Mortality risk is higher for coronary artery disease (CAD) associated with radiation treatment than that from typical atherosclerosis, an observational study of patients undergoing percutaneous coronary intervention (PCI) suggested.
Patients with CAD associated with prior radiation therapy had higher mortality risk during more than 6 years of follow-up than did those with atherosclerotic CAD (38% versus 27% for atherosclerosis group, P=0.04). Even after multivariable adjustment, radiation exposure was an independent predictor for all-cause mortality (hazard ratio [HR] 1.85, 95% CI 1.21-2.85).
Mortality from cardiovascular causes was also elevated in the prior radiation group (adjusted HR 1.70, 95% CI 1.06-2.89), according to the investigation published in the June 2016 issue of Circulation: Cardiovascular Interventions.
“This is the first study to establish previous external beam radiation therapy exposure as an independent risk factor for all-cause and cardiovascular mortality after PCI,” wrote authors Milind Y. Desai, MD, of Cleveland Clinic, and colleagues.
“Furthermore, our results are supportive of the premise that cardiovascular death is common among patients with malignancy who initially survive external beam radiation therapy (i.e., radiation survivors), particularly those previously treated with thoracic radiation that have developed concomitant CAD requiring PCI.”
“We have previously demonstrated that previous external beam radiation therapy exposure was an independent risk factor for increased long-term mortality in patients undergoing cardiac surgery, including isolated coronary artery bypass graft [CABG] and combined CABG and valvular surgery,” they added.
The authors concluded that their data “seem to validate that alternative treatment strategies may be warranted in patients with previous external beam radiation therapy exposure requiring cardiac surgery.”
After multivariable adjustment, other predictors of long-term mortality after PCI were:
- Balloon angioplasty or bare metal stents (HR 2.50, 95% CI 1.61-3.97)
- SYNTAX score greater than 10 (HR 1.99, 95% CI 1.32-3.04)
- New York Heart Association functional class 3 or worse (HR 1.83, 95% CI 1.15-2.91)
- Current or previous smoking (HR 1.88, 95% CI 1.10-3.09)
- Age 65 or older (HR 1.70, 95% CI 1.07-2.75)
Desai’s single-center study included patients undergoing PCI at one tertiary care center, with the 157 with prior external beam radiation therapy matched with 157 with atherosclerotic CAD and no prior radiation therapy exposure.
“As ours was a population of patients selected for PCI, our cohort did not include patients who underwent CABG or patients with asymptomatic CAD. Thus, the true prevalence of ostial CAD in patients with radiation-associated CAD is likely higher than observed in this PCI-only population,” the authors cautioned.
“In addition, although valvular heart disease is a known complication of external beam radiation therapy, in our sample, few patients had moderate or severe valvular pathology. This is likely because that at our institution, these patients are routinely selected for combined valve replacement surgery and CABG rather than PCI.”
Another caveat was that the radiation and atherosclerotic CAD cohorts had several differing baseline and procedural characteristics despite matching. There were different rates of:
- Hypertension (61% for the radiation group versus 48% for the atherosclerosis group, P=0.027)
- History of chronic heart failure (25% versus 13%, P<0.011)
- Aortic insufficiency (0% versus 2%, P=0.037)
- Severe mitral regurgitation (3% versus 2%, P=0.003)
- Complex B2/C lesions (71% versus 36%, P<0.001)
Of note, “when stratified by the type of PCI, patients treated with bare metal stents or balloon angioplasty were at particularly high risk for both all-cause and cardiovascular mortality in the external beam radiation therapy group, but not in the comparison group,” the investigators commented.
Desai and colleagues suggested this may be due to certain comorbidities in the balloon angioplasty and bare metal stenting groups — bleeding, subsequent surgery, for example — that prevented drug-eluting stent (DES) implantation in patients in the first place.
“However, given our data, it may be reasonable to consider DES in patients with previous external beam radiation therapy whenever possible,” they concluded.
Desai reported no relevant relationships with industry.
Circulation: Cardiovascular Interventions
Reed GW, et al “Long-term mortality in patients with radiation-associated coronary artery disease treated with percutaneous coronary intervention” Circ Cardiovasc Interv 2016; DOI: 10.1161/CIRCINTERVENTIONS.115.03483.