Is There a Role for ASCT in Patients with Desmoplastic Small Round Cell Tumor of the Peritoneum?
Authors: Cook Rachel J , Wang Zhiwei , Arora Mukta , Lazarus Hillard M. , Kasow Kimberly A. , Champagne Martin A. , Saber Wael , Van Besien Koen M. , Hale Gregory A. , Copelan Edward A. , Elmongy Mohamed , Ueno Naoto T , Horn Biljana N. , Slavin Shimon , Stadtmauer Edward A. 
Published: October 2019

Abstract
Abstract 3092
Desmoplastic small round cell tumor of the peritoneum (DSRCTP) is a rare, frequently fatal solid tumor that occurs most commonly in adolescent males. Tumor characteristics were first described in 1989 and the largest review of 101 patients in 1996 demonstrated a median survival of 17 months (range 3–72) in patients with a median age of 21 years (range 6–38), none of whom underwent transplant. Survivorship has improved with the use of intensive alkylator regimens and incorporation of autologous stem cell transplant (ASCT). This study represents the largest reported cohort of patients with DSRCTP who have undergone ASCT. Increasingly aggressive chemotherapy regimens and ASCT have been used to try to prolong response and increase cure. The purpose of this study was to examine the outcomes in the largest reported cohort of patients with DSRCTP who have undergone ASCT.
We identified 36 patients with DSRCTP reported to the Center for International Blood and Marrow Transplant Research between 1999 and 2007 who received an autologous hematopoietic stem cell transplant. The median age was 19 years (range 8–46) and 29 (81%) were male. Pre-transplant disease status was known in 31 patients, 13 of whom were in complete remission (CR). Twenty different conditioning regimens were identified for the 30 patients on which data was available with the most common agents being thiotepa (19 patients), etoposide (12 patients), mephalan (12 patients), cyclophosphamide (9 patients) and carboplatin (8 patients). The median follow up was 44 months. A subset of 18 patients had supplemental information obtained for confirmation of diagnosis (verification of the presence of translocation: t(11;22)(p13;q12)) and expanded clinical detail. We performed descriptive statistics to characterize the patients and outcomes.
The probability of disease free survival (DFS) at one year for those patients in CR and not in CR was 75% (95% CI: 48–94%) and 35% (15–59%), respectively. For the entire cohort, 1 year DFS was 53% (39–69%). DFS at 3 years was 40% (15–69%) and 9% (0–29%) in the two groups, respectively. The probability of overall survival at three years was 57% (29–83%) for patients in CR and 28% (9–51%) for patients not in CR. Median survival for the entire cohort was 31 months (36 months for those in CR, 21 months for those not in CR). Treatment related mortality was low with only 1 death in the first 100 days. Engraftment at 42 days was 97% (88–100%).
In summary, ASCT appears to be a tolerable approach in patients with DSCRTP with the greatest benefit seen in those patients who obtain CR. High intensity chemotherapy and ASCT leads to the longest DFS and OS in those patients who obtain a CR pre-transplant as might be expected. For those not in CR, the median OS in this series is greater (21 months) than previously reported (17 months) in patients not treated with ASCT suggesting a potential role for ASCT to prolong DFS and OS even in patients with residual or persistent disease pre-transplant. Overall, with low treatment related mortality and prolonged survival compared to historical controls, ASCT is a reasonable option for patients with DSRCTP though its role should be confirmed in larger studies.

Disclosures:
No relevant conflicts of interest to declare.