Belly Board Research Articles

Dose-volume parameters comparison of organs at risk between the prone and supine positions in pelvic tumors using 3D-CRT.

Cancer is a major public health problem worldwide, the leading cause of death in developed countries. Radiotherapy is an important treatment for many malignancies. The main purpose of this study was to compare the two techniques of supine and prone in prostate and rectal cancers using DVH extraction parameters. Clinical and dosimetry data of 41 rectal and prostate cancer patients were evaluated in both the supine and prone positions with belly board. Administered dose was daily 180 cGy. The four box fields in the first phase and two lateral fields in the second phase with 18 MV photon fields were used. Each patient underwent CT scan, at both the positions using a contrast agent with a full bladder. By using IBM SPSS software v23, all the data were described. The normal distribution of the data was performed using the KS sample statistical test. For data analysis, paired t test was used in the normal data and the Wilcoxon test was used in the non-normal data. In patients with rectal cancer, there is no change in the received minimum dose by organs at risk. A significant decrease in received maximum dose, except for the prostate organ, could be due to the spatial proximity of the two organs to each other. Also, the received average dose in the small intestine was significantly reduced (P = 0.005). But in other organs, the dose reduction was not significant. In patients with prostate cancer, there is no change in the received minimum dose by OARs, except for the bladder organ (P = 0.003). Except the bladder organs (P = 0.011), there is no significant decrease in the received average dose by OARs. The maximum dose of the OARs is significantly reduced, except for the colon where there was not much overlap in the PTV, in addition to receiving the dose in the range. There was no significant relationship between CI in the rectal field and UI in the prostate field (P > 0.05), but there was a significant relationship between CI in the prostate field and UI in the rectal field with change in patient position. In the prone position, in both patients' groups, the OARs receive an optimal and better dose than the supine position, especially the small intestine organ in the rectal field and the bladder and rectum organs in the prostate field. However, it seems that this change in the position of rectal cancer patients is ineffective in reducing the dose of prostate and needs further investigation.

Factors Affecting Isocenter Displacement and Planning Target Volume Margin for Patients With Rectal Cancer Receiving Radiation Therapy

PurposeSetup errors are inherent in the process of daily radiation therapy (RT) delivery. Pelvic RT for rectal cancer is one of the body sites associated with the largest shift among other body sites. This study aimed to evaluate interfraction random and systematic errors and hence propose the optimum planning target volume (PTV) in patients with rectal cancer. Methods and MaterialsTranslational and angular isocenter displacements were retrospectively collected for 189 patients. Random and systematic errors were determined, and then the PTV margin was computed. Effect of positioning, body mass index (BMI), and type of immobilization were studied. Portal images before and after online correction were used to define PTV for no-daily image-guided radiotherapy (IGRT) and daily IGRT respectively. ResultsBefore the online correction, the systematic errors were 2.5, 2.8, and 3.0 mm for superior-inferior (SI), right-left (RL), and anterior-posterior (AP) directions, respectively, compared with 2.1, 1.7, and 1.8 mm after online correction. The random errors were 6.2, 7.4, and 8.2 mm in SI, RL, and AP, respectively, before online correction, compared with 4, 4.2, and 4.5 mm after online correction. The recommended PTV margin was 0.7 and 1.0 cm for daily IGRT and no-daily IGRT, respectively. The prone position and BMI >30 kg/m2 warrant higher margins in no-daily IGRT cases, 1.2 and 1.4 cm, respectively. ConclusionsThe prone position, BMI >30 kg/m2, and belly board device are associated with larger daily setup errors warranting higher PTV margins for no-daily IGRT; however, that can be avoided by using daily IGRT.

Effect of Abdominal Circumference on the Irradiated Bowel Volume in Pelvic Radiotherapy for Rectal Cancer Patients: Implications for the Radiotherapy-Related Intestinal Toxicity.

BackgroundTo effectively reduce the irradiated bowel volume so as to reduce intestinal toxicity from pelvic radiotherapy, treatment in the prone position with a full bladder on a belly board is widely used in pelvic radiotherapy for rectal cancer patients. However, the clinical applicable condition of this radiotherapy mode is unclear. The aim of this study was to preliminarily identify patients who were not eligible for this radiotherapy mode by analyzing the effect of abdominal circumference on the irradiated bowel volume.MethodsFrom May 2014 to September 2019, 179 patients with locally advanced rectal cancer were retrospectively reviewed in our center. All patients received pelvic radiotherapy. Weight, height, AC, and body mass index (BMI) were used as the research objects, and the irradiated bowel volume at different dose levels (V10, V20, V30, V40, V50) was selected as the outcome variable. Multivariate linear regression and sensitivity analyses were used to evaluate the correlation between AC and irradiated bowel volume. Generalized additive model (GAM) and piecewise linear regression were used to further analyze the possible nonlinear relationship between them.ResultsAmong the four body size indicators, AC showed a negative linear correlation with the irradiated bowel volume, which was the most significant and stable. In adjuvant radiotherapy patients, we further discovered the threshold effect between AC and irradiated bowel volume, as AC was greater than the inflection point (about 71 cm), irradiated bowel volume decreased rapidly with the increase in AC. t-test showed that in patients with small AC (<71 cm), the irradiated bowel volume was significantly higher than that of patients with medium-large AC (≥71 cm). Especially in patients with adjuvant radiotherapy, the mean irradiated bowel volume of patients with small AC was the highest in this study. Compared with adjuvant radiotherapy, in neoadjuvant radiotherapy, the mean difference of irradiated bowel volume between patients with medium-large AC and those with small AC was larger.ConclusionAC is an independent factor influencing the irradiated bowel volume and has a strong negative linear correlation with it. Patients with small AC may not benefit from this common mode of radiotherapy, especially in adjuvant radiotherapy.

Active small bowel sparing in intracavitary brachytherapy for cervical cancer.

To propose and evaluate an active method for sparing the small bowel in the treatment field of cervical cancer brachytherapy by prone position procedure. The prone position procedure consists of five steps: making bladder empty, prone-positioning a patient on belly board, making the small bowel move to abdomen, filling the bladder with Foley catheter and finally turning the patient into the supine position. The proposed method was applied for the treatment of seven cervical cancer patients. Its effectiveness was evaluated and a correlation between the patient characteristics and the volumetric dose reduction of small bowel was also investigated. Brachytherapy treatment plans were built before and after the proposed method, and their dose-volume histograms were compared for targets and organs-at-risk. In this comparison, all plans were normalized to satisfy the same D90% for high-risk clinical target volume. For the enrolled patients, the average dose of small bowel was significantly reduced from 75.2±4.9Gy before to 60.2±4.0Gy after the prone position procedure, while minor dosimetric changes were observed in rectum, sigmoid and bladder. The linear correlation to body mass index, thickness and width of abdominopelvic cavity and bladder volume were 76.2, 69.7, 28.8 and-36.3%, respectively. The application of prone position procedure could effectively lower the volumetric dose of the small bowel. The dose reduction in the small bowel had a strong correlation with the patient's obesity and abdominal thickness. This means the patients for whom the proposed method would be beneficial can be judiciously selected for safe brachytherapy.

PO-1562 Analysis of interfractional displacements for rectal cancer patients positioned on Belly Board

PO-1562 Analysis of interfractional displacements for rectal cancer patients positioned on Belly Board

Mesorectal shape variation in rectal cancer radiotherapy in prone position using a belly board.

In rectal cancer patients, radiotherapy in prone position using a belly board can reduce the dose to organs at risk. For this patient group we investigated inter-fraction shape variation of the mesorectal part of the clinical target volume (CTV) and determined planning target volume (PTV) margins. Patients with rectal cancer receiving neoadjuvant (chemo)radiotherapy were eligible. For each patient a planning computed tomography (pCT) and five cone-beam CT (CBCT) scans were acquired in prone position using a belly board. The mesorectal CTV was delineated on all scans. Mesorectal shape variation was quantified relative to the pCT. PTV margins were derived locally and averaged for separate subregions of the mesorectal CTV. For each patient a total PTV was constructed using our clinical margins for mesorectal and lymph node CTVs. An artificial dose distribution conforming to this PTV was used to calculate the coverage for the mesorectal CTV using the CBCT delineations. In 19 rectal cancer patients the derived PTV margins were smallest in the upper-lateral region (6mm) and largest in the upper-anterior region (16mm). PTV margins for the upper-anterior region were larger for female patients (19mm) compared to male patients (14mm). Clinical margins for the total PTV were sufficient for a coverage of at least 97% of the mesorectal CTV for all patients. Mesorectal shape variation is heterogeneous and largest in the upper-anterior region, in rectal cancer patients irradiated in prone position and using a belly board.

Carbon Fiber Belly Board Quality Assurance in Radiotherapy

Carbon Fiber Belly Board Quality Assurance in Radiotherapy

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.

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.

Is AIO belly board device advantageous in all rectal cancer patients

Purpose. To compare the prone position on a flat table vs an “All in one” belly board device (AIO BBD) in rectal cancer patients (RCPs). Material and methods. Fifteen RCPs scheduled for irradiation were scanned in the two evaluated positions. After tomography, they completed a questionnaire concerning positioning. The dose-volume histograms (DVHs) for the small bowel and bladder were compared for both immobilization methods and setup accuracy was analyzed in electronic portal imaging devices (EPIDs) and X-ray volume imaging (XVI) procedures. Results. AIO BBD was accepted by the majority of RCPs and provided better DVHs for the small bowel than the prone position on a flat table. The setup reproducibility was within tolerance limit for patients with BMI ≤ 29 kg/m2. Patients with obesity regarded AIO BBD as uncomfortable and they presented mean setup shifts out of the tolerance limit in the Y axis — 5.9 mm. Conclusions. The AIO BBD should be recommended for RCPs, especially for those with BMI ≤ 29 kg/m2.

Volumetric and dosimetric comparison of organs at risk between the prone and supine positions in postoperative radiotherapy for prostate cancer

BackgroundThe aim of this study was to evaluate the effects of patient positioning on the volume of organs at risk (OARs) in or near the planning target volume (PTV) and the dose distribution in adjuvant or salvage radiotherapy for prostate cancer after prostatectomy.MethodsSeventeen patients who received intensity-modulated radiation therapy (66 Gy in 33 fractions) as adjuvant or salvage therapy after prostatectomy were evaluated. All patients underwent CT scans in both the prone (on a belly board) and supine positions. The target volumes and OARs were delineated on each CT series. The planning target volume (PTV) was extended in every direction to generate the PTV + 0.5 cm, PTV + 1 cm, PTV + 2 cm, PTV + 3 cm, and PTV + 4 cm values. The volumes of the OARs overlapping with the PTV and the extended target volumes in the prone and supine position were compared using the Wilcoxon signed-rank test. Dose-volume histogram (DVH) parameters in the prone and supine position were compared using the paired t-test.ResultsThe mean overlapping volumes of the small intestine for each of the PTV values were as follows (prone position vs. supine position [mean ± SD]): PTV, 1.5 ± 5.5 cm3 vs. 7.9 ± 15.7 cm3 (P = 0.028); PTV + 0.5 cm, 2.6 ± 8.9 cm3 vs. 12.1 ± 22.6 cm3 (P = 0.028); PTV + 1 cm, 3.5 ± 11.4 cm3 vs. 17.1 ± 29.8 cm3 (P = 0.028); PTV + 2 cm, 5.6 ± 14.5 cm3 vs. 26.8 ± 46.9 cm3 (P = 0.028); and PTV + 3 cm, 9.0 ± 17.4 cm3 vs. 36.5 ± 63.2 cm3 (P = 0.019), respectively. Some of the overlapping volumes of the rectum and bladder were significantly smaller in the prone position. On the other hand, when the target volume was extended by ≥2 cm, the overlapping volumes of the femurs were significantly larger in the prone position. V15 of the rectum and mean dose and V65 of the bladder were significantly lower in the prone position.ConclusionsThis study indicated that the volumes of the small intestine, rectum, and bladder in or near the PTV decreased when the patient was placed in the prone position on a belly board in postoperative radiotherapy for prostate cancer. The dose distribution seemed superior in the prone position to the supine position.

Effect of different patient positions on target dose coverage in rectal cancer IMRT

Objective To compare the effect between the supine and prone patient positions upon target dose coverage during intensity-modulated radiotherapy (IMRT) for rectal cancer, aiming to provide clinical reference for the selection of position for rectal cancer patients. Methods Twenty-four patients diagnosed with rectal cancer receiving postoperative adjuvant radiotherapy were selected and divided into the supine (n=12) and prone position groups (n=12). Before and during the IMRT (1-4 weeks), all patients received CT scans, which were defined as: Plan, 1W, 2W, 3W and 4W, respectively. The organs at risk were delineated based on CT scan images. Plan, 1W, 2W, 3W and 4W CT scan images were fused. The CTV and PTV from Plan CT scan were copied to the 1-4W CT scan images, and the therapeutic plans from Plan CT scan were copied as well. The target dose coverage was assessed and the failure rate of target dose coverage was calculated. The couch-position data for each patient during each cycle of IMRT were recorded by using the MOSAIQ network and the overall deviation (S) of couch position was calculated. Results The failure rates of CTV and PTV target dose coverage in the prone position group were higher than those in the supine position group (18.60% VS 0%, 69.76% VS 53.65%). The S value was significantly correlated with the target dose coverage (r=-0.683, P=0.000). The S value in the prone position group was (1.23±0.76) cm, significantly greater than (0.28±0.18) cm in the supine position (P=0.001), and the most significant deviation was noted in the y (head and foot) and z (frontal and dorsal) directions (P=0.003 and 0.003). Compared with the supine group, the V5 and V10 of the small intestine were significantly less (P=0.003 and 0.004) and the chronic toxicity (NTCPC) was considerably reduced (P=0.041) in the prone position group. Conclusions A better target dose coverage can be maintained during IMRT with a supine position during rectal cancer IMRT, whereas the positioning repeatability is worsened with a prone position due to use of the belly board, thereby affecting the target dose coverage. Although the prone position combined with belly board can reduce the tolerated dosage of the small intestine, effective measures should be taken to guarantee the patient positioning repeatability. Key words: Rectal neoplasms/intensity-modulated radiotherapy; Radiotherapy dosage; Belly board

In vivo Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device.

Purpose:We recently developed a novel, open-source in vivo dosimetry that uses the electronic portal imaging device to detect dose delivery discrepancies. We applied our method on patients with rectal cancer treated on a belly board device.Methods: In vivo dosimetry was performed on 10 patients with rectal cancer treated prone on the belly board with a 4-field box arrangement. Portal images were acquired approximately once per week from each treatment beam. Our dosimetry method used these images along with the planning CT to reconstruct patient planar dose at isocenter depth.Results:Our algorithm proved sensitive to dose discrepancies and detected discordances in 7 patients. The majority of these were due to soft tissue differences between planning and treatment, present despite matching to bony anatomy. As a result of this work, quality assurance procedures have been implemented for our immobilization devices.Conclusion: In vivo dosimetry is a powerful quality assurance tool that can detect delivery discrepancies, including changes in patient setup and position. The added information on actual dose delivery may be used to evaluate equipment and process quality and to guide for adaptive radiotherapy.

EP-1814: Is AIO belly board device advantageous in all irradiated rectal cancer patients?

EP-1814: Is AIO belly board device advantageous in all irradiated rectal cancer patients?

The impact of patient positioning and use of belly board on small bowel toxicity in patients receiving pelvic radiotherapy for gynecological malignancies.

To determine the efficacy of belly board device in patients receiving postoperative radiation for gynecological malignancies in terms of setup error and acute small bowel toxicity. Patients requiring postoperative radiation for gynecological malignancies were prospectively randomized to either treatment with supine position (supine arm) or prone position using belly board (prone arm). Each patient underwent computed tomography simulation in the assigned treatment position, and a three-dimensional conformal radiation was planned. Weekly two to three treatment sessions were verified using portal imaging and setup errors were noted. All patients were reviewed weekly to assess for symptoms and toxicity using a structured format. The systematic and random errors were calculated along the three axes. Twenty-four patients were randomized and 22 patients were available for the final analysis. The systematic error in supine arm versus prone arm was 3.9 versus 3.5 mm, 2.1 versus 4.8 mm and 3.1 versus 3.1 mm along lateral, antero-posterior (AP) and cranio-caudal (CC) direction. The random error in supine arm versus prone arm was 5 versus 3.9 mm, 2.9 mm versus 4.4 mm and 4.3 versus 3.4 mm along lateral, AP and CC direction. The calculated planning target volume margin for supine arm was 1.3, 0.7, and 1.0 cm and margin for prone arm was 1.1, 1.5, and 1.0 cm along lateral, AP, and CC direction, respectively. One patient in supine arm developed Grade 3 toxicity. The systematic error and random error is more along AP direction for prone position. The acute small bowel toxicity was less using belly board.

Impact of prone versus supine positioning on small bowel dose with pelvic intensity modulated radiation therapy

PurposeTo report the results of a prospective study that compares small bowel doses during prone and supine pelvic intensity modulated radiation therapy. Methods and materialsTen patients receiving pelvic radiation therapy each had 2 intensity modulated radiation therapy plans generated: supine and prone on a belly board (PBB). Computed tomography on rails was performed weekly throughout treatment in both positions (10 scans per patient). After image fusion, doses to small bowel (SB) loops and clinical target volume were calculated for each scan. Changes between the planned and received doses were analyzed and compared between positions. The impact of bladder filling on SB dose was also assessed. ResultsProne treatment was associated with significantly lower volumes of SB receiving ≥20 Gy. On average, prone on a belly board positioning reduced the volume of SB receiving a given dose of radiation by 28% compared with supine positioning. Target coverage throughout the treatment course was similar in both positions with an average minimum clinical target volume dose of 88% of the prescribed prone dose and 89% of the supine (P = .54). For supine treatment, SB dose was inversely correlated with bladder filling (P = .001-.013; P > .15 for prone). For 96% of treatments, the volume of SB that received a given dose deviated >10% from the plan. The deviation between the planned and delivered doses to SB did not differ significantly between the positions. ConclusionsProne positioning on a belly board during pelvic IMRT consistently reduces the volume of SB that receives a broad range of radiation doses. Prone IMRT is associated with interfraction dose variation to SB that is similar to that of supine positioning. These findings suggest that prone positioning with daily image guided radiation therapy is an effective method for maximizing SB sparing during pelvic IMRT.

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.

Reduced dose to small bowel with the prone position and a belly board versus the supine position in neoadjuvant 3D conformal radiotherapy for rectal adenocarcinoma.

IntroductionNo consensus exists regarding the optimal treatment setup for neoadjuvant radiotherapy of rectal cancer using a 3D conformal (3D CRT) technique. Positioning the patient prone with a belly board aims to reduce the amount of small bowel irradiated.MethodsTwenty‐five patients with locally advanced rectal cancer underwent computed tomography (CT) planning for neoadjuvant chemoradiotherapy. Patients were simulated prone with a belly board and then in the supine position. Questionnaires rating the comfort of each position were completed. 3D CRT plans were generated for both positions to a prescribed dose of 50.4 Gy in 1.8 Gy daily fractions. Dose–volume parameters in 5 Gy increments for small bowel, large bowel and bladder wall were compared.ResultsSmall bowel V5 Gy, V10 Gy, V15 Gy and V20 Gy values were significantly higher in the supine position (398, 366, 245, 151 cm3 for supine vs. 243, 213, 161, 122 cm3 for prone respectively; P < 0.001, <0.001, <0.001 and 0.025). Large bowel V5 Gy, V10 Gy and V15 Gy values were significantly higher in the supine position (266, 209, 147 cm3 supine, 175, 139, 108 cm3 prone respectively; P = 0.001, <0.001, 0.003). There was a significant difference in comfort scores favouring the supine position (P = 0.015).ConclusionA significant increase in small and large bowel dose was seen in the supine plans. Treatment in the prone position with a belly board may reduce toxicity when using a 3D CRT technique. Whilst both setup positions were tolerable the supine was more comfortable.

Role of belly board device in the age of intensity modulated radiotherapy for pelvic irradiation

Small bowel dose often represents a limiting factor for radiation treatment of pelvic malignancies. To reduce small bowel toxicity, a belly board device (BBD) with a prone position is often recommended. Intensity modulated radiotherapy (IMRT) could reduce dose to small bowel based on the desired dose-volume constraints. We investigated the efficacy of BBD in conjunction with IMRT. A total of 11 consecutive patients with the diagnosis of rectal cancer, who were candidates for definitive therapy, were selected. Patients were immobilized with BBD in prone position for simulation and treatment. Supine position computed tomography (CT) data were either acquired at the same time or during a diagnostic scan, and if existed was used. Target volumes (TV) as well as organs at risk (OAR) were delineated in both studies. Three-dimensional conformal treatment (3DCRT) and IMRT plans were made for both scans. Thus for each patient, 4 plans were generated. Statistical analysis was conducted for maximum, minimum, and mean dose to each structure. When comparing the normalized mean Gross TV dose for the different plans, there was no statistical difference found between the planning types. There was a significant difference in small bowel sparing when using prone position on BBD comparing 3DCRT and IMRT plans, favoring IMRT with a 29.6% reduction in dose (p = 0.007). There was also a statistically significant difference in small bowel sparing when comparing supine position IMRT to prone-BBD IMRT favoring prone-BBD IMRT with a reduction of 30.3% (p = 0.002). For rectal cancer when small bowel could be a limiting factor, prone position using BBD along with IMRT provides the best sparing. We conclude that whenever a dose escalation in rectal cancer is desired where small bowel could be limiting factor, IMRT in conjunction with BBD should be selected.