Factors Impacting Microwave Ablation Zone Sizes: A Retrospective Analysis.

PURPOSE: Evaluation of the influence of intrinsic and extrinsic conditions on ablation zone volumes (AZV) after microwave ablation (MWA). METHODS: Retrospective analysis of 38 MWAs of therapy-naïve liver tumours performed with the NeuWave PR probe. Ablations were performed either in the 'standard mode' (65 W, 10 min) or in the 'surgical mode' (95 W, 1 min, then 65 W, 10 min). AZV measurements were obtained from contrast-enhanced computed tomography immediately post-ablation. RESULTS: AZVs in the 'standard mode' were smaller than predicted by the manufacturer (length 3.6 ± 0.6 cm, 23% below 4.7 cm; width 2.7 ± 0.6, 23% below 3.5 cm). Ablation zone past the tip was limited to 6 mm in 28/32 ablations. Differences in AZV between the 'surgical mode' and 'standard mode' were not significant (15.6 ± 7.8 mL vs. 13.9 ± 8.8 mL, p = 0.6). AZVs were significantly larger in case of hepatocellular carcinomas (HCCs) (n = 19) compared to metastasis (n = 19; 17.8 ± 9.9 mL vs. 10.1 ± 5.1 mL, p = 0.01) and in non-perivascular tumour location (n = 14) compared to perivascular location (n = 24, 18.7 ± 10.4 mL vs. 11.7 ± 6.1 mL, p = 0.012), with both factors remaining significant in two-way analysis of variance (HCC vs. metastasis: p = 0.02; perivascular vs. non-perivascular tumour location: p = 0.044). CONCLUSION: Larger AZVs can be expected in cases of HCCs compared with metastases and in non-perivascular locations. Using the 'surgical mode' does not increase AZV significantly.

Robotic-Assisted Laparoscopic Resection of Tailgut Cysts.

INTRODUCTION: Tailgut cysts are rare remnants of the embryological hindgut. Resections are difficult to perform due to the narrow and delicate presacral space where they are usually located. Many different approaches have been described, but to date, no studies have been performed concerning robotic assisted surgery for this entity. Therefore, we conducted a retrospective analysis to evaluate the feasibility and outcome parameters of the robotic anterior approach for resection of tailgut cysts and to compare our results with available literature. MATERIAL AND METHODS: Data was retrospectively obtained from hospital records of all patients who underwent robotic assisted resection of tailgut cysts between January 1, 2017 and June 30, 2020. Outcomes include baseline characteristics, pre-operative radiological workup, operative time, intra- and postoperative complications, and histopathological results. RESULTS: Between January 1, 2017 and June 30, 2020, five patients underwent robotic resection of tailgut cysts. All patients were female and mean age was 47.2 years (range 31.6-63.1 years). Only one patient reported to have local symptoms that could be attributed to the tailgut cyst. Median tumor size was 42 mm (range 30-64 mm). There was no conversion and median operating time was 235 minutes (range 184-331 minutes). Four patients had additional procedures. Intra- and postoperative complications included one intra-operative injury of the rectal wall, which was immediately oversewn, and one postoperative presacral hematoseroma with mild neurological symptoms. None of the specimens showed signs of malignant transformation in histopathological workup. CONCLUSION: This retrospective analysis shows that robotic resections of tailgut cysts are feasible and safe. Regarding the localization of tailgut cysts in the presacral space, the robotic assisted anterior approach is excellently suited, especially if the cysts are localized above the levator muscle. Longer operative times and higher material costs are outweighed by precise and safe preparation with a robotic platform in this delicate region and confined space. We recommend the robotic assisted anterior approach for the resection of tailgut cysts and retrorectal lesions in general.

The value of intravenous contrast medium in PSMA PET/CT imaging in patients with biochemical recurrence of prostate cancer.

PURPOSE: To investigate the added value of diagnostic abdominal contrast-enhanced computed tomography (ceCT) in Ga-68 PSMA PET/CT in prostate cancer patients with biochemical recurrence (BCR). METHODS: Eighty-two consecutive patients (median age, 69 years; range, 45-86 years) with BCR underwent Ga-68 PSMA PET/CT with low-dose nonenhanced (ne) whole-body CT and diagnostic ceCT. Imaging results were retrospectively reviewed by two readers (R1, R2) for diagnostic certainty, local recurrence, lymph node metastasis (LNM) and bone metastasis. Interobserver agreement was assessed. Histopathology served as reference standard in 7, imaging and clinical follow-up in 65 and clinical follow-up alone in 10 patients. RESULTS: Certain local recurrence, LNM and bone metastasis diagnoses increased substantially from ceCT (R1: 5%/18%/32%; R2: 37%/50%/82%) to nePET/CT (R1: 78%/87%/93%; R2: 81%/87%/95%) for both readers, but the difference between nePET/CT and cePET/CT (R1: 77%/96%/92%; R2: 89%/94%/96%) was marginal. Interobserver agreement was minimal with ceCT (Krippendorff's alpha: 0.04-0.26), substantial with nePET/CT (0.60-0.86) and best with cePET/CT (0.76-0.86). The areas under the receiver operating characteristic curve (AUCs) for local recurrence for R1/R2 were 0.60/0.65 for ceCT, 0.81/0.79 for nePET/CT and 0.81/0.82 for cePET/CT. AUCs for LNMs for R1/R2 were 0.67/0.77 for ceCT, 0.91/0.82 for nePET/CT and 0.92/0.87 for cePET/CT. AUCs for BMs for R1/R2 were 0.60/0.53 for ceCT, 0.93/0.84 for nePET/CT and 0.93/0.86 for cePET/CT. CONCLUSION: Diagnostic abdominal ceCT increases the diagnostic certainty and interobserver agreement in Ga-68 PSMA PET/CT in BCR of prostate cancer. The diagnostic performance of cePET/CT is significantly better than ceCT alone but not nePET/CT.