Intensity-modulated radiotherapy with a belly board for rectal cancer

Radiation Therapy for Rectal Cancer: An ASTRO Clinical Practice Guideline Focused Update

PURPOSE

With the results of several recently published clinical trials, this guideline focused update provides evidence-based recommendations for the indications and dose-fractionation regimens for neoadjuvant radiation therapy (RT), optimal sequencing of RT and systemic therapy in the context of total neoadjuvant therapy (TNT), and considerations for selective omission of RT and surgery for rectal cancer.

METHODS

The American Society for Radiation Oncology convened a multidisciplinary task force to update 3 key questions that focused on the role of RT for patients with operable rectal cancer. The key questions addressed (1) indications for neoadjuvant RT, (2) selection of neoadjuvant regimens, and (3) indications for consideration of a nonoperative management (NOM) or local excision approach after definitive/preoperative chemoradiation. Recommendations were based on a systematic literature review and created using a predefined consensus-building methodology and system for quality of evidence grading and strength of recommendation.

RESULTS

For patients with stage II-III rectal cancer, neoadjuvant RT was strongly recommended; however, among patients deemed at lower risk of locoregional recurrence, consideration of omission of neoadjuvant RT was conditionally recommended in favor of neoadjuvant chemotherapy with a favorable treatment response or upfront surgery. For patients with T3-T4 and node-positive rectal cancer undergoing neoadjuvant RT, a TNT approach was strongly recommended. Among patients with higher risk of locoregional recurrence, TNT with chemotherapy before or after long-course chemoradiation was strongly recommended, whereas TNT with short-course RT followed by chemotherapy was conditionally recommended. For patients with rectal cancer for whom NOM is a priority, concurrent chemoradiation followed by consolidation chemotherapy was strongly recommended. Selection of RT dose-fractionation regimen, sequencing of therapies, and consideration of NOM should be determined by multidisciplinary consensus and based on disease extent, disease location, patient preferences, and quality of life considerations.

CONCLUSIONS

The task force proposed recommendations to inform best clinical practices on the use of RT for rectal cancer with strong emphasis on multidisciplinary care. Future studies should focus on further addressing optimal treatment regimens to allow for more personalized recommendations based on individual risk stratification and patient priorities regarding quality of life.

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

Background

To 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.

Methods

From 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.

Results

Among 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.

Conclusion

AC 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.

Locally Advanced Rectal Cancer: What We Learned in the Last Two Decades and the Future Perspectives

The advancement in surgical techniques, optimization of systemic chemoradiotherapy, and development of refined diagnostic and imaging modalities have brought a phenomenal shift in the treatment of the locally advanced rectal cancer. Although each therapeutic option has shown substantial progress in their field, it is finding their ideal amalgamation which has baffled the clinician and researchers alike. In the effort to identifying the perfect salutary treatment plan, we have even shifted our attention from the trimodal approach to non-operative "watchful waiting" to more recent individualized care. In this article, we acknowledge the scientific progress in the management of locally advanced rectal cancer and compare the opportunities as well as the obstacles while implementing them clinically. We also explore the current challenges and controversies surrounding the multidisciplinary approach and highlight the new trends and recent advances with an ultimate goal to improve the patients' quality of life.

Radiation Therapy for Rectal Cancer: Executive Summary of an ASTRO Clinical Practice Guideline

PURPOSE

This guideline reviews the evidence and provides recommendations for the indications and appropriate technique and dose of neoadjuvant radiation therapy (RT) in the treatment of localized rectal cancer.

METHODS

The American Society for Radiation Oncology convened a task force to address 4 key questions focused on the use of RT in preoperative management of operable rectal cancer. These questions included the indications for neoadjuvant RT, identification of appropriate neoadjuvant regimens, indications for consideration of a nonoperative or local excision approach after chemoradiation, and appropriate treatment volumes and techniques. Recommendations were based on a systematic literature review and created using a predefined consensus-building methodology and system for grading evidence quality and recommendation strength.

RESULTS

Neoadjuvant RT is recommended for patients with stage II-III rectal cancer, with either conventional fractionation with concurrent 5-FU or capecitabine or short-course RT. RT should be performed preoperatively rather than postoperatively. Omission of preoperative RT is conditionally recommended in selected patients with lower risk of locoregional recurrence. Addition of chemotherapy before or after chemoradiation or after short-course RT is conditionally recommended. Nonoperative management is conditionally recommended if a clinical complete response is achieved after neoadjuvant treatment in selected patients. Inclusion of the rectum and mesorectal, presacral, internal iliac, and obturator nodes in the clinical treatment volume is recommended. In addition, inclusion of external iliac nodes is conditionally recommended in patients with tumors invading an anterior organ or structure, and inclusion of inguinal and external iliac nodes is conditionally recommended in patients with tumors involving the anal canal.

CONCLUSIONS

Based on currently published data, the American Society for Radiation Oncology task force has proposed evidence-based recommendations regarding the use of RT for rectal cancer. Future studies will look to further personalize treatment recommendations to optimize treatment outcomes and quality of life.

Robust dose planning objectives for mesorectal radiotherapy of early stage rectal cancer - A multicentre dose planning study

BACKGROUND AND PURPOSE

Organ preservation strategies are increasingly being explored for early rectal cancer. This requires revision of target volumes according to disease stage, as well as new guidelines for treatment planning. We conducted an international, multicentre dose planning study to develop robust planning objectives for modern radiotherapy of a novel mesorectal-only target volume, as implemented in the STAR-TReC trial (NCT02945566).

MATERIALS AND METHODS

The published literature was used to establish relevant dose levels for organ at risk (OAR) plan optimisation. Ten representative patients with early rectal cancer were identified. Treatment scans had mesorectal target volumes as well as bowel cavity, bladder and femoral heads outlined, and were circulated amongst the three participating institutions. Each institution produced plans for short course (SCRT, 5 × 5 Gy) and long course (LCRT, 25 × 2 Gy) treatment, using volumetric modulated arc therapy on different dose planning systems. Optimisation objectives for OARs were established by determining dose metric objectives achievable for ≥90% of plans.

RESULTS

Sixty plans, all fulfilling target coverage criteria, were produced. The planning results and literature review suggested optimisation objectives for SCRT: V 10Gy < 180 cm3, V 18Gy < 110 cm3, V 23Gy < 85 cm3 for bowel cavity; V 21Gy < 15% and V 25Gy < 5% for bladder; and V 12.5Gy < 11% for femoral heads. Corresponding objectives for LCRT: V 20Gy < 180 cm3, V 30Gy < 130 cm3, V 45Gy < 90 cm3 for bowel cavity; V 35Gy < 22% and V 50Gy < 7% for bladder; and V 25Gy < 15% for femoral heads. Constraints were validated across all three institutions.

CONCLUSION

We utilized a multicentre planning study approach to develop robust planning objectives for mesorectal radiotherapy for early rectal cancer.

Effects of varying radiation dosages on MMP1 expression, and MMP1 knockdown on the viability and migration of SW620 cells

Colorectal cancer (CRC), also known as bowel cancer, is one of the leading causes of cancer-associated mortality worldwide at present. The aim of the present study was to detect the effects of matrix metalloproteinase 1 (MMP1) on the viability and migration of a CRC cell line in the presence or absence of variation X-ray radiation doses. The CRC cell line, SW620, was cultured and treated with different X-ray doses (0, 0.1, 0.5, 1, 3 and 6 Gy). MMP1 expression was downregulated via the application of a specific small interfering (si)-RNA. The viability and migration of SW620 cells prior to and following transfection were detected with MTT and Transwell chamber assays, respectively. The application of siRNA transfection to silence MMP1 in SW620 cells resulted in reduced cell viability and migration (P<0.05). Compared with the control, the cell viability and migration of cells were significantly reduced when exposed to 0.5, 1, 3, and 6 Gy X-ray radiation (P<0.05). In SW620 cells treated with different X-ray doses, the mRNA expression levels of MMP1 were significantly reduced (P<0.05). Cells treated with 0.5 Gy X-ray exposure exhibited the lowest mRNA expression levels of MMP1 when compared with other doses of X-ray radiation. The expression of MMP1 was associated with the promotion of the viability and migration of SW620 cells. X-ray radiation with 6 Gy dosages significantly reduced cell viability when compared with the control. Thus, MMP1-targeted therapy combined with radiotherapy could be used for treating CRC.

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

Introduction

No 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.

Methods

Twenty‐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.

Results

Small 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).

Conclusion

A 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.

Therapeutic approaches in the management of locally advanced rectal cancer

Combined-modality therapy, using radiotherapy and chemotherapy with surgery, has been the traditional therapeutic algorithm for locally advanced rectal cancer. Standard of care in the United States has evolved to include neoadjuvant concurrent chemotherapy and radiotherapy followed by surgical excision and adjuvant chemotherapy. This approach has led to a significant improvement in local recurrences (LR), to the point where distant sites are the more common site of failure. Further improvements in local control have failed to improve overall survival. This article reviews historical trials that shifted the treatment paradigm to the current standard of care, as well as recent research trials, which have sought to incorporate new treatment methodologies, and treatment agents to improve outcomes. Finally this article describes ongoing studies and their potential impact on the future of therapeutic management of locally-advanced rectal cancer.

Evaluating QUANTEC Small Bowel Dose-Volume Guidelines for Rectal Cancer Patients Treated Using a Couch Top Inclined Belly Board

PURPOSE

The goal of this work was to analyse small bowel (SB) dose-volume following the Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) guidelines for rectal cancer patients treated using a couch top inclined belly board (iBB). As part of this, the consistency in SB displacement was evaluated using on-treatment cone-beam computed tomographic (CBCT) imaging.

METHODS

Twenty-four patients with rectal cancer were treated on a commercially available iBB. All patients went through the standard radiochemotherapy protocol in either a pre- or postoperative setup. All patients underwent weekly CBCT imaging during the course of radiation treatment. The planning computed tomographic data sets were used to analyze the quality of SB displacement, and the CBCT data sets were used to assess the reproducibility in SB displacement during treatment. The SB dose volume was evaluated and compared with QUANTEC-recommended dose limitations. Similarly, the impact of body mass index on dose volume and SB displacement was evaluated.

RESULTS

The SB displacement was assessed respectively as "good" and "very good" by both independent evaluating radiation oncologists. The consistency of SB displacement through the course of radiation treatment was scored as "excellent" for 22 of 24 and 23 of 24 patients by both radiation oncologists, respectively. The QUANTEC recommendation was met for all patients without bowel adhesions; however, the most benefit was observed for patients with body mass index > 23 kg/m².

CONCLUSIONS

Our study has shown that QUANTEC recommendations for SB dose during rectal cancer treatment can easily be met by treating patients on a couch top iBB. This technique is robust and produces consistent SB displacement.

Can a Belly Board Reduce Respiratory-Induced Prostate Motion in the Prone Position? — Assessed by Cine-Magnetic Resonance Imaging

The purpose of this study is to evaluate the real-time respiratory motion of the prostate and surrounding tissues/organs in the supine and prone positions and to investigate, using cine-MRI, whether a belly board can reduce respiratory-induced motion in the prone position. Cine-MRI scans were made of 13 volunteers in the supine and prone positions on a flat board and in two different prone positions using a belly board. Images in cine mode were recorded for 20 seconds. For each session, the points of interest (POIs) were located at the apex, base, mid-anterior surface and mid-posterior surface of the prostate; the tip of the seminal vesicle; the pubic symphysis; and the sacrum. The maximum range and standard deviation (SD) of the displacement from the mean value were calculated. The SDs for each of the four different positions were compared using a paired t-test. Respiratory-induced prostate motion was significantly larger in the prone position than in the supine position. However, when a belly board was used in the prone position, motion in the prostate and surrounding tissues/organs was significantly reduced. There were no significant differences between the two different positions using a belly board in any of the POIs.

Preoperative short-course concurrent chemoradiation therapy followed by delayed surgery for locally advanced rectal cancer: a phase 2 multicenter study (KROG 10-01)

PURPOSE

A prospective phase 2 multicenter trial was performed to investigate the efficacy and safety of preoperative short-course concurrent chemoradiation therapy (CRT) followed by delayed surgery for patients with locally advanced rectal cancer.

METHODS AND MATERIALS

Seventy-three patients with cT3-4 rectal cancer were enrolled. Radiation therapy of 25 Gy in 5 fractions was delivered over 5 consecutive days using helical tomotherapy. Concurrent chemotherapy was administered on the same 5 days with intravenous bolus injection of 5-fluorouracil (400 mg/m(2)/day) and leucovorin (20 mg/m(2)/day). After 4 to 8 weeks, total mesorectal excision was performed. The primary endpoint was the pathologic downstaging (ypStage 0-I) rate, and secondary endpoints included tumor regression grade, tumor volume reduction rate, and toxicity.

RESULTS

Seventy-one patients completed the planned preoperative CRT and surgery. Downstaging occurred in 20 (28.2%) patients, including 1 (1.4%) with a pathologic complete response. Favorable tumor regression (grade 4-3) was observed in 4 (5.6%) patients, and the mean tumor volume reduction rate was 62.5 ± 21.3%. Severe (grade ≥3) treatment toxicities were reported in 27 (38%) patients from CRT until 3 months after surgery.

CONCLUSIONS

Preoperative short-course concurrent CRT followed by delayed surgery for patients with locally advanced rectal cancer demonstrated poor pathologic responses compared with conventional long-course CRT, and it yielded considerable toxicities despite the use of an advanced radiation therapy technique.

Effect of belly board with bladder compression device on small bowel displacement from the radiotherapy field for rectal cancer

BACKGROUND

The aim of this study was to investigate the effect of a belly board (BB) with the addition of a bladder compression device (BCD) for small bowel (SB) displacement from the radiotherapy field for rectal cancer.

PATIENTS AND METHODS

Computed tomography (CT) scans of 38 rectal cancer patients positioned on a BB were analyzed and compared with CT scans from the same patients after the addition of a BCD. The BCD moves the inferior border of the BB from the pubic symphysis to the lumbosacral junction. The treated and irradiated volumes of the SB and bladder were compared. The irradiated volume ratio of SB to abdominopelvic cavity (APC) and that of bladder to APC were analyzed.

RESULTS

With the BCD, the treated and irradiated volumes of SB decreased significantly (49.1 ± 48.0 vs. 60.9 ± 50.9 cc, p = 0.006 and 207.5 ± 140.8 vs. 482.8 ± 214.2 cc, p < 0.001, respectively). The irradiated volume ratio of bladder to APC with the BCD increased considerably compared to that without the BCD (25.2 ± 11.5 vs. 18.7 ± 10.5%, p < 0.001), and the ratio of irradiated volume of SB to APC decreased significantly with the BCD (18.8 ± 12.4 vs. 31.8 ± 12.1%, p < 0.001).

CONCLUSION

This study showed that the addition of a BCD to the BB could effectively provide further displacement of SB from the rectal cancer radiotherapy field.

Radiation therapy in anal and rectal cancer

Historically, squamous cell carcinoma of the anal canal was treated with abdominoperineal resection. Nigro discovered that radiation therapy combined with 5-fluorouracil and mitomycin resulted in high rates of local control and colostomy-free and overall survival without surgical intervention. Recent advances include the integration of PET into staging, radiation treatment planning, disease monitoring, and the use of intensity-modulated radiation therapy. For rectal cancer, clinical trials have established the role for neoadjuvant therapy for T3-4 and/or node-positive tumor presentations. Chemotherapy and targeted agents are under study in both anal and rectal cancers to improve on the standard combinations of chemotherapy and radiation.

Planning target volume margin evaluation and critical structure sparing for rectal cancer patients treated prone on a bellyboard

AIMS

To calculate a planning target volume (PTV) margin that would account for inter-fractional systematic and random clinical target volume positional errors for patients treated prone on a recently available couch top bellyboard and to evaluate potential critical structure dose reduction using intensity-modulated radiotherapy (IMRT) techniques.

MATERIALS AND METHODS

Twenty-four patients (12 men and 12 women) were included in this study, all treated on a commercial bellyboard. Cone beam computed tomography (CBCT) data were acquired once every five fractions for a total of five images per patient. A three-dimensional-three-dimensional bony anatomy auto-match was carried out off-line and the residual difference in position used as a surrogate for clinical target volume inter-fractional positional errors. Systematic (Σ) and random (σ) variations were evaluated and used in PTV(margin)=1.96Σ+0.7σ. The influence of intra-fractional positional errors was evaluated in the margin analysis by introducing published values. Critical structure sparing, as a function of PTV(margin) size, was investigated through the evaluation of three-dimensional conformal radiation therapy (3DCRT) and IMRT treatment plans developed using the margin derived from this work, the American Society for Radiation Oncology Contouring Atlas and the Radiation Therapy Oncology Group 0822 trial specifications.

RESULTS

The PTV(margin) that accounts for only the inter-fractional positional errors was calculated to be (anterior-posterior (AP), superior-inferior (SI), left-right (LR))=(5.2mm, 3.1mm, 2.8mm). If we assumed a combined intra-fractional motion up to 3.0mm then the required PTV(margin) increased to (AP, SI, LR)=(7.0mm, 5.0mm, 5.0mm). Treatment plan evaluation showed that the bellyboard provides excellent small bowel sparing regardless of planning technique. In most cases, IMRT reduced the average femoral head, bladder and small bowel dose by 20, 15 and 40% with respect to 3DCRT planning.

CONCLUSION

A PTV(margin) expansion of (AP, SI, LR)=(7.0mm, 5.0mm, 5.0mm) is required to account for all positional uncertainties. The use of a bellyboard with IMRT provides better critical structure sparing when compared with a bellyboard with 3DCRT.

An update on preoperative radiotherapy for locally advanced rectal cancer

Even in patients undergoing an optimal surgical technique (e.g., total mesorectal excision), radiotherapy provides a significant benefit in the local control of rectal cancer. Compared with postoperative treatment, chemoradiotherapy given preoperatively has been shown to decrease local recurrence rates and toxicity. Additionally, preoperative chemoradiotherapy permits the early identification of tumor responses to this cytotoxic treatment by surgical pathology. Pathological parameters reflecting the tumor response to chemoradiotherapy have been shown to be surrogate markers for long-term clinical outcomes. Post-chemoradiotherapy downstaging from cStage II-III to ypStage 0-I indicates a favorable prognosis, with no difference between ypStage 0 and ypStage I. Research is ongoing to develop useful tools (clinical, molecular, and radiological) for clinical determination of the pathologic chemoradiotherapeutic response before surgery, and possibly even before preoperative treatment. In the future, risk-adapted strategies, including intensification of preoperative therapy, conservative surgery, or the selective administration of postoperative chemotherapy, will be realized for locally-advanced rectal cancer patients based on their response to preoperative chemoradiotherapy.

Systematic review of the role of a belly board device in radiotherapy delivery in patients with pelvic malignancies

PURPOSE

This review analyses the literature concerning the influence of the patient position (supine, prone and prone on a belly board device (BB) on the irradiated small-bowel-volume (SB-V)) and the resulting morbidity of radiation therapy (RT) in pelvic malignancies.

METHODS

A literature search was performed in MEDLINE, web of science and Scopus.

RESULTS

Forty-six full papers were found, of which 33 met the eligibility criteria. Fifteen articles focussed on the irradiated SB-V using dose volume histograms (DVHs). Twenty-seven articles studied the patient setup in different patient positions. This review showed that a prone treatment position can result in a lower irradiated SB-V as compared to a supine position, but a more significant reduction of the SB-V can be reached by the additional use of a BB in prone position, for both 3D-CRT and IMRT treatment plans. This reduction of the irradiated SB-V might result in a reduced GI-morbidity. The patient position did not influence the required PTV margins for prostate and rectum.

CONCLUSIONS

The irradiated SB-V can be maximally reduced by the use of a prone treatment position combined with a BB for both 3D-CRT and IMRT, which might individually result in a reduction of GI-morbidity.

Bowel exposure in rectal cancer IMRT using prone, supine, or a belly board

PURPOSE

To investigate bowel exposure using prone, supine, or two different belly boards for rectal cancer intensity modulated RT plans using a full bladder protocol.

METHODS AND MATERIALS

For 11 volunteers four MR scans were acquired, on a flat table in prone, supine, and on two different belly boards (IT-V Medizintechnik GmbH® (BB1) and CIVCO® (BB2)), using a full bladder protocol. On each scan a 25×2 Gy IMRT plan was calculated.

RESULTS

BB2 led to an average bowel area volume reduction of 20-30% at any dose level compared to prone. BB1 showed a smaller dose reduction effect, while no differences between prone and supine were found. Differences between BB2 and prone, supine or BB1 were significant up to a level of respectively, 45, 35, and 30 Gy. The reducing effect varied among individuals, except for the 50 Gy region, where no effect was found. An increase in bladder volume of 100 cc led to a significant bowel area V15 reduction of 16% independent of scan type.

CONCLUSIONS

In the low and intermediate dose region a belly board still attributes to a significant bowel dose reduction when using IMRT and a full bladder protocol. A larger bladder volume resulted in a significant decreased bowel area dose.

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

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Predicting grade 3 acute diarrhea during radiation therapy for rectal cancer using a cutoff-dose logistic regression normal tissue complication probability model

PURPOSE

Understanding the dose-volume relationship of small bowel irradiation and severe acute diarrhea may help reduce the incidence of this side effect during adjuvant treatment for rectal cancer.

METHODS AND MATERIALS

Consecutive patients treated curatively for rectal cancer were reviewed, and the maximum grade of acute diarrhea was determined. The small bowel was outlined on the treatment planning CT scan, and a dose-volume histogram was calculated for the initial pelvic treatment (45 Gy). Logistic regression models were fitted for varying cutoff-dose levels from 5 to 45 Gy in 5-Gy increments. The model with the highest LogLikelihood was used to develop a cutoff-dose normal tissue complication probability (NTCP) model.

RESULTS

There were a total of 152 patients (48% preoperative, 47% postoperative, 5% other), predominantly treated prone (95%) with a three-field technique (94%) and a protracted venous infusion of 5-fluorouracil (78%). Acute Grade 3 diarrhea occurred in 21%. The largest LogLikelihood was found for the cutoff-dose logistic regression model with 15 Gy as the cutoff-dose, although the models for 20 Gy and 25 Gy had similar significance. According to this model, highly significant correlations (p <0.001) between small bowel volumes receiving at least 15 Gy and toxicity exist in the considered patient population. Similar findings applied to both the preoperatively (p = 0.001) and postoperatively irradiated groups (p = 0.001).

CONCLUSION

The incidence of Grade 3 diarrhea was significantly correlated with the volume of small bowel receiving at least 15 Gy using a cutoff-dose NTCP model.

Elective clinical target volumes for conformal therapy in anorectal cancer: a radiation therapy oncology group consensus panel contouring atlas

PURPOSE

To develop a Radiation Therapy Oncology Group (RTOG) atlas of the elective clinical target volume (CTV) definitions to be used for planning pelvic intensity-modulated radiotherapy (IMRT) for anal and rectal cancers.

METHODS AND MATERIALS

The Gastrointestinal Committee of the RTOG established a task group (the nine physician co-authors) to develop this atlas. They responded to a questionnaire concerning three elective CTVs (CTVA: internal iliac, presacral, and perirectal nodal regions for both anal and rectal case planning; CTVB: external iliac nodal region for anal case planning and for selected rectal cases; CTVC: inguinal nodal region for anal case planning and for select rectal cases), and to outline these areas on individual computed tomographic images. The imaging files were shared via the Advanced Technology Consortium. A program developed by one of the co-authors (I.E.N.) used binomial maximum-likelihood estimates to generate a 95% group consensus contour. The computer-estimated consensus contours were then reviewed by the group and modified to provide a final contouring consensus atlas.

RESULTS

The panel achieved consensus CTV definitions to be used as guidelines for the adjuvant therapy of rectal cancer and definitive therapy for anal cancer. The most important difference from similar atlases for gynecologic or genitourinary cancer is mesorectal coverage. Detailed target volume contouring guidelines and images are discussed.

CONCLUSION

This report serves as a template for the definition of the elective CTVs to be used in IMRT planning for anal and rectal cancers, as part of prospective RTOG trials.

Multi-institutional comparison of intensity modulated radiation therapy (IMRT) planning strategies and planning results for nasopharyngeal cancer

The intensity-modulated radiation therapy (IMRT) planning strategies for nasopharyngeal cancer among Korean radiation oncology facilities were investigated. Five institutions with IMRT planning capacity using the same planning system were invited to participate in this study. The institutions were requested to produce the best plan possible for 2 cases that would deliver 70 Gy to the planning target volume of gross tumor (PTV1), 59.4 Gy to the PTV2, and 51.5 Gy to the PTV3 in which elective irradiation was required. The advised fractionation number was 33. The planning parameters, resultant dose distributions, and biological indices were compared. We found 2-3-fold variations in the volume of treatment targets. Similar degree of variation was found in the delineation of normal tissue. The physician-related factors in IMRT planning had more influence on the plan quality. The inhomogeneity index of PTV dose ranged from 4 to 49% in Case 1, and from 5 to 46% in Case 2. Variation in tumor control probabilities for the primary lesion and involved LNs was less marked. Normal tissue complication probabilities for parotid glands and skin showed marked variation. Results from this study suggest that greater efforts in providing training and continuing education in terms of IMRT planning parameters usually set by physician are necessary for the successful implementation of IMRT.

Adjuvant and neoadjuvant chemoradiation or radiotherapy in rectal cancer--a review focusing on open questions

BACKGROUND

The therapy of rectal cancer has been a matter of debate since decades, especially with regard to the benefits of neoadjuvant or adjuvant therapies. Principles of additional therapies have been established nearly two decades ago and are questioned nowadays on the basis of more recently modified operative techniques. Benefits and sequelae of therapies have to be balanced against each other, and it seems somewhat likely that a more differentiated strategy than simply stating that every patient with stage II and III rectal cancer needs chemoradiation or radiotherapy will, in long term, be recommended.

CONCLUSION

It should be kept in mind that results of centers of excellence and of phase-III studies with their positively selected patient populations are not representative for all the patients with rectal cancer and physicians treating them.

Patterns of locoregional recurrence after surgery and radiotherapy or chemoradiation for rectal cancer

PURPOSE

To identify patterns of locoregional recurrence in patients treated with surgery and preoperative or postoperative radiotherapy or chemoradiation for rectal cancer.

METHODS AND MATERIALS

Between November 1989 and October 2001, 554 patients with rectal cancer were treated with surgery and preoperative (85%) or postoperative (15%) radiotherapy, with 95% receiving concurrent chemotherapy. Among these patients, 46 had locoregional recurrence as the first site of failure. Computed tomography images showing the site of recurrence and radiotherapy simulation films were available for 36 of the 46 patients. Computed tomography images were used to identify the sites of recurrence and correlate the sites to radiotherapy fields in these 36 patients.

RESULTS

The estimated 5-year locoregional control rate was 91%. The 36 patients in the study had locoregional recurrences at 43 sites. There were 28 (65%) in-field, 7 (16%) marginal, and 8 (19%) out-of-field recurrences. Among the in-field recurrences, 15 (56%) occurred in the low pelvis, 6 (22%) in the presacral region, 4 (15%) in the mid-pelvis, and 2 (7%) in the high pelvis. Clinical T stage, pathologic T stage, and pathologic N stage were significantly associated with the risk of in-field locoregional recurrence. The median survival after locoregional recurrence was 24.6 months.

CONCLUSIONS

Patients treated with surgery and radiotherapy or chemoradiation for rectal cancer had a low risk of locoregional recurrence, with the majority of recurrences occurring within the radiation field. Because 78% of in-field recurrences occur in the low pelvic and presacral regions, consideration should be given to including the low pelvic and presacral regions in the radiotherapy boost field, especially in patients at high risk of recurrence.