Sarcoma and Cutaneous Tumors

PV QA 2 - Poster Viewing Q&A 2

MO_21_2480 - Association Between Radiation Dose and Ureteral Strictures in the Treatment of Retroperitoneal Sarcoma

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Association Between Radiation Dose and Ureteral Strictures in the Treatment of Retroperitoneal Sarcoma
G. H. Boyd1, R. Miao1, K. W. Jee1, R. Sethi1, J. T. Mullen2, A. B. Haynes1, F. J. McGovern1, K. D. Bernstein3, T. F. DeLaney3, and Y. L. E. Chen3; 1Massachusetts General Hospital, Boston, MA, 2Department of Surgical Oncology, Massachusetts General Hospital, Boston, MA, 3Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA

Purpose/Objective(s): Incidence of ureteral stricture following radiation therapy (RT) is low and dose tolerance of the ureter is not well described in the literature. Ureters are often closely associated with retroperitoneal sarcomas (RPS) and are at risk for receiving high radiation doses during treatment. We assessed risk factors for ureteral stricture (US) after treatment of RPS and aimed to identify an evidence-based dose constraint for the ureters.

Materials/Methods: We identified 75 RPS patients treated with RT from 2006-2016 at our institution and reviewed clinicopathologic variables, treatment details, and adverse events. We used 61 available RT treatment plans to contour all retained ureters as a total ureter or separated into upper, middle, and lower third segments based on anatomical landmarks.  Dose-volume histograms were extracted from RT plans. Primary event was development of US.  Multivariate analysis was performed to identify predictors of US.

Results: Of the 61 patients analyzed, median age was 60 years, median follow up was 43.3 months (1.4-137.4 mo) and median total external beam radiation therapy (EBRT) dose was 54.8 Gy (19.8-70.2 Gy). Common histology types were dedifferentiated liposarcoma (44.3%), leiomyosarcoma (26.2%) and well-differentiated liposarcoma (16.4%).  50 (81.9%) received preop RT, 6 (9.8%) received postop RT only, and 5 (8.2%) received RT only. 87 ureters were retained across all patients after resection. Five (8.3%) patients developed US after treatment (two grade 1, one grade 2, two grade 3 requiring stenting) with median latency period of 5.1 months (2.9-44.5 mo) post-RT and 5.8 months (3.1-44.5 mo) post-surgery. None required dialysis. There is no difference in clinical characteristics between the outcome groups. All patients with US had pre-op RT with both IMRT and protons, 4 had manipulation of ureter during surgery, 2 had IOERT, and 1 had ureteral stent placed prior to treatment. On MVA, V50.4 to the middle third of the ureter was identified as a risk factor for development of US (HR 1.074, p=0.0495) and so was surgical manipulation of the ureter (HR=36, p=0.007).

Stricture (n=5)

No Stricture (n=82)

P

Tumor size (median, cm)

12 (9 to 19)

15.2 (2.3-30)

Total EBRT dose (median)

61.6 (48-63)

54.7 (19.8-70.2)

NS

IOERT use

40%

16.1%

0.22

R0/R1

80%

67.9%

0.90

Surgical ureter manipulation

80%

25%

0.035

Total ureter (mean values)

    Mean Dose (Gy)

22.84

15.47

0.213

    Max Dose (Gy)

44.56

30.18

0.099

    V45 (%)

25.75

15.12

0.092

    V50.4 (%)

16.49

5.39

0.078

Middle 3rd

    Mean Dose (Gy)

33.79

19.61

0.119

    Max Dose (Gy)

44.46

27.34

0.068

    V45 (%)

48.14

22.58

0.095

    V50.4 (%)

32.43

9.89

0.035

Table 1. Clinical and DVH comparison between patients with US and those without

Conclusion: Ureteral stricture is a rare complication after RT treated RPS.  V50.4 appears to be more predictive than mean or max point dose. Surgical manipulation of ureter is also associated with increased US risk. Prior stenting and IOERT may also influence US risk. Current RPS protocols at our institution constrain ureters to ²50.4 Gy.

Author Disclosure: G.H. Boyd: Reseacher; Mass General Hospital. R. Miao: None. K. Jee: None. R. Sethi: None. J.T. Mullen: None. F.J. McGovern: None. K.D. Bernstein: None. T.F. DeLaney: Honoraria; UpToDate, Oakstone Medical Publishing, Gerson Lehman Group. Consultant; Gerson Lehman Group. Advisory Board; Amgen’s (T-VEC) Sarcoma Scientific Advisory Board. Y.E. Chen: Employee; Beth Israel Deaconess Medical Center.

Send Email for Graham Boyd


Assets

MO_21_2480 - Association Between Radiation Dose and Ureteral Strictures in the Treatment of Retroperitoneal Sarcoma



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Association Between Radiation Dose and Ureteral Strictures in the Treatment of Retroperitoneal Sarcoma