Analysis of Irradiated Lung and Heart Volumes using Virtual Simulation in Postoperative Treatment of Stage I Breast Carcinoma

Dosimetric comparison of three different external beam whole breast irradiation techniques

INTRODUCTION

The purpose of this study was to compare the dosimetries of three different external beam whole breast radiotherapy techniques: two-dimensional RT (2D-RT), three-dimensional conformal RT (3D-CRT), and field-in-field intensity-modulated RT (FiF-IMRT). In addition, we aimed to evaluate the patients who needed more or less complex treatment modalities.

METHODS

Thirty patients were included in the study. All the patients had early-stage breast cancer and conserving surgery had been performed. Plans that employed the three techniques were generated for each patient. Dosimetric comparisons were conducted, and correlations with patient characteristics and dosimetric outcomes were analyzed.

RESULTS

The 2D-RT technique was found to be suboptimal for treating the intact breast. Its dose homogeneity index (DHI) was 20.68. The authors were unable to define a patient characteristic in which 2D-RT dosimetry would perform better. FiF-IMRT was found to be the superior technique with a better homogeneity in the breast (DHI=9.35 and P=0.000002 when compared to 3D-CRT). When compared according to patient characteristics, again the FiF-IMRT planning is the best for all subgroups, but the DHI gets worse by increased breast volume and separation. While FiF-IMRT achieves better DHI in the breast, it has little effect on heart and lung doses. But the normal tissues' volume (cc) that gets the 100% of the prescribed dose (V100) was lowered because of the treatment without wedges and scatter and with less monitor unit.

CONCLUSIONS

2D-RT could not be performed safely on the intact breast in any of the subgroups. FiF-IMRT is a superior technique for breast dosimetry, and normal tissue. For patients with large breast size or separation, further intensive techniques must be investigated.

Recent advances in breast cancer radiotherapy: Evolution or revolution, or how to decrease cardiac toxicity?

Radiation therapy has a major role in the management of breast cancers. However, there is no consensus on how to irradiate and on volume definitions, and there are strong differences in strategies according to different centers and physicians. New treatment protocols and techniques have been used with the principal purpose of decreasing lung and heart toxicity and adapting radiation treatment to patients’ anatomy. There is evidence that indicates internal mammary chain radiotherapy should be used carefully and that high quality techniques should be used for decreasing the dose delivered to the heart. This review of the literature presents the state of the art on breast cancer radiotherapy, with special focus on the indications, techniques, and potential toxicity.

Breast radiotherapy in the lateral decubitus position: A technique to prevent lung and heart irradiation

PURPOSE

To present an original technique for breast radiotherapy, with the aim of limiting lung and heart irradiation, satisfying quality assurance criteria.

METHODS AND MATERIAL

An original radiotherapy technique for breast irradiation has been developed at the Institute Curie in January 1996. It consists of isocentric breast irradiation in the lateral decubitus position (isocentric lateral decubitus [ILD]). This technique is indicated for voluminous or pendulous breasts needing breast irradiation only. Thin carbon fiber supports and special patient positioning devices have been developed especially for this technique. In vivo measurements were performed to check the dose distribution before the routine use of the technique.

RESULTS

ILD has been successfully implemented in routine practice, and 500 patients have been already treated. Breast radiotherapy is performed using a dose of 50 Gy at ICRU point in 25 fractions. ILD shows good homogeneity of the dose in breast treatment volume, treatment fields are perpendicular to the skin ensuring its protection, and extremely low dose is delivered to the underlying lung and heart.

CONCLUSION

In cases of voluminous breasts or patients with a history of lung and heart disease, our technique provides several advantages over the conventional technique with opposing tangential fields. This technique improves the dose homogeneity according to the ICRU recommendations.

Advances in Radiation Treatments of Breast Cancer

During the past decade, improvements in treatment-planning tools, computer and imaging technologies, and new therapeutic modalities have allowed radiation to be delivered in a conformal fashion while minimizing treatment toxicity. It is important that physicians involved in breast cancer treatment recognize the numerous advances that have occurred in the delivery of radiation therapy. Changes in 3 specific areas in treatment planning and delivery have revolutionized the way we approach breast cancer treatment: the design of radiation fields using computed tomography (CT) data sets, the development of 3-dimensional dose-calculation algorithms, and the development of new methods to modulate the delivery of radiation dose. With the advent of CT simulators, individual patient anatomy and pathology can be readily visualized and reconstructed in axial, coronal, and sagittal views. With an improved anatomic delineation between the target volumes and critical organ structures, the treatment fields can be designed to be more congruous to the areas at highest risk. In the past few years, new 3-dimensional dose-calculation algorithms have been generated that more accurately calculate dose distributions throughout the treatment-planning volume. Finally, modern linear accelerators allow for modulation of the dose intensity of the radiation beam, which may lead to improved aesthetics and decreased side effects while ensuring that the volumes at high risk receive the prescribed dose. Radiation therapy can be delivered safely and effectively to patients with breast cancer.