Irradiated Small Bowel Volume Research Articles

Dosimetric comparison of irradiated small bowel volume with intensity modulated radiotherapy and volumetric modulated arc therapy in adjuvant pelvic radiation therapy for endometrial carcinoma

Newer treatment techniques help in reducing dose to small bowel (SB) which is an organ at risk (OAR) for pelvic radiotherapy (RT). However, instead of SB, bowel bag is contoured routinely and constraints are given. In this retrospective case series, we compared the dose received by SB while using intensity modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques in patients receiving adjuvant pelvic RT for endometrial carcinoma. 10 patients with stage II EC who received VMAT were included in this single institution study. SB was contoured retrospectively in the planning computed tomography scan of these patients. An IMRT plan was also generated with a similar planning target volume coverage and organ at risk (OAR) constraints of the previously approved VMAT plan. Volume receiving 10 Gy, 20 Gy, 30 Gy, 40 Gy and 45 Gy of SB was analysed and a dosimetric comparison was made among the two plans. Anaylysis of variance (ANOVA) and unpaired t tests were used for dosimetric comparison. Mean SB volume receiving 10 Gy (V10 Gy) was 85.3% and 83.7% with IMRT and VMAT respectively. Mean SB volume receiving 45 Gy (V45 Gy) was 4.1% and 5% with IMRT and VMAT respectively. No statistically significant difference was noted in the low dose or high dose irradiated volume of SB using both techniques; however, the volume of SB getting irradiated in the absence of optimisation was found to be high in both the groups which can translate in to acute and late bowel toxicity. Further prospective studies have to be conducted to know the clinical significance of this dose-volume relationship to SB.

The effect of patient positioning (prone or supine) on the dose received by small bowel in pelvic radiotherapy in rectal cancer patients

PurposeThe small bowel is a main dose-limiting organ in pelvic radiotherapy in the patients with rectal cancer. Conventionally, pelvic radiotherapy of patients with rectal cancer is performed in the prone position. Material and MethodsThirty-nine patients underwent CT planning scan in the treatment position (20 patients in prone position group and 19 patients in supine position group). After radiation treatment planning optimization, the volumes of the irradiated small intestines were investigated. ResultsThe volume of irradiated small bowel was higher in the supine position (mean difference; 36,274 cm3). However, it was not statistically significant (P value=0.187) ConclusionSupine position could be accepted for the patients undergoing preoperative rectal cancer chemo-radiation.

Effect of prone and supine treatment positions for postoperative treatment of rectal cancer on target dose coverage and small bowel sparing using intensity-modulated radiation therapy.

BackgroundTo evaluate the influence of patient positioning on target dose coverage and dose distribution to the small bowel in intensity-modulated radiation therapy (IMRT) for rectal cancer patients.MethodsTwenty-four consecutive rectal cancer patients undergoing postoperative radiation were selected and set up in either a prone or supine position. All patients received computed tomography (CT) scans before and during treatment (1–4 weeks). The CT images were defined as plan, 1W, 2W, 3W, or 4W. The plan, 1W, 2W, 3W and 4W CT images were fused. The clinical target volume (CTV) and planning target volume (PTV) delineated on the plan CT were copied onto the 1–4W CT. The treatment plans based on the plan CT were also copied onto the 1–4W CT. The target dose coverage rate was assessed. The couch-position data of the linear accelerator were acquired.ResultsFailure rates of the CTV and PTV target dose coverage were higher in the prone group than in the supine group (18.60% vs. 0% and 69.76% vs. 53.65%) during the treatment. The total couch-position deviation for the prone group (1.23±0.76 cm) was significantly greater than that of the supine group (0.28±0.18 cm; P=0.001). Compared with the supine group, the prone group had significantly less irradiated small bowel volume at V5 (P=0.003) and V10 (P=0.004).ConclusionsThe supine position maintained better target dose coverage and setup reproducibility in rectal cancer patients treated with IMRT. The prone position combined with the belly board can reduce the dose received by the small bowel.

Overview of patient preparation strategies to manage internal organ motion during radiotherapy in the pelvis

AbstractIntroduction:Pelvic internal organs change in volume and position during radiotherapy. This may compromise the efficacy of treatment or worsen its toxicity. There may be limitations to fully correcting these changes using online image guidance; therefore, effective and consistent patient preparation and positioning remain important. This review aims to provide an overview of the extent of pelvic organ motion and strategies to manage this motion.Methods and Materials:Given the breadth of this topic, a systematic review was not undertaken. Instead, existing systematic reviews and individual high-quality studies addressing strategies to manage pelvic organ motion have been discussed. Suggested levels of evidence and grades of recommendation for each strategy have been applied.Results:Various strategies to manage rectal changes have been investigated including diet and laxatives, enemas and rectal emptying tubes and rectal displacement with endorectal balloons (ERBs) and rectal spacers. Bladder-filling protocols and bladder ultrasound have been used to try to standardise bladder volume. Positioning the patient supine, using a full bladder and positioning prone with or without a belly board, has been examined in an attempt to reduce the volume of irradiated small bowel. Some randomised trials have been performed, with evidence to support the use of ERBs, rectal spacers, bladder-filling protocols and the supine over prone position in prostate radiotherapy. However, there was a lack of consistent high-quality evidence that would be applicable to different disease sites within the pelvis. Many studies included small numbers of patients were non-randomised, used less conformal radiotherapy techniques or did not report clinical outcomes such as toxicity.Conclusions:There is uncertainty as to the clinical benefit of many of the commonly adopted interventions to minimise pelvic organ motion. Given this and the limitations in online image guidance compensation, further investigation of adaptive radiotherapy strategies is required.

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.

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.

Is the irradiated small bowel volume still a predictor for acute lower gastrointestinal toxicity during preoperative concurrent chemo-radiotherapy for rectal cancer when using intensity-modulated radiation therapy?

BackgroundThe small bowel (SB) represents the most important dose-limiting structure in pelvic radiotherapy (RT). However, we observed that the majority of rectal cancer patients who received preoperative pelvic intensity modulated RT (IMRT) developed acute tenesmus without watery diarrhea. The objective of this study is to determine if the RT dose to SB affects the acute lower gastrointestinal toxicity (ALGIT) in rectal cancer patients who received neoadjuvant concurrent chemotherapy-IMRT. We will also evaluate if patient and tumor factors affect the ALGIT.MethodsWe retrospectively analyzed 63 rectal cancer patients that consecutively received preoperative IMRT (45 Gy for pelvis and 50 Gy for gross tumor in 25 fractions) with concurrent chemotherapy (oxaliplatin 130 mg/m2 on day 1 and capecitabine 825 mg/m2, twice per day from day 1 to day 14, week 1 and 4) between May 2012 and May 2013. The ALGIT was assessed with Common Terminology Criteria for Adverse Events version 3. The patients were stratified into two groups (with and without grade ≥2 ALGIT). The effect of SB volume receiving 5 to 40 Gy (V5 to V40) at a 5 Gy interval dose level on grade ≥2 ALGIT was evaluated. The volume of small bowel is defined as the volume of the small bowel loop. Other factors evaluated include patient’s age and gender, tumor size and location and preexisting number of daily bowel movements.ResultsOverall, grade ≥2 ALGIT occurred in 57 % (36/63) patients. There was no significant difference between the two groups of patients (with and without grade ≥2 ALGIT) in SB V5 to V40, patient’s age and gender, tumor location and preexisting number of daily bowel movements. There was a significant difference between the two groups of patients in tumor volume (with grade ≥2 ALGIT: 115.5 ± 85.5 cm3 versus without grade ≥2 ALGIT: 58.5 ± 25.2 cm3, p = 0.0001). Multivariate analysis revealed no association between the dose SB received (V5 to V40) and the grade ≥2 ALGIT after adjusting for the tumor volume.ConclusionsWith IMRT technique used in rectal cancer patients undergoing preoperative chemo-radiotherapy, the acute lower GI toxicity is not associated with small bowel V5 to V40; instead it is associated with rectal tumor size.

Acute toxicity after a diverting stoma and spacer prior to chemoradiation in locally advanced rectal cancer

Background and purposeChemoradiotherapy (CRT) followed by surgery is the standard of care for locally advanced rectal cancer (LARC). For grade ⩾3 acute diarrhea there is a relationship between dose and irradiated small bowel volume. The aim of this study was to evaluate whether combined placement of a diverting stoma and sigmoid spacer (DSSS) led to reduced irradiated small bowel volume and less grade ⩾3 acute diarrhea in the treatment of LARC. Materials/methodsBetween 2003 and 2010, 54 of 189 LARC patients treated with CRT in two institutions had a DSSS prior to CRT. Data on patient and treatment characteristics and outcomes were collected retrospectively. Delineation of small bowel was performed with planning CT-scans. CTCAE version 4.0 was used for acute toxicity. ResultsPatients with a DSSS had significantly less small bowel volume irradiated up to doses of 20Gy. This difference was not observed for the higher dose levels. CRT induced grade ⩾3 acute diarrhea was not different between the two groups (8.3% vs. 12.8%; p=0.41). ConclusionDSSS is not clearly beneficial to reduce grade ⩾3 acute diarrhea, and it must be considered whether placement of a DSSS is justified for this purpose.

Evaluation of a Belly Board immobilisation device for rectal cancer patients receiving pre-operative chemoradiation

AbstractPurposeTo evaluate the efficacy of a Belly Board immobilisation device for rectal cancer patients.Materials and methodsA randomised trial in patients receiving neo-adjuvant chemoradiation for rectal carcinoma was established. Patients were treated, prone with control arm, according to standard departmental protocol and experimental arm with the use of a Belly Board. All treatments were planned using a three-field technique. The primary endpoints were reproducibility and irradiated small bowel volume. Questionnaires were used to assess secondary endpoints of patient comfort, ease of set-up and acute toxicities.ResultsPre-planned interim analysis was performed after recruiting 30 patients. In all, 348 portal images were analysed retrospectively. Around 8 out of 12 parameters measuring set-up reproducibility were in favour of the Belly Board arm. Random error in the anterior–posterior direction was improved and statistically significant in the experimental arm (95% CI; p≤0·05). Small bowel V15 was significantly lower in the Belly Board position (mean V15=14·5%) compared with the standard position (mean V15=21·4%), paired t-test 95% CI; p=0·035. Also, patients’ comfort satisfaction was greater in the Belly Board arm.ConclusionsSet-up reproducibility, small bowel V15, patient comfort and satisfaction were all significantly improved by the use of the Belly Board.

Adjuvant volumetric-modulated arc therapy with simultaneous integrated boost in endometrial cancer. Planning and toxicity comparison

Objective. To report dosimetric and acute toxicity data in prospectively enrolled high-intermediate risk endometrial cancer (HIR-EC) patients postoperatively irradiated by simultaneous integrated boost volumetric modulated arc therapy (SIB-VMAT). Methods. Thirty prospectively enrolled HIR-EC patients were postoperatively treated by SIB-VMAT. Target coverage, dose homogeneity, and sparing of organs at risk (OARs) were compared with corresponding data retrieved from an historical control (30 consecutive selected matched patients) treated by concomitant boost three-dimensional conformal radiotherapy (3D CRT CB) from a previously published study (ADA-I trial). All patients received 45 Gy on pelvic lymph nodes plus 10 Gy boost on the vaginal vault. Results. The SIB-VMAT technique produced more inhomogeneous plans than 3D CRT CB, but showed significantly better conformity index (CIs) for both PTVs. SIB-VMAT was associated with significant reduction in the irradiated small bowel (SB) volume compared with 3D CRT CB for all dose range > 10 Gy (e.g. V15: 163.5 cm3 vs. 341.3 cm3, p = 0.001 and V40: 43.8 cm3 vs. 85.2 cm3, p = 0.008). With regard to bladder and rectum, SIB-VMAT showed a significant sparing advantage at all dose levels with respect to 3D CRT CB retrieved plans. Moreover, overall OARs Dmean were significantly reduced by the SIB-VMAT (p = 0.001). According to CTCAE v.4.0, acute (within three months) GI toxicities were more frequent in 3D CRT CB versus SIB-VMAT (90.0% vs. 66.7%; p-value 0.028). Conclusions. Compared to data from a historical database of patients administered 3D CRT CB, SIB-VMAT significantly improves the dose conformity and sparing of OARs in HIR-EC patients undergoing postoperative radiotherapy. The improvement in terms of acute toxicity justifies further prospective clinical evaluation.

Effect of different treatment plans on irradiated small-bowel volume in gynecologic patients undergoing whole-pelvic irradiation

To evaluate the effect of different treatment plans for whole-pelvic irradiation on small-bowel volumes (SBVs) in patients with gynecologic malignancies, 40 patients were enrolled in this study. Computed tomography (CT) simulations were performed, and the small bowel of each patient was outlined manually. Treatment plans with equal-weighted (EW) and non-equal-weighted (NEW) (70% in bilateral directions) techniques of four-field and intensity-modulated radiation therapy (IMRT) were performed. The V10–V100 represented the volume (cm3) at different levels of the prescribed doses (10–100%). The V10–V100 was compared among the different treatment planning techniques, and patients who were suitable for IMRT or NEW were identified. IMRT and NEW significantly reduced the V50–V100 and V40–V60 levels compared with EW, respectively. NEW caused a significant reduction in the V30–V60 levels in patients with a BMI ≥26 kg/m2. Patients with IMRT demonstrated lower V70–V100 levels compared with those with NEW. In patients with a BMI ≥26 kg/m2 or an age ≥55 years, lower V20–V50 levels were noted using NEW compared with IMRT. Treatment planning with larger weighting in the bilateral directions in four-field radiotherapy reduces the low-dose SBV in patients with gynecologic malignancies, especially in those with a high BMI or the elderly. IMRT effectively reduces high-dose SBV, especially in patients with a low BMI.

Is Belly Board Still Needed in IMRT for Rectal Cancer? The Change of Bladder Volume Affects the Determination

Prone positioned with belly board is an efficiency method to reduce the irradiated small bowel volume (ISBV) in three-dimensional conformal radiation therapy (3DCRT) for rectal cancer patients. The downside of treating patients in prone position is that compared to supine, the setup is less reproducible between and during fractions. Intensity-modulated radiation therapy (IMRT) technique has previously been demonstrated to be effective in reducing small bowel dose in comparison to 3DCRT for rectal cancer. Whether the belly board still needed in IMRT for rectal cancer is not well answered. The aim of this study was to compare the ISBV between prone positioned with belly board and supine positioned with flat table in IMRT for rectal cancer patients. Twenty patients scheduled to receive postoperative radiation therapy for rectal cancer underwent two series of CT scans, prone positioned with a belly board and supine positioned with a flat board, both combined using a full bladder protocol. On each scan, a 7-field IMRT plan was calculated. Bladder and individual loops of small bowel were contoured on each slice of the planning CT scan. A comparison of volume for small bowel and bladder in different position were performed. Comparison of V15 (volume received dose more than 15 Gy) for small bowel was made between prone and supine position with different device. Compared with supine position, all bladder volumes were decreased in the prone position. The ISBV of eight patients were increased when use belly board. The increase of ISBV was related to the decrease of bladder volume. If the relative change of bladder volume was more than 16%, the ISBV might increase when use belly board. There were no significant differences between patients undergoing IMRT with belly board and those without in terms of V15 for small bowel and ISBV (p = 0.245 and p = 0.944, respectively). If we used 16% as cutoff value to select patients, V15 for small bowel and ISBV of different position could meet marginal statistical significant (p = 0.062 and p = 0.072, respectively). The change of bladder volume in two different positions affected the ISBV. If the change less than 16%, a belly board still attributed to a significant bowel dose reduction when using IMRT and a full bladder protocol.

Comparison of conventional and three-dimensional conformal CT planning techniques for preoperative chemoradiotherapy for locally advanced rectal cancer

We assessed the impact of three-dimensional (3D) conformal planning vs conventional planning of preoperative chemoradiotherapy (CRT) for locally advanced rectal cancer (LARC) on small bowel and bladder sparing and in optimising coverage of tumour target volume. Conformal and conventional plans were created for 50 consecutive patients. The conformal plan delineated a gross tumour volume (GTV), a clinical target volume (CTV) 1 to cover potential subclinical disease spread, a CTV2 to outline the mesorectum and lymph node areas at risk, and a planning target volume (PTV) to cover set-up error and organ movement. The conventional plan was created using digitally reconstructed radiographs (DRRs). Patients were treated with a dose of 45 Gy in 25 fractions with concurrent chemotherapy over 5 weeks. Dose-volume histograms (DVHs) were created and compared for GTV, PTV, small bowel and bladder. The GTV was covered by the conventional plan in all patients. Significant differences were shown for median PTV coverage with conformal planning compared with conventional planning: 99.2% vs 94.2% (range 95.9-100% vs 75.5-100%); p<0.05. The median volume of irradiated small bowel was significantly lower for CT plans at all DVH levels. Median bladder doses did not differ significantly. 3D conformal CT planning is superior to conventional planning in terms of coverage of the tumour volume. It significantly reduces the volume of small bowel irradiated with no decrease in the rate of R0 resection compared with published data, and at the present time should be considered as the standard of care for rectal cancer planning.

Dose de tolérance à l’irradiation des tissus sains : intestin grêle

The small bowel is a hollow organ involved in the transit and absorption of food. In relation to its anatomical location, a significant amount of this organ is exposed in whole or in part to ionizing radiation in external radiotherapy during abdominal or pelvic irradiation either for primary cancers or metastasis. The acute functional changes during external beam radiation are mainly leading to diarrhea, abdominal pain and bloating. The main late side effects of irradiation of the small intestine are chronic diarrhea, malabsorption with steatorrhea, abdominal spasms, intestinal obstruction, bleeding and fistulas. The architecture of the small intestine may be considered as parallel with a significant correlation between the irradiated volume of small bowel and the likelihood of acute toxicity, whatever the dose. The literature analysis recommends to consider the volume of small bowel receiving 15 Gy (threshold of 100 to 200 cm 3) but also 30 and 50 Gy (thresholds of 35 to 300 cm 3, depending on the level of dose considered). Modern techniques of conformal radiotherapy with modulated intensity will probably have beneficial impact on small bowel toxicity.

Reduction of irradiated small bowel volume with Trendelenburg position in gynecologic pelvic radiotherapy

The aim of this study was to assess the effect of Trendelenburg position in comparison to prone position on small bowel volume and treatment dose in gynecologic pelvic external beam radiotherapy using three-dimensional conformal treatment plans. Eight patients with gynecologic cancers, treated with definitive or postoperative pelvic radiotherapy were investigated. Pelvic computerized tomography (CT) scans for treatment planning were performed in prone and 25 degree Trendelenburg positions for each patient. The dose-volume histograms of small bowel within the treatment fields were obtained and compared for both positions. The clinical target volume (CTV) and the planning target volume (PTV) were also defined and evaluated in the subjects. Treatment dose was 5040 cGy to PTV with 180 cGy daily fraction doses in both techniques for all patients. The average irradiated small bowel volume was 726 cc for prone position and 458 cc for the Trendelenburg position. The average irradiated small bowel volume reduction in the Trendelenburg position was 38.0% (95% CI 19.5 +/- 38%) compared with the prone position. The average small bowel percent dose was 25.4% (1280 cGy) for Trendelenburg position and 39.9% (2010 cGy) for prone position. PTV doses were similar in both techniques. The results of this dosimetric study suggest that gynecologic pelvic radiotherapy in the Trendelenburg position decreases the volume of irradiated small bowel compared to prone position and may decrease treatment related small bowel morbidity. Clinical benefit of this position should be evaluated in further clinical studies.

Study of the status of bladder ( full or empty) on the pelvic radiotherapy in posthysterectomy cervical carcinoma

Objective To explore the status of bladder (full or empty)on the planning target volume (PTV)of the -dimensional conformal radiotherapy and the intensity-modulated radiotherapy Methods During 2006-2007, patients with cervical carcinoma underwent hysterectomy with high-risk of recurrence were selected for this study. The following observations and measurements were used for study: To measure different status of bladder(full or empty) and influence on irradiated volume of bladder and small bowel. Results The percentage of irradiated volume of bladder and small bowel were smaller when bladder was full status compared with empty status if other factors balanced. Conclusion The status of bladder should be controlled during radio-therapy and full status seemed better. Key words: Cervical cancer; Radiotherapy; Bladder; 3 DCRT; IMRT

Preoperative Helical Tomotherapy and Megavoltage Computed Tomography for Rectal Cancer: Impact on the Irradiated Volume of Small Bowel

Preoperative (chemo)radiotherapy is considered to be standard of care in locally advanced rectal cancer, but is associated with significant small-bowel toxicity. The aim of this study was to explore to what extent helical tomotherapy and daily megavolt (MV) CT imaging may reduce the irradiated volume of small bowel. A 3D-conformal radiotherapy (3D-CRT) plan with CTV-PTV margins adjusted for laser-skin marks (15, 15, and 10 mm for X, Y, and Z directions, respectively) was compared with helical tomotherapy (IMRT) using the same CTV-PTV margins, and to helical tomotherapy with margins adapted to daily MV-CT imaging (IMRT/IGRT; 8, 11, 7, and 10 mm for X, Y(ant), Y(post) and Z resp.) for 11 consecutive patients. The planning goals were to prescribe 43.7 Gy to 95% of the PTV, while minimizing the volume of small bowel receiving more than 15 Gy (V(15 SB)). The mean PTV was reduced from 1857.4 +/- 256.6 cc to 1462.0 +/- 222.3 cc, when the CTV-PTV margins were adapted from laser-skin marks to daily MV-CT imaging (p < 0.01). The V(15 SB) decreased from 160.7 +/- 102.9 cc to 110.9 +/- 74.0 cc with IMRT and to 81.4 +/- 53.9 cc with IMRT/IGRT (p < 0.01). The normal tissue complication probability (NTCP) for developing Grade 2+ diarrhea was reduced from 39.5% to 26.5% with IMRT and to 18.0% with IMRT/IGRT (p < 0.01). The combination of helical tomotherapy and daily MV-CT imaging significantly decreases the irradiated volume of small bowel and its NTCP.

The Dose–Volume Relationship of Small Bowel Irradiation and Acute Grade 3 Diarrhea During Chemoradiotherapy for Rectal Cancer

Previous work has found a highly significant relationship between the irradiated small-bowel volume and development of Grade 3 small-bowel toxicity in patients with rectal cancer. This study tested the previously defined parameters in a much larger group of patients. A total of 96 consecutive patients receiving pelvic radiation therapy for rectal cancer had treatment planning computed tomographic scans with small-bowel contrast that allowed the small bowel to be outlined with calculation of a small-bowel dose-volume histogram for the initial intended pelvic treatment to 45 Gy. Patients with at least one parameter above the previously determined dose-volume parameters were considered high risk, whereas those with all parameters below these levels were low risk. The grade of diarrhea and presence of liquid stool was determined prospectively. There was a highly significant association with small-bowel dose-volume and Grade 3 diarrhea (p < or = 0.008). The high-risk and low-risk parameters were predictive with Grade 3 diarrhea in 16 of 51 high-risk patients and in 4 of 45 low-risk patients (p = 0.01). Patients who had undergone irradiation preoperatively had a lower incidence of Grade 3 diarrhea than those treated postoperatively (18% vs. 28%; p = 0.31); however, the predictive ability of the high-risk/low-risk parameters was better for preoperatively (p = 0.03) than for postoperatively treated patients (p = 0.15). Revised risk parameters were derived that improved the overall predictive ability (p = 0.004). The highly significant dose-volume relationship and validity of the high-risk and low-risk parameters were confirmed in a large group of patients. The risk parameters provided better modeling for the preoperative patients than for the postoperative patients.

A special device (double-hole belly board) and optimal radiation technique to reduce testicular radiation exposure in radiotherapy of rectal cancer

Purpose Patients with rectal cancer are treated in prone position on a belly board to reduce the volume of irradiated small bowel. With this technique the testes obtain radiation doses, which often result in partial or complete impairment of the spermatogenesis and a dose-dependent decrease of testosterone levels. We developed a double-hole belly board (DHBB) and evaluated its potential to reduce testicular dose. Methods and materials In nine consecutive male patients (3 very low tumor localisations [inguinal RT], 3 low [RT perineum], 3 high [lower border ischial tuberosities]) CT scans were performed on a conventional single-hole belly board (SHBB) and on a DHBB. Dose–volume histograms of the testes were analysed for both belly boards and for different treatment techniques (3-field and 4-field). Results To reduce testicular dose in high tumors, positioning on DHBB was most effective ( V 1.5Gy 20–30% vs. 60% for SHBB, V 4Gy 7% vs. 35%). In low tumors, a 3-field technique reduced high testicular doses ( V 14Gy 0–6% vs. 28–34% for 4-fields). In very low tumors a combination of DHBB and 3-fields led to a decrease of high dose exposure ( V 33Gy 0% vs. 24–78%). Conclusion In male patients with rectal cancer the use of a DHBB and a 3-field technique is recommended to reduce testicular radiation exposure.

SU‐FF‐T‐452: Whole Pelvic IMRT Treatment for Post Operative Gynecological Malignancies, Sheba Experience

Background and Purpose: To evaluate the use of IMRT treatment for post operative gynecological malignancies for better organ at risk sparing to reduce treatment toxicity that will allow dose escalation. Creating guidelines for that treatment. Recognize treatment limits and problems in ITPS and QA for very large IMRT volumes and fields. Patients and Methods: five patients were selected with endometrial cancer treated postoperatively. Bladder, rectal wall, small and large bowel were delineated as organs at risk. A seven field IMRT plan prescription dose 50.4 Gy and compared with conformal 4 fields plan (DVH). QA performed with film dosimetry and ion chambers. Results: significant improvements were observed for irradiated volume of rectal wall and bladder. With IMRT the average irradiated volume of small and large bowel was reduced dramatically and the impact of IMRT was large for postoperative patients, in one patient treatment volume was very large (24833cc of normal tissue) the ITPS could calculate only if the calculation grid was 10mm spaced, that lead to a disagreement in QA and patient was treated 3D conformal. Conclusions: IMRT significantly reduced the absolute volume of rectal wall, bladder and bowel irradiated at the prescribed dose level in post operative gynecologic patients. Due to large treatment volumes we have to be aware of disagreements between calculations and dosimetry.