DSRCT Cancer: Symptoms, Diagnosis, and Treatment

Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive cancer that most often arises in the abdomen and pelvis, primarily affecting adolescent and young adult males. It belongs to a family of “small round cell” cancers but is set apart by a distinctive genetic fingerprint and a hallmark fibrous tissue reaction that surrounds its tumor cell clusters. Because it is so uncommon, many patients go weeks or months with vague symptoms before anyone suspects the diagnosis, and the treatment path that follows is intense, combining heavy chemotherapy, extensive surgery, and radiation.

Who Gets DSRCT

DSRCT overwhelmingly favors young men. One retrospective cohort from a tertiary cancer center reported a median age at diagnosis of 29 years, with 96% of patients being male.¹ A population-level analysis using the U.S. Surveillance, Epidemiology, and End Results (SEER) database found age-adjusted incidence rates of roughly 0.4 cases per million for males and 0.1 per million for females.² A separate SEER-based study noted that incidence has been rising since 2000, with a white male predominance and slightly higher rates in nonmetropolitan counties than in metropolitan ones.³ Whether that upward trend reflects genuinely more cases or improved recognition of a tumor that used to be mislabeled as something else is still debated.

Although the abdomen is by far the most common site, DSRCT can appear in unusual locations. Case reports have documented tumors arising from the pleura, with metastases later spreading to the brain, which highlights just how unpredictable this cancer can be.⁴

Common Symptoms

The symptoms of DSRCT are frustratingly nonspecific, which is one reason the diagnosis tends to come late. Abdominal pain is the most frequently reported complaint.⁵ One published case described a 35-year-old man who initially noticed only occasional abdominal pain and later felt a growing mass in his abdomen. By the time imaging was performed, the tumor had already spread across the peritoneum and into the omentum and pelvis.⁶ Other symptoms people report include bloating, a feeling of fullness, constipation, urinary changes, and weight loss. These all stem from the tumor growing large enough to press on surrounding organs.

DSRCT can also cause complications as it spreads. In one institutional series, half of all patients eventually developed intestinal obstruction requiring surgery, and a quarter developed ureteral obstruction from tumor pressure on the tubes that drain the kidneys.⁷ These obstructive complications sometimes become the first reason a patient seeks emergency care, which is when the underlying tumor is finally discovered.

What Makes DSRCT Distinctive Under the Microscope

DSRCT has a recognizable appearance that pathologists look for: islands of small, monotonous, round cells surrounded by dense fibrous tissue called desmoplastic stroma.⁸ One of the more peculiar features is that DSRCT cells express markers from multiple tissue types simultaneously — epithelial, mesenchymal, and neural — which is unusual and can initially confuse diagnosis.⁹ This “polyphenotypic” staining pattern is part of what ultimately clues pathologists in, since few other tumors light up for so many different marker categories at once.

Interestingly, when DSRCT metastasizes to distant sites, the characteristic desmoplastic stroma can disappear. In a case of a pleural DSRCT that spread to the brain, the brain metastasis lacked the fibrous stroma seen in the original tumor, which made pathological identification harder and underscores the need for molecular confirmation.⁴

The Genetic Hallmark

The defining feature of DSRCT at the molecular level is a fusion between two genes: EWSR1 and WT1. This translocation creates a hybrid protein that acts as a powerful activator of gene expression. Research has shown that the EWS-WT1 fusion protein binds to enhancer regions across the genome, turning on a broad oncogenic program. When the fusion protein is experimentally removed from tumor cells, the chemical marks of active gene expression at those sites drop sharply, confirming how central this single abnormal protein is to driving the cancer.¹⁰

This fusion is not just biologically important — it is also the primary diagnostic tool. Fluorescence in situ hybridization (FISH) to detect rearrangement of the EWSR1 gene and reverse transcription polymerase chain reaction (RT-PCR) to detect the specific EWSR1-WT1 fusion transcript are routine tests ordered when DSRCT is suspected. In one large institutional series, FISH detected EWSR1 rearrangement in about 91% of confirmed cases, and when both FISH and RT-PCR were used together, nearly all cases returned a positive result with at least one method.¹¹ If a biopsy shows the right histological appearance and the molecular test confirms the EWSR1-WT1 fusion, the diagnosis is considered definitive.

How Imaging Guides the Workup

CT scanning is typically the first imaging study, and what it usually reveals is striking: multiple large soft-tissue masses throughout the abdomen and pelvis that do not appear to originate from any specific organ. These masses often have patchy areas of lower density within them, reflecting internal necrosis or cystic change. Associated findings commonly include peritoneal seeding, fluid in the abdomen, enlarged lymph nodes, and metastases to the liver or bone.¹²

PET/CT adds another layer by showing where the tumor is metabolically active. In one multimodal imaging study, PET/CT showed multiple foci of abnormally high metabolic activity scattered throughout the abdomen, pelvis, retroperitoneum, and liver, with maximum standardized uptake values (a rough measure of metabolic intensity) ranging from about 6.6 to 11.2.¹³ PET/CT is also increasingly used after treatment to check for recurrence, since new metabolic hotspots can appear before masses become visible on conventional CT.

Chemotherapy and the P6 Protocol

The backbone of DSRCT treatment has long been an intensive, multiagent chemotherapy regimen known as P6, originally developed at Memorial Sloan Kettering Cancer Center. This protocol alternates cycles of several drugs and has remained the standard first-line approach for decades despite its toxicity, largely because nothing else has shown a better initial response. The original trial found that tumors responded to the high-dose cyclophosphamide, doxorubicin, and vincristine portion of the regimen, with some patients achieving complete remission lasting over three years.¹⁴

The benefit of combining all three treatment modes — chemotherapy, surgery, and radiation — became clearer in a study of 66 patients, where three-year survival was 55% for those who received the full combination, compared with 27% for those who did not receive all three.¹⁵ Improved survival was also tied to the degree of surgical debulking (removing at least 90% of visible tumor) and the quality of response to the multimodality approach.¹⁶

The Role of Surgery

Because DSRCT typically presents as dozens of tumor nodules scattered across the peritoneum rather than a single discrete mass, surgery is more akin to what oncologic surgeons call cytoreductive surgery — the goal is to remove every visible piece of tumor, no matter how many implants are present. Complete cytoreductive surgery (CCS), when achievable, is one of the strongest predictors of better outcomes. In a large institutional analysis, patients who underwent CCS had significantly better overall survival than those who were deemed inappropriate surgical candidates, and roughly 75% of patients who went to surgery achieved the expected level of tumor clearance.¹⁷

Some centers have added hyperthermic intraperitoneal chemotherapy (HIPEC) — heated chemotherapy solution bathed directly inside the abdomen after surgical debulking — as an extra step. A phase 2 trial using cisplatin-based HIPEC after complete cytoreductive surgery found the approach was effective in carefully selected patients.¹⁸ HIPEC remains somewhat controversial in DSRCT since the evidence base is still small, but it is used at several high-volume sarcoma centers as part of the treatment plan.

Radiation to the Whole Abdomen and Pelvis

Given that DSRCT has a tendency to recur across the entire peritoneal surface, radiation in this disease is not the typical focused beam aimed at a single spot. Instead, the standard approach has been whole abdominopelvic radiation therapy (WAP-RT), delivering about 30 Gy across the abdomen and pelvis after chemotherapy and surgery.¹⁹ Treating such a large area with conventional two-dimensional radiation inevitably exposes a lot of healthy tissue, leading to side effects — particularly drops in blood cell counts from bone marrow irradiation and gastrointestinal toxicity.

The shift to intensity-modulated radiation therapy (IMRT) has eased this problem. WAP-IMRT, given with concurrent radiosensitizing chemotherapy, has been shown to be well tolerated after aggressive surgery, with better bone sparing that results in less severe drops in blood counts compared to the older conventional technique.²⁰ Updates to this experience confirmed that IMRT maintained the same treatment coverage while reducing toxicity, and it is now the preferred radiation method at centers experienced with DSRCT.²¹

Targeted and Hormonal Therapies

The discovery that a substantial fraction of DSRCTs express the androgen receptor opened an unexpected therapeutic door. Early work found that about 37% of tested tumor samples were positive for the androgen receptor by immunohistochemistry, and that exposing DSRCT cells to male sex hormones in the lab stimulated their growth — suggesting the receptor was functional, not just passively present. A small number of patients with androgen-receptor-positive tumors received combined androgen blockade (drugs that suppress testosterone signaling), and three of six achieved some clinical benefit, including partial response or stable disease lasting several months.²²

More recent preclinical work has strengthened the case. Both enzalutamide (a newer androgen receptor blocker used in prostate cancer) and an experimental androgen-receptor-targeting antisense oligonucleotide slowed DSRCT cell growth in the lab and reduced tumor burden in mouse models with similar effectiveness during the initial treatment period.²³ The male predominance of DSRCT and the functional role of androgens in these tumors give anti-androgen strategies a biological rationale that few other approaches in this disease can claim, though clinical trials are still needed to measure how well this translates to meaningful patient outcomes.

Beyond hormonal approaches, researchers have explored multityrosine kinase inhibitors — drugs like pazopanib, imatinib, and sorafenib — either alone or combined with mTOR inhibitors.²⁴ Small case series using antiangiogenic agents (drugs that starve tumors of blood supply), including sunitinib, sorafenib, and bevacizumab, have been compiled from the French national sarcoma registry, though the numbers remain tiny and the responses modest.²⁵ The honest assessment is that no single targeted agent has produced durable responses in most patients, and the field is still hunting for the right drug or combination.

Immunotherapy and CAR-T on the Horizon

DSRCT cells express a surface molecule called GD2, a target already used in immunotherapy for neuroblastoma.²⁴ GD2 expression across multiple sarcoma subtypes has attracted attention from researchers developing both antibody-based therapies and chimeric antigen receptor (CAR) T-cell therapies. An EU-funded project is specifically developing CAR-T therapy against DSRCT, citing the disease’s poor prognosis — with five-year survival estimated around 15% — as motivation for pursuing more radical immunological approaches.²⁶ This work is still in the preclinical and early-phase stage, but for a cancer with so few effective options at relapse, the promise of engineered immune cells is generating real interest among patients and specialists.

Prognosis and Long-Term Survival

DSRCT carries a sobering prognosis overall. A nationwide analysis of 104 patients found an estimated median overall survival of 26 months. One-year survival was about 80%, but that dropped to roughly 54% at two years and 33% at three years. Independent predictors of better outcomes included the absence of metastatic disease, undergoing surgery, and receiving adjuvant chemotherapy.²⁷

Long-term survivors do exist, but they are a small minority. In a single-institution analysis of 38 patients, five (about 13%) qualified as long-term survivors, alive at follow-ups ranging from 37 to 209 months. None of those five had liver or extra-abdominal metastases at diagnosis, and all had surgery that achieved complete or near-complete resection. Three of the five had received whole abdominopelvic radiation.²⁸ The profile that emerges is consistent across studies: the patients who do best are those whose disease is still confined to the abdomen, who respond to chemotherapy, and who can undergo a thorough surgical debulking followed by radiation. For patients with advanced disease — particularly liver metastases or tumors outside the abdomen — symptom control and quality of life become the primary treatment focus.²⁹

Monitoring After Treatment With Circulating Tumor DNA

Because the EWSR1-WT1 fusion is unique to the tumor, it can be used as a personalized blood-based marker. Researchers have designed assays that detect circulating tumor DNA (ctDNA) carrying the specific genomic breakpoint of the fusion in a patient’s blood. In one genomic case study, this biomarker was tested on blood samples taken three years after surgery and found no trace of the fusion, consistent with imaging and the patient’s good health at the time.³⁰

Broader experience with ctDNA monitoring in translocation-associated sarcomas, including DSRCT, has shown that tracking ctDNA levels can provide highly specific information for early detection of recurrence. However, ctDNA alone does not catch every single-site recurrence, so it works best as a complement to conventional imaging rather than a replacement for it.³¹ For a disease that recurs frequently and often diffusely across the peritoneum, having a blood test that can flag rising tumor burden before masses become large enough to see on a scan is a meaningful practical advance, even if it still has limitations.