Physics Contribution
How Important Is a Reproducible Breath Hold for Deep Inspiration Breath Hold Breast Radiation Therapy?

https://doi.org/10.1016/j.ijrobp.2015.06.010Get rights and content

Purpose

Deep inspiration breath hold (DIBH) for left-sided breast cancer has been shown to reduce heart dose. Surface imaging helps to ensure accurate breast positioning, but it does not guarantee a reproducible breath hold (BH) at DIBH treatments. We examine the effects of variable BH positions for DIBH treatments.

Methods and Materials

Twenty-five patients who underwent free breathing (FB) and DIBH scans were reviewed. Four plans were created for each patient: FB, DIBH, FB_DIBH (the DIBH plans were copied to the FB images and recalculated, and image registration was based on breast tissue), and P_DIBH (a partial BH with the heart shifted midway between the FB and DIBH positions). The FB_DIBH plans give a “worst-case” scenario for surface imaging DIBH, where the breast is aligned by surface imaging but the patient is not holding their breath. Kolmogorov-Smirnov tests were used to compare the dose metrics.

Results

The DIBH plans gave lower heart dose and comparable breast coverage versus FB in all cases. The FB_DIBH plans showed no significant difference versus FB plans for breast coverage, mean heart dose, or maximum heart dose (P≥.10). The mean heart dose differed between FB_DIBH and FB by <2 Gy for all cases, and the maximum heart dose differed by <2 Gy for 21 cases. The P_DIBH plans showed significantly lower mean heart dose than FB (P<.01). The mean heart doses for the P_DIBH plans were <FB for 22 cases, the maximum dose was <FB for 18 cases.

Conclusions

A DIBH plan delivered to a FB patient setup with surface imaging will yield dosimetry similar to that of a plan created and delivered FB. A DIBH plan delivered with even a partial BH can give reduced heart dose compared with FB techniques.

Introduction

Radiation therapy has been shown to improve local control and overall survival in patients undergoing breast conservation (1). With long-term follow-up, however, an increased incidence of cardiac events among irradiated patients has been observed (2). Techniques to limit heart dose while delivering the prescribed dose to the breast, such as deep inspiration breath hold (DIBH), have been shown to be effective tools to limit both heart and lung dose for left-sided breast radiation therapy 3, 4, 5, 6, 7, 8. The 2 key technical components of DIBH breast treatments are ensuring that (1) the breast tissue/chest wall is in the correct position for treatment relative to the treatment machine and (2) the heart is in the correct position relative to the breast and treatment fields. The position of the breast/chest wall for treatment is of concern for conventional free breathing (FB) radiation therapy and for DIBH. Tattoos, lasers, and portal imaging have traditionally been used to position the patient in the treatment room, and more recently 3-dimensional (3D) surface imaging has become a popular tool to position breast patients 9, 10. Concern for heart position is of greater importance to DIBH treatments. The heart position during treatment can be directly monitored only with radiographic or magnetic resonance imaging using commercially available tools. However, concerns about radiation exposure for this group of patients make direct monitoring with ionizing radiographic imaging undesirable (with the caveat that cine portal imaging may provide 2-dimensional information in some cases with no additional dose), and treatment machines with on-board magnetic resonance imaging are not in wide use at this time. In place of direct monitoring of the heart position, lung expansion is often used as a surrogate for heart position during treatment. Lung expansion may be directly monitored with spirometry 11, 12, 13 at DIBH treatments. Lung expansion can be indirectly monitored with external surrogates, such as surface imaging 14, 15, 16, 17, 18, 19 or infrared markers 7, 20, 21, 22.

As mentioned above, surface imaging has shown the ability to accurately position breast patients for FB treatments 9, 10 and for DIBH treatments 15, 16, 19, 21. However, because surface imaging is only a surrogate for breath hold, a common question for DIBH treatments based on surface imaging is “How can one be sure that the patient takes the same breath every time?” In practice, this question expresses concern over the position of the heart on a per breath basis, rather than the actual breath hold itself. The answer to the question of heart position is that one cannot be sure the heart is in the correct place every time. Several studies have shown that surface imaging is a reasonable indicator of heart position 19, 21 at initial setup, but clearly it is not capable of providing definitive conformation of heart position for every breath hold. Perhaps a more relevant question is “How important is it that the heart is in the same position for every breath hold?”

In this work we looked at a series of 25 patients treated for left-sided breast cancer using a DIBH technique based on surface imaging. Surface imaging helps ensure that the breast tissue is in the correct position, but it does not ensure the heart is in the correct place. One would expect that in a worst-case scenario for DIBH guided by surface imaging the breast tissue would be localized, but the patient would not be able to generate any sort of DIBH (ie would be FB) and the heart would be in the FB position for treatment. We investigated the effects of varying heart position by evaluating heart and breast dosimetry for cases where DIBH plans were delivered to patients who were FB, in full DIBH positions, or in partial DIBH positions.

Section snippets

Methods and Materials

Twenty-five patients with left-sided breast cancer were retrospectively reviewed in this study. Each patient was set up on a commercial breast board (QFix, Avondale, PA) at a 10° to 15° angle with both arms raised above the head. All the patients underwent FB and DIBH computed tomography (CT) scans on a Philips Big Bore (Philips Healthcare, Andover, MA) scanner with nominal 3-mm slice thickness and the field of view set to include the patient and immobilization device. The DIBH was monitored

Results

The mean centroid displacement of the heart contours between the FB and DIBH scans was 2.9 cm ± 1.2 cm (range, 1.8-4.2 cm). Representative isodose lines for the different plans are shown in Figure 2. The average dose metrics over all the patients in each group of plans is shown in Table 1. Mean dose, maximum dose, volume receiving 20 Gy, volume receiving 30 Gy, and volume receiving 40 Gy are listed for the heart in Table 1. Mean dose, maximum dose, minimum dose, volume receiving 95% of the

Discussion

Not surprisingly, the DIBH plans showed decreased heart dose and comparable target coverage relative to the FB plans. Of more interest is that the FB_DIBH plans show statistically similar heart and target dose to the FB plans. On a per-patient basis, comparisons between the FB and FB_DIBH groups showed no large outliers in target coverage. Minor changes in breast and lumpectomy cavity coverage may be attributed to slightly different cavity definitions and small breast deformations between the

References (25)

Cited by (26)

  • Prone Positioning With Deep Inspiration Breath Hold for Left Breast Radiotherapy

    2021, Clinical Breast Cancer
    Citation Excerpt :

    Thus, methods for reducing cardiac dose during RT are anticipated to reduce the long-term risk of cardiac disease. The 2 methods frequently used to reduce cardiac dose during breast RT are prone positioning on a breast-board9-13 and deep inspiratory breath-hold treatment (DIBH).14-20 Despite the general benefit with prone positioning, some patients with left-sided cancers may have increased cardiac doses in the prone position.

  • Cardiotoxicity in breast cancer patients treated with radiation therapy: From evidences to controversies

    2020, Critical Reviews in Oncology/Hematology
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    DIBH can be used for the majority of breast cancer patients, provided that they have a sufficient respiratory function. Multiple dosimetric studies have shown that MHD and other cardiac dosimetric parameters were substantially decreased with DIBH (Bergom et al., 2018; Oechsner et al., 2019; Wiant et al., 2015); a retrospective study including 319 patients demonstrated that DIBH reduced heart V20Gy from 7.8 % to 2.3 % (p < 0.01), heart V40Gy from 3.4 % to 0.3 % (p < 0.01) and MHD from 5.2 Gy to 2.7 Gy (p < 0.01) (Nissen and Appelt, 2013). Additionally, DIBH significantly reduces LADCA radiation exposure (Lawler and Leech, 2017).

  • The Role of Optical Surface Imaging Systems in Radiation Therapy

    2018, Seminars in Radiation Oncology
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    With verbal or audio-visual coaching, it is possible for a patient to perform the DIBH voluntarily and reproducibly.13,34 A reproducible deep inspiration chest wall excursion and stable chest wall position for the duration of the breath hold are important for ensuring dosimetric benefit from the DIBH technique.36,37 To that end, surface imaging has been widely applied towards the guidance of DIBH.

  • Monte Carlo dose calculation in presence of low-density media: Application to lung SBRT treated during DIBH

    2017, Physica Medica
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    First of all, during a DIBH, pulmonary volume is close to its maximum value, which can strongly reduce the irradiated lung fraction, and decrease the treatment toxicity [23]. The heart can also be spared during tangential fields for left-sided breast cancer treatment [24,25]. More generally, all thoracic structures have a stable and reproducible position.

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Note—An online CME test for this article can be taken at http://astro.org/MOC.

Conflict of interest: none.

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