In-vivo dosimetry comparison of supraclavicular junction dose for breast and chest-wall patients with and without deep inspiration breath hold (DIBH)

Feasibility and efficacy of active breathing coordinator assisted deep inspiration breath hold technique for treatment of locally advanced breast cancer

BACKGROUND

Active breathing coordinator (ABC)-assisted deep inspiration breath hold (DIBH) is an important organ sparing radiation therapy (RT) technique for left-sided breast cancer patients. Patients with advanced breast cancer undergoing chest wall and regional nodal irradiation often require a field matching technique. While field matching has been demonstrated to be safe and effective in free breathing patients, its safety and accuracy in DIBH/ABC use has not been previously reported.

PURPOSE

To report the accuracy, feasibility, and safety of field matching with ABC/DIBH for patients receiving breast/chest wall irradiation with nodal irradiation using a three-field technique.

METHODS

From December 2012 to May 2018, breast cancer patients undergoing ABC/DIBH-based RT at a single institution were reviewed. For each fraction, the amount of overlap/gap between the supraclavicular and the tangential field were measured and recorded. Patient characteristics, including acute and delayed skin toxicities, were analyzed.

RESULTS

A total of 202 patients utilized ABC/DIBH and 4973 fractions had gap/overlap measurements available for analysis. The average gap/overlap measured at junction was 0.28 mm ± 0.99 mm. A total of 72% of fractions had no measurable gap/overlap (0 mm), while 5.6% had an overlap and 22.7% a gap. There was no significant trend for worsening or improvement of gap/overlap measurements with increasing fraction number per patient. OSLD measurements were compared to the planned dose. The median dose 1 cm above the junction was 106% ± 7% of planned dose (range 94%-116%). One centimeter below the junction, the median dose was 114% ± 11% of planned dose (range 95%-131%). At the junction, the median dose was 106% ± 16.3% of planned dose (range 86%-131%). Acute skin toxicity was similar to historically reported values (grade 3, 5.4%, grade 4, 0%).

CONCLUSION

ABC-assisted DIBH is a safe and technically feasible method of delivering RT in the setting of complex matching field technique for breast and regional nodal treatments.

Investigation of dose profile across the junction of deep inspiration breath hold, breast with supra-clavicle fossa treatments

Breast with supraclavicular fossa (Br+SCF) radiotherapy treatments can utilise a monoisocentric technique to concurrently treat the breast area (tangent fields) and supraclavicular area (opposing fields). The region where these treatment areas adjoin is known as the junction region, field junction, or match line. Dose variations that may occur about the junction region, due to geometrical inaccuracies, are typically feathered out in patient free-breathing treatments. However, there is limited information on how dose at the junction is influenced in deep inspiration breath hold (DIBH) treatments. This study aims to investigate dose variation at the field junction for a patient population undertaking a DIBH Br+SCF treatment course. GAFChromic EBT3 film was used to record the dose across the junction at skin surface for approximately one third of the 25 fraction treatment course for 11 patients undergoing DIBH Br+SCF treatment. Single fraction and summated fraction profiles for each patient were compared to profiles in the treatment planning system and assessed the: (1) local dose variations, (2) position of the 50% dose gradient, and (3) relative dose at the nominal junction. Local dose variations of 10% or greater, position displacement of the junction greater than 5 mm, and relative dose differences at the match line greater than 10% can be found within single fraction dose profiles. When these single fractions are summed over the treatment course, the position variations reduce to 2 mm and dose variations reduced to within 10% for 10 of the 11 patients. Only one of 11 patients recorded a summed dose difference greater than ±10% over their treatment, recording 76% ± 8% of the planned dose in this region. This was due to a small overall position displacement of 1.8 ± 1.6 mm from the nominal junction. A feathering of the dose at the junction is present for DIBH Br+SCF patient treatments. The feathering effect is sufficient, in the majority of cases studied, to reduce any differences in dose and displacement present in single fractions. This work also demonstrates that there may be exceptions from this observed behavior that should be considered. Further study in this area using a larger patient cohort is recommended.

AAPM task group report 302: Surface guided radiotherapy

The clinical use of surface imaging has increased dramatically with demonstrated utility for initial patient positioning, real-time motion monitoring, and beam gating in a variety of anatomical sites. The Therapy Physics Subcommittee and the Imaging for Treatment Verification Working Group of the American Association of Physicists in Medicine commissioned Task Group 302 to review the current clinical uses of surface imaging and emerging clinical applications. The specific charge of this task group was to provide technical guidelines for clinical indications of use for general positioning, breast deep-inspiration breath-hold (DIBH) treatment, and frameless stereotactic radiosurgery (SRS). Additionally, the task group was charged with providing commissioning and on-going quality assurance (QA) requirements for surface guided radiation therapy (SGRT) as part of a comprehensive QA program including risk assessment. Workflow considerations for other anatomic sites and for computed tomography (CT) simulation, including motion management are also discussed. Finally, developing clinical applications such as stereotactic body radiotherapy (SBRT) or proton radiotherapy are presented. The recommendations made in this report, which are summarized at the end of the report, are applicable to all video-based SGRT systems available at the time of writing. Review current use of non-ionizing surface imaging functionality and commercially available systems. Summarize commissioning and on-going quality assurance (QA) requirements of surface image-guided systems, including implementation of risk or hazard assessment of surface guided radiotherapy as a part of a total quality management program (e.g., TG-100). Provide clinically relevant technical guidelines that include recommendations for the use of SGRT for general patient positioning, breast DIBH, and frameless brain SRS, including potential pitfalls to avoid when implementing this technology. Discuss emerging clinical applications of SGRT and associated QA implications based on evaluation of technology and risk assessment. This article is protected by copyright. All rights reserved.

Predictors of cardiac and lung dose sparing in DIBH for left breast treatment

This retrospective study of left breast radiation therapy (RT) investigates the correlation between anatomical parameters and dose to heart or/and left lung in deep inspiration breath-hold (DIBH) compared to free-breathing (FB) technique. Anatomical parameters of sixty-seven patients, treated with a step-and-shoot technique to 50 Gy or 50.4 Gy were included. They consisted of the cardiac contact distances in axial (CCD_ax) and parasagittal (CCD_ps) planes, and the lateral heart-to-chest distance (HCD). Correlation analysis was performed to identify predictors for heart and lung dose sparing. Paired t-test and linear regression were used for data analysis with significance level of p = 0.05. All dose metrics for heart and lung were significantly reduced with DIBH, however 21% of patients analyzed had less than 1.0 Gy mean heart dose reduction. Both FB-CCD_psdistance and FB-HCD correlated with FB mean heart dose and mean DIBH heart dose reduction. The strongest correlation was observed for the ratio of FB-CCD_psand FB-HCD with heart dose sparing. A FB-CCD_ps and FB-HCD model was developed to predict DIBH induced mean heart dose reduction, with 1.04 Gy per unit of FB-CCD_ps/FB-HCD. Variation between predicted and actual mean heart dose reduction ranged from -0.6 Gy to 0.6 Gy. In this study, FB-CCD_ps and FB-HCD distance served as predictors for heart dose reduction with DIBH equally, with FB-CCD_ps/FB-HCD as a stronger predictor. These parameters and the prediction model could be further investigated for use as a tool to better select patients who will benefit from DIBH.