Reliability of Stereotactic Radiofrequency Ablation (SRFA) for Malignant Liver Tumors: Novice versus Experienced Operators

PURPOSE

To compare the results of a novice with those of experienced interventional radiologists (IRs) for stereotactic radiofrequency ablation (SRFA) of malignant liver tumors in terms of safety, technical success, and local tumor control.

METHODS

A database, including all SRFA procedures performed in a single center between January 2011 and December 2018 was retrospectively analyzed. A total of 39 ablation sessions performed by a novice IR were compared to the results of three more experienced IRs. Comparative SRFA sessions were selected using propensity score matching considering tumor type, age, sex, tumor size, and tumor number as matching variables. Overall, 549 target tumors were treated in 273 sessions. Median tumor size was 2.2 cm (1.0-8.5 cm) for 178 hepatocellular carcinomas (HCCs) and 3.0 cm (0.5-13.0 cm) for 371 metastases. A median of 2 (1-11) tumors were treated per session.

RESULTS

No significant differences were observed when comparing the results of more experienced IRs with those of a novice IR regarding the rates of major complications (6.8% [16/234] vs. 5.1% [2/39]; p = 0.477), mortality (1.3% [2/234] vs. 0% [0/39]; p = 0.690), primary technical efficacy (98.5% [525/533] vs. 98.9% [94/95]; p = 0.735), and local recurrence (5.6% [30/533] vs. 5.3% [5/95]; p = 0.886). However, the median planning/placement time was significantly shorter for the experienced IRs (92 min vs. 119 min; p = 0.002).

CONCLUSIONS

SRFA is a safe, effective, and reliable treatment option for malignant liver tumors and favorable outcomes can be achieved even by inexperienced operators with minimal supervision.

Stereotactic radiofrequency ablation of tumors at the hepatic venous confluence

BACKGROUND

Radiofrequency ablation (RFA) is subject to "heat-sink" effects, particularly for treatment of tumors adjacent to major vessels.

METHODS

In this retrospective study, 104 patients with 137 tumors (40 HCC, 10 ICC and 54 metastatic liver tumors) close to (≤1 cm from) the hepatic venous confluence underwent stereotactic RFA (SRFA) between June 2003 and June 2018. Median tumor size was 3.7 cm (1.4-8.5) for HCC, 6.4 cm (0.5-11) for ICC and 3.8 cm (0.5-13) for metastases. Endpoints comprised safety, local tumor control, overall and disease-free survival.

RESULTS

The overall major complication rate was 16.0% (20/125 ablations), where 8 (40%) were successfully treated by the interventional radiologist in the same anesthetic session and did not prolong hospital stay. 134/137 (97.8%) tumors were successfully ablated at initial SRFA. Local recurrence (LR) developed in 19/137 tumors (13.9%). The median and overall survival (OS) rates at 1-, 3-, and 5- years from the date of the first SRFA were 51.5 months, 73.5%, 67.0%, and 49.7% for HCC, 14.6 months, 60.0%, 32.0% and 32.0% for ICC and 38.1 months, 91.4%, 56.5% and 27.9% for metastatic disease, respectively.

CONCLUSION

SRFA represents a viable alternative to hepatic resection for challenging tumors at the hepatic venous confluence.

Stereotactic radiofrequency ablation as a valid first-line treatment option for hepatocellular adenomas

OBJECTIVES

This study aimed to assess the safety and efficacy of stereotactic radiofrequency ablation (SRFA) in patients with hepatocellular adenomas (HCA).

METHODS

Retrospective analyses of all patients referred for SRFA treatment at our institution between January 2010 and October 2020 revealed 14 patients (10 women; mean age 34.4 [range, 17-73 years]) with 38 HCAs treated through 18 ablation sessions. Ablations were considered successful if a safety margin >5 mm was achieved. Demographic, interventional, and outcome data were collected and analyzed. Primary and secondary technical efficacy rates were assessed based on follow-up images consisting of contrast-enhanced CT or MR scans.

RESULTS

The mean tumor size was 22 mm (range, 7-75 mm). Overall, 37/38 (97.4%) tumors were successfully ablated at the initial SRFA (primary efficacy rate of 97.4%). The median follow-up duration was 49.6 months. No deaths or adenoma-related complications (hemorrhage or malignant transformation) were observed. Disease-free survival rates at 1, 3, and 5 years from the date of the first SRFA were 100%, 85.8%, and 85.8%, respectively. Two patients developed new distant tumors retreated with consecutive re-ablation. No major complications occurred during any of the 18 ablation sessions.

CONCLUSIONS

Percutaneous thermal ablation is efficient in the treatment of HCAs and may thus be considered a valid first-line treatment option. In addition, SRFA allows for an effective, minimally invasive treatment of large and multiple hepatic tumors within one session.

Technical efficacy and local recurrence after stereotactic radiofrequency ablation of 2653 liver tumors: a 15-year single-center experience with evaluation of prognostic factors

PURPOSE

To assess the technical outcome and local tumor control of multi-probe stereotactic radiofrequency ablation (SRFA) in a large series of patients. Furthermore, to determine factors accounting for adverse outcomes.

MATERIAL AND METHODS

Between 2003 and 2018, 865 patients were treated by SRFA for 2653 primary and metastatic liver tumors with a median tumor size of 2.0 cm (0.5 - 19 cm). Primary technical efficacy (PTE) and local recurrence (LR) were evaluated, and possible predictors for adverse events analyzed using uni- and multi-variable binary logistic regression.

RESULTS

Overall, 2553 of 2653 tumors were successfully ablated at initial SRFA resulting in a PTE rate of 96.2%. Predictors of lower PTE rates were age > 70 years, tumor size > 5 cm, number of probes, location close to liver capsule/organs and segment II. LR occurred in 220 of 2653 tumors (8.3%) with the following predictors: age, tumor type/size, conglomerates, segments I/IVa/IVb, number of probes and location close to major vessels/bile duct. Multivariable analysis revealed tumor size > 5 cm (odds ratio [OR] 3.153), age > 70 years (OR 1.559), and location in segment II (OR 1.772) as independent prognostic factors for PTE, whereas tumor location close to major vessels (OR 1.653) and in segment IVb (OR 2.656) were identified as independent prognostic factors of LR.

CONCLUSIONS

Stereotactic RFA is an attractive option in the management of primary or metastatic liver tumors with good local tumor control, even in large tumors. The presented prognostic factors for adverse local oncological outcome might help to stratify unfavorable tumors for ablation.

Can accurate evaluation of the treatment success after radiofrequency ablation of liver tumors be achieved by visual inspection alone? Results of a blinded assessment with 38 interventional oncologists

OBJECTIVES

To assess the difficulties in the immediate judgment of treatment success after radiofrequency ablation (RFA) of liver tumors by visual inspection alone and to evaluate whether radiologist's expertise affects the resultant judgment.

METHODS

Peri-interventional CT-scans of nine patients with nine hepatocellular carcinomas with known outcomes after RFA were presented to 38 participants from 14 different countries. In a total of 342 reads, all interventional oncologists assessed the pre- and immediate post-interventional CT-scans through conventional side-by-side juxtapositioning of images and judged whether complete ablation (i.e., technical success and technique efficacy) was achieved. Results were compared regarding expertise in percutaneous tumor ablation (>50 interventions performed). An 'overcall' was defined as insufficient ablation that was misjudged as sufficient, and an 'undercall' as an erroneous assessment of complete ablation.

RESULTS

Overall 3.97 ± 1.27 out of 9 (44.1%) cases per radiologist were misjudged. The mean number of overcalls and undercalls per radiologist were 0.74 ± 0.50 out of 2 (37.0%), and 3.24 ± 1.28 out of 7 (46.3%), respectively. 18/38 (47.4%) participants had considerable experience in percutaneous tumor ablation, with such expertise having no significant influence on the results (overall: p = 0.70; overcalls: p = 0.87; undercalls: p = 0.75).

CONCLUSIONS

Conventional side-by-side evaluation of treatment success after RFA of liver tumors by the juxtaposition of pre- and post-interventional CT-scans is very difficult for experienced radiologists. The implementation of advanced processing techniques such as rigid/non-rigid image fusion with the assessment of the periablational margin is thus likely needed in order to decrease errors and objectively evaluate technical success and predict technique efficacy of liver RFA.

Stereotactic Radiofrequency Ablation of Breast Cancer Liver Metastases: Short- and Long-Term Results with Predicting Factors for Survival

Purpose

To evaluate safety, local oncological control, long-term outcome and potential prognostic factors of stereotactic RFA (SRFA) for the treatment of BCLMs.

Methods

Between July 2003 and December 2019, 42 consecutive female patients with median age 54.0 years were treated with SRFA at our institution for 110 BCLMs in 48 ablation sessions. Median tumor size was 3.0 cm (0.8–9.0). Eighteen (42.9%) patients had extrahepatic metastasis at initial SRFA.

Results

Technical success rate was 100%, i.e., all coaxial needles were inserted with appropriate accuracy within 10 mm off plan and 107/110 (92.3%) BCLMs were successfully ablated at initial SRFA. Four Grade 1 (8.3%, 4/48) and one Grade 2 (2.1%, 1/48) complications occurred. No perioperative deaths occurred. Local recurrence developed in 8 of 110 tumors (7.3%). Overall survival (OS) rates of all patients at 1, 3, and 5 years from the date of the first SRFA were 84.1%, 49.3%, and 20.8% with a median OS of 32.3 months. Univariable cox regression analyses revealed age > 60 years and extrahepatic disease (without bone only metastases) as significant predictors of worse OS (p = 0.013 and 0.025, respectively). Size and number of metastases, hormone receptor status and time onset did not significantly affect OS after initial SRFA.

Conclusions

SRFA is a safe, minimally invasive treatment option in the management of BCLMs, especially in younger patients without advanced extrahepatic metastasis, including those with large liver tumors.

Volumetric assessment of the periablational safety margin after thermal ablation of colorectal liver metastases

OBJECTIVES

To retrospectively assess the periablational 3D safety margin in patients with colorectal liver metastases (CRLM) referred for stereotactic radiofrequency ablation (RFA) and to evaluate its influence on local treatment success.

METHODS

Forty-five patients (31 males; mean age 64.5 [range 31-87 years]) with 76 CRLM were treated with stereotactic RFA and retrospectively analyzed. Image fusion of pre- and post-interventional contrast-enhanced CT scans using a non-rigid registration software enabled a retrospective assessment of the percentage of predetermined periablational 3D safety margin and CRLM successfully ablated. Periablational safety zones (1-10 mm) and percentage of periablational zone ablated were calculated, analyzed, and compared with subsequent tumor growth to determine an optimal safety margin predictive of local treatment success.

RESULTS

Mean overall follow-up was 36.1 ± 18.5 months. Nine of 76 CRLMs (11.8%) developed local tumor progression (LTP) with mean time to LTP of 18.3 ± 11.9 months. Overall 1-, 2-, and 3-year cumulative LTP-free survival rates were 98.7%, 90.6%, and 88.6%, respectively. The periablational safety margin assessment proved to be the only independent predictor (p < 0.001) of LTP for all calculated safety margins. The smallest safety margin 100% ablated displaying no LTP was 3 mm, and at least 90% of a 6-mm circumscribed 3D safety margin was required to achieve complete ablation.

CONCLUSIONS

Volumetric assessment of the periablational safety margin can be used as an intraprocedural tool to evaluate local treatment success in patients with CRLM referred to stereotactic RFA. Ablations achieving 100% 3D safety margin of 3 mm and at least 90% 3D safety margin of 6 mm can predict treatment success.

KEY POINTS

• Volumetric assessment of the periablational safety margin can be used as an intraprocedural tool to evaluate local treatment success following thermal ablation of colorectal liver metastases. • Ablations with 100% 3D periablational safety margin of 3 mm and ablations with at least 90% 3D safety margin of 6 mm can be considered indications of treatment success. • Image fusion of pre- and post-interventional CT scans with the software used in this study is feasible and could represent a useful tool in daily clinical practice.

Thermal ablation of CT 'invisible' liver tumors using MRI fusion: a case control study

Purpose: To evaluate whether 'invisible' liver tumors on CT can be treated by stereotactic radiofrequency ablation (SRFA) using fusion of pre-ablation MRI.Methods: In this retrospective case-control study, 60 patients (14 with Hepatocellular carcinoma (HCC) and 46 with metastatic liver tumors) with CT 'invisible' lesions underwent SRFA using MRI-fusion between June 2005 and June 2018 ('fusion group'). For comparison, 60 patients who underwent SRFA without image fusion were selected using nearest neighbor propensity score matching ('control group'). Endpoints consisted of local tumor control, safety, overall and disease-free survival.Results: Major complications occurred in 6/69 ablations (8.7%) in the fusion group and in 6/89 ablations (6.7%) in the control group (p = 0.434). Primary technical efficacy rate (i.e., successful initial ablation) was 96.6% (28/29) for HCC and 97.9% (166/170) for metastatic disease in the fusion group and 100% (33/33) and 93.3% (184/194) in the control group, respectively (p = 0.468 and 0.064). Local recurrence (LR) was observed in 1/29 (3.5%) HCCs and in 6/170 metastases (4.0%) in the fusion group and 1/33 (3.0%) and 21/196 (10.7%) in the control group, respectively. The LR rate of metastasis in the control group was significantly higher (p = 0.007), although differences in OS and DFS did not reach statistical significance.Conclusions: Image fusion using pre-procedural MRI allows for ablation of CT-'invisible' liver tumors that are otherwise untreatable. Moreover, local oncological control was higher in metastatic liver tumors versus matched controls which suggests it could be useful tool for all stereotactic radiofrequency ablation procedures.

Frequency and risk factors for major complications after stereotactic radiofrequency ablation of liver tumors in 1235 ablation sessions: a 15-year experience

Objectives

To assess the frequency of major complications after multi-probe stereotactic radiofrequency ablation (SRFA) in a large cohort of patients over 15 years and to elucidate risk factors for adverse events.

Materials and methods

A retrospective study was carried out between July 2003 and December 2018. Seven hundred ninety-three consecutive patients (median 65.0 years (0.3–88), 241 women and 552 men, were treated in 1235 SRFA sessions for 2475 primary and metastatic liver tumors with a median tumor size of 3.0 cm (0.5–18 cm). The frequency of major complications was evaluated according to SIR guidelines and putative predictors of adverse events analyzed using simple and multivariable logistic regression.

Results

Thirty-day mortality after SRFA was 0.5% (6/1235) with an overall major complication rate of 7.4% (91/1235). The major complication rate decreased from 11.5% (36/314) (before January 2011) to 6.0% (55/921) (p = 0.001). 50.5% (46/91) of major complications were successfully treated in the same anesthetic session by angiographic coiling for hemorrhage and chest tube insertion for pneumothorax. History of bile duct surgery/intervention, number of coaxial needles, and location of tumors in segment IVa or VIII were independent prognostic factors for major complications following multivariable logistic regression analysis. Simple logistic regression revealed the number of tumors, tumor size, location close to the diaphragm, tumor conglomerate, and segment VII as other significant predictors.

Conclusion

SRFA of liver tumors is safe and can extend the treatment spectrum of conventional RFA. Adaptations over time combined with increasing experience resulted in a significant decrease in complications.

Key Points

• In 1235 ablation sessions in 793 patients over 15 years, we found a mortality rate of 0.5% (6/1235) and an overall major complication rate of 7.4%, which fell from 11.5 (36/314) to 6.0% (55/921, p = 0.001) after January 2011, likely due to procedural adaptations.

• History of bile duct surgery/intervention (p = 0.013, OR = 3.290), number of coaxial needles (p = 0.026, OR = 1.052), and location of tumors in segment IVa (p = 0.016, OR = 1.989) or VIII (p = 0.038, OR = 1.635) were found to be independent prognostic factors.

• Simple logistic regression revealed that number of tumors, tumor size, location close to the diaphragm, tumor conglomerates, and segment VII were other significant predictors of major complications.

Simultaneous Stereotactic Radiofrequency Ablation of Multiple (≥ 4) Liver Tumors: Feasibility, Safety, and Efficacy

PURPOSE

To assess feasibility, safety, and clinical outcome of simultaneous stereotactic radiofrequency (RF) ablation of multiple (≥ 4) primary and metastatic liver tumors.

MATERIALS AND METHODS

This retrospective observational study included 92 patients (29 women, 62 men), 35 with ≥ 4 hepatocellular carcinomas (HCCs) and 57 with ≥ 4 metastatic liver tumors at initial stereotactic RF ablation between 2005 and 2018. The median size of 178 HCCs and 371 metastases was 2.2 cm (range, 1.0-8.5 cm) and 3.0 cm (range, 0.5-13 cm), respectively. At initial stereotactic RF ablation, 17 (48.6%) patients with HCC and 19 (33.3%) with metastases had 4 liver tumors, 11 (31.4%) and 19 (33.3%) had 5 tumors, and 7 (20%) and 19 (33.3%) had ≥ 6 tumors.

RESULTS

Major complications occurred in 2 of 35 ablations (5.4%) in patients with HCCs and in 7 of 63 (10%) with metastases. The primary technical efficacy rate (ie, successful initial ablation) was 100% (178/178) in HCCs and 98.8% (363/371) in metastases. Local recurrence was observed in 4 of 178 (2.2%) HCCs and in 17 of 371 (4.6%) metastases. Overall survival (OS) rates at 1, 3, and 5 years from the date of the first stereotactic RF ablation were 88.0%, 54.0%, and 30.4% for patients with HCCs with a median OS of 38.2 months and 86.1%, 53.1%, and 37.3% for patients with metastases with a median OS of 37.4 months.

CONCLUSIONS

Stereotactic RF ablation is a feasible, safe, and efficacious option in simultaneous management of multiple primary and metastatic liver tumors.

Stereotactic radiofrequency ablation of subcardiac hepatocellular carcinoma: a case-control study

Purpose: The purpose of this study is to evaluate the safety and efficacy of stereotactic radiofrequency ablation (SRFA) for the treatment of subcardiac hepatocellular carcinoma (HCC). Material and methods: From 2003 to 2018, 79 consecutive patients underwent 104 multi-probe SRFA sessions for the treatment of 114 subcardiac HCC with a median size of 2.5 cm (0.5-9.5 cm). The results were compared with a randomly selected control group of 79 patients with 242 HCC with a median size of 2.0 cm (0.5-12 cm) following SRFA in other (non-subcardiac) locations with propensity score matching. Results: The 95.6% of the tumors were successfully treated by the first ablation session (primary technical efficacy rate) and 99.1% after the second session (secondary technical efficacy rate). Local tumor recurrence developed in 8 nodules (7.0%). Major complication and perioperative mortality rates were 7.7% (8/104) and 1% (1/104), respectively. The overall survival (OS) rates from the date of the first SRFA with single subcardiac HCCs were 92%, 77% and 65% at 1, 3 and 5 years, respectively, with a median OS of 90.6 months. The disease-free survival (DFS) after SRFA was 75, 34 and 34%, at 1, 3 and 5 years, respectively, with a median DFS of 19.1 months. There was no statistically significant difference with the control group in terms of local tumor control, safety, OS and DFS. Conclusion: SRFA of subcardiac tumors is as safe and efficacious as when treating tumors remote from the heart.

Safety and efficacy of stereotactic radiofrequency ablation for very large (≥8 cm) primary and metastatic liver tumors

To assess the safety and clinical outcomes of multi-probe stereotactic radiofrequency ablation (SRFA) for very large (≥8 cm) primary and metastatic liver tumors with curative treatment intent. A retrospective, single center study carried out between 01.2005 and 06.2018. 34 consecutive patients had a total of 41 primary and metastatic liver tumors with a median size of 9.0 cm (8.0–18.0 cm) at initial SRFA. Patients were treated under CT guidance using a 3D navigation system. Endpoints consisted of (i) technical efficacy; primary - requiring one treatment, and secondary – requiring two treatments (ii) complication and mortality rates (iii) local and distant recurrence (LR), (iv) disease free survival (DFS), (v) overall survival (OS). 33/41 tumors were successfully ablated at initial SRFA (80.5% primary technical efficacy rate (PTE)). Four tumors required repeat ablation, resulting in a secondary technical efficacy (STE) rate of 90.2%. Local tumor recurrence (LR) developed in 4 of 41 tumors (9.8%). The 30-day perioperative mortality was 2.3% (1/ 44 ablations). The total major complication rate was 20.5% (9 of 44 ablations). Three of nine (33.3%) major complications, such as pleural effusion, pneumothoraces or perihepatic hemorrhages were relatively easy to treat. The overall survival (OS) rates at 1-, 3-, and 5- years from the date of the first SRFA were 87.1%, 71.8%, and 62.8% for patients with hepatocellular carcinoma (HCC) and 87.5%, 70.0% and 70.0% for patients with intrahepatic cholangiocarcinoma (ICC) respectively. Patients with metastatic disease had OS rates of 77.8% and 22.2% at 1- and 3- years. The clinical results of SRFA in this study are encouraging and warrant a prospective multicenter study. SRFA may become one of the best therapeutic choices for a growing number of patients with primary and metastatic liver cancer.

Minimal ablative margin (MAM) assessment with image fusion: an independent predictor for local tumor progression in hepatocellular carcinoma after stereotactic radiofrequency ablation

Objectives

To assess the minimal ablative margin (MAM) by image fusion of intraprocedural pre- and post-ablation contrast-enhanced CT images and to evaluate if it can predict local tumor progression (LTP) independently. Furthermore, to determine a MAM with which a stereotactic radiofrequency ablation (SRFA) can be determined successful and therefore used as an intraprocedural tool to evaluate treatment success.

Methods

A total of 110 patients (20 women, 90 men; mean age 63.7 ± 10.2) with 176 hepatocellular carcinomas were assessed by retrospective analysis of prospectively collected data. The MAM was determined through image fusion of intraprocedural pre- and post-ablation images using commercially available rigid imaging registration software. LTP was assessed in contrast-enhanced CTs or MR scans at 3–6-month intervals.

Results

The MAM was the only significant independent predictor of LTP (p = 0.036). For each millimeter increase of the MAM, a 30% reduction of the relative risk for LTP was found (OR = 0.7, 95% CI 0.5–0.98, p = 0.036). No LTP was detected in lesions with a MAM > 5 mm. The overall LTP rate was 9 of 110 (8.2%) on a patient level and 10 of 173 (5.7%) on a lesion level. The median MAM was 3.4 (1.7–6.9) mm. The mean overall follow-up period was 26.0 ± 10.3 months.

Conclusions

An immediate assessment of the minimal ablative margin (MAM) can be used as an intraprocedural tool to evaluate the treatment success in patients treated with stereotactic RFA. A MAM > 5 mm has to be achieved to consider an ablation as successful.

Key Points

• An intraoperatively measured minimal ablative margin (MAM) > 5 mm correlates with complete remission.

• MAM is the only significant independent predictor of LTP (OR = 0.7, 95% CI 0.5–0.98, p = 0.036) after stereotactic RFA of hepatocellular carcinoma.

• Image fusion using commercially available rigid imaging registration software is possible, even though considerably complex. Therefore, improved (semi-)automatic fusion software is highly desirable.

Stereotactic Radiofrequency Ablation of Hepatocellular Carcinoma: a Histopathological Study in Explanted Livers

This retrospective study was performed to evaluate the efficacy of three-dimensional (3D)-navigated multiprobe radiofrequency ablation (RFA) with intraprocedural image fusion for treatment of hepatocellular carcinoma (HCC) by histopathological examination. From 2009 to 2018, 97 patients (84 men, 13 women; median age, 60 years; range, 1-71) were transplanted after bridging therapy of 195 HCCs by stereotactic RFA (SRFA). The median interval between the first SRFA and transplantation was 6.8 months (range, 0-71). The rate of residual vital tissue (RVT) could be assessed in 188 of 195 lesions in 96 of 97 patients by histological examination of the explanted livers using hematoxylin and eosin (H&E) and Tdt-mediated UTP nick-end labeling (TUNEL) stains. Histopathological results were compared with the findings of the last computed tomography (CT) imaging before liver transplantation (LT). Median number and size of treated tumors were 1 (range, 1-8) and 2.5 cm (range, 1-8). Complete radiological response was achieved in 186 of 188 nodules (98.9%) and 94 of 96 patients (97.9%) and complete pathological response in the explanted liver specimen in 183 of 188 nodules (97.3%) and 91 of 96 patients (94.8%), respectively. In lesions ≥3 cm, complete tumor cell death was achieved in 50 of 52 nodules (96.2%). Residual tumor did not correlate with tumor size (P = 0.5). Conclusion: Multiprobe SRFA with intraprocedural image fusion represents an efficient, minimally invasive therapy for HCC, even with tumor sizes larger than 3 cm, and without the need of a combination with additional treatments. The results seem to justify the additional efforts related to the stereotactic approach.

Brucellae through the food chain: the role of sheep, goats and springbok (Antidorcus marsupialis) as sources of human infections in Namibia

A confirmed case of human brucellosis motivated an investigation into the potential source of infection in Namibia. Since domestic animals are principal sources of Brucella infection in humans, 1692 serum samples were screened from sheep, goats and cattle from 4 presumably at-risk farms and 900 springbok (Antidorcas marsupialis) serum samples from 29 mixed farming units for Brucella antibodies by the Rose-Bengal test (RBT) and positive cases confirmed by complement fixation test (CFT). To assess the prevalence of human brucellosis, 137 abattoir employees were tested for Brucella antibodies using the standard tube agglutination test (STAT) and by enzyme linked immunosorbent assay (ELISA). Cattle and sheep from all 4 farms were negative by RBT and CFT but 2 of the 4 farms (Ba and C) had 26/42 and 12/285 seropositive goats, respectively. Post mortem examination of seropositive goats revealed no gross pathological lesions typical of brucellosis except enlarged mesenteric and iliac lymph nodes seen in a single buck. Culture for brucellae from organs of seropositive animals was negative. None of the wildlife sera tested positive by either RBT or CFT. Interviews revealed that besides the case that prompted the investigation, a family and another person from other farms with confirmed brucellosis shared a common history of consumption of unpasteurised goat milk, home-made goat cheese and coffee with raw milk and prior contact with goats, suggesting goats as the likely source of infection. All 137 abattoir employees tested negative by STAT, but 3 were positive by ELISA. The 3 abattoir workers were clinically normal and lacked historical connections with clinical cases. Although goats are often associated with B. melitensis, these studies could not explicitly implicate this species owing to cross-reactivity with B. abortus, which can also infect goats. Nevertheless, these data reinforce the need for a better National Control Programme for brucellosis in Namibia.

Quantification of specific DNA O-alkylation products in individual cells by monoclonal antibodies and digital imaging of intensified nuclear fluorescence

We report the establishment of a standardized, monoclonal antibody (Mab)-based immunocytological assay (quantitative ICA) for the visualization and quantification of low levels of specific DNA O-alkylation products in individual cells by electronically intensified, indirect or direct immunofluorescence. In terms of specific binding to alkali-denatured nuclear DNA and low background noise, 10 Mabs from a collection of 154 Mabs specific for O6-methyl-2'-deoxyguanosine (O6-MedGuo), O6-ethyl-2'-deoxyguanosine (O6-EtdGuo), O6-n-butyl-2'-deoxyguanosine (O6-BudGuo) and O4-ethyl-2'-deoxythymidine (O4-EtdThd) with antibody affinity constants ranging between 1.0 x 10(6)-3.0 x 10(10) l/mol, were found to be best suited for ICA. At present, > or = 200 O6-EtdGuo residues (corresponding to an O6-EtdGuo/dGuo molar ratio in DNA of > or = 8.4 x 10(-8)), > or = 400 O6-BudGuo residues (O6-BudGuo/dGuo, > or = 1.7 x 10(-7)), > or = 1800 O4-EtdThd residues (O4-EtdThd/dThd, > or = 7.5 x 10(-7)) and > or = 4800 O6-MedGuo residues (O6-MedGuo/dGuo, > or = 2.0 x 10(-6)), can be quantified per diploid genome. Using a SIT video camera in combination with multiparameter image digital analysis, DNA adduct-specific rhodamine fluorescence signals are measured relative to nuclear DNA content (DAPI fluorescence). Adduct-specific fluorescence recordings in three different rat cell lines (BT3Ca, Fao and NO) were in excellent agreement with the data obtained by competitive radioimmunoassay (RIA) for hydrolysates of DNA isolated from the respective cells exposed in parallel to the same alkylating carcinogens (N-methyl-, N-ethyl- and N-[n-butyl]-N-nitrosourea). Accordingly, the kinetics of O6-EtdGuo repair, as determined by ICA and RIA, respectively, were superimposable. Cell-specific, quantitative ICA can, therefore, be used for the quantification of specific, stable DNA adducts induced by alkylating carcinogens or chemotherapeutic agents and for DNA repair measurements in individual (e.g. human) cells. Work is currently underway to extend the spectrum of carcinogen--DNA adduct-specific Mabs suited for quantitative ICA.

Immunoaffinity purification and gas chromatography-mass spectrometric quantification of 3-alkyladenines in urine: metabolism studies and basal excretion levels in man

Immunoaffinity gels were prepared by coupling monoclonal antibody (Mab) EM-6-47 to protein A-Sepharose, and were used to make small columns retaining 3-alkyladenines (3-alkAde) of diverse structure. An analytical procedure for determination of 3-methyladenine (3-MeAde), 3-ethyladenine (3-EtAde), 3-(2-hydroxyethyl)adenine (3-HOEtAde) and 3-benzyladenine (3-BzAde) was developed. Deuterated internal standards (d3-3-MeAde, d5-3-EtAde, d4-3-HOEtAde and d7-3-BzAde) were synthesized and added to urine samples prior to immunoaffinity purification. 3-alkAde were separated and quantitated as tert-butyl-dimethylsilyl (TBDMS) derivatives by capillary gas chromatography-low resolution mass spectrometry (GC-MS). Detection limits for 3-MeAde, 3-EtAde and 3-HOEtAde were 0.2 pmol/ml urine and for 3-BzAde, 1 pmol/ml urine. Studies in two volunteers showed that 3-MeAde and 3-HOEtAde were excreted almost quantitatively (> 90%) within 24 h, that 3-EtAde was less well excreted (67-74%) and that 3-BzAde was poorly excreted (21-25%). Studies on basal levels of 3-alkAde urinary excretion in three volunteers showed that 3-MeAde was > 90% derived from the diet as the preformed product. 3-HOEtAde was present at approximately 10 nmol/day and was reduced to approximately 1 nmol/day when the diet was standardized suggesting that it is also dietary in origin. 3-BzAde was not detected in human urine. 3-EtAde was not only excreted at low levels (< 1 nmol/day) but was also only very slightly affected by diet. This general and sensitive method will be useful in biomonitoring studies in subjects exposed to alkylating agents of diverse structure.

Second-harmonic generation with partially poled polymers

The poling of polymers leads in general to inhomogeneous polarization distributions within the polymer film. These polarization distributions affect any nonlinear-optic experiment based on second-order nonlinearities. Second-harmonic generation measurements are presented for a partially poled ferroelectric polyvinylidene fluoride film. By partial poling, we mean that the film is polarized only within a part of the film thickness. The measured angle-dependent second-harmonic signal is explained only if the polarization distribution as measured by the piezoelectric pressure pulse technique is taken into account.

Developmental regulation and tissue distribution of the liver transcription factor LFB1 (HNF1) in Xenopus laevis

The transcription factor LFB1 (HNF1) was initially identified as a regulator of liver-specific gene expression in mammals. It interacts with the promoter element HP1, which is functionally conserved between mammals and amphibians, suggesting that a homologous factor, XLFB1, also exists in Xenopus laevis. To study the role of LFB1 in early development, we isolated two groups of cDNAs coding for this factor from a Xenopus liver cDNA library by using a rat LFB1 cDNA probe. A comparison of the primary structures of the Xenopus and mammalian proteins shows that the myosin-like dimerization helix, the POU-A-related domain, the homeo-domain-related region, and the serine/threonine-rich activation domain are conserved between X. laevis and mammals, suggesting that all these features typical for LFB1 are essential for function. Using monoclonal antibodies, we demonstrate that XLFB1 is present not only in the liver but also in the stomach, intestine, colon, and kidney. In an analysis of the expression of XLFB1 in the developing Xenopus embryo, XLFB1 transcripts appear at the gastrula stage. The XLFB1 protein can be identified in regions of the embryo in which the liver diverticulum, stomach, gut, and pronephros are localized. The early appearance of XLFB1 expression during embryogenesis suggests that the tissue-specific transcription factor XLFB1 is involved in the determination and/or differentiation of specific cell types during organogenesis.

Highly sensitive, specific detection of O6-methylguanine, O4-methylthymine, and O4-ethylthymine by the combination of high-performance liquid chromatography prefractionation, 32P postlabeling, and immunoprecipitation

A highly sensitive and specific method for the detection of O6-methylguanine (O6-meG), O4-methylthymine (O4-meT), and O4-ethylthymine (O4-etT) has been established by combining prefractionation by high-performance liquid chromatography (HPLC), 32P postlabeling, and immunoprecipitation by monoclonal antibodies (PREPI method). DNA was enzymatically hydrolyzed to 2'-deoxynucleoside-3'-monophosphates (3'-dNps). Each alkyl 3'dNp was separated by reverse-phase HPLC, radiolabeled at the 5' position with [gamma-32P]ATP and polynucleotide kinase. After removing 3'-phosphate for better recognition by the antibodies, the resulting alkyl nucleotides were further fractionated by HPLC and finally precipitated specifically with respective antibodies. The detection limits were 1 fmol for all the alkyl nucleotides analyzed, so that one adduct in 10(8) of its normal counterpart nucleotide can be determined using approximately 100 micrograms (O4-meT and O4-etT) or approximately 150 micrograms (O6-meG) of DNA, i.e., 3-5 x 10(7) cells corresponding to approximately 10 ml of peripheral blood or a few hundred milligrams of tissue. By the use of the PREPI method, three leukocyte and three liver DNA samples from Japanese living in the Tokyo area were analyzed with respect to O-alkyl adduct content. O6-meG was detected in all three of the leukocyte samples (O6-meG:G molar ratio, 1.1 x, 0.8 x, and 1.6 x 10(-8) as molar ratios to guanine). Neither O4-meT nor O4-etT was detected (detection limit, O4-alkylT:thymine molar ratio less than 0.5 x 10(-8)). Among the liver samples analyzed, two cases showed positive O6-meG values (4.2 x and 1.1 x 10(-7) O6-meG:guanine molar ratios). Contrary to the leukocyte DNA, O4-meT (3.9 x, 4.3 x, and 7.5 x 10(-8) as O4-meT:thymine) and O4-etT (1.9 x, 4.9 x, and 8.7 x 10(-8) as O4-etT:thymine) were detected in all the liver samples. These results indicate the validity of the PREPI method for molecular epidemiological studies on DNA alkylation products.

E-cadherin-mediated cell-cell adhesion prevents invasiveness of human carcinoma cells

The ability of carcinomas to invade and to metastasize largely depends on the degree of epithelial differentiation within the tumors, i.e., poorly differentiated being more invasive than well-differentiated carcinomas. Here we confirmed this correlation by examining various human cell lines derived from bladder, breast, lung, and pancreas carcinomas. We found that carcinoma cell lines with an epithelioid phenotype were noninvasive and expressed the epithelium-specific cell-cell adhesion molecule E-cadherin (also known as Arc-1, uvomorulin, and cell-CAM 120/80), as visualized by immunofluorescence microscopy and by Western and Northern blotting, whereas carcinoma cell lines with a fibroblastoid phenotype were invasive and had lost E-cadherin expression. Invasiveness of these latter cells could be prevented by transfection with E-cadherin cDNA and was again induced by treatment of the transfected cells with anti-E-cadherin mAbs. These findings indicate that the selective loss of E-cadherin expression can generate dedifferentiation and invasiveness of human carcinoma cells, and they suggest further that E-cadherin acts as an invasion suppressor.

Repair of O6-ethylguanine in DNA protects rat 208F cells from tumorigenic conversion by N-ethyl-N-nitrosourea

O6-Ethylguanine (O6-EtGua) is one of about a dozen different alkylation products formed in the DNA of cells exposed to the alkylating N-nitroso carcinogen N-ethyl-N-nitrosourea (EtNU). We have evaluated selectively the relative capacity of cells for the specific enzymatic repair of O6-EtGua as a determinant for the probability of malignant conversion. Eleven O6-EtGua-repair-proficient (R+) variant subclones were isolated from the O6-EtGua-repair-deficient (R-) clonal rat fibroblast line 208F by selection for resistance to 1,3-bis-(2-chloroethyl)-1-nitrosourea (frequency, approximately equal to 10(-5). Contrary to the 208F wild-type cells, all variants expressed O6-methylguanine-DNA methyltransferase activity, while both kinds of cells were deficient for repair of the DNA ethylation products O2- and O4-ethylthymine. After exposure to EtNU (less than or equal to 500 micrograms/ml; 20 min), cells were analyzed for the formation of piled-up foci in monolayer culture and of anchorage-independent colonies in semisolid agar medium. Depending on the EtNU concentration, the frequencies of piled-up foci and agar colonies, respectively, in the R+ variants were as low as 1/28th and 1/56th of those in the R- wild type. Contrasting with the cells from R+ variant-derived agar colonies, cells from 208F (R-) agar colonies gave rise to highly malignant tumors when implanted subcutaneously into syngeneic rats. No significant differences in the frequencies of piled-up foci were found between wild-type and variant cells after exposure to the major reactive metabolite of benzo[a]pyrene, (+)-7 beta, 8 alpha-dihydroxy-9,10 alpha-epoxy-7,8,9,10 alpha-tetrahydrobenzo[a] pyrene, for which stable binding to guanine O6 in cellular DNA has not been observed. The relative capacity of cells for repair of O6-alkylguanine is, therefore, a critical determinant for their risk of malignant conversion by N-nitroso carcinogens.

Monoclonal antibodies for the specific detection of 3-alkyladenines in nucleic acids and body fluids

We describe an immunoanalytical procedure for the detection and quantitation of 3-alkyladenines in biological samples with the use of anti-(3-alkyladenine) monoclonal antibodies (Mab). A new hapten-protein conjugate, 3-ethyl-8-(3-carboxypropyl)-adenine, was used for immunization of BALB/c mice after conjugation to carrier proteins via the carboxyl group. Eighty-nine hybridomas were established which secrete anti-(3-alkyladenine) Mab with antibody affinity constants ranging from 1 x 10(7) to 5 x 10(9) l/mol for 3-ethyladenine (3-EtAde). One of these Mab (EM-6-47) had detection limits of 30 fmol for 3-EtAde, 17 fmol for 3-n-butyladenine (3-BuAde) and 475 fmol for 3-methyladenine (3-MeAde) respectively, at 25% inhibition of tracer-antibody binding. The binding pattern of Mab EM-6-47 revealed high specificity for adenine substituted at N-3 with different alkyl residues and no, or very low, cross-reactivity with other alkylated or unmodified nucleic acid components or structurally related compounds. 3-MeAde and 3-EtAde can be well separated from nucleic acids, and from rat and human urine samples, using HPLC with two successive stationary phases. Using Mab EM-6-47 in conjunction with a competitive RIA, both 3-MeAde and 3-EtAde were detected in the range of 100-300 ng (3-MeAde) and 2-10 ng (3-EtAde) in urine samples (10 +/- 2 ml) of untreated rats collected over a 24 h period. Only 3-MeAde (range 1.3-24.20 micrograms) was found in human urine samples. The concentration of 3-EtAde in rat urine increased significantly during the 24 h following a single i.v. application of N-ethyl-N-nitrosourea. After i.p. application of known amounts of 3-MeAde and 3-EtAde, greater than 90% of 3-MeAde and greater than 70% of 3-EtAde were excreted in rat urine within the subsequent 24 h. The concentration of 3-alkyladenines in body fluids (urine) may thus provide a useful indicator of environmental exposure to nucleic acid-reactive agents, and the immunoanalytical procedure described here permits the sensitive determination of adenines carrying different substituents at N-3.

Investigations on the relationship between DNA ethenobase adduct levels in several organs of vinyl chloride-exposed rats and cancer susceptibility

The levels of 1,N6-ethenodeoxyadenosine (epsilon dAdo) and 3,N4-ethenodeoxycytidine (epsilon dCyd) were measured in DNA of several target organs of vinyl chloride (VC)-exposed rats. Seven-day-old (group I) and 13-week-old (group II) BD VI rats were exposed during 2 weeks to 500 ppm VC in air (7 hr per day and 7 days per week). epsilon dAdo and epsilon dCyd were measured by a combination of prepurification of DNA hydrolysates by HPLC and competitive radioimmunoassay using specific murine monoclonal antibodies. Both ethenodeoxynucleosides were detected in liver, lungs and brain (levels ranging from 0.6 x 10(-7) to 1.3 x 10(-7) for epsilon dAdo/2'-deoxyadenosine and from 1.95 x 10(-7) to 4.92 x 10(-7) for epsilon dCyd/2'-deoxycytidine) but not in kidneys of group I rats. In group II rats, only liver DNA was analysed and the levels of each adduct were six times lower than in young (group II) rats. These findings are in good agreement with the organotropism and the age-related sensitivity of VC-induced carcinogenesis in rodents.

1,N6-etheno-2'-deoxyadenosine and 3,N4-etheno-2'-deoxycytidine detected by monoclonal antibodies in lung and liver DNA of rats exposed to vinyl chloride

1,N6-Etheno-2'-deoxyadenosine (epsilon dAdo) and 3,N4-etheno-2'-deoxycytidine (epsilon dCyd) are formed in vitro by reaction of DNA with the electrophilic metabolites of vinyl chloride (VC), chloroethylene oxide and chloroacetaldehyde. To detect and quantitate these DNA adducts in vivo, we have raised a series of specific monoclonal antibodies (Mab). Among those, Mab EM-A-1 and Mab EM-C-1, respectively, were used for detection of epsilon dAdo and epsilon dCyd by competitive radioimmunoassay (RIA), following pre-separation of the etheno adducts from DNA hydrolysates by high performance liquid chromatography. At 50% inhibition of tracer-antibody binding, both Mab had a detection limit of 187 fmol and antibody affinity constants (K) of 2 x 10(9) l/mol. The levels of epsilon dAdo and epsilon dCyd were quantitated in the DNA of lung and liver tissue of young Sprague-Dawley rats exposed to 2000 p.p.m. of VC for 10 days. The epsilon dAdo/2'-deoxyadenosine and epsilon dCyd/2'-deoxycytidine molar ratios were 1.3 x 10(-7) and 3.3 x 10(-7), respectively, in lung DNA, and 5.0 x 10(-8) and 1.6 x 10(-7) in liver DNA. When hydrolysates of 3 mg of DNA were analyzed by RIA at 25% inhibition of tracer-antibody binding, epsilon dAdo and epsilon dCyd were not detected in liver DNA from untreated rats above the limiting epsilon dAdo/2'-deoxyadenosine and epsilon dCyd/2'-deoxycytidine molar ratios of 2.2 x 10(-8) and 3.1 x 10(-8), respectively.

Quantitation and visualization of alkyl deoxynucleosides in the DNA of mammalian cells by monoclonal antibodies

Conventional radiochromatographic procedures for the quantitation of carcinogen/mutagen-induced structural DNA modifications have a number of limitations. Thus, these techniques for the most part require application of radioactively labeled carcinogens and the use of relatively large amounts of DNA for analysis at low levels of DNA modification. Radiochromatographic methods also preclude analyses at the level of single cells and DNA molecules. Recently developed immunoanalytical methods have improved this situation considerably. Monoclonal antibodies (Mab) characterized by a high substrate specificity and affinity, in combination with radio- and enzyme-immunoassays, or with "immuno-slot-blot" techniques, now permit the detection of femtomole to subfemtomole amounts of, e.g., alkyldeoxynucleosides in small samples of DNA isolated from tissues or cultured cells previously exposed to nonradioactive N-nitroso compounds. Furthermore, selected Mab can be used to quantitate by direct immunofluorescence (with the aid of computer-based image analysis of electronically intensified fluorescence signals), specific alkyldeoxynucleosides in the nuclear DNA of single cells. With this method, the detection limit for the alkylation product O6-ethyldeoxyguanosine (O6-EtdGuo) is presently of the order of 10(2) -10(3) O6-EtdGuo residues per diploid mammalian genome. Individual cells can thus be monitored for the presence of specific carcinogen-DNA adducts, and with respect to their capacity for enzymatic removal of such modified structures from DNA (as exemplified here by the kinetics of the enzymatic elimination of O6-EtdGuo from the DNA of malignant neurogenic rat cell lines). In combination with transmission electron microscopy, Mab also permit direct visualization (via Mab binding sites) of specific carcinogen-modified structures in individual DNA molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

[Prophylaxis of dental caries using sugar substitutes]

Among the three measures, which are capable of producing a preventive effect against caries only when applied combined, i.e. adequate fluoride supply, proper mouth hygiene and healthy nutrition, the latter is dealt with in greater detail. The use of sugar substitutes is discussed under the aspects of caries prevention, substitute composition and production technology as well as from a medical point of view. Among the presently available sugar substitutes with nutritive value are mentioned Xylite, Lycasine, Mannite, Sorbite, Palatinite, the non-calorific substitutes such as the natural Aspartame as well as the synthetic sweetening agents Saccharine and Cyclamate. The possibilities and limitations of using these sugar substitutes in the prevention of caries in adults and children are presented.

The expression of fragile X chromosomes in members of the same family at different times of examination

Three brothers with fragile X chromosomes were repeatedly examined using the same culture and preparation techniques. It was observed that a given individual showed a very constant frequency of fragile sites at his X chromosomes, whereas large differences in the fragile X counts occurred between the three brothers.

Cocultivation studies with cells of patients bearing fragile X chromosomes

Fourteen cocultivation studies were carried out with cells of our patients with fragile X, one obligate and two possible female heterozygotes, two female controls, and a rabbit. In all cocultivations the number of fragile X chromosomes was sharply reduced in the patient cells. The strongest effect was causes by the animal cells. A distinct difference between the two controls in the reducing ability was observed. No such difference was found between the obligate and possible heterozygotes on the one hand and the controls on the other. To test the influence of the residual serum in the mixed blood cultures, the serum of a patient's blood sample was replaced by the serum of a control. The frequency of fragile X chromosomes was not decreased by this procedure. Therefore a soluble factor is supposed to exist which is produced by normal or heterozygote cells in culture and which reduces the expression of fragile sites in patient cells.

[Experimental infection of mice, gerbils, and rats with mycoplasms from canine pericardium and cardial value (author's transl)]

Mycoplasms isolated from heart valves (A. laidlawii (A 42 Hzbtl)) and pericardium (M. canis (A 56 Hzkl)) of dogs were investigated for infectivity of rats, mice and gerbils (Meriones unguiculatus). In mice the species M. spumans (PG 13), M. maculosum (PG 15), M. edwardii (PG 24) and M. molare (H 542) were investigated too. The mycoplasmas were inoculated by oral, subcutaneous, intravenous and intraperitoneal route. Intraperitoneally the mycoplasmas were given without and with complete and incomplete Freund adjuvants. The injected Mycoplasmas did not produce any disease and could not be reisolated from rats and gerbils. From mice A. laidlawii (A 42 Hzbtl), M. canis (A 56 Hzkl) and M. edwardii (PG 24) could be reisolated after intraperitoneal administration in emulsion with complete and incomplete Freund adjuvants. Whereas M. canis (A 56 Hzkl) and M. edwardii (PG 24) could be reisolated from lung, liver and spleen only, A. laidlawii (A 42 Hzbtl) was present in heart muscle too. In histological investigations the mice which got A. laidlawii (A 42 Hzbtl) intraperitoneally with complete Freund adjuvants showed focal lymphocytic infiltrations in the myocardium.