The Role of Small Bowel in Cervical Cancer Brachytherapy
Y Liao*, V Dandekar, J Chu, D Bernard, J Turian, K Kiel, Rush University Medical Center, Chicago, ILSU-E-T-708 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Small bowel (SB) is the organ at risk (OAR) that has the highest rate of radiation induced late toxicity in brachytherapy of cervical cancer. Historically, however, its dose has not been systematically reported as other OARs even during image guided brachytherapy (IGBT). This study aims to evaluate the effect of including SB in BT plan optimization and to propose a possible reporting schema.
Thirteen patients were included in this retrospective study. All patients were treated with external beam radiotherapy of 45Gy in 25 fractions followed by high dose rate (HDR)-BT of 28Gy in 4 fractions/2 implants using tandem/ring applicator. MRI and CTs were obtained to define the GTV and HR-CTV, and OARs. Treatment plans were generated for each patient without considering small bowel dose constraint, and revised for those with D2cc of SB >5Gy.
Six of 13 cases required plan revision due to high D2cc for SB. By sparing the SB with an average reduction of 19% in D2cc, only 2 of the 6 replanned cases resulted in less optimal target coverage, i.e. D90 of HR-CTV less than 77Gy. However, one of them already had difficulty in achieving the coverage in the first plan due to other OAR dose restriction. On the other hand, SB mobility was noticed in the CT images, which could help in SB tolerance.
Although SB is typically mobile compared to other OARs, it is strongly recommended that it be used as an OAR for plan optimization. Prospective reporting of D2cc index will help to better define its potential association with late complications in the future.