Abstract Book

ESTRO 37

S417

ureteral paracervical and direct draining to para-aortic LNs). Results In evaluated 36 women sentinel LNs were visualized in 31 cases: in average 2,6 sentinel LNs per patient. We detrmined following distribution of sentinel LN according to anatomical subregions: external iliac –64.5%, internal iliac –54,8%, obturator - 32.2%, common iliac - 35.5%, para-aortic – 16.1% and presacral 3,2% cases. The monolateral pattern of lymph flow was mentioned in 9 (29%), bilateral – in 22 (71%) observations. In 31 cases we were able to determine patterns of lymph flow from cervical cancer: supra-ureteral paracervical route was identified in 22, infra-ureteral paracervical – in 4 and their combination – in other 5 patients. We didn’t see any case of direct lymph flow from primary tumour to para- aortic LNs. We proposed that in women without lymph flow to presacral LNs these nodes can be excluded from irradiation volume. Efficacy of prophylactic irradiation of para-aortic LNs must be studied in patients with lymph flow to this region. Conclusion Visualization of individual pattern of lymph flow from primary cervical cancer can be considered as promising tool for optimization the volume of irradiated regional LNs. PO-0803 Risk factors for severe late bowel toxicity after primary radiotherapy for cervical cancer J.J. Laan 1 , L.R.C.W. Van Lonkhuijzen 2 , R.M. Van Os 1 , K.M. Tytgat 3 , R. Dávila Fajardo 4 , B.R. Pieters 1 , L.J.A. Stalpers 1 , G.H. Westerveld 1 1 Academic Medical Center, Radiotherapy, Amsterdam, The Netherlands 2 Academic Medical Center, Gynaecology, Amsterdam, The Netherlands 3 Academic Medical Center, Gastroenterology, Amsterdam, The Netherlands 4 University Medical Centre Utrecht, Radiotherapy, Amsterdam, The Netherlands Purpose or Objective Gastrointestinal complaints are among the most common and debilitating symptoms of chronic pelvic radiation disease. Severe late bowel toxicity is often chronic and can cause perpetual impairment in the ability to perform daily and occupational tasks. Nevertheless, data on possibly modifiable risk factors in patients treated for cervical cancer remain limited and inconclusive. The purpose of this study was to evaluate the frequency of and risk factors for severe late bowel toxicity after curative radiotherapy in women treated for locally advanced cervical cancer. Material and Methods We conducted a retrospective mono-center cohort study. All patients treated from June 1992 until January 2013 with primary radiotherapy with curative intent for cervical cancer were included. Bowel toxicity was graded according to the Common Terminology Criteria for Adverse Events version 3 (CTCAEv3.0). Severe toxicity was defined as grade 3 or higher in the CTCAEv3.0. The following items were scored: diarrhea, proctitis, gastrointestinal bleeding, fistula, and stenosis. Associations between risk factors and severe late bowel toxicity were assessed using Cox proportional hazards regression models. Results Included were 515 women. Median follow-up was 78 months. Fifty-nine patients developed severe late bowel toxicity. The actuarial 3-year and 5-year severe late bowel toxicity rates were both 13% (Figure 1). In the multivariable analysis, factors significantly associated with severe late bowel toxicity were: smoking (HR 2.59

[95% CI 1.48-4.55]), severe acute bowel toxicity (HR 2.46 [1.24-4.49]), previous major abdominal surgery (HR 2.35 [1.20-4.60]), hypertension (HR 2.33 [1.23-4.40]), parametrial boost (HR 2.18 [1.10-4.33]), low socioeconomic status (HR 2.05 [1.17-3.59]) and low BMI (HR 0.93 [0.88-0.99]) (Table 1). First symptoms of severe late bowel toxicity were reported after a median follow- up of 9 months, but occurred up to 10 years after end of treatment. Only one third of the patients with severe late bowel toxicity were referred to a gastroenterologist. Table 1. Significant

risk factors for severe late bowel toxicity in the multivariabl e analysis

95% CI Haza rd Ratio

95%

CI

Hazar d Ratio

p- valu e

Attributa ble risk

Attributa ble risk

n=389

Factor

0.00 1

Smoking

2.59 1.48 - 4.55

38%

19 - 57

Severe acute bowel toxicity

0.01 0

12%

2 - 22

2.46 1.24 - 4.49

Major abdominal surgery Hypertensio n Parametrial boost

0.01 3 0.00 9 0.02 6 0.01 2 0.01 4

13%

-2 to 28

2.35 1.20 - 4.60

2.33 1.23 - 4.40

2%

-15 to 19

2.18 1.10 - 4.33

34%

4 - 65

Socioecono mic status 2.05 1.17 - 3.59

27%

-3 to 58

Body mass index

0.93 0.88 - 0.99

28%

6 - 50

Conclusion Severe late bowel toxicity is a frequent complication of definitive radiotherapy for cervical cancer. Several new independent risk factors were found which warrant further research. A standardized and structured approach in the early diagnostics and management of bowel toxicity is needed.