Prior Radiation Therapy for Cancer Increases Mortality Risk After PCI

Patients who are treated with radiotherapy for cancer and then develop coronary disease years later have a higher risk of death after PCI compared with patients who have ischemic disease. 

“Inherently, this points to the fact that the radiation group is much sicker and there are a lot of other factors at play in these patients that make them more prone to greater mortality risk compared with those who have CAD but never had radiation therapy,” said the paper’s senior author, Milind Y. Desai, MD (Cleveland Clinic, Cleveland, OH), in an interview with TCTMD.

For the study, Desai and colleagues led by Grant W. Reed, MD,

looked at 157 patients with previous external beam radiation therapy and 157 age- and sex-matched controls who had CAD but no previous radiation therapy. Participants were relatively young, with an average age of 65 years, and most patients in the radiation group were women who had been treated for breast cancer.

The average length of time since radiation treatment and the PCI procedure was 13 years. The primary indication for PCI in more than half of patients in both groups was ACS. As previous studies of cancer patients have shown, many of those in the radiation therapy group—approximately one-third—had left main or ostial CAD. Among patients in both groups who received stents, 39% of all those implanted were BMS and 53% were DES.

Radiation Linked to Higher Mortality

Published June 16, 2016, in Circulation: Cardiovascular Interventions, the study found that over an average time frame of 6.65 years after PCI, more patients with versus without prior radiation therapy died (59% vs 42%; P = 0.04). Sixty-nine of the 101 deaths were due to cardiovascular causes, again with more deaths among those with versus without a history of radiation therapy. Among the radiation therapy patients, more deaths were due to cardiovascular causes than to malignancy or other reasons.

After multivariable adjustment, previous radiation therapy was an independent predictor of increased all-cause and cardiovascular mortality.

Interestingly, when stratified by PCI type, balloon angioplasty or BMS were associated with greater increases in both all-cause and cardiovascular mortality compared with DES. However, this finding only held true on Kaplan-Meier analysis through 16 years for patients with radiation-associated CAD.

“I was surprised that it showed up, but it was not a knock-my-socks-off kind of surprise,” Desai said. “Techniques evolve, and we know that DES are better than plain old balloon angioplasty or BMS.”

He and his colleagues say that while it is possible that patients selected for angioplasty or BMS had comorbidities such as bleeding issues or upcoming surgeries, which precluded DES use, they encourage physicians to consider DES in these patients whenever possible.

Delayed Consequences of Radiation

To TCTMD, Desai said a hallmark of radiation-associated CAD in many patients is aggressive disease such as left main or multivessel involvement at an early age. “They present with a nasty brand of aggressive disease often 10 or more years down the road from when they’ve been treated,” he noted. “It’s not entirely out of left field to see somebody with prior Hodgkin’s lymphoma treated with radiation who has 50-60% left main disease.”

Both clinicians and patients need to be aware of the increased risks and take appropriate steps to prevent and treat CAD, Desai observed, adding that patients should ask their primary care physicians around the 5-year mark postradiation therapy if they should be seeing a cardiologist.

“People in this study had radiation therapy about 15 or so years ago, which was a time when we were not very cognizant of being careful about [radiation dose],” he added. “Now things have evolved to a point where we are planning radiation treatments to minimize collateral damage. Hopefully, the good things that people are doing now in terms of radiation will make a difference 15 years from now, so that we might see a different result than what we see in this study.”

Source:

• Reed GW, Masri A, Griffin BP, et al. Long-term mortality in patients with radiation-associated coronary artery disease treated with percutaneous coronary intervention. Circ Cardiovasc Interv. 2016;Epub ahead of print.  

Disclosures:

• Reed and Desai report no relevant conflicts of interest.