The results of this study demonstrate that catheter ablation is an effective and safe modality for treating AF in selected patients with cancer. The success rate, defined as freedom from recurrent AF, with or without AAD, and need for repeat ablation at 12 months post-ablation, in patients with cancer was similar to that observed in non-cancer controls. At the same time, safety outcomes, including post-procedural bleeding, pulmonary vein stenosis, stroke, and cardiac tamponade within the first 3 months after catheter ablation, were also similar to non-cancer controls.
There is limited data evaluating the effectiveness and safety of catheter ablation for AF in patients with cancer. A prior propensity-matched cohort study evaluated the effectiveness and safety of cryoablation for AF in 70 patients with cancer and 70 non-cancer controls21. In this study, arrhythmia free survival at 12 months did not differ significantly between patients with cancer and controls (67.1 ± 5.8% vs. 77.8 ± 5.1%, p = 0.16). Our results agree with and add to the results of this prior study. Importantly, compared to this prior study, our study included a larger number of patients, more patients with active cancer, and both radiofrequency and cryoablation procedures.
The safety of catheter ablation for AF in patients with cancer has been evaluated in 2 prior studies. Eitel et al. evaluated safety outcomes including the development of phrenic nerve palsy, femoral pseudoaneurysms, peri-procedural bleeding, cardiac tamponade, and death and found no difference between cancer and non-cancer patients21. In contrast, Giustozzi et al. found a significantly higher risk of clinically relevant bleeding within 1 month after catheter ablation in 21 patients with cancer compared to 163 non-cancer controls 22. A potential reason for the excess bleeding risk observed by Giustozzi et al. includes their practice of bridging with low molecular weight heparin after the procedure rather than continuing anticoagulation without interruption, as is the usual practice at the institutions included in our study. Furthermore, more than half the patients included in the study by Giustozzi et al. had a history of gastrointestinal and genitourinary malignancies that are more prone to bleeding with anticoagulation than other cancers 23.
In our study, radiofrequency ablation was used more frequently in patients with cancer, while cryoablation was used more commonly in controls. While we do not have data to explain the rationale behind this discrepancy, one possible explanation may be the reduced fluoroscopic exposure with radiofrequency ablation compared to cryoablation. However, both techniques have been shown to be equally efficacious and safe in randomized clinical trials and therefore it is not surprising that outcomes were similar between cancer and non-cancer controls in our cohort24. Additionally, we performed multivariate regression analysis and the type of ablation performed was not identified as a significant predictor of outcomes.
We used multivariable analysis to identify potential predictors of recurrent AF after a 90-day blanking period in patients with and without cancer. BMI was identified as a significant predictor in both groups (Central Illustration). This result is not surprising since obesity has been associated with an increased risk of recurrent AF after ablation in prior studies.25,26 Moreover, it has been shown that 10% or more weight loss prior to ablation or bariatric surgery prior to ablation, are both associated with a significant reduction in the risk of recurrent AF.27,28
Thoracic radiation therapy for cancer has been postulated to promote inflammation and tissue fibrosis, potentially leading to an increased risk of recurrent AF after ablation. Prior studies have had conflicting results regarding the impact of thoracic radiation therapy for cancer on left atrial scar volume. One study of 7 cancer patients (6 lymphoma and 1 esophageal cancer) treated with thoracic radiation demonstrated a linear relationship between mean cardiac radiation dose and left atrial scar volume on cardiac magnetic resonance imaging.29 In contrast, another study comparing 38 patients with breast cancer to non-cancer controls did not find any difference in LA scar volumes during electrophysiology mapping30. Interestingly, our results did not identify left sided radiation as a significant predictor of recurrent AF in patients with cancer. Similarly, Etial et al. found that arrhythmia-free survival was not reduced in patients with a history of thoracic radiation relative those who did not receive thoracic radiation.21
Our study has several limitations. Given that this was a retrospective cohort study, we cannot rule out the possibility of selection bias among patients referred for ablation. While this is the largest cohort study to date of cancer patients undergoing catheter ablation for AF, the number of patients is still relatively low, with a small proportion of patients with active cancer (18.3%). Therefore, the true impact of active cancer therapy on the effectiveness, and more importantly, safety of catheter ablation may not be accurately assessed in this study. The types of cancer and cancer therapies were also heterogeneous in our study and further studies are needed to evaluate the effectiveness of catheter ablation for certain cancer therapies, such as Bruton’s tyrosine kinase inhibitors, that are associated with a higher risk of AF.
In conclusion, the results of our retrospective cohort study demonstrate that catheter ablation for AF is effective and safe in patients with cancer. The outcomes observed in cancer patients are similar to those seen in patients without cancer, supporting the recommendation that ablation should be offered as a therapeutic modality to treat AF in selected patients with cancer.