Tumor Seeding along the Puncture Tract in CT-Guided Interstitial High-Dose-Rate Brachytherapy
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Buttner, L., Ludemann, W. M., Jonczyk, M., Denecke, T., Schnapauff, D., Wieners, G., . . . Boning, G. (2020). Tumor Seeding along the Puncture Tract in CT-Guided Interstitial High-Dose-Rate Brachytherapy. J Vasc Interv Radiol, 31(5), 720-727. doi:10.1016/j.jvir.2019.10.006
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Single-center, retrospective review
Research support from the National Cancer Institute and National Institute of Arthritis and Musculoskeletal and Skin Diseases
Departments of Radiology, Radiooncology, and Radiotherapy
Charité, Universitätsmedizin Berlin, Germany
Figure 3. Examples of tumor seeding.
CT-guided high-dose-rate brachytherapy (CT-HDRBT) is a local radiotherapy treatment which has shown positives outcomes for the treatment of primary and secondary liver and lung cancers, as well as adrenal, renal, and lymph node tumors. CT-HDRBT involves percutaneously placing a radiation source (iridium-192) into or near a tumor via a catheter and subsequently removing the source after the treatment is complete. CT-HDRBT does not pose the risk of damaging thermosensitive structures and lacks the heat sink effects of other percutaneous ablation techniques. One concern with CT-HDRBT is the lack of post-treatment thermal tract ablation and the potential for tumor seeding. The goal of this study was to quantify tumor seeding after CT-HDBRT and identify potential risk factors.
The authors retrospectively reviewed 1,765 CT-HDRBT treatments in 1,034 patients. The treated tumors included HCC, CRC, and breast cancer in the liver (92.3%), lung (3.9%), and lymph nodes (1.6%). 56.4% of patients received a single treatment, 25.8% received two treatments, and 9.8% received three treatments. 8.2% of patients underwent combined therapy with either TACE, DEB TACE, irinotecan TACE, or TAE. The median follow-up imaging was 15.4 months.
The authors defined tumor tract seeding as tumor cell displacement along a previous catheter or biopsy needle tract. Tumor tract seeding was further classified as outside the treated organ (extraorganic) or inside the treated organ (intraorganic). Only extraorganic tumor seeding was included in this study in order to more precisely differentiate seeding from local recurrence. Tumor seeding was diagnosed based on imaging findings.
Tumor seeding occurred at a median of 8 months and at a rate of 1.5% per intervention, corresponding to a seeding risk of 0.7% per catheter. Tumor seeding most commonly occurred in the context of primary disease progression. Patient age was the only detectable potential risk factor for tumor seeding. Hyper-vascularization may be a risk factor for seeding and patients in this study with hypervascular tumors were treated with CT-HDRBT coupled with either TACE or TAE. While the seeding rate was lower with the combined treatment, the sample size was not large enough to make a definite conclusion. Percutaneous tract irradiation had no effect on tumor seeding occurrence. Cancer type, tumor size, number of catheters used, and previous therapies were not risk factors for tumor seeding.
The authors reviewed 1,034 patients with 1,765 CT-HDRBT treatments and displayed a 1.5% overall tumor seeding rate. The study is limited by its retrospective design, the exclusion of intraorganic tumors, and the reliance on imaging diagnosis of tract seeding. The study demonstrated an impressively small tumor seeding rate in an extensive patient population. The 1.5% seeding rate is comparable to the published ranges for other percutaneous ablation procedures. This result is contradictory to the concern that absence of tract ablation raises the risk of seeding. Future studies investigating intraorganic seeding as well as the associated clinical outcomes will be helpful to better understand the risks and clinical impact of tract seeding. Nevertheless, these results suggest that the seeding rate is low and the concern for tumor seeding risk should not discourage treatment in an otherwise ideal candidate.
Resident Physician, Integrated Interventional Radiology
Dotter Department of Interventional Radiology
Oregon Health & Science University