Should we customize PTV expansions for BMI? Daily cone beam computerized tomography to assess organ motion in postoperative endometrial and cervical cancer patients

Current Alberta radiation therapy care practices for patients with obesity and recommendations for improvement

INTRODUCTION

Obesity has been associated with increased incidence of cancer thereby impacting the number of patients with obesity who may require radiation therapy (RT) treatment. Previous studies have detailed the impacts of obesity on RT treatment delivery including considerations when positioning, imaging, and communicating with patients. However, there is limited literature regarding best clinical practices used by Canadian RT departments when treating patients with obesity. This study aimed to answer the following question: How can the current standards of care (SOC) used by Alberta RT departments be improved to ensure safe and quality care of patients with obesity?

METHODS

Semi-structured interviews were conducted with 19 practitioners including three RT managers, two medical physicists, two clinical educators, two radiation oncologists, a senior practice lead, and nine radiation therapists from five cancer centers across Alberta. Interviews were transcribed and analyzed independently by two researchers and used to inform recommendations for improvement to existing care practices.

RESULTS

Four themes emerged as unique considerations for patients with obesity undergoing RT, which included technical factors, interpersonal interactions, patient care factors, and education and training. Recommendations to improve the current SOC in Alberta RT departments included the need for longer appointment times, sufficient staff, accessible mobility equipment, and additional education and training for HCPs tailored towards patients with obesity.

CONCLUSION

SOC in Alberta could be improved for patients with obesity with modified appointment time, increased staff and resources, and more in depth and tailored education. Implementation of these considerations and recommendations for improvement to the current SOC used by Alberta RT departments has the potential to ensure safe and quality care of patients with obesity.

Consensus Guidelines for Delineation of Clinical Target Volumes for Intensity Modulated Radiation Therapy for Intact Cervical Cancer: An Update

PURPOSE

Accurate target delineation is essential when using intensity modulated radiation therapy for intact cervical cancer. In 2011, the Radiation Therapy Oncology Group published a consensus guideline using magnetic resonance imaging (MRI). The current project expands on the previous atlas by including computed tomography (CT)-based contours, contours with MRI and positron emission tomography (PET) registrations, the addition of common and complex scenarios, and incorporating information on simulation and treatment planning techniques.

METHODS AND MATERIALS

Twenty-eight experts in gynecologic radiation oncology contoured 3 cases, first on a noncontrast CT simulation scan and then with registered diagnostic scans. The cases included (1) International Federation of Gynecology and Obstetrics (FIGO) IIIC1 with a bulky tumor and vaginal metastasis, (2) FIGO IIB with calcified uterine fibromas, and (3) FIGO IIIC2 with large lymph nodes. The contours on all 6 data sets (3 CT simulations without diagnostic images and 3 with registered images) were analyzed for consistency of delineation using an expectation-maximization algorithm for simultaneous truth and performance level estimation with kappa statistics as a measure of agreement. The contours were reviewed, discussed, and edited in a group meeting prior to finalizing.

RESULTS

Contours showed considerable agreement among experts in each of the cases, with kappa statistics from 0.67 to 0.72. For each case, diagnostic PET ± MRI was associated with an increase in volume. The largest increase was the clinical target volume (CTV) primary for case 2, with a 20% increase in volume and a 54% increase in simultaneous truth and performance level estimation volume, which may be due to variance in registration priorities. For the third case, 92.9% increased their CTVs based on the addition of the diagnostic PET scan. The main areas of variance were in determining the superior extent of CTV coverage, coverage of the mesorectum, and simulation and planning protocols.

CONCLUSIONS

This study shows the value and the challenges of using coregistered diagnostic imaging, with an average increase in volumes when incorporating MRI and PET.

A model to guide the management and decision of re-planning during radiotherapy for cervical cancer

BACKGROUND

To establish a model to predict whether re-planning is needed in the process of cervical cancer radiotherapy.

METHODS

We collected the clinical indexes of 132 patients diagnosed with cervical cancer receiving concurrent chemotherapy and radiotherapy, including 33 factors about tumor markers [carcinoembryonic antigen (CEA), cancer antigen 125 (CA-125), squamous cell carcinoma antigen (SCC)], tumor volume, rectal volume, bladder volume, volumes receiving 30-50 Gy in organs-at-risk (OARs), and the maximum dose (Dmax) received by 1-2 cc in OARs. We established a multivariate model for re-planning evaluation via principal component analysis, and then verified the model based on the internal data.

RESULTS

We identified the dose index (P1), tumor size index (P2), and volumes receiving 30-50 Gy in OARs and the tumor (P3) as the three most weighted factors of the re-planning model. We set the cut-off for the re-planning modification requirement at 1. The model was consistent with R = 0.12P1 + 0.21P2 + 0.31P3, and it performed accurately that area under the test set characteristics curve (AUC) =0.826].

CONCLUSIONS

Our proposed method can help to reduce image re-examination during treatment, decrease toxicities in OARs, shorten the radiotherapy course, lessen oncologists' efforts, and save medical resources.