The local institutional review board approved this study. All patients provided informed consent for both SRFA and QoL assessment. Since 2011, all patients undergoing SRFA for the treatment of primary or secondary liver tumors were asked to complete a HRQoL questionnaire once after the RF procedure (within first few weeks). Until 2017, of a total of 577 treated patients, 303 (52.5%) patients returned 363 questionnaires (311 via mail and 52 via telephone, 50 patients > 1 questionnaires in case of > 1 SRFA sessions). The SF-12 part was correctly completed in 337 of 363 cases (93%). The detailed patient characteristics are presented in Table 1.
The method of SRFA has previously been reported in detail14,15,16. In brief, the key steps are as follows:
(I) Preparation: treatment is performed under general anesthesia with muscle paralysis and immobilization facilitated by a single (Bluebag, Medical Intelligence Schwabmünchen, Germany) or double vacuum fixation technique (BodyFix, Medical Intelligence, Germany); 10–15 broadly to the skin attached registration markers (Beekley Spots, Beekley Corporation, USA) are used for image-to-patient registration.
(II) Planning: contrast-enhanced (CE) CT (SOMATOM Sensation Open, Siemens AG, Germany) with 3 mm slice thickness in the arterial and portal-venous phase; the obtained CT-data is transmitted to an optical based navigation system (Stealth Station Treon plus, Medtronic Inc., USA); needle trajectories are planned using multiplanar and reconstructed 3D images.
(III) Execution—needle placement: to minimize respiratory motion, temporary disconnections of the endotracheal tube are executed during the planning CT, each stereotactic needle placement and the final CT; after registration, an accuracy check and sterile draping, the ATLAS aiming device (Medical Intelligence Inc., Germany) is used for navigated trajectory alignment; 15G, 17.2 cm coaxial needles (Bard Inc., USA) are placed with the aiming device (without real-time imaging); the coaxial needles serve as guides for the radiofrequency electrodes; to verify proper needle placement, an unenhanced CT is fused with the planning CT by the navigation system; a 16G biopsy sample is obtained via one of the coaxial needles in patients with lack of histological confirmation.
(III) Execution—RF ablation: three 17G radiofrequency electrodes (Cool-tip, Medtronic, USA, 25 cm length with 3 cm exposure) are simultaneously placed through the coaxial needles for serial ablation using the unipolar Cool-tip radiofrequency generator with switching control (Cool-tip, Medtronic, USA); the standardized ablation time for three electrodes is 16 min; however, in case of significant increase of impedance (the so-called roll-off effect) the ablation process is finished; track ablation is done during every repositioning and final removal to avoid bleeding and tumor seeding;
(IV) Final control: post-ablation completion contrast-enhanced CT in the arterial and portal venous phase, fused with the planning CT for verification of ablation zone coverage and for assessment of complications;
In CTX, therapeutics were used in standard dosage, frequency and duration according to international guidelines. All liver resections were performed under laparotomy. TACE was carried out in standard technique with administration of an emulsion of Lipiodol (Guerbet, Roissy, France) with epi- or doxorubicine. None of the patient was treated by stereotactic body radiotherapy for liver tumors.
Instruments for HRQoL assessment
The HRQoL was primarily investigated using a specifically developed questionnaire consisting of general items, disease and current therapy related items, symptoms after treatment related items and if available, other items with direct comparison of previous and or additional treatments, such as CTX, TACE or HR (see Table 5 for details).
For comparison and reproducibility an internationally validated questionnaire, SF 12 consisting of twelve questions that measure eight health domains to assess physical and mental health, was used. Physical and mental component summary (PCS and MCS) are computed using the scores of twelve questions and range from 0–100, where 0 indicates the lowest level of health and 100 indicates the highest level of health. We administered the questionnaire once after treatment within the first few weeks. The comparative values of the German normal population were gathered from the SF-12 scoring manual.
SPSS (SPSS Inc., Chicago, USA; version 24.0) was used for statistical analysis. Continuous variables were presented as the median with range. Categorical variables were reported both as numbers and as percentages. The Wilcoxon signed rank test was used for 1-sample testing. The distributions of categorical and numerical variables between independent groups were compared using Fisher’s exact test, Mann–Whitney U test (two independent variables) and Kruskal–Wallis test (more than two independent variables), respectively. A p value < 0.05 was considered as statistically significant.