Reduced Toxicity With Intensity Modulated Radiation Therapy (IMRT) for Desmoplastic Small Round Cell Tumor (DSRCT): An Update on the Whole Abdominopelvic Radiation Therapy (WAP-RT) Experience

Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York.
International journal of radiation oncology, biology, physics (Impact Factor: 4.26). 10/2012; 85(1). DOI: 10.1016/j.ijrobp.2012.09.005
Source: PubMed


Desmoplastic small round cell tumor (DSRCT) is a rare malignancy typically involving the peritoneum in young men. Whole abdominopelvic radiation therapy (WAP-RT) using conventional 2-dimensional (2D) radiation therapy (RT) is used to address local recurrence but has been limited by toxicity. Our objectives were to assess the benefit of intensity modulated radiation therapy (IMRT) on toxicity and to update the largest series on radiation for DSRCT.

Methods and materials:
The records of 31 patients with DSRCT treated with WAP-RT (22 with 2D-RT and 9 with IMRT) between 1992 and 2011 were retrospectively reviewed. All received multi-agent chemotherapy and maximal surgical debulking followed by 30 Gy of WAP-RT. A further focal boost of 12 to 24 Gy was used in 12 cases. Boost RT and autologous stem cell transplantation were nearly exclusive to patients treated with 2D-RT. Toxicities were assessed with the Common Terminology Criteria for Adverse Events. Dosimetric analysis compared IMRT and simulated 2D-RT dose distributions.

Of 31 patients, 30 completed WAP-RT, with a median follow-up after RT of 19 months. Acute toxicity was reduced with IMRT versus 2D-RT: P=.04 for gastrointestinal toxicity of grade 2 or higher (33% vs 77%); P=.02 for grade 4 hematologic toxicity (33% vs 86%); P=.01 for rates of granulocyte colony-stimulating factor; and P=.04 for rates of platelet transfusion. Post treatment red blood cell and platelet transfusion rates were also reduced (P=.01). IMRT improved target homogeneity ([D05-D95]/D05 of 21% vs 46%) and resulted in a 21% mean bone dose reduction. Small bowel obstruction was the most common late toxicity (23% overall). Updated 3-year overall survival and progression-free survival rates were 50% and 24%, respectively. Overall survival was associated with distant metastasis at diagnosis on multivariate analysis. Most failures remained intraperitoneal (88%).

IMRT for consolidative WAP-RT in DSRCT improves hematologic toxicity in particular. Although the long-term efficacy of current treatment options remains disappointing, the improved therapeutic index of IMRT may aid in generalizing its use and allowing the addition of novel approaches such as intraperitoneal immunotherapy.

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    • "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. "
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    ABSTRACT: Purpose: To study the clinical, radiological, and pathological characteristics of abdominal desmoplastic small round cell tumor (DSRCT) and investigate the optimal therapy modalities. Patients and methods: A retrospective cohort study was performed on 12 abdominal DSRCT patients; all pathological, radiological, and prognostic data were analyzed. There were 3 patients (25%) with metastatic disease at presentation. In all 12 cases, 6 cases underwent operation and adjuvant chemotherapy (group 1, 6/12, 50%). The other 6 cases were diagnosed by fine needle aspiration or exploratory laparotomy biopsy (group 2, 6/12, 50%); all cases received four to six courses of multiple agents chemotherapy, respectively. Results: All cases were finally diagnosed as DSRCT pathologically. Among group 1, all cases underwent en bloc resection (2/6, 33%) or tumor debulking (4/6, 67%) and, following four courses of multiple agents chemotherapy, Kaplan-Meier analysis revealed that 3-year survival was 50% in group 1 versus 16.7% in group 2 (P < 0.05). Gross tumor resection was highly significant in prolonging overall survival; patients with localized solitary lesion have a better prognosis, most likely due to increased feasibility of resection. Conclusions: DSRCT is a rare malignant tumor with poor prognosis. Surgical excision with combination chemotherapy as an adjunct is mandatory for nonmetastatic cases because these modalities used in isolation may have less impact.
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