CORONADO, CALIF. – Skin injury following fenestrated endovascular aortic stent grafting is less prevalent than expected, results from a single-center retrospective study showed.
“Radiation-induced skin injury is a serious potential complication of fluoroscopically guided interventions,” Dr. Melissa L. Kirkwood said at the annual meeting of the Western Vascular Society. “These injuries are associated with a threshold radiation dose, above which the severity of injury increases with increasing dose. Instances of these injuries are mostly limited to case reports of coronary interventions, TIPS procedures, and neuroembolizations.”
Dr. Melissa L. Kirkwood
These radiation-induced skin lesions can be classified as prompt, early, mid-term, or late depending on when they present following the fluoroscopically guided intervention. “The National Cancer Institute has defined four grades of skin injury, with the most frequent being transient erythema, a prompt reaction within the first 24 hours occurring at skin doses as low as 2 Gy,” said Dr. Kirkwood of the division of vascular and endovascular surgery at the University of Texas Southwestern Medical Center, Dallas. “With increasing skin doses, more severe effects present themselves. Atrophy, ulceration, and necrosis are possibilities.”
She went on to note that fenestrated endovascular aneurysm repairs often require high doses of radiation, yet the prevalence of deterministic skin injury following these cases is unknown. In a recent study, Dr. Kirkwood and her associates retrospectively reviewed 61 complex fluoroscopically guided interventions that met substantial radiation dose level criteria (SRDL), which is defined by the National Council on Radiation and Protection Measurements as a reference air kerma (RAK) greater than or equal to 5 Gy (J. Vasc. Surg. 2014; 60[3]:742-8). “Despite mean peak skin doses as high as 6.5 Gy, ranging up to 18.5 Gy, we did not detect any skin injuries in this cohort,” Dr. Kirkwood said. “That study, however, was limited by its retrospective design. There was no postoperative protocol in place to ensure that a thorough skin exam was performed on each patient at every follow-up visit. Therefore, we hypothesized that a more thorough postoperative follow-up of patients would detect some skin injury following these cases.”
For the current study, she and her associates sought to examine the prevalence of deterministic effects after FEVAR as well as well as any patient characteristics that may predispose patients to skin injury.
In June 2013, the researchers implemented a new policy regarding the follow-up of FEVAR patients, which involved a full skin exam at postoperative week 2 and 4, and at 3 and 6 months, as well as questioning patients about any skin-related complaints. For the current study, they retrospectively reviewed all FEVARs over a 7-month period after the change in policy and highlighted all the cases that reached a RAK of 5 Gy or greater. The RAK was the dose metric used in this study. It is a measure of the radiation dose to air at the interventional reference point, which, on standard fluoroscopes, is 15 cm along the beam axis toward the focal spot from isocenter. Dr. Kirkwood characterized RAK as “the best real-time indicator of patient dose, because it roughly estimates the dose at the entry point on the patient’s skin.” Peak skin dose, a dose index, and simulated skin dose maps were calculated using customized software employing input data from fluoroscopic machine logs.
Of 317 cases performed, 22 met or exceeded a RAK of 5 Gy. Of these, 21 were FEVARs and one was an embolization. Most patients (91%) were male and their mean body mass index was 30 kg/m2. Comorbidities and risk factors for skin injury included smoking, diabetes, and the concomitant applications of chemotherapeutic agents.
Dr. Kirkwood reported that the average RAK for all FEVARs was 8 Gy, with a range of 5-11 Gy. Slightly more than half of patients (52%) had multiple fluoroscopically guided interventions within 6 months of their SRDL event. The average RAK for this subset of patients was 10 Gy (range of 5 to 15).
The mean peak skin dose for all FEVARs was 5 Gy (a range of 2 to 10 Gy), and the dose index was 0.69. The average peak skin dose for the subset of patients with multiple procedures was 7 Gy (a range of 3 to 9 Gy).
In terms of the follow-up, all 21 FEVAR patients were examined at the 1- or 2-week mark, 81% were examined at 1 month, 52% were examined at 3 months, and 62% were examined at 6 months. No radiation skin injuries were reported. “Based on the published data, we would expect to see all grades of skin injury, especially in the cohort of the 5-10 Gy,” Dr. Kirkwood said.