The efficacy and safety of microwave ablation in patients with retroperitoneal metastases

Percutaneous Microwave Ablation for Treatment of Retroperitoneal Tumors

Purpose To determine if microwave ablation (MWA) of retroperitoneal tumors can safely provide high rates of local tumor control. Materials and Methods This retrospective study included 19 patients (median age, 65 years [range = 46-78 years]; 13 [68.4%] men and six [31.6%] women) with 29 retroperitoneal tumors treated over 22 MWA procedures. Hydrodissection (0.9% saline with 2% iohexol) was injected in 17 of 22 (77.3%) procedures to protect nontarget anatomy. The primary outcomes evaluated were local tumor progression (LTP) and complication rates. Oncologic outcomes, including overall survival (OS), progression-free survival (PFS), and treatment-free interval (TFI), were examined as secondary outcome measures. Results Median follow-up was 18 months (range = 0.5-113). Hydrodissection was successful in displacing nontarget anatomy in 16 of 17 (94.1%) procedures. The LTP rate was 3.4% (one of 29; 95% CI: 0.1, 17.8) per tumor and 5.3% (one of 19; 95% CI: 0.1, 26.0) per patient. The overall complication rate per patient was 15.8% (three of 19), including two minor complications and one major complication. The OS rate at 1, 2, and 3 years was 81.8%, 81.8%, and 72.7%, respectively, with a median OS estimated at greater than 7 years. There was no evidence of a difference in OS (P = .34) and PFS (P = .56) between patients with renal cell carcinoma (six of 19 [31.6%]) versus other tumors (13 of 19 [68.4%]) and patients treated with no evidence of disease (15 of 22 [68.2%]) versus patients with residual tumors (seven of 22 [31.8%]). Median TFI was 18 months (range = 0.5-108). Conclusion Treatment of retroperitoneal tumors with MWA combined with hydrodissection provided high rates of local control, prolonged systemic therapy-free intervals, and few serious complications. Keywords: Ablation Techniques (ie, Radiofrequency, Thermal, Chemical), Retroperitoneum, Microwave Ablation, Hydrodissection © RSNA, 2024.

Combined use of microwave ablation and cell immunotherapy induces nonspecific immunity of hepatocellular carcinoma model mice

Microwave ablation (MWA) has been widely used in the treatment of solid tumors. Studies have been less conducted on the efficacy of MWA used with cell immunotherapy in treating hepatocellular carcinoma (HCC). The current study aimed at exploring the efficacy of MWA in combination with cell immunotherapy in treating HCC. Hepa1-6 HCC mice were treated by MWA, blockade, or the combined therapy (MWA used with blockade), or left untreated. Survival rates of the mice were plotted by Kaplan-Meier Curve, followed by log-rank test. 25 days after the operation, surviving mice were monitored for tumor recurrence, and tumor volumes were calculated every 5 days. Immunohistochemistry and flow cytometry were performed to detect the numbers of CD4⁺ and CD8⁺ cells in the tumors and spleens of mice. The expressions of related cytokines were detected and measured by ELISPOT and ELISA. The results showed that MWA combined with anti-PD-1/anti-CTLA-4 not only increased the survival time, protected the mice against tumor recurrence, but also enhanced the intratumoral infiltration of cytotoxic T lymphocyte and systemic T-cell immune responses induced by MWA through activation of synergistically specific antitumor immunity. In addition, the combined therapy increased T-helper 1 cell (Th1-type) cytokines, but reduced Th2-type cytokines, resulting in the polarization of Th1 cells. T-cell immune responses of HCC cells were activated by MWA. In addition, the combined therapy of MWA and anti-PD-1/anti-CTLA-4 induced Th1-type immune response, and showed specific antitumor immunity.