“Loops” Versus “Bowel Bag”: Which Is Better for Bowel Contouring in Gynecologic Cancer Patients Receiving IMRT to the Para-Aortic Nodes?

Poorvu, Philip D.; Sadow, Cheryl A.; Townamchai, Kanokpis; Damato, A.L.; Lee, L.J.; Viswanathan, Anand

doi:10.1016/j.ijrobp.2014.05.1534

Cited by 1 publication

(6 citation statements)

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“…When investigating the dose-volume constraints applied to bowel bag on CT F (V45 195 cm 3 ), PBS resulted in higher V45 than IMRT (p ¼ 0.02). However, both PBS and IMRT plans exceeded bowel bag dose constraints in CT F with PBS median V45 of 499 cm 3 and IMRT median V45 of 471 cm 3 , with 0% of PBS and 0% of IMRT plans meeting SB bag V45 volume constraints.…”

Section: Resultsmentioning

confidence: 94%

“…We investigated the range of SB doses that could be expected due to patient setup and proton range uncertainty (Supplementary Figure 3, available online at http://www.informahealthcare.com). The mean difference between the worst case scenario and nominal plan PBS dose to SB loops for V15 was 46 cm 3 (range 6-91 cm 3 ). The worst case V15 for SB loops from the shifted plans underestimated the actual V15 for 63% of the on-treatment scans.…”

Section: Resultsmentioning

confidence: 99%

“…As these recommendations are based on studies of a heterogeneous population of patients receiving pelvic irradiation for rectal, cervical, or endometrial cancers, it is unclear whether contouring methodologies should differ for different clinical scenarios. Whether loops or bowel bag contouring is better for gynecologic malignancies was recently addressed by Poorvu et al [3]. The preliminary study findings did not find clinically meaningful differences between the two methods.…”

mentioning

confidence: 80%

“…For bladder and rectum, the dose-volume constraints were as low as reasonably achievable. SB goal constraints were to limit the bowel bag V45 to less than 195 cm 3 .…”

Section: Treatment Planning and Analysismentioning

confidence: 99%

“…Several studies have sought to correlate radiation dose and SB toxicity to better define dose-volume constraints. A recent Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) analysis, which reviewed six quantitative studies, recommended dose-volume constraints of V15 120 cm 3 when SB is contoured as bowel loops and V45 195 cm 3 when SB is contoured as a bowel bag [2].…”

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confidence: 99%

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Bag and loop small bowel contouring strategies differentially estimate small bowel dose for post-hysterectomy women receiving pencil beam scanning proton therapy

Kirk

Zhai

et al. 2016

Acta Oncologica

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Background Small bowel (SB) dose-volume relationships established during initial computed tomography (CT) simulations may change throughout therapy due to organ displacement and motion. We investigated the impact of organ motion on SB dose-volume histograms (DVHs) in women with gynecologic malignancies treated with pencil beam scanning (PBS) proton therapy and compared PBS SB DVHs to intensity-modulated radiation therapy (IMRT). Material and methods Post-hysterectomy patients (n ¼ 11) treated for gynecologic cancers were enrolled on an image-guided proton therapy protocol involving CT simulation with full (CT F ) and empty (CT E ) bladders and weekly/biweekly on-treatment scans. IMRT plans were generated for comparative analysis. SB was contoured as bowel loops or bowel bag. Wilcoxon signed-rank tests were used for matched-pair comparisons of SB, bladder, and rectum dose-volumes between CT scans and between PBS and IMRT plans. Results In PBS loops analysis, on-treatment DVH was significantly higher than CT F for doses <45 Gy (p < 0.05), and not significantly different than CT E . Specifically, V15 for loops was higher on-treatment (median 240 cm 3 ) compared to CT F (median 169 cm 3 , p ¼ 0.03). In PBS bag analysis, on-treatment DVH was not significantly different from CT F across all dose ranges. Bowel bag V45 was not significantly different between on-treatment (median 540 cm 3 ) and CT F (median 499 cm 3 , p ¼ 0.53). Decreasing bladder volume was associated with increasing V15 for loops and V45 for bowel bag (p < 0.005, both). Comparing PBS and IMRT, PBS resulted in significantly lower DVHs at low dose regions (<38 Gy) and higher DVHs at high dose regions (42.5-45.5 Gy) in both loops and bag analysis. IMRT plans demonstrated higher on-treatment SB loop DVHs and only minimal differences in bowel bag DVHs compared to CT F . Conclusions SB DVHs were well estimated by CT F bowel bag and underestimated by CT F loops in the setting of inconsistent bladder filling. Verifying bladder filling prior to treatment or using CT E for planning may more conservatively estimate SB dose-volume relationships.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 80%

“…For bladder and rectum, the dose-volume constraints were as low as reasonably achievable. SB goal constraints were to limit the bowel bag V45 to less than 195 cm 3 .…”

Section: Treatment Planning and Analysismentioning

confidence: 99%

mentioning

confidence: 99%

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