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

Executive Summary of the American Radium Society on Appropriate Use Criteria for Nonoperative Management of Rectal Adenocarcinoma: Systematic Review and Guidelines

For patients with rectal cancer, the standard approach of chemotherapy, radiation therapy, and surgery (trimodality therapy) is associated with significant long-term toxicity and/or colostomy for most patients. Patient options focused on quality of life (QOL) have dramatically improved, but there remains limited guidance regarding comparative effectiveness. This systematic review and associated guidelines evaluate how various treatment strategies compare to each other in terms of oncologic outcomes and QOL. Cochrane and Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) methodology were used to search for prospective and retrospective trials and meta-analyses of adequate quality within the Ovid Medline database between January 1, 2012, and June 15, 2023. These studies informed the expert panel, which rated the appropriateness of various treatments in 6 clinical scenarios through a well-established consensus methodology (modified Delphi). The search process yielded 197 articles that advised voting. Increasing data have shown that nonoperative management (NOM) and primary surgery result in QOL benefits noted over trimodality therapy without detriment to oncologic outcomes. For patients with rectal cancer for whom total mesorectal excision would result in permanent colostomy or inadequate bowel continence, NOM was strongly recommended as usually appropriate. Restaging with tumor response assessment approximately 8 to 12 weeks after completion of radiation therapy/chemoradiation therapy was deemed a necessary component of NOM. The panel recommended active surveillance in the setting of a near-complete or complete response. In the setting of NOM, 54 to 56 Gy in 27 to 31 fractions concurrent with chemotherapy and followed by consolidation chemotherapy was recommended. The panel strongly recommends primary surgery as usually appropriate for a T3N0 high rectal tumor for which low anterior resection and adequate bowel function is possible, with adjuvant chemotherapy considered if N+. Recent data support NOM and primary surgery as important options that should be offered to eligible patients. Considering the complexity of multidisciplinary management, patients should be discussed in a multidisciplinary setting, and therapy should be tailored to individual patient goals/values.

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

AIMS

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.

METHODS AND MATERIAL

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.

STATISTICAL ANALYSIS USED

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.

RESULTS

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.

CONCLUSIONS

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.

A critical literature review on the use of bellyboard devices to control small bowel dose for pelvic radiotherapy

Delivering curative radiotherapy doses for rectal and gynaecological tumours has historically been complicated by the dose tolerance of the small bowel. Acute radiation-induced small bowel toxicity includes side effects such as abdominal pain, nausea and diarrhoea. With the advent of new treatment delivery modalities, such as IMRT (Intensity modulated radiotherapy) and VMAT (Volumetric modulated Arc radiotherapy), there has been an expectation that small bowel doses can be better controlled with the use of these technologies. These capabilities enable the creation of treatment plans that can better avoid critical radiosensitive organs. The purpose of this review is to look beyond advances in linear accelerator technology in seeking improvements to small bowel dose and toxicity. This review examines whether an alternative prone patient positioning approach using a bellyboard device in conjunction with IMRT and VMAT treatment delivery can reduce small bowel doses further than using these technologies with the patient in a traditional supine position.