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CT Guided Ablation of T1 Renal Tumors
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. (Uroradiologisk forskargrupp)
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The widespread use of medical imaging contributes to the increased detection of incidentally detected small renal tumors, a majority which are often indolent masses found in elderly patients with preexisting chronic kidney disease. In Sweden, partial nephrectomy with minimal invasive surgical approach is the current standard for removing these tumors, although another option is percutaneous image-guided tumor ablation that allows treatment of elderly patients with comorbidities for who surgery is a risk. Due to the lack of long-term follow-up studies and prospective randomized trials, ablation is still considered an alternative option to surgery in Sweden. The aim of this thesis was to evaluate treatment of T1 renal tumors with CT guided radiofrequency (RFA) and microwave ablation (MWA).

Factors affecting the efficacy rate of complete tumor ablation with RFA after a single session were evaluated (Paper I). Optimal electrode placement and a long tumor distance to the collecting system were associated with an increased primary efficacy. Renal tumor RFA was compared with laparoscopic partial nephrectomy (LPN: Papers II-III): both methods had comparable secondary efficacy rates, but RFA involved several treatment sessions. Total session times and hospitalization times were shorter and complications less frequent for RFA than for LPN (Paper II). After treatment, renal function impact was assessed by evaluation of both renal function quantity and quality through determination of the split renal function (SRF: Paper III). Standard renal function measurements were assessed and both RFA and LPN were nephron sparing when treating small renal tumors and did not affect creatinine or GFR. However, LPN involved greater SRF reduction in the affected kidney than RFA. Initial experience with microwave ablation was evaluated and this new ablation technique demonstrated high efficacy rates with fewer complications, and was comparable with the mid-term results of now established ablation techniques (Paper IV).

In conclusion, CT guided RFA and MWA are safe and effective treatments for the removal of T1 renal tumors. This thesis provides further insights into the field of thermal ablation of small renal masses, which can aid future treatment selection and patient management.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. , p. 71
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1598
Keywords [en]
Renal tumor, Ablation, Radiofrequency ablation, Microwave ablation
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
URN: urn:nbn:se:uu:diva-392318ISBN: 978-91-513-0750-3 (print)OAI: oai:DiVA.org:uu-392318DiVA, id: diva2:1348475
Public defence
2019-11-01, Grönwallsalen, Akademiska sjukhuset, ingång 70, bv, Uppsala, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2019-10-11 Created: 2019-09-04 Last updated: 2019-11-12
List of papers
1. Predictive factors for complete renal tumor ablation using RFA
Open this publication in new window or tab >>Predictive factors for complete renal tumor ablation using RFA
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2016 (English)In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, no 7, p. 886-893Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Radiofrequency ablation (RFA) can be used to treat renal masses in patients where surgery is preferably avoided. As tumor size and location can affect ablation results, procedural planning needs to identify these factors to limit treatment to a single session and increase ablation success.

PURPOSE: To identify factors that may affect the primary efficacy of complete renal tumor ablation with radiofrequency after a single session.

MATERIAL AND METHODS: Percutaneous RFA (using an impedance based system) was performed using computed tomography (CT) guidance. Fifty-two renal tumors (in 44 patients) were retrospectively studied (median follow-up, 7 months). Data collection included patient demographics, tumor data (modified Renal Nephrometry Score, histopathological diagnosis), RFA treatment data (electrode placement), and follow-up results (tumor relapse). Data were analyzed through generalized estimating equations.

RESULTS: Primary efficacy rate was 83%. Predictors for complete ablation were optimal electrode placement (P = 0.002, OR = 16.67) and increasing distance to the collecting system (P = 0.02, OR = 1.18). Tumor size was not a predictor for complete ablation (median size, 24 mm; P = 0.069, OR = 0.47), but all tumors ≤2 cm were completely ablated. All papillary tumors and oncocytomas were completely ablated in a single session; the most common incompletely ablated tumor type was clear cell carcinoma (6 of 9).

CONCLUSION: Optimal electrode placement and a long distance from the collecting system are associated with an increased primary efficacy of renal tumor RFA. These variables need to be considered to increase primary ablation success. Further studies are needed to evaluate the effect of RFA on histopathologically different renal tumors.

Keywords
Radiofrequency ablation (RFA); renal tumor; predict; ablation; radiofrequency; ablation success; complete ablation
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-264586 (URN)10.1177/0284185115605681 (DOI)000378051200020 ()26452975 (PubMedID)
Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2019-09-04Bibliographically approved
2. Periprocedural outcome after laparoscopic partial nephrectomy versus radiofrequency ablation for T1 renal tumors:: A modified R.E.N.A.L nephrometry score adjusted comparison.
Open this publication in new window or tab >>Periprocedural outcome after laparoscopic partial nephrectomy versus radiofrequency ablation for T1 renal tumors:: A modified R.E.N.A.L nephrometry score adjusted comparison.
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2018 (English)In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 60, no 2, p. 260-268Article in journal (Refereed) Published
Abstract [en]

Background: Comparable oncological outcomes have been seen after surgical nephrectomy and thermal ablation of renal tumors recently. However, periprocedural outcome needs to be assessed for aiding treatment decision.

Purpose: To compare efficacy rates and periprocedural outcome (technical success, session time, hospitalization time, and complications) after renal tumor treatment with laparoscopic partial nephrectomy (LPN) or radiofrequency ablation (RFA).

Material and Methods: The initial experience with 49 (treated with LPN) and 84 (treated with RFA) consecutive patients for a single renal tumor (diameter ≤ 5 cm, limited to the kidney) during 2007-2014 was evaluated. Patient and tumor characteristics, efficacy rates, and periprocedural outcome were collected retrospectively. The stratified Mantel Haenzel and Van Elteren tests, adjusted for tumor complexity (with the modified R.E.N.A.L nephrometry score [m-RNS]), were used to assess differences in treatment outcomes.

Results: Primary efficacy rate was 98% for LPN and 85.7% for RFA; secondary efficacy rate was 93.9% for LPN and 95.2% for RFA; and technical success rate was 87.8% for LPN and 100% for RFA. Median session (m-RNS adjusted P < 0.001; LPN 215 min, RFA 137 min) and median hospitalization time were longer after LPN (m-RNS adjusted P < 0.001; LPN 5 days, RFA 2 days). Side effects were uncommon (LPN 2%, RFA 4.8%). Complications were more frequent after LPN (m-RNS adjusted P < 0.001; LPN 42.9%, RFA 10.7%).

Conclusion: Both methods achieved equivalent secondary efficacy rates. RFA included several treatment sessions, but session and hospitalization times were shorter, and complications were less frequent than for LPN. The differences remained after adjustment for renal tumor complexity.

Keywords
Ablation procedures, interventional, kidney, percutaneous, primary neoplasms
National Category
Urology and Nephrology
Identifiers
urn:nbn:se:uu:diva-354169 (URN)10.1177/0284185118780891 (DOI)000459621200017 ()29911400 (PubMedID)
Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2019-09-04Bibliographically approved
3. Split Renal Function after Treatment of Small Renal Masses: Comparison between Radiofrequency Ablation and Laparoscopic Partial Nephrectomy
Open this publication in new window or tab >>Split Renal Function after Treatment of Small Renal Masses: Comparison between Radiofrequency Ablation and Laparoscopic Partial Nephrectomy
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(English)Manuscript (preprint) (Other academic)
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-392376 (URN)
Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-04
4. Percutaneous CT Guided Microwave Ablation of 105 T1a-T1b Renal Tumors: Technique Efficacy with a Mean 2-Year Follow-up
Open this publication in new window or tab >>Percutaneous CT Guided Microwave Ablation of 105 T1a-T1b Renal Tumors: Technique Efficacy with a Mean 2-Year Follow-up
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(English)Manuscript (preprint) (Other academic)
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-392380 (URN)
Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-09-04

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