Myocardial perfusion imaging in breast cancer patients treated with or without post-mastectomy radiotherapy

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Abstract

Purpose: To assess the occurrence and location of myocardial perfusion defects in left-sided mastectomized breast cancer patients, treated with or without postoperative radiotherapy according to the guidelines from the Danish Breast Cancer Cooperative Group (DBCG).

Patients and methods: Seventeen left-sided breast cancer patients, with a median age of 59 years (range, 47–75 years), randomized to post-mastectomy irradiation plus systemic treatment, or systemic treatment alone, were examined after a median follow-up of 7.9 years (range, 6.0–12.2 years). The chest wall and the ipsilateral internal mammary nodes had been treated through two anterior-shaped electron fields, and the electron energy was chosen according to chest wall thickness, measured individually by ultrasound. The median absorbed dose was 50 Gy in 25 fractions, with 5 fractions/week. Information on clinical history was obtained and symptoms of ischemic heart disease (IHD), as well as major risk factors, were recorded. All patients had a physical examination, blood chemistry, electrocardiogram (ECG), chest X-ray and myocardial perfusion imaging by sestamibi-single photon emission computerized tomography (SPECT). SPECT-scanning was performed as a rest/dipyridamole 2-day protocol. The evaluation of regional myocardial perfusion was based on scintigrams using a 20-segment model.

Results: There was no significant difference between the scintigraphic findings in the two groups. Four of ten irradiated patients and four of seven non-irradiated patients showed scintigraphic defects. An anterior defect was found in one non-irradiated patient.

Conclusions: This study does not indicate that the described radiotherapy technique induces detectable coronary artery disease. However, the small number of patients does not allow strong conclusions to be drawn.

Introduction

Radiotherapy in breast cancer has, in some studies, been associated with an increased risk of cardiovascular mortality, which has been suggested to be caused by accelerated atherosclerosis in irradiated coronary arteries [6], [18], [20], [23], [34], [35]. Some of this mortality is believed to be a result of sub-optimal radiotherapy techniques [27]. Nevertheless, even contemporary techniques include anterior parts of the heart, such as the anterior interventricular branch of left coronary artery, in the treatment volume [9], [22]. The clinical impact of this is difficult to assess, partly because the morphology of coronary artery disease following radiation is no different from that of spontaneous atherosclerosis and, therefore, can not be diagnosed specifically [38].

Myocardial perfusion scintigraphy is recognized as a reliable non-invasive approach for the assessment of regional myocardial perfusion [24], [25], and has previously been used to evaluate the relation between radiotherapy and coronary artery disease [4], [5], [10], [11], [13], [14], [15], [28], [29], [37]. If a given radiotherapy technique causes damage to the coronary vessels, one would expect an increased prevalence of perfusion defects in irradiated patients compared with non-irradiated patients, and these defects would be located in the irradiated region of the heart.

The aim of this study was to assess the occurrence and location of abnormal regional myocardial perfusion at rest and during stress in left-sided mastectomized patients, randomized to treatment with or without postoperative radiotherapy according to the guidelines from the Danish Breast Cancer Cooperative Group (DBCG).

Section snippets

Patients

This study includes 17 recurrence-free patients, who had been randomized in the DBCG 82b and 82c trials, conducted from 1982 to 1990. The design and results of the trial have been described previously [2], [8], [30], [31], [32]. In brief, mastectomized high-risk breast cancer patients were randomized to adjuvant systemic treatment, with or without postoperative irradiation. Pre- and peri-menopausal women were randomized to post-mastectomy radiotherapy plus 600 mg/m2 cyclophosphamide, 40 mg/m2

Medical history

The median age was 59 years (range, 47–75 years), and the patients had been followed for a median of 7.9 years (range, 6.0–12.2 years). Ten patients received systemic treatment plus radiotherapy (RT-group), and seven received systemic treatment alone (no-RT group). The systemic treatment, age at scintigraphy and length of follow-up for the individual patients are given in Table 1. One patient (no. 13) had known paroxystic tachycardia not requiring treatment, and another patient (no. 12) was on

Discussion

Several studies have evaluated late cardiac complications after radiotherapy using myocardial scintigraphy. Most of these studies are dealing with patients irradiated for Hodgkin's disease using treatment techniques that include a large part of the heart to a total dose of 30 Gy or more, and the results are contradictory [4], [10], [11], [13], [28], [29], [37]. Irradiation for breast cancer differs substantially from irradiation in Hodgkin's disease, as the clinical target in breast cancer only

Conclusion

The present study does not indicate that the radiotherapy technique used in the DBCG 82b and 82c trials causes IHD. However, the small number of patients does not allow strong conclusions to be drawn.

Acknowledgements

Inger Højris was supported by grants from the Danish Cancer Society, Dr Agnethe Løvgreens Legat and the Clinical Research Unit at the Oncology Center, Aarhus University Hospital. Niels Peter Rønnow Sand was supported by grants from the Danish Heart Foundation and the Institution of Experimental Clinical Research, Aarhus University Hospital.

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