Dosimetric correlation of acute urinary toxicity in patients with rectal cancer treated with IMRT
PO-1098
Abstract
Dosimetric correlation of acute urinary toxicity in patients with rectal cancer treated with IMRT
Authors: Secerov Ermenc|, Ajra(1)*[asecerov@onko-i.si];But Hadzic|, Jasna (1);
(1)Institute of Oncology Ljubljana, Department of Radiation Oncology, Ljubljana, Slovenia;
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Purpose or Objective
Preoperative chemoradiation followed by surgery is the standard care for patients with locally advanced rectal cancer. The implementation of intensity modulated radiotherapy (IMRT) resulted in reducing the acute side effect during treatment, however they may still cause patient discomfort. We dosimetrically analyzed IMRT plans in locally advanced rectal cancer patients and correlated them with acute urinary toxicity.
Material and Methods
We analyzed the data from patients with rectal cancer who were included in a prospective phase II study at our institution. From January 2014 till March 2015 we treated 51 patients with operable stage II-III rectal adenocarcinoma, they received preoperative IMRT with pelvic dose of 41.8 Gy and simultaneously delivered 46.2 Gy toT2/3 and 48,4 Gy to T4 tumors in 22 fractions, concomitant with capecitabine 825mg/m2/12 hours weekends included. Patients were weekly evaluated to assess acute toxicity. Toxic side effects were assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. We calculated the mean dose (Dmean) to the whole bladder and the relative and absolute volume of the bladder that received 10 Gy (V10Gy), 20 Gy (V20Gy), 30 Gy (V30Gy), 35 Gy (V35Gy) and 40 Gy (V40Gy), respectively. Student''s t-test was used for correlating the doses received by the bladder with the grade of acute toxicity.
Results
Forty-eight patients with rectal cancer were available for analysis. No urinary discomfort was experienced by 27 (56.3%), grade 1 cystitis by 19 (39,6%) and grade 2 by 2 (4,2%) patients, respectively. We found no statistically significant correlation between Dmean, relative and absolute V10Gy, V20Gy, V30Gy, V35Gy, V40Gy and the grade of acute toxicity (Table 1).
Conclusion
We recorded mild urinary toxicity for patients with rectal adenocarcinoma treated with IMRT concomitant with capecitabine. We found no correlation between the dose to the whole bladder and cystitis. We need further investigation to achieve the optimal cut-off value for dose to the bladder in correlation with cystitis in order to optimize future IMRT plans for patients with rectal adenocarcinoma.