentation. We also found that the patient’s gender and size of the presenting tumours do not have an impact on survival. Although uncommon, patients who did not have disease in the abdomen appeared to have a better outcome. This is likely to be related to earlier presentation, less advanced disease and in some cases the feasibility of radical resection.
Chemotherapy
DSRCT is sensitive to chemotherapy although a transient response followed by disease progression is the norm. Chemotherapeutic regimes used are normally similar to those for treating Ewing’s sarcoma. Farhat
et al. treated five patients with a chemotherapeutic regime consisted of cisplatin, etoposide, cyclophosphamide and an anthracycline – disease stabilisation lasting 4 to 9 months were noted in four patients with intra-abdominal DSRCT after initial surgery, whereas one patient with relapsed metastatic disease from an initial paratesticular primary attained a complete response (CR) [
11]. The authors also reviewed the literature of 60 patients who were treated by chemotherapy with or without abdominal radiotherapy, and objective responses were found in 17 patients, eight of whom achieved a CR. The chemotherapy agents associated with CR were those of doxorubicin, cyclophosphamide, vincristine and cisplatin. These are in line with our results, with these drugs providing the longest TTP. Chemotherapy is often given in the metastatic setting; and although often used, the role of neoadjuvant and adjuvant chemotherapy in localised disease remains unknown.
Kushner
et al. reported 12 patients (10 treatment-naïve and two had previous chemotherapy) who received the P6 protocol, which has seven courses of chemotherapy consisting of cyclophosphamide, doxorubicin, vincristine (HD-CAV), etoposide and ifosfamide [
12]. This was followed by surgery, radiotherapy, and myeloablative chemotherapy using thiotepa and carboplatin with stem cell rescue in some cases. All tumours showed a PR with this regimen although there was no CR, and survival of around 20 months was reported. This protocol is used in many centres, mainly in resectable cases, although treatment-related toxicities could be severe. Whether the intensive P6 regimen is better than standard first-line chemotherapy regimens used in other small round blue cell tumours, such as Ewing’s sarcoma, is unknown. In two prospective studies by Bertuzzi
et al., a total of 17 patients were treated with induction chemotherapy consisting of ifosfamide, epirubicin and vincristine – those who responded were then treated with high-dose chemotherapy and stem cell rescue in conjunction with local therapy (surgery and/or radiotherapy) [
13,
14]. Approximately half of them achieved an initial PR to induction chemotherapy, but no CR was achieved with high-dose chemotherapy. The MS reported was 14 months, leading the authors to question the role of high-dose chemotherapy in the treatment of DSRCT. More recently in a retrospective study using data obtained from the Center for International Blood and Marrow Transplant Research, Cook
et al. reported the outcome of 36 DSRCT patients who had undergone autologous stem cell transplantation [
15]. The benefit was much greater for those who achieved a CR pre-transplantation compared to those who did not, with MS of 36 and 21 months, respectively.
The use of other chemotherapy drugs has been reported, including irinotecan, temozolomide and vinorelbine, but none of them showed superiority [
16,
17]. Evidence and experience is emerging on the role of trabectedin in the management of metastatic DSRCT [
18‐
20]. In a case report, an 18-year-old boy with abdominal DSRCT was initially treated by complete surgical excision, followed by adjuvant chemotherapy with cyclophosphamide, doxorubicin/actinomycin D, vincristine, alternating with ifosfamide and etoposide [
20]. Disease recurrence was treated with surgery and cisplatin and irinotecan, but this was followed by further progression for which trabectedin was given, resulting in PR. This resulted in a survival of 4 years from diagnosis.
Similar to ovarian cancer, the use of hyperthermic intraperitoneal chemotherapy has also been reported given the tendency of the disease to spread within the peritoneum. Heated cisplatin is given at a dose 100 to 150 mg/m
2 intraperitoneally after optimal cytoreductive surgery. The series reported by the MDACC showed that this method is safe and might have activity in paediatric patients, and a survival benefit has also been reported [
10,
21‐
23]. Further studies are required before this could be widely adopted.
Radiotherapy
Whole-abdominopelvic radiotherapy (WAP-RT) after maximal surgery was first reported by Kushner
et al. at the MSKCC as part of a multimodality treatment using the P6 protocol, with the aim of improving local control [
12]. A total dose of 30 Gy was delivered post-operatively, with simultaneous boost given to sites of gross residual disease. Conventional two-dimensional radiotherapy was associated with significant gastrointestinal and haematologic toxicities, with long term side effects including small bowel obstruction and ureteral stenosis [
24]. For this reason, the use of WAP intensity-modulated radiation therapy (WAP-IMRT) was studied by Pinnix
et al. at the MDACC [
25]. All of the eight patients had received prior chemotherapy and surgical debulking (seven of them also had intraperitoneal cisplatin). One patient was still disease-free 20 months after treatment, although the rest experienced either local or distant failure after a median of 8.73 months from WAP-IMRT. A retrospective analysis at the MSKCC looked at 31 patients who underwent WAP-RT, either with conventional two-dimensional radiotherapy (n = 22) or IMRT (n = 9) after chemotherapy and maximal debulking surgery [
26]. IMRT was associated with lower incidence of acute gastrointestinal and haematologic toxicities. The 3-year overall survival and progression-free survival (PFS) rates were 50% and 24%, respectively. Anecdotally, a patient in this series who received WAP-RT developed a serious malabsorption syndrome subsequent to gastrointestinal damage. Given the limited data of efficacy, WAP-RT is currently not routinely used in the management of DSRCT.
Targeted therapies
In recent years, targeted therapies have been studied in DSRCT. Drugs that have shown activity against this disease include the TKI sunitinib and the mTOR inhibitor temsirolimus [
27,
28]. In our cohort of patients, other non-standard agents used include the anti-IGF-1R antibody figitumumab, the TKIs axitinib, pazopanib, sorafenib and sunitinib, as well as the mTOR inhibitor sirolimus. The number of patients is too small to draw any conclusion about their efficacy. Due to the fact that DSRCT has a predilection to occur in young males, Fine
et al. discovered that androgen receptor is expressed in 37% of DSRCT [
29]. Six of their patients were treated with combined androgen blockade and three attained a clinical benefit. In our study, one patient had received the gonadotropin-releasing hormone agonist goserelin. However, no significant anti-tumoural efficacy was noted.
Chromosomal translocation resulting in the fusion of the
EWSR1 and
WT1 genes is the molecular characteristic of DSRCT. The resulting fusion protein has been found to activate the IGF-1R gene promoter, causing the expression of this anti-apoptotic receptor tyrosine kinase [
30‐
32]. The understanding of this mechanism has provided a novel target for the treatment of this disease. In a recent phase II study, 16 patients with DSRCT who had had previous treatments were given 12 mg/kg of the anti-IGF-1R antibody ganitumab intravenously [
33]. Common side effects include fatigue, nausea, dyspnoea and peripheral oedema. PR was noted in one (6%) patient, whereas 10 (63%) had stable disease (SD) as their best response, with 3 (18%) achieving SD lasting ≥24 weeks. Median PFS was 19 months, indicating a potential role of ganitumab used either alone or in combination with chemotherapy for patients with DSRCT. In a phase I study of another anti-IGF-1R antibody cixutumumab in combination with temsirolimus, two out of three patients with previously-treated DSRCT had SD lasting longer than 5 months [
34].
Tumour-specific antigens have also been studied as targets for immunotherapy, including the disialoganglioside GD2 and the antigen recognised by the antibody 8H9 (expressed in 70% and 96% of DSRCT, respectively) [
35]. In particular, studies of anti-GD2 antibodies have shown some promising results in the treatment of neuroblastoma [
36]. Another potential therapeutic target is the lysine-specific demethylase 1, a key histone modification enzyme involved in controlling gene expression which if dysregulated, could result in tumourigenesis [
37]. It is found to be highly expressed in several highly malignant sarcomas including DSRCT [
38]. It could be inhibited by small molecule inhibitors and further investigation is warranted.