|Year : 2017 | Volume
| Issue : 3 | Page : 519-523
The impact of patient positioning and use of belly board on small bowel toxicity in patients receiving pelvic radiotherapy for gynecological malignancies
Milan Anjanappa1, Rajeev Kavalakara Raghavan1, Francis V James1, Aswin Kumar1, Susan Mathews1, Sarin Bhaskaran2, Shaiju Vasudevannair Sreedevi2, Puthuveetil Govindan Jayaprakash1
1 Department of Radiation Oncology, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
2 Department of Radiation Physics, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
|Date of Web Publication||31-Aug-2017|
Department of Radiation Oncology, Regional Cancer Centre, Thiruvananthapuram, Kerala
Source of Support: None, Conflict of Interest: None
Aim: 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.
Materials and Methods: 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.
Results: 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.
Conclusion: The systematic error and random error is more along AP direction for prone position. The acute small bowel toxicity was less using belly board.
Keywords: Belly board, setup error, small bowel toxicity
|How to cite this article:|
Anjanappa M, Raghavan RK, James FV, Kumar A, Mathews S, Bhaskaran S, Sreedevi SV, Jayaprakash PG. The impact of patient positioning and use of belly board on small bowel toxicity in patients receiving pelvic radiotherapy for gynecological malignancies. J Can Res Ther 2017;13:519-23
|How to cite this URL:|
Anjanappa M, Raghavan RK, James FV, Kumar A, Mathews S, Bhaskaran S, Sreedevi SV, Jayaprakash PG. The impact of patient positioning and use of belly board on small bowel toxicity in patients receiving pelvic radiotherapy for gynecological malignancies. J Can Res Ther [serial online] 2017 [cited 2020 May 27];13:519-23. Available from: http://www.cancerjournal.net/text.asp?2017/13/3/519/179519
| > Introduction|| |
Postoperative whole pelvic radiation is used as an adjuvant treatment in uterine (uterine corpus and cervix) malignancies to improve the clinical outcomes in selected patients.,, The most commonly used four-field box technique irradiates a significant volume of small bowel, leading to acute and chronic enteritis., These complications seem to correlate well with the irradiated volume and the total radiation dose delivered.,
Several methods have been described for reducing small bowel volume within the radiation fields, and belly board is one among them.,, Many investigators have evaluated the volume of small bowel irradiated in prone position using belly board and supine position. The volume of small bowel receiving radiation is significantly low when patient is positioned prone using belly board.,,,, Although this is a simple and noninvasive option for reducing small bowel toxicity, it has its own pitfalls. Treating the patient in a reproducible and comfortable position is of utmost importance. Certain patient factors like slow healing surgical scar, obesity, and osteoarthritis influence the patient positioning on belly board. Setup variations using belly board has not been studied widely. In this study, we aim to compare the treatment setup variation and assess acute small bowel toxicity between prone position using belly board and supine positions.
| > Materials and Methods|| |
Gynecological cancer (uterine corpus and cervix) patients requiring postoperative adjuvant radiation to pelvis were considered for the study. A total of 24 patients were recruited from May 2013 to July 2014 from our institute. Randomization was carried out using a 1:1 computer-generated random table and patients were allocated either to supine or prone arm.
Simulation and treatment planning
In arm I, patients were put in supine position on the couch with both hands on chest. A knee support and a foot rest were used. In arm II, a commercially available belly board device (CIVCO carbon fiber belly board) was used [Figure 1]. The pubic lock system in the belly board was used to align the patient for proper displacement of small bowel into the aperture. For all patients a contrast enhanced computed tomography (CT) scan was taken with 3 mm slices from L1 vertebra to mid-thigh level. The anterior and two lateral laser position on the skin was tattooed. In the prone arm, the vertical laser position on belly board scale was noted for reference and alignment during treatment. After target volume and organ at risk delineation, a four field conformal radiation plan was generated. The small bowel was contoured both as bowel bag and individual bowel loops. A planning target volume (PTV) margin of 1 cm around the clinical target volume was used for all patients as per institution protocol.
Treatment setup and verification
After initial setup using skin tattoo and room lasers, an antero-posterior (AP) and lateral radiograph was taken using on board electronic portal imaging device. The orthogonal radiographs were taken using a kilo voltage (kV) X-ray source. Then the kV images were matched with the digitally reconstructed radiograph using bony landmarks. The differences in lateral or left-right (LR), AP and cranio-caudal (CC) directions were noted and an online correction protocol was used if there was any shift, following which patient was treated. With weekly 2–3, a total of 9–13 treatment sessions were verified per patient.
Setup error is calculated as shift in the isocentric position when an image is compared with its corresponding reference. Differences between the simulation and treatment positions were noted in LR, AP and CC directions. The setup variation is calculated as follows.
For each patient, LR1, LR2, LR3 … LR9 are the variation along lateral direction, AP1, AP2, AP3 … AP9 are the variation along AP direction and CC1, CC2, CC3 … CC9 are the variation along CC direction, which were obtained from consecutive portal images. The arithmetic mean along each direction gives the mean setup error for that particular patient. For all patients the mean setup error is calculated. At the same time, standard deviation of LR1, LR2, LR3 … LR9 (variation along lateral direction), AP1, AP2, AP3 … AP9 (variation along AP direction) and CC1, CC2, CC3 … CC9 (variation along CC direction) are calculated using “nonbiased” or “n − 1” method. With the help of these mean and standard deviation values the systematic and random errors for the population is calculated. The individual mean setup error and standard deviation represent systematic error and random error respectively for that particular individual.
Systematic error for the population (Σ) is calculated by taking the standard deviation of the average value of individual mean setup error along LR, AP and CC directions respectively for supine and prone position. Random error for the population (σ) is calculated by taking the mean of individual standard deviations along LR, AP and CC directions respectively for supine and prone position. The PTV margin for AP direction, lateral direction and CC direction for both supine and prone arm is determined using the van Herk formula.
PTV margin = 2.5 Σ +0.7 σ.
All patients were reviewed weekly to assess treatment toxicity. Patient symptoms were assessed using a structured format and a complete blood count was done. Toxicity scoring was done using CTCAE version 4.0 (CIVCO Bellyboard) acute toxicity scoring system. Treatment interruption of a maximum of 1 week was permitted if patients developed Grades 3–4 small bowel toxicity.
| > Observations and Results|| |
Out of the 24 patients randomized, 11 patients were in the supine, and 13 patients were in the prone arm. Two patients in the prone arm were excluded (one patient in the prone arm did not report for radiation and another patient developed vaginal introitus skip lesions during radiation, requiring re-planning and treatment) and 22 patients were included in the final analysis. All patients had uterine corpus malignancy. The patient characteristics are detailed in [Table 1].
An average of 11 images was obtained per patient, with a minimum of 9 and a maximum of 13. A total of 122 and 123 treatment sessions were imaged and analyzed in supine and prone arm respectively. The [Table 2] and [Table 3] shows the mean setup error and standard deviation of individual patient.
|Table 2: Individual patient mean setup errors and standard deviation in supine arm|
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|Table 3: Individual patient mean setup errors and standard deviation in prone arm|
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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 LR, AP and CC direction. The systematic error was more for prone position compared to supine position in the AP 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 LR, AP and CC direction. The random error was more for prone position compared to supine position in the AP direction. The calculated PTV margin is using van Herk formula is shown below in [Table 4].
The volume of small bowel irradiated was considerably less in prone arm compared to supine arm [Table 5]. The mean volume of bowel bag in prone arm was 569.3 cc (range 232.4–1013.6 cc) and in supine arm was 1054.41 cc (range 561.8–1495.8 cc) showing 46% (485.11 cc) reduction in prone arm. The mean small bowel loop volume in prone arm was 131.51 cc
|Table 5: Small bowel volume - delineated as bowel bag and individual loop|
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(16–241.2 cc) and in supine arm it was 433.41 cc (197.4–739.4 cc) showing 69.65% (301.9 cc) reduction in prone arm.
All patients completed the treatment without any interruptions. There was no loss of body weight and hematologic toxicity noted during treatment. Only one patient in supine arm developed Grade 3 bowel toxicity. There was no Grade 4 toxicity. The majority of patients in prone arm had only Grade 1 toxicity at the end of the treatment [Figure 2].
|Figure 2: Graph showing number of patients and small bowel toxicity grades|
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| > Discussion|| |
One among the many challenges in delivering therapeutic radiation is to reduce normal tissue toxicity. The modern day radiation techniques aim to achieve this goal without comprising on treatment outcome. This is very important as far as postoperative pelvic radiation is concerned. The small bowel is a key dose limiting structures in pelvic radiation. Its toxicity can have an impact on early and late quality of life (QOL). Belly board is a simple device used for reducing the small bowel volume within the radiation fields and thus the toxicity. Various clinical studies have shown the efficacy of belly board in reducing the volume of small bowel irradiated, but the reproducibility has not been studied extensively with this device.
In the present study, we observed an increase in systematic error in prone arm compared to supine in the AP direction or vertical couch movement (2.1 mm vs. 4.8 mm). The systematic error in the other two directions did not show significant difference. Similarly, the random error in prone arm was more in AP direction (2.9 mm vs. 4.4 mm). The increase in error in AP direction could be due to daily variation in positioning of patient on the belly board. The random errors in the other two directions were more for supine arm (5 mm vs. 3.9 mm for LR direction and 4.3 mm vs. 3.4 mm for CC direction). This increase in error in supine arm could be due to greater degree in freedom of movement compared to prone position. Finally, the derived PTV margin was more in AP direction for prone position compared to supine position.
At present, we do not have robust data on the evaluation of setup errors using belly board. Italia et al. showed that the mean setup error in superior-inferior direction was more in prone position using belly board compared to supine (23% vs. 11% for > 5 mm). The reported random error was also more in superior inferior direction. In our study, the error in superior-inferior direction was less in prone compared to supine arm. This was probably due to utilization of vertical laser position on the belly board scale to align the patient. However, many other studies demonstrated a similar increase in errors in AP direction. Martin et al. reported a 68% requirement in repositioning maneuvers when using belly board. It mostly involved in vertical movement of couch (65%) and rotation (35%).
Similarly, Allal et al. reported a larger patient setup variation using belly board for treating rectal cancer patients. In this study, nine patients were treated with belly board and 14 without belly board in prone position. The mean displacements in lateral, CC and anterior-posterior direction were 3.2/4.2/4.5 mm with belly board and 1.5/1.55/1.8 mm without belly board. A large difference in vertical couch movement or AP direction was noted. Another study by Siddiqui et al. demonstrated that the systematic error was more in prone position using belly board compared to supine whereas random error was more in supine position (5.5/4.6/6.2 vs. 3.7/4.4/5.4 mm for x/y/z). The large systematic error could be due to couch sag and random error due to increased skin mobility in supine patients as explained by the author.
An online correction protocol was used in this study to reduce the setup errors. In the present study, an average of 11 (9–13) of 23 treatment sessions per patient were imaged. A good imaging and correction protocol used during treatment have shown to reduce the setup errors. Cranmer-Sargison et al. has shown that with kV image matching the accuracy can be improved to ± 2.0 mm. Siddiqui et al. has shown that increased frequency of imaging during treatment helps in reducing the errors. Another important aspect in patient setup is the training of radiotherapy technicians (RTTs). A proper instruction and training of RTTs has shown to decrease such errors.
There was significant reduction of acute small bowel toxicity in the prone arm using belly board. None of the patients experienced Grade 3 or 4 toxicities. The development of acute toxicity was also delayed in the prone arm compared to supine arm. The majority of the patients developed Grade 1 or 2 toxicities during the 4th week in prone arm but it was during the 3rd week for patients in supine arm. This decrease in toxicity is due to large reduction in small bowel volume radiated. Martin et al. in their study reported that majority of patients had Grade 1 or Grade 2 toxicity in prone position using belly board. Grade 3 toxicity was seen in 6.9% (two patients, n = 29) and no reported Grade 4 toxicity.
Reduction in small bowel volume irradiation also has implication on long term treatment related morbidity and QOL. Late complications were analyzed in few studies. Gallagher et al. with a median follow-up of 16 months and Letschert et al. with a minimal follow-up of 2 years have confirmed the reduction in late toxicity with reduction in irradiated small bowel volume.,
There are a few limitations in this study. With respect to setup error, we did not evaluate the rotational errors and any residual setup error after correction. By utilizing cone beam CT imaging, better characterization of the target volumes in relation to the setup could have been obtained. We have not evaluated the bowel volumes in supine and prone position for the same patient. By having such a comparison, a true reduction in small bowel volume for a particular patient would be available. The QOL was not evaluated in particular. Although there is less acute toxicity in prone arm, more number of patients is needed to make a conclusion with a statistical significance. Long-term follow-up would be of more use in understanding the late toxicities and the impact of reducing small bowel volume.
| > Conclusion|| |
Prone position using belly board is an effective method in reducing the acute small bowel toxicities in patients undergoing pelvic radiotherapy. However, this method has comparatively more setup errors, especially in the AP direction. This requires careful planning and execution of treatment sessions with a good imaging protocol to reduce the errors.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]