Comparison of Different Techniques in Breast Cancer Radiotherapy Planning

A retrospective comparison of setup accuracy from CBCT and SGRT data in breast cancer patients

INTRODUCTION

Both cone-beam computed tomography (CBCT) and surface-guided radiotherapy (SGRT) are used for breast patient positioning verification before treatment delivery. SGRT may reduce treatment time and imaging dose by potentially reduce the number of CBCT needed. The aim of this study was to compare the displacements resulting in positioning from the Image Guided Radiation Therapy (IGRT) 3D and SGRT methods and to design a clinical workflow for SGRT implementation in breast radiotherapy to establish an imaging strategy based on the data obtained.

METHODS

For this study 128 breast cancer patients treated with 42.5 Gy in 16 fractions using 3D conformal radiotherapy with free breathing technique were enroled. A total of 366 CBCT images were evaluated for patient setup verification and compared with SGRT. Image registrations between planning CT images and CBCT images were performed in mutual agreement and in online mode by three health professionals. Student's paired t-test was used to compare the absolute difference in vector shift, measured in mm, for each orthogonal axis (x, y, z) between SGRT and CBCT methods. The multidisciplinary team evaluated a review of the original clinical workflow for SGRT implementation and data about patients treated with the updated workflow were reported.

RESULTS

Comparison of the shifts obtained with IGRT and SGRT for each orthogonal axis (for the x-axes the average displacement was 0.9 ± 0.7 mm, y = 1.1 ± 0.8 mm and z = 1.0 ± 0.7 mm) revealed no significant statistical differences (p > 0.05). Using the updated workflow the difference between SGRT and IGRT displacements was <3 mm in 91.4 % of patients with a reduction in total treatment time of approximately 20 %, due to the reduce frequency of the CBCT images acquisition and matching.

CONCLUSIONS

This study has shown that IGRT and SGRT agree in positioning patients with breast cancer within a millimetre tolerance. SGRT can be used for patient positioning, with the advantages of reducing radiation exposure and shorter overall treatment time.

Dosimetric comparative study of 3DCRT, IMRT, VMAT, Ecomp, and Hybrid techniques for breast radiation therapy

Purpose

To assess and compare the dosimetric parameters obtained between three-dimensional conformal radiotherapy (3DCRT), three-dimensional field-in-field (3DFIF), 5-field intensity-modulated radiotherapy (IMRT MF5), tangential IMRT (tIMRT), tangential volumetric modulated arc therapy (tVMAT), electronic tissue compensation (Ecomp), and Hybrid treatment plans.

Material and Methods

Thirty planning computed tomography datasets obtained from patients previously treated with whole breast radiation therapy (WBRT) were utilized in this study. Treatment plans were created for 3DCRT, 3DFIF, IMRT MF5, tIMRT, tVMAT, Ecomp, and Hybrid techniques using Eclipse Treatment Planning System (version 13.6) with a prescribed dose of 42.5 Gy in 16 fractions.

Results

Techniques with tangential beams produced statistically significantly better organs-at-risk (OARs) dosimetry (p < 0.001). Planning target volume Homogeneity Index (HI) was found to be significantly different among all techniques (p < 0.001), with Ecomp resulting in better HI (1.061 ± 0.029). Ecomp was also observed to require relatively shorter planning time (p < 0.001).

Conclusions

Techniques using tangential fields arrangements produced improved OARs dosimetry. Of all the treatment planning techniques employed in this study, Ecomp was found to be relatively easy to plan and produce acceptable dosimetry for WBRT in a short time.

Intraoperative Period and Breast Cancer: Review

Intraoperative radiation therapy in breast cancer (IORT) delivers a concentrated dose of radiation therapy to a tumor bed during surgery. IORT offers some of the following advantages with typically fewer complications like; maximum effect, sparing healthy tissues and organs, to help the patients finish treatment and get back to their normal activities. The goal of IORT is to improve local tumor control and survival rates for patients with breast cancer. IORT can both be performed with electron beams (ELIOT) and X-rays. Two main randomised trials testing intraoperative partial breast radiotherapy are TARGIT trial and the ELIOT (intraoperative radiotherapy with electrons) trial, but the techniques are fundamentally different. Whereas TARGIT delivers radiation from within the undisturbed tumour bed, for ELIOT, the mammary gland is mobilised, a prepectoral lead shield is inserted, the edges of the tumour bed are apposed, and radiation is delivered from without.