Volume Of Bowel Research Articles

Relationship between MRI quantified small bowel motility and abdominal symptoms in Crohn's disease patients-a validation study.

Objective:Previous single-centre MRI data suggests an inverse correlation between normal small bowel motility variance and abdominal symptoms in Crohn’s disease (CD) patients. The current work prospectively assesses this observation in a larger, two-centre study.Methods:MR enterography datasets were analysed from 82 patients (38 male, aged 16–68), who completed a contemporaneous Harvey-Bradshaw index (HBI) questionnaire. Dynamic “cine motility” breath-hold balanced steady-state free precession sequences were acquired through the whole small bowel (SB) volume. Regions of interest (ROIs) were manually applied to encompass all morphologically normal SB (i.e. excluding Crohn’s affected bowel) and a validated registration technique used to produce motility maps. Mean and variance motility metrics were correlated with HBI and symptom components (well-being, pain and diarrhoea) using Spearman’s correlation statistics.Results:Overall, motility variance was non-significantly negatively correlated with the total HBI score, (r = −0.17, p = 0.12), but for subjects with a HBI score over 10, the negative correlation was significant (r = −0.633, p = 0.027). Motility variance was negatively correlated with diarrhoea (r = −0.29, p < 0.01). No significant correlation was found between mean motility and HBI (r = −0.02, p = 0.84).Conclusion:An inverse association between morphologically normal small bowel motility variance and patient symptoms has been prospectively confirmed in patients with HBI scores above 10. This association is particularly apparent for the symptom of diarrhoea.Advances in knowledge:This study builds on preliminary work by confirming in a large, well-controlled prospective multicentre study a relationship between normal bowel motility variance and patient reported symptoms which may have implications for drug development and clinical management.

Prone Positioning on a Belly Board Decreases Rectal and Bowel Doses in Pelvic Intensity-Modulated Radiation Therapy (IMRT) for Prostate Cancer.

The presence of normal tissues in the irradiated volume limits dose escalation during pelvic radiotherapy (RT) for prostate cancer. Supine and prone positions on a belly board were compared by analyzing the exposure of organs at risk (OARs) using intensity modulated RT (IMRT). The prospective trial included 55 high risk, localized or locally advanced prostate cancer patients, receiving definitive image-guided RT. Computed tomography scanning for irradiation planning was carried out in both positions. Gross tumor volume, clinical and planning target volumes (PTV) and OARs were delineated, defining subprostatic and periprostatic rectal subsegments. At the height of the largest antero-posterior (AP) diameter of the prostate, rectal diameters and distance from the posterior prostate wall were measured. IMRT plans were generated. Normal tissue exposure and structure volumes were compared between supine and prone plans using paired t-test. In the volumes of the prostate, PTV, colon and small bowel, no significant differences were found. In prone position, all rectal volumes, diameters, and rectum-prostate distance were significantly higher, the irradiated colon and small bowel volume was lower in dose ranges of 20-40Gy, and the exposure to all rectal segments was more favorable in 40-75Gy dose ranges. No significant difference was found in the exposure of other OARs. Prone positioning on a belly board is an appropriate positioning method aiming rectum and bowel protection during pelvic IMRT of prostate cancer. The relative reduction in rectal exposure might be a consequence of the slight departure between the prostate and rectal wall.

The impact of daily bladder filling on small bowel dose for intensity modulated radiation therapy for cervical cancer

Research demonstrates that instructing patients to have a full bladder for pelvic radiotherapy results in highly variable bladder volumes at daily treatment. We aimed to determine bladder volume variation in patients with intact cervical cancer treated with intensity-modulated radiotherapy (IMRT) on an empty bladder and estimate the difference in radiation dose to the small bowel compared to treating on a full bladder. We identified 29 patients treated with IMRT from 2010 to 2013 who underwent 2 planning computed tomography (CT) scans, 1 with a full bladder followed by 1 with an empty bladder. Interfractional variation in bladder volume was measured using 782 daily cone beam computed tomography (CBCT) scans. To estimate dose to small bowel, radiation plans were created on both empty and full bladder CT scans using an automated knowledge-based planning modeling program. Mean bladder volume with empty bladder instructions was 67 ± 26 cc compared to 91 ± 43 cc for no bladder instructions and 154 ± 54 cc for full bladder instructions (p < 0.001). There was a significant reduction in the absolute bladder volume variation in patients given empty bladder instructions compared to full bladder instructions (p < 0.05) The intraclass correlation coefficient showed low reliability of bladder filling across all groups (p = 0.6). The average bowel V45 for the empty bladder plans was 188 cc, compared to 139 cc for the full bladder plans (p < 0.05). More plans created on an empty bladder exceeded Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) guidelines but this was not significant (31% vs 14%, p = 0.12). Reliability of bladder volume at the time of radiation treatment is low, regardless of bladder filling instructions, although an empty bladder reduces absolute variation in bladder volume. Radiation planning on an empty bladder predicts a larger volume of small bowel receiving 45 Gy compared to a full bladder, although bowel dose on average is still within QUANTEC guidelines (V45 < 195 cc).

Incidence of radiation enteritis in cervical cancer patients treated with definitive radiotherapy versus adjuvant radiotherapy.

The study aimed to evaluate the incidence of early and late radiation enteritis in cervical cancer patients receiving definitive or adjuvant radiotherapy (RT). Three hundred and twenty-four cervical cancer patients receiving definite or adjuvant RT in our hospital from January 2010 to December 2012 were divided into definitive (132 patients) or adjuvant RT (192 patients) and performed detailed analysis. Early radiation enteritis was found in 54.3%, and late radiation enteritis was found in 17.9% of cervical patients. Early (P < 0.007) and late (P < 0.003) radiation enteritis appeared more frequently in patients treated with definitive RT than that with adjuvant RT. In the definitive RT group, incidence of both early and late radiation enteritis in the RT group was higher than in the radiochemotherapy (RCHT) group, and the difference was statistically significant (P < 0.004). Severe cases of late radiation enteritis (Grade 3 and 4) can be seen higher in the definitive radiation group (both the RT and RCHT group) than in the adjuvant radiation group, and the difference was statistically significant (P < 0.005). The incidence of both early and late radiation enteritis in the definitive RT group is higher than in the adjuvant RT group. The occurrence of side effects was associated with the prolongation of total irradiation time due to necessary interruptions of RT. Methods to decrease the interruptions in the RT and the irradiated volume of the small bowel will further lessen enteric morbidity.

Use of expanders for bowel protection in pediatric pelvic tumor radiation therapy: 15 years of tolerance results

PurposeBowel is often the dose-limiting organ in curative pelvic irradiation because of radiation enteritis when dose exceeds 40 to 45 Gy. To limit radiation enteritis, a silicone tissue-expander prothesis (STEP) connected to a subcutaneous self-sealing valve was prospectively used in children undergoing pelvic or abdominal radiation therapy. This study reports the 15-year long-term outcomes of this prospective series. Methods and materialsBetween 1987 and 2008, 29 children from 3 Paris institutions received pelvic radiation therapy after surgical placement of a STEP in the pelvis. The median prescribed dose was 50.4 Gy (44.1-55 Gy) using 5 daily fractions of 1.8 Gy per week, except for 1 patient receiving 4 fractions of 2.5 Gy per week. The median treatment duration was 40 days (29-49 days). After 2000, computed tomography (CT) conformal 3-dimensional radiation therapy was used, and 12 patients had CT simulation. Four had CT before and after insertion of the STEP, enabling us to compare pre- and postprosthesis insertion bowel dose-volume histograms. Acute and late toxicities were captured using the Radiation Therapy Oncology Group or the National Cancer Institute Common Terminology Criteria for Adverse Events 4.0 scale. ResultsNo patient experienced significant perioperative complications. Pre- and post-STEP insertion small bowel dose-volume histograms show significant reductions in small bowel: 51%, 45%, and 64%, respectively, in V10, V15, and V40 (Vx = irradiated volume by x Gy). Twenty-five patients (86%) completed their radiation therapy with no or minimal small bowel toxicity. One patient also treated with neutrons developed delayed grade 4 toxicities. The 15-year complication-free survival for those surviving was 70.3%. ConclusionsWe report the long-term follow-up of STEP prosthesis insertion in children to reduce the small bowel volume in the radiation field. The acute and long-term tolerances were excellent. The STEP reduced the bowel dose over 40 Gy by 64%.

Dose Volume Effect of Acute Diarrhea in Post-Operative Radiation for Gynecologic Cancer

Diarrhea is the primary symptom of concern in acute post-operative radiation-induced enteritis in gynecologic cancer. We retrospectively studied the correlation between the volume of irradiated small bowel and the development of acute diarrhea in these patients. A total of 100 post-operative gynecologic cancer patients were analyzed. Pelvic computed tomography was performed to calculate the volume of irradiated small bowel. A dose-volume histogram was calculated from 5 to 40 Gy at 5 Gy intervals. Patients receiving conventional whole pelvic radiation therapy (RT) were assigned to Group I, and those who received intensity-modulated RT (IMRT) were assigned to Group II. A total dose of 40-50 Gy was delivered at 1.8-2.0 Gy per fraction daily. Acute diarrhea during treatment was scored. All data were expressed as a mean ± standard deviation. Different dose-volume parameters for small bowel in Grades 0-1 and Grades 2-3 diarrhea were calculated by the independent t-test. Univariate analysis of diarrhea risk factors was performed with the independent t-test or Chi-square/Fisher exact test. Of the 77 patients who received conventional RT, 44 (57.14%) experienced Grades 2-3 toxicities. Of the 23 patients who received IMRT, 9 (39.13%) experienced Grades 2-3 toxicities. Concurrent chemotherapy was slightly associated with a higher damage score in both groups (p = 0.028). None of the patient factors (weight, percentage depth dosage, dose fraction, distance from skin to tumor, lymph node metastasis, chemotherapy, block, brachytherapy, hypertension, or diabetes) were correlated with diarrhea in the two groups. The volumes of irradiated small bowel in patients who experienced Grades 2-3 diarrhea were significantly larger than those in patients who experienced Grades 0-1 diarrhea at all dose levels in Group I. V20 (372.19 ± 133.26 cm3, p = 0.004) was an independent factor for developing Grades 2-3 diarrhea in Group I. V25 (290.35 ± 130.22 cm3, p = 0.001) was an independent risk factor for all patients who developed higher score diarrhea. The volume of irradiated small bowel was an independent risk factor for all patients who developed diarrhea, especially those undergoing conventional RT.

Does the Use of Volumetric Modulated Arc Therapy Reduce Gastrointestinal Symptoms after Pelvic Radiotherapy?

AimsGrowing numbers of patients with cancer are surviving after treatment with pelvic radiotherapy. We evaluated the technique of volumetric modulated arc therapy (VMAT), which delivers a decreased dose to the organs at risk. We aimed to determine outcomes of this technique in terms of patient-reported acute toxicity and late effects and correlate the frequency of gastrointestinal symptoms with the volume of bowel receiving radiation dose. Materials and methodsPatients who were to receive VMAT for gynaecological malignancy completed patient-reported outcomes at baseline, the end of treatment, 8 weeks and 1 year. The rates of patient-reported toxicity were correlated with the volume of bowel irradiated. ResultsThe frequencies of patient-reported gastrointestinal symptoms increased in the acute toxicity phase and tended to improve at 1 year, with the exception of faecal incontinence and rectal bleeding (P < 0.05). There was not a strong association between the volume of small bowel that was irradiated (P > 0.05 at all dose levels) and reported toxicity, suggesting that other factors are involved in the development of toxicity. ConclusionAlthough VMAT decreases the dose delivered to the small bowel, this does not translate into a reduction in patient-reported toxicity.

Dose-escalated radiotherapy for unresectable or locally recurrent pancreatic cancer: Dose volume analysis, toxicity and outcome of 28 consecutive patients

PurposeThe role of radiotherapy for unresectable pancreatic cancer is controversial. A benefit of additional radiotherapy is supported by some observations. A dose-effect relationship was recently found by dose escalation employing image guided and intensity modulated radiotherapy.MethodsWe retrospectively evaluated 28 consecutive patients, all with history of extensive prior therapies for unresectable locally advanced/ recurrent pancreatic cancer (LAPC/LRPC). Treatment was delivered by helical tomotherapy after daily position verification with computed tomography. Dose to the planned target volume (PTV) was 51 Gy, while the dose to the macroscopic tumor was escalated by a simultaneous integrated boost to a median cumulative dose of 66 Gy (60–66 Gy). Concomitant chemotherapy consisted mainly of capecitabine (n = 23).Results10 of 28 patients presented acute toxicities > grade 2, one patient succumbed to gastrointestinal bleeding after treatment. No correlations of toxicities and dose volume histograms (DVH) of retrospectively delineated small bowel loops were observed, although average small bowel volume receiving ≥ 20 Gy was 374 ml. DVH analyses revealed a correlation of splenic parameters and acute toxicity: Vomiting, anorexia, dehydration, hematologic toxicity, fatigue, combined gastro-intestinal toxicity wit R-values between 0.392 and 0.561 (all p-values > 0.05). Only one patient developed late toxicities > grade 2. With an average follow-up time in surviving patients of 14 months median overall survival time was 19 months and median time to local recurrence 13 months. In 8 patients with available imaging of local recurrence: 5 in field recurrences, 2 marginal recurrences and one lymph node recurrence outside the high dose radiation field were observed. In univariate analysis only ΔCA-19-9 during radiotherapy was associated with local control (p = 0.029) and overall survival (p = 0.049).ConclusionDose escalated normo-fractionated radiotherapy for LAPC/LRPC seems feasible and suitable to prolong local control and in consequence long-term survival. However, in-field local progression is still frequently observed and possibilities to increase the local effectiveness should be evaluated. Exposure of the spleen was predictive for acute toxicity and should be further investigated.

Comparison of Dose-Volume Histogram Between Intensity-Modulated Proton Therapy Versus Volumetric-Modulated Arc Therapy for the Irradiation of Pelvic Lymph Nodes and Prostate in High-Risk Prostate Cancer

To compare DVH of the organs at risk (OAR) and clinical target volumes (CTV1: prostate and seminal vesicles; CTV2: regional pelvic lymph nodes) between IMPT and VMAT for high-risk Pca. A study of moderate hypofractionation proton therapy treating CTV1 and CTV2 is in progress for high-risk Pca since August 2016. CTV1 and CTV2 receive 6750 cGy and 4500 cGy in 25 fractions over 5 weeks, respectively, with an IMPT plan. Seven accrued patients, as of November 2016, were the subjects for DVH comparison between IMPT and VMAT. Two treatment plans (IMPT and VMAT) were prepared for each patient with pre-defined planning objectives for CTVs, PTVs, and OARs. IMPT plans were prepared with 2 lateral beams, and VMAT plans with 2 arcs. Coverage of CTV1 and CTV2 was adequate for both plans with 99% of CTVs receiving 100.7 - 101.7% of the prescription doses. Mean doses to the bladder, rectum, large bowel, and small bowel were lower with IMPT vs. VMAT. Mean dose to femoral heads was slightly higher with IMPT. % volumes of rectum and large bowel receiving V10-45 Gy, % volumes of small bowel receiving V10-40 Gy, and % volumes of bladder receiving V10-30 Gy were smaller with IMPT vs. VMAT. IMPT did not produce the typical low-dose ‘‘bath’’ to the pelvis seen with VMAT. % volumes of femoral heads receiving V20-30 Gy were smaller with VMAT, while that of femoral heads receiving V10 Gy were smaller with IMPT.Abstract 2532; TableBladderRectumLarge bowelSmall bowelLeft femurRight femurIMPTVMATIMPTVMATIMPTVMATIMPTVMATIMPTVMATIMPTVMATMean (Gy)39.246.834.8*48.731.1*43.510.5*26.323.222.224.421.7V66Gy (%)3.53.1*4.83.8*00000000V61Gy (%)5.95.1*8.06.900000000V57Gy (%)7.66.7*10.19.200000000V45Gy (%)16.316.616.3*20.14.17.22.62.20000V40Gy (%)23.123.820.0*28.817.923.25.77.10.500.30V30Gy (%)37.446.936.3*55.940.250.810.120.211.04.314.92.9V20Gy (%)57.976.150.9*81.952.3*79.115.7*42.042.431.643.428.2V10Gy (%)80.3*10063.7*89.464.0*89.821.5*61.265.369.668.871.6*Statistically significant, paired t-test Open table in a new tab *Statistically significant, paired t-test IMPT can significantly reduce the dose to OARs while providing adequate target coverage, compared with VMAT, when the pelvic lymph nodes, along with prostate and seminal vesicles, are irradiated.

Acute toxicity of the bowel after stereotactic robotic radiotherapy for abdominopelvic oligometastases

Aim: To correlate dose-volume histogram (DVH) parameters with appearance of grade ≥2 acute and late gastrointestinal toxicity of stereotactic body radiotherapy (SBRT) in patients with abdominopelvic solitary or oligometastatic disease outside the liver.Material and methods: Acute and late bowel toxicity of 84 abdominopelvic oligometastatic patients was registered. A logistic regression was performed between different DVH parameters and presence of grade ≥2 acute and late toxicity. A Normal Tissue Complication Probability (NTCP) model was built with significant parameters to determine complication probabilities (CP).Results: Thirteen (15%) of 84 patients experienced of grade ≥2 acute toxicity, while 8 (10%) reported late toxicity complications. A significant relationship was found for EQD2 (V30Gy, V40Gy, V50Gy and V65Gy) and grade ≥2 acute toxicity. Dmax and D2 were not significant. Late grade ≥2 toxicity was not significantly correlated with any DVH parameter. According to our NTCP model for V40Gy, an irradiated bowel volume of 10 cm3 of V40Gy resulted in CP of grade ≥2 acute toxicity of less than 10%. Local control was 87% at 2 years and 82% at 5 years. Overall survival was 61% at 2 years and 32% at 5 years.Conclusions: After SBRT for abdominopelvic oligometastases, in general, the presence of acute and late toxicity was low. A significant relationship was found for V30Gy, V40Gy, V50Gy and V65Gy and grade ≥2 acute toxicity. We estimated acute complication probabilities per volume of irradiated bowel by V40Gy and V50Gy

Late small bowel toxicity after aggressive abdominopelvic intensity modulated radiation therapy

PurposeWe retrospectively analyzed late small bowel toxicity in patients who received abdominal or pelvic intensity modulated radiation therapy (IMRT) to the small bowel with a maximum dose greater than the generally accepted maximal tolerable dose of 45 Gy. Methods and materialsAll patients (N = 94) who received IMRT with a point dose of at least 45 Gy to tightly contoured small bowel between 2005 and 2014 at our institution were included. The median prescribed treatment dose was 70.2 Gy. The median follow-up was 20.1 months. Late small bowel toxicity was assessed using the Common Terminology Criteria for Adverse Events Version 3.0. Dosimetric variables and clinical factors were assessed for their relationship to small bowel toxicity. ResultsThe median maximal small bowel point dose (Dmax) was 6546.5 cGy. The estimated 5-year rates of freedom from at least grade 1, at least grade 2, and at least grade 3 late small bowel toxicity were 72.4% (95% confidence interval [CI], 60.7%-86.5%), 91.9% (95% CI, 84.1%-100%), and 93.6% (95% CI, 86.2%-100%), respectively. One patient (1.1%) developed grade 3 late toxicity, and 2 patients (2.1%) developed grade 4 late toxicity. Use of capecitabine/5-fluorouracil treatment was a significant predictor (P < 0.001) of at least grade 1 and at least grade 2 small bowel toxicity. No other clinical factors were associated with toxicity. None of the dose-volume parameters were significant predictors of small bowel toxicity. ConclusionIt may be possible with IMRT to deliver high doses to small volumes of small bowel with low rates of significant long-term complications. Further studies should explore tolerable dose-volume relationships in cases in which aggressive abdominal or pelvic treatment may be warranted to treat the underlying malignancy.

CyberKnife with integrated CT-on-rails: System description and first clinical application for pancreas SBRT.

This article reports on the integration of a sliding-gantry CT-on-rails with a robotic linear accelerator. The system consists of a SOMATOM Definition AS CT scanner (Siemens Healthcare, Forchheim, Germany) and a CyberKnife M6 FIM (Accuray, Inc., Sunnyvale, CA, USA). Additional movement programs were implemented in the robotic treatment table (RoboCouch, Accuray Inc.) to move between CT and treatment position. Acceptance testing was performed on the CT scanner according to AAPM83 guidelines, as well as safety tests for collision avoidance and electromagnetic (EM) compatibility. For the first clinical application of the system, daily dose was evaluated in five pancreas SBRT patients. A second envisioned use is the optimal alignment of the treatment beams to soft-tissue targets without the use of implanted fiducials. To this end, an offset vector feature has been implemented, which shifts the treatment center according to the daily position of the tumor relative to the spine (established by a CT scan). This offset can be applied by either moving the treatment couch (physical couch shift) or by moving the CyberKnife robot (virtual couch shift). An End-to-End (E2E) test was specifically designed to evaluate the accuracy of this feature using the Xsight Lung Tracking Phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA). The position of the tumor with respect to the spine was varied by moving the insert inside the phantom and a CT scan was made for each position. The treatment plan was subsequently delivered to the phantom employing spine tracking. The test was repeated four times for a physical couch shift and four times for a virtual couch shift. All acceptance, safety and EM compatibility testing was successful. For the first pancreas SBRT patients treated using daily CT imaging, the volume of stomach, duodenum, or small bowel receiving >35 Gy was found to increase or remain constant during treatment; however, the clinical constraint of 5 cc was not violated. For the offset vector E2E test, the reference accuracy (without any tumor shift) was (0.74, -0.61, -0.33) mm in the inferior, left, and anterior direction respectively. The difference in deviation with respect to the reference was (-0.1 ± 0.15, 0.01 ± 0.16, -0.17 ± 0.25) mm, when applying a physical couch shift. With a virtual couch shift, the deviations were (0.02 ± 0.15, 0.06 ± 0.23, -0.4 ± 0.31) mm. The first combination of a CyberKnife treatment unit with a sliding-gantry CT scanner is operational in our department enabling future developments toward image-guided online-adaptive SBRT supported by diagnostic-quality CT imaging.

The Factors Affecting Small Bowel Volume in the Pelvis of Patients Receiving Radiotherapy for Rectal Cancer

The Factors Affecting Small Bowel Volume in the Pelvis of Patients Receiving Radiotherapy for Rectal Cancer

The Factors Affecting Small Bowel Volume in the Pelvis of Patients Receiving Radiotherapy for Rectal Cancer

The Factors Affecting Small Bowel Volume in the Pelvis of Patients Receiving Radiotherapy for Rectal Cancer

Predictors of Radiation Therapy–Related Gastrointestinal Toxicity From Anal Cancer Dose-Painted Intensity Modulated Radiation Therapy: Secondary Analysis of NRG Oncology RTOG 0529

NRG Oncology RTOG 0529 assessed the feasibility of dose-painted intensity modulated radiation therapy (DP-IMRT) to reduce the acute morbidity of chemoradiation with 5-fluorouracil (5FU) and mitomycin-C (MMC) for T2-4N0-3M0 anal cancer. This secondary analysis was performed to identify patient and treatment factors associated with acute and late gastrointestinal (GI) adverse events (AEs). NRG Oncology RTOG 0529 treatment plans were reviewed to extract dose-volume data for tightly contoured small bowel, loosely contoured anterior pelvic contents (APC), and uninvolved colon outside the target volume (UC). Univariate logistic regression was performed to evaluate association between volumes of each structure receiving doses ≥5 to 60Gy(V5-V60) in 5-Gy increments between patients with and without grade ≥2 acute and late GI AEs, and grade ≥3 acute GI AEs. Additional patient and treatment factors were evaluated in multivariate logistic regression (acute AEs) or Cox proportional hazards models (late AEs). Among 52 evaluable patients, grade ≥2 acute, grade ≥2 late, and grade ≥3 acute GI AEs were observed in 35, 17, and 10 patients, respectively. Trends (P<.05) toward statistically significant associations were observed between grade ≥2 acute GI AEs and small bowel dose (V20-V40), grade ≥2 late GI AEs and APC dose (V60), grade ≥3 acute GI AEs and APC dose (V5-V25), increasing age, tumor size >4cm, and worse Zubrod performance status. Small bowel volumes of 186.0cc, 155.0cc, 41.0cc, and 30.4cc receiving doses greater than 25, 30, 35, and 40Gy, respectively, correlated with increased risk of acute grade ≥2 GI AEs. Acute and late GI AEs from 5FU/MMC chemoradiation using DP-IMRT correlate with radiation dose to the small bowel and APC. Such associations will be incorporated in the dose-volume normal tissue constraint design for future NRG oncology anal cancer studies.

Clinical implementation of coverage probability planning for nodal boosting in locally advanced cervical cancer

PurposeTo implement coverage probability (CovP) for dose planning of simultaneous integrated boost (SIB) of pathologic lymph nodes in locally advanced cervical cancer (LACC). Material and methodsCovP constraints for SIB of the pathological nodal target (PTV-N) with a central dose peak and a relaxed coverage at the perimeter were generated for use with the treatment planning system Eclipse: PTV-N D98 >90%, CTV-N D98 >100% and CTV-N D50 >101.5% of prescribed dose. Dose of EBRT was 45Gy/25 fx with a SIB of 55–57.5Gy depending on expected dose from brachytherapy (BT). Twenty-five previously treated patients with 47 boosted nodes were analysed. Nodes were contoured on cone beam CT (CBCT) and the accumulated dose in GTV-NCBCT and volume of body, pelvic bones and bowel receiving >50Gy (V50) were determined. ResultsNearly all nodes (89%) were visible on CBCT and showed considerable concentric regression during EBRT. Total EBRT and BT D98 was >57 GyEQD2 in 98% of the visible nodes. Compared to treatment plans aiming for full PTV-N coverage, CovP significantly reduced V50 of body, bones and bowel (p<0.001) ConclusionCovP is clinically feasible for SIB of pathological nodes and significantly decreases collateral SIB dose to nearby OAR.

Highly Efficient Training, Refinement, and Validation of a Knowledge-based Planning Quality-Control System for Radiation Therapy Clinical Trials

To demonstrate an efficient method for training and validation of a knowledge-based planning (KBP) system as a radiation therapy clinical trial plan quality-control system. We analyzed 86 patients with stage IB through IVA cervical cancer treated with intensity modulated radiation therapy at 2 institutions according to the standards of the INTERTECC (International Evaluation of Radiotherapy Technology Effectiveness in Cervical Cancer, National Clinical Trials Network identifier: 01554397) protocol.The protocol used a planning target volume and 2 primary organs at risk: pelvic bone marrow (PBM) and bowel. Secondary organs at risk were rectum and bladder. Initial unfiltered dose-volume histogram (DVH) estimation models were trained using all 86 plans. Refined training sets were created by removing sub-optimal plans from the unfiltered sample, and DVH estimation models… and DVH estimation models were constructed by identifying 30 of 86 plans emphasizing PBM sparing (comparing protocol-specified dosimetric cutpoints V10 (percentage volume of PBM receiving at least 10 Gy dose) and V20 (percentage volume of PBM receiving at least 20 Gy dose) with unfiltered predictions) and another 30 of 86 plans emphasizing bowel sparing (comparing V40 (absolute volume of bowel receiving at least 40 Gy dose) and V45 (absolute volume of bowel receiving at least 45 Gy dose), 9 in common with the PBM set).To obtain deliverable KBP plans, refined models must inform patient-specific optimization objectives and/or priorities (an auto-planning "routine"). Four candidate routines emphasizing different tradeoffs were composed, and a script was developed to automatically re-plan multiple patients with each routine. After selection of the routine that best met protocol objectives in the 51-patient training sample (KBPFINAL), protocol-specific DVH metrics and normal tissue complication probability were compared for original versus KBPFINAL plans across the 35-patient validation set. Paired t tests were used to test differences between planning sets. KBPFINAL plans outperformed manual planning across the validation set in all protocol-specific DVH cutpoints. The mean normal tissue complication probability for gastrointestinal toxicity was lower for KBPFINAL versus validation-set plans (48.7% vs 53.8%, P<.001). Similarly, the estimated mean white blood cell count nadir was higher (2.77 vs 2.49 k/mL, P<.001) with KBPFINAL plans, indicating lowered probability of hematologic toxicity. This work demonstrates that a KBP system can be efficiently trained and refined for use in radiation therapy clinical trials with minimal effort. This patient-specific plan quality control resulted in improvements on protocol-specific dosimetric endpoints.

Influence of position and radiation technique on organs at risk in radiotherapy of rectal cancer.

The influence of the position and radiation technique on the organs at risk (OARs) in radiotherapy of rectal cancer was evaluated. The relationship between the volume of irradiated small bowel (VSB) and acute bowel toxicity was determined. A total of 97 cases of rectal cancer were retrospectively randomized to receive radiotherapy with the designated treatment positions and radiation plans. Among 64 patients in the supine position, 32 patients were given three-dimensional conformal radiotherapy (3DCR) and 32 patients were subjected to intensity-modulated radiation therapy (IMRT) respectively. The rest 33 patients were treated with 3DCRT in the prone position with a belly board. The VSB was calculated for doses from 5 to 45 Gy at an interval of 5 Gy. With prescription dose in planned target volume (PTV) of 50 Gy, the dose distribution, conformal index for PTV (CIPTV), dose-volume histogram (DVH) of OARs, the correlation of VSB and the acute toxicity were compared. The results were shown as follows: (1) Among the 3 methods, there were no differences in PTV's converge including V95 and D95; (2) For IMRT under a supine position, CIPTV was closest to 1, the mean dose of small bowel decreased (P<0.05), and the mean VSB from V30 to V45 significantly decreased (P<0.05). (3) For 3DCRT with a belly board under a prone position, the mean dose and the mean VSB from 40 to 45 Gy were less than those for 3DCRT under a supine position (P<0.05); (4) Mean proportion of VSB was significantly greater in the patients experiencing diarrhea grade 2-4 than in those with diarrhea grade 0-1 at dose levels from V30 to V45 (P<0.05). It was concluded that for the radiotherapy of rectal cancer, IMRT technique might decrease the high-dose VSB to reduce the risk of acute injury. 3DCRT with a belly board under a prone position is superior to 3DCRT under a supine position, which could be a second choice for radiation of rectal cancer.

SU‐F‐P‐29: Impact of Oral Contrast Agent for Assisting in Outlining Small Intestine On Pelvic IMAT Dose in Patients with Cervical Cancer

Purpose:As the advanced intensity modulated arc therapy(IMAT) delivery systems becoming a main role of treatment ways, which places even greater demands on delivering accuracy. The impact of oral contrast agent (meglumine diatrizoate) for assisting in outlining the small intestine on pelvic IMAT dose in patients with cervical cancer was investigated.Methods:Ten cervical cancer patients for postoperative radiotherapy underwent CT scans, and the planning target volumes (PTV) and organs at risk (including the small intestine, rectum, bladder, colon and the left and right femoral head) were contoured. The IMAT plans were generated on Oncentra v4.1 planning system for each case, PTV was prescribed to 50.4 Gy in 28 fractions. Then another plan was generated by re‐calculating the radiation dose after changing the electron density of the small bowel. The first plan (plan A) was the conventional IMAT plan (with oral contrast agent), and the second one (plan B) specified the electron density of the small bowel (without oral contrast agent). Paired t‐test was used to compare the dose distribution between the two plans.Results:The PTV's D2, D50, D95, V110, conformity index, and homogeneity index of plans A and B were 5610.5 vs. 5611.4 cGy (P=0.175), 5348.5 vs. 5348.0 cGy (P=0.869), 5039 vs. 5042.3 (P=0.518), 6.0% vs. 6.1 %(P=0.886), 0.1269 vs. 0.1271 (P=0.34) and 0.8421 vs. 0.8416 (P=0.598), respectively. The volumes of the small bowel receiving at least 30 Gy (V30) and the minimum dose of 2% volume accepted (D2) for plans A and B were 31.6% vs. 31.9% (P=0.371) and 5067.8 vs. 5085.4 cGy (P=0.377), while rectum V50 of the two plans was 12.4% vs. 12.1% (P=0.489).Conclusion:The oral contrast agent (meglumine diatrizoate) filling the small intestine does not lead to a significant increase in the pelvic IMAT dose in patients with cervical cancer.

Low-Energy Brachytherapy Sources for Pelvic Sidewall Treatment

Purpose: The CivaSheet (CivaTech Oncology, Inc., Research Triangle Park, NC) is a Pd-103 brachytherapy device with radiation directionality for the treatment of cancer. The device has individual elements (i.e., CivaDots) spaced in a rectangular array (0.8 cm center-to-center spacing) within a flexible bioabsorbable substrate to mitigate the hotand coldspots of radiation dose typically prevalent with Pd-103 implants. The current study compares dose distributions and critical structure doses for the CivaSheet (CivaTech Oncology, Inc., Research Triangle Park, NC) to those of conventional, low dose-rate (LDR), low-energy photon-emitting brachytherapy seeds. Materials and Methods: The VariSeed (Varian Medical Systems, Palo Alto, CA) LDR brachytherapy treatment planning software is the most popular system. Version 9 enables directional orientation of the sources away from the imaging scanning axis. Post-implant CT scans (120 kVp) of the first patient treated with the CivaSheet for cancer at the pelvic sidewall were compared for three low-energy seeds (model 200 Pd-103, model 6711 I-125, and model CS-131 Rev2 Cs-131). Based on starting with a 6x12 array, a total of 70 CivaDots (1.34 U each, 93.8 U in total) were implanted for a prescription dose of 60 Gy to 0.5 cm with customization of device sizing within the operating room to conform to the surgical tumor bed. Dose distributions were assessed near the tumor bed and adjacent to critical structures (i.e., bowel and bladder). Source strength for each element of the CivaSheet was 1.340 U. For a direct comparison at the prescription depth, theoretical meshes containing Pd103, I-125, and Cs-131 seeds were set at source strengths of 1.285 U, 0.189 U, and 0.957 U each, respectively, and scaled inversely with the dose-rate constant and half-life. The contoured bowel and bladder volumes were 433 cm and 289 cm, respectively. Clinically-relevant dose-volume histogram (DVH) metrics of 2 cm and 0.1 cm were determined. For the CivaSheet, differences between dose to water-inwater and dose to tissue-in-tissue were evaluated. These treatment planning data were obtained using Monte Carlo methods according to the methodology of the TG-43U1 and AAPM/ESTRO TG-186 reports. Commissioning results for these treatment planning data are included in another presentation. Results: The CivaSheet imaged clearly. Even with a metal prosthetic hip, all 70 CivaDots were discernable. However, spatial localization of individual CivaDots, and determination of their orientation and resultant radiation directionality, would benefit from improvements in the acquired 0.3 cm slice thickness and large field-of-view (50 cm). Dose distributions are depicted in the Figure. The directional source minimized radiation dose away from the implant in comparison to meshes loaded with conventional brachytherapy seeds. For the bowel, doses to 2 cm volumes for the CivaSheet, Pd-103 seeds, I-125 seeds, and Cs-131 seeds were 3.0, 25.8, 31.8, and 34.7 Gy, respectively. Doses to 0.1 cm volumes were 6.9, 46.5, 51.0, and 52.5 Gy, respectively. For the bladder, doses to 2 cm volumes for the CivaSheet, Pd-103 seeds, I-125 seeds, and Cs-131 seeds were 12.3, 41.7, 44.7, and 45.3 12.3 Gy, respectively. Doses to 0.1 cm volumes were 39.1, 102.6, 89.6, and 85.7 Gy. Dose generally increased with increasing photon energy of the source. The CivaSheet reduced the bowel and bladder dose metrics by factors of 7 and 2 over the seed-based results. For the same CivaSheet source strength, DVH metrics for dose to tissue-in-tissue for these organs were similar to those of dose to water-in-water, largely due to the 2% difference in dose-rate constants (0.566 and 0.579, respectively) and the tissues being within a few centimeters of the CivaSheet implant. Conclusions: Gold shielding in the CivaDots attenuates radiation for directional bracytherapy. The CivaSheet provides a therapeutic target dose while substantially minimizing critical structure doses.