Background and purpose: In patients with Hodgkin's disease treated by radiotherapy with a moderate total dose and a low (mean) fraction dose to the heart, the risk of ischemic heart disease was investigated during long-term follow-up.
Materials and methods: The medical records of 258 patients treated in the period 1965-1980 with radiotherapy alone as the primary treatment were reviewed. The median follow-up was 14.2 years (range 0.7-26.2). The mean total dose and fraction dose to the heart were 37.2 Gy (SD 2.9) and 1.64 Gy (SD 0.09), respectively. The impact on the development of ischemic heart disease of treatment-related parameters, such as the applied (fraction) dose, irradiation technique (one or two fields per day), and chemotherapy in case of a relapse, was investigated. The incidence of ischemic heart disease in this patient population was compared with the expected incidence based on gender, age and calendar period-specific data for the Dutch population.
Results: Thirty-one patients (12%) experienced ischemic heart disease (actuarial risk at 20-25 years: 21.2% (95% C.I. 15-30). Twenty-five of them were hospitalized. When compared with the expected incidence, the relative risk (RR) of hospital admission for ischemic heart disease was 2.7 (95% C.I. 1.7-4.0). There were 12 deaths (4.7%) due to ischemic myocardial or sudden death (actuarial risk at 25 years: 10.2% (95% C.I. 5.3-19), compared to 2.3 cases that were expected to have died from these causes, yielding a standardized mortality ratio (SMR) of 5.3 (95% C.I. 2.7-9.3). Gender (male), pretreatment cardiac medical history and increasing age appeared to be the only significant factors for the development of ischemic heart disease.
Conclusions: Despite the moderate total dose and the low (mean) fraction dose to the heart, the observed incidence of ischemic heart disease is high, especially after long follow-up periods. Treatment related cardiac disease in patients treated for Hodgkin's disease has only been reported for doses above 30 Gy. Although the optimum curative dose is still under debate, some studies recommend a dose as low as 32.5 Gy. The observed high rate of severe heart complications in this study advocates a dose reduction to this level, particularly in the regions where the coronary arteries are located.