Liver Surgery, Including Ablative Procedures: An Expert Interview with Prof. Dr. med. Merten Hommann

At the Zentralklinik Bad Berka, Prof. Dr. med. Merten Hommann combines outstanding medical expertise with a deep sense of compassion. As Chief of the Department of General and Visceral Surgery, he specializes particularly in the treatment of neuroendocrine tumors, liver surgery, and pancreatic surgery. Under his leadership, the department provides state-of-the-art, interdisciplinary care that offers excellent treatment to patients with complex medical conditions. The Zentralklinik Bad Berka is a center recognized throughout Europe for the treatment of neuroendocrine tumors. Since 2013, the center has held the coveted certification from the European Neuroendocrine Tumor Society (ENETS) as a Center of Excellence, which confirms the outstanding quality of its medical care.

Prof. Dr. Hommann and his team rely on innovative treatment methods that include minimally invasive techniques as well as state-of-the-art technologies for precise diagnosis and therapy. This includes the high-energy gamma probe, which allows for the precise localization of tiny neuroendocrine tumors and metastases during surgery. In pancreatic surgery as well, the team relies on state-of-the-art methods, including irreversible electroporation (IRE), a procedure for targeted tumor ablation.

Interdisciplinary collaboration plays a central role at the Zentralklinik. Experts from surgery, internal medicine, radiology, and nuclear medicine work closely together to develop a tailored treatment strategy for each patient. This close collaboration not only enables precise diagnosis and treatment but also ensures holistic care that places the patient—as a person—at the center.

Prof. Dr. Hommann’s dedication to his patients is particularly impressive. He is not only committed to the highest medical standards but also places great emphasis on providing personalized and empathetic care. Each patient is thoroughly informed about their condition and individual treatment options, ensuring they are actively involved in the decision-making process. This philosophy builds trust and provides patients with a sense of security in what is often a challenging life situation.

Thanks to his many years of experience, his continuous pursuit of medical innovation, and his tireless dedication, Prof. Dr. Hommann has achieved a leading position in the treatment of pancreatic and liver diseases and neuroendocrine tumors. Patients at the Zentralklinik Bad Berka benefit from state-of-the-art medical technology, in-depth expertise, and a unique standard of care that is recognized far beyond Germany’s borders.

In a detailed and engaging discussion, Prof. Dr. Hommann explained the field of liver surgery and provided information on possible additional ablative procedures (e.g., microwave ablation).

Liver surgery plays a central role in the treatment of benign and malignant liver diseases and encompasses both surgical procedures for tumor removal and modern minimally invasive techniques. Particularly in the case of malignant liver tumors, innovative ablation procedures such as microwave ablation are increasingly being used alongside traditional resections. This minimally invasive method makes it possible to selectively destroy tumor tissue without unnecessarily damaging healthy liver tissue. By combining surgical procedures with advanced ablation techniques, patients can receive individually tailored treatment strategies that improve the chances of recovery and minimize the burden of therapy.

Surgical resection of the liver is primarily preferred when the tumor is anatomically resectable, there is no extensive liver disease such as advanced cirrhosis, and the patient has sufficient (residual) liver function to tolerate the procedure. It is considered the best curative option, particularly, for example, in cases of liver metastases of colorectal origin.

“Tumor resection is typically considered for malignant tumors or metastases—that is, secondary tumors. Liver metastases are more common than primary liver tumors, and they occur most frequently in colorectal carcinoma. In cases of benign lesions, resection is rarely considered. Of course, resection is also an option for benign tumors—large adenomas are a key consideration here. For malignant tumors, the gold standard is resection followed by histological examination. This allows for the assessment of resection margins and confirmation of complete removal. Ablative procedures certainly have their place, especially when it is determined that resection is not possible. This is the case, for example, when the lesions are distributed throughout the liver in such a way that resection would leave too little functioning liver tissue, or when the liver tissue is pathologically altered. Even if the patient has cardiopulmonary limitations, the decision is sometimes made against resection due to the risks associated with anesthesia. The advantage of ablative procedures is that they affect only a small amount of functioning liver tissue. Treatment can be targeted with precision, while maintaining a necessary safety margin from the surrounding tissue. This preserves as much healthy tissue as possible. For example, if there is a small lesion—such as a centrally located liver metastasis—that would require removal along with a significant amount of healthy tissue, the decision tends to favor ablation. “Ablation techniques have become much better and more precise, and there is no risk of losing too much healthy tissue. After all, the option of a subsequent resection surgery is still available,” explains Prof. Dr. Hommann at the beginning of our conversation.

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“A person needs at least five grams of functioning, healthy liver tissue per kilogram of body weight. There are methods to measure this before surgery. You can perform a volumetric assessment using MRI or CT. Using various measurement methods, one can also determine liver function, including the potential remaining liver function. With volumetry, it’s always important to take into account that the liver’s fat content accounts for a certain percentage, which must be subtracted from the result of the remaining functional reserve. “The healthier the liver, the more favorable the treatment options. If the tissue is severely diseased, ablation is often the only viable treatment option,” explains Prof. Dr. Hommann.

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Tumor size is also a decisive factor in choosing a treatment method. While smaller tumors are suitable candidates for resection or ablation, larger lesions (> 5 cm) are preferably removed surgically, as ablation therapies for large tumors result in incomplete tumor destruction and a higher risk of recurrence. Location also plays an important role: If the tumor is located near large blood vessels, ablation may be less effective due to the “heat sink effect”—in which the flowing blood dissipates the heat, thereby reducing the treatment’s efficacy. Another important consideration is the number of tumors and their distribution within the liver. A complex distribution pattern—such as one affecting both sides—often indicates that ablation or a combination of resection and ablation is the appropriate treatment.

“Unfortunately, there are also patients—for example, those with colorectal liver metastases—who are primarily suitable for resection but in whom the distribution pattern of the lesions in the liver means that too little functioning liver tissue can be preserved. In such cases, we usually plan ablation therapy. And if the distribution pattern of the metastases—in terms of both size and number—is too extensive, we must also rule out ablation and focus on another (systemic) therapy. There are other treatment options available, depending on the size and number of liver metastases, such as transarterial chemoembolization (TACE) or selective internal radiation therapy (SIRT), which are suitable for complex distribution patterns. To successfully perform ablation, there is a basic rule: a maximum of five lesions, the largest of which may be no more than five cm in diameter. If there are more lesions or if one lesion is larger, ablation is still possible in principle, subject to case-by-case decisions. “It is also conceivable to first use a therapy to reduce the size of the lesions and then perform a resection or ablation,” explains Prof. Dr. Hommann. 

Microwave ablation (MWA) is a modern and highly effective procedure for the targeted destruction of tumor tissue, which has established itself—particularly in the treatment of liver tumors—as a valuable alternative or supplement to surgical interventions.

“There are thermal and non-thermal ablation methods. Thermal methods include those that use heat, such as microwave ablation and radiofrequency ablation, which generate heat that then destroys the tumor. Cryoablation is a method that destroys the tumor using cold. And then there are non-thermal procedures that use lasers (LIT = Laser-Induced Therapy) or irreversible electroporation, which destroys the cell membrane with high-voltage electrical pulses, leading to the destruction of metastases or tumors. Overall, there are differences in application, complexity, and, of course, cost. In the vast majority of cases, the medical team agrees on a practical, highly effective procedure to use in treating liver lesions and may have a second procedure “up their sleeve.” We have focused on thermal procedures because they can be applied at any time—for example, if it becomes apparent during surgery that resection is not feasible and the surgical strategy must be adjusted. Thermal ablation procedures are very effective and precise. They work regardless of the type of tumor. A non-thermal procedure may sometimes be more suitable if the metastases or the tumor are located very close to blood vessels or the bile ducts, because this approach causes less damage to surrounding structures. Ablation procedures can also be performed percutaneously, guided by ultrasound, CT, or MRI, or via laparoscopy or open surgery. “Of course, we always try to use the least invasive method possible for the patient, and for percutaneous procedures, we ask our colleagues in radiology or internal medicine to perform the ablation,” explains Prof. Dr. Hommann, adding:

“Ablation procedures have been around since the 1990s, and they are becoming technically better and more effective. There are increasingly better applicators and instruments, and the goal, of course, is to work very effectively with minimal side effects in the shortest possible time and with minimal effort (using only one applicator). Over the past 25 years, the application and speed of these procedures have improved, and their effectiveness has also increased. The effectiveness and safety of ablation procedures improve the prognosis for patients. The gold standard is still the complete removal of tumors and/or metastases. The combination of surgical liver resection and ablation procedures, such as microwave ablation or radiofrequency ablation, can also significantly improve the long-term prognosis for patients with liver tumors. This combined therapy enables a personalized treatment approach that allows for both the complete removal of large or centrally located tumors and the targeted destruction of smaller, hard-to-reach lesions.”

The aggressiveness of a liver tumor depends on its type, growth pattern, and ability to metastasize. 

Benign tumors such as hemangiomas or focal nodular hyperplasia grow slowly, remain confined to the liver, and rarely cause local symptoms. Malignant tumors, on the other hand, such as hepatocellular carcinoma (HCC) or cholangiocarcinoma, grow rapidly, invade surrounding tissue, and can form metastases. Liver metastases originating from other types of cancer are aggressive, indicating advanced cancer. The nature of the mass significantly influences the choice of treatment and the prognosis.

“Tumors naturally vary in aggressiveness and blood supply. But ultimately, metastases from colon cancer or hepatocellular carcinoma, for example, are ablated using the same technical approach. The crucial question is whether it is possible to completely destroy the metastases or the primary tumor. With resection, confirmation is done under the microscope after the procedure, since this allows us to verify that there are truly no tumor cells remaining at the margins of the incision. With ablation, this cannot be verified in the same way; here, we must be certain and confident that the ablation was performed as effectively as possible. “The only way to check whether a focus is still active is through periodic monitoring using tumor markers or contrast-enhanced imaging, up to and including PET/CT,” explains Prof. Dr. Hommann.

The use of equipment for ablation procedures requires the highest precision and careful planning to ensure safe and effective treatment. 

“The colleagues performing the ablation—whether internists, surgeons, or radiologists—must be familiar with the procedure and know the applicators and generators they are using. With a skilled hand, a good team, and properly functioning equipment, ablation is neither better nor worse at any one location. The technique is easy to learn. You have to be able to think in three dimensions, use intraoperative ultrasound to know where you are within the organ, and also know which structures could be damaged,” says Prof. Dr. Hommann regarding the skills necessary for a successful ablation.

In addition, experience in managing potential complications is required. This includes avoiding damage to adjacent organs and blood vessels, as well as properly handling the so-called “heat sink effect” when treating nearby vessels. Postoperative care and follow-up are also crucial for ensuring the success of the ablation and for responding early to possible recurrences or side effects.

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Commenting on the future of AI and robotics, Prof. Dr. Hommann says: “There will certainly be AI- or robot-assisted systems in the future to improve navigation and target the metastasis or tumor with pinpoint accuracy. This is already being used extensively in the field of neurosurgery, so it will likely find its way into liver ablation procedures as well.”

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The prognosis for liver cancer has improved significantly in recent years thanks to improved diagnostic and treatment options. Advances in imaging allow for earlier detection of tumors, which increases the chances of successful treatment.

“The prognosis for patients has improved, but not because it can be attributed to any single procedure; rather, it is due to the availability of multiple procedures that can also be used in combination. The treatment sequence and the next step in treatment are always discussed in a tumor board. It is the option to combine these approaches that ultimately increases the effectiveness of guideline-based therapy. And this ultimately leads to an improved overall prognosis for the patient due to the complexity of the treatment,” explains Prof. Dr. Hommann. To conclude our conversation, he offers a few tips on how to take care of your liver:

“The liver naturally thrives on a healthy diet—for example, a Mediterranean-style diet rich in vegetables and good water. What the liver particularly loves are bitter compounds. Unfortunately, these have been weeded out of our diet because most people apparently don’t like the taste. If you think of chicory or radicchio, these vegetables used to taste much more bitter. However, you can also consume these bitter compounds as tea or powder, which can even be incorporated into a 3-month diet. Examples include bitter compounds from bitter root, wormwood, gentian, dandelion, milk thistle, or artichoke, which are available at health food stores in the form of non-alcoholic capsules or powders.”

Thank you very much, Professor Dr. Hommann, for this insightful look into the treatment of liver diseases!