Ischemic heart disease after mantlefield irradiation for Hodgkin's disease in long-term follow-up

Radiation-associated cardiovascular disease

As the number of cancer survivors grows because of advances in therapy, it has become more important to understand the long-term complications of these treatments. This article presents the current knowledge of adverse cardiovascular effects of radiotherapy to the chest. Emphasis is on clinical presentations, recommendations for follow-up, and treatment of patients previously exposed to irradiation. Medline literature searches were performed, and abstracts related to this topic from oncology and cardiology meetings were reviewed. Potential adverse effects of mediastinal irradiation are numerous and can include coronary artery disease, pericarditis, cardiomyopathy, valvular disease and conduction abnormalities. Damage appears to be related to dose, volume and technique of chest irradiation. Effects may initially present as subclinical abnormalities on screening tests or as catastrophic clinical events. Estimates of relative risk of fatal cardiovascular events after mediastinal irradiation for Hodgkin's disease ranges between 2.2 and 7.2 and after irradiation for left-sided breast cancer from 1.0 to 2.2. Risk is life long, and absolute risk appears to increase with length of time since exposure. Radiation-associated cardiovascular toxicity may in fact be progressive. Long-term cardiac follow-up of these patients is therefore essential, and the range of appropriate cardiac screening is discussed, although no specific, evidence-based screening regimen was found in the literature.

Partial irradiation of the heart

Radiation-induced heart disease (RIHD) includes pericarditis, ischemic heart disease, and myocardial infarction and leads in some cases to fatal complications. It has been shown that the increased survival due to radiotherapy could be negated by excess deaths from RIHD in breast cancer radiotherapy for left-sided tumors. Subclinical effects following irradiation have been detected in several studies both of breast cancer and Hodgkin's irradiation. The dose-volume response relationships describing cardiac complications have been studied for pericarditis and cardiac mortality by means of biologic models, including the well-known Lyman-Kutcher-Burman (LKB) model and Källman's relative seriality model. Studies by Martel and coworkers on pericarditis and by Gagliardi and coworkers on cardiac mortality are reviewed. The anatomical and functional definition of the heart represents a key issue in modeling, as it affects strongly the dosimetrical data to be used as input data in the models. Several treatment strategies to decrease heart irradiation, based on models and/or based on dose-distribution evaluations, are reviewed. It is concluded that left-sided breast cancer patients should always be 3-dimensional (3D) dose planned.

Structural changes in the auricles of the rat heart after local ionizing irradiation

BACKGROUND AND PURPOSE

Irradiation of the heart may lead to late cardiovascular complications and depending on the dose to cardiac-related death. There is increasing evidence that left atrial appendages play an important role in left ventricular filling especially in cardiac disease. The aim of the present study was to investigate the radiation response of the atria of the rat heart (auricles in particular) at morphological, histological and transcriptional level.

MATERIAL AND METHODS

Sprague-Dawley rats were irradiated with a single dose locally on the heart (0-22.5 Gy). End-diastolic diameters of left auricles were measured during evaluation of cardiac function. Histopathological evaluations were performed at various time points up to 16 months post irradiation. Changes in mRNA expression of procollagen types I and III and pro-fibrogenic cytokines (TGF-beta1 and IL-1beta) were investigated using competitive PCR.

RESULTS

Irradiation leads to a dose-dependent decrease in end-diastolic diameter of the left auricles. This decrease was observed at 4 months post-irradiation, where no gross damage of the ventricle has been reported. Histologically, epicardial fibrosis was found already 1 month post irradiation, and the frequency/severity of the structural changes appeared to be dose-dependent and progressive with time post irradiation. At 9 months, fibrosis was observed in all three layers (epicardium, myocardium and endocardium) of both auricles. On the level of gene expression, increases in procollagen types I and III were observed at 12 and 3 months post irradiation, respectively. Increases in IL-1beta and TGF-beta1, cytokines known to influence collagen deposition at different levels, preceded the upregulation of procollagen mRNA.

CONCLUSIONS

Auricles of the rat heart show a marked pathological response to ionizing radiation, characterized by generalized accumulation of collagen (fibrosis) and a reduction of end-diastolic diameter. The reduction of auricular volume and loss of elasticity will negatively contribute to the pump function of the irradiated ventricle.

Post mediastinal radiation coronary artery disease and its effects on arterial conduits

Therapeutic mediastinal radiation predisposes patients to an increased risk of developing premature coronary artery disease. Other structures surrounding the heart within the radiation field are also susceptible to injury. This case report highlights the importance of recognizing concurrent damage to the internal mammary artery that, in this particular group of patients, may not be the ideal arterial conduit for coronary artery bypass surgery.

Thallium-201 scintigraphy is not predictive of late cardiac complications in patients with Hodgkin's disease treated with mediastinal radiation

PURPOSE

To assess whether abnormalities depicted by Thallium-201 scintigraphy can predict the occurrence of late cardiac complications in patients with Hodgkin's disease treated with mantle field radiation therapy.

METHODS AND MATERIALS

Thallium scintigraphy was performed in 49 patients at a median of 75 months after initial treatment (range 28-208 months). Initial treatment consisted in chemotherapy, given to two-thirds of the patients and mantle field radiation, delivered to all patients, using a 25-MV linear accelerator. Myocardial perfusion defects were observed in 78% of patients on thallium scintigraphy. These patients had their cardiac status reassessed at a median follow-up of 13.5 years after treatment.

RESULTS

Forty-two patients were assessable, as data on the cardiac status were missing in 7 patients. The majority of patients received at least 40 Gy, and 75% of them were treated with one field per day. The median follow-up of patients is 13.5 years (range 9-24.5). Eleven cardiac complications were observed in 9 patients (coronary artery disease [n = 2], conduction-system abnormalities [n = 3], valvular defects [n = 5], and congestive heart disease [n = 1]). The median 15-year actuarial incidence of cardiac complications was 21% (95% confidence interval of 9-40%). The positive and negative predictive value of thallium scintigraphy was 19% and 77%, respectively. The univariate analysis showed that the extent of left ventricle exposure to irradiation was an adverse prognostic factor, and chemotherapy administered before mantle field irradiation was of borderline significance.

CONCLUSION

Thallium scintigraphy is not predictive of late cardiac complications. The extent of left ventricle exposure to radiation and possibly chemotherapy given before radiation treatment are adverse prognostic factors.

Three-dimensional intravascular ultrasound assessment of noninjured edges of beta-irradiated coronary segments

BACKGROUND

The "edge effect," late lumen loss at the margins of the treated segment, has become an important issue in the field of coronary brachytherapy. The aim of the present study was to assess the edge effect in noninjured margins adjacent to the irradiated segments after catheter-based intracoronary beta-irradiation.

METHODS AND RESULTS

Fifty-three vessels were assessed by means of 3-dimensional intravascular ultrasound after the procedure and at 6- to 8-month follow-up. Fourteen vessels (placebo group) did not receive radiation (sham source), whereas 39 vessels were irradiated. In the irradiated group, 48 edges (5 mm in length) were identified as noninjured, whereas 18 noninjured edges were selected in the placebo group. We compared the volumetric intravascular ultrasound measurements of the noninjured edges of the irradiated vessels with the fully irradiated nonstented segments (IRS, n=27) (26-mm segments received the prescribed 100% isodose) and the noninjured edges of the vessels of the placebo patients. The lumen decreased (6 mm(3)) in the noninjured edges of the irradiated vessels at follow-up (P:=0. 001). We observed a similar increase in plaque volume in all segments: noninjured edges of the irradiated group (19.6%), noninjured edges of the placebo group (21.5%), and IRS (21.0%). The total vessel volume increased in the IRS in the 3 groups. No edge segment was subject to repeat revascularization.

CONCLUSIONS

The edge effect occurs in the noninjured margins of radiation source train in both irradiated and placebo patients. Thus, low-dose radiation may not play an important role in this phenomenon, whereas nonmeasurable device injury may be considered a plausible alternative explanation.