The John Palmer Lecture

ADVANCES IN HEPATIC SURGERY

John Palmer

John Palmer lived from 1925-1984. He trained in general and plastic surgery at the University of Toronto and then completed fellowships in Edinborough in plastic surgery and colorectal surgery at St. Mark’s in London. He was a self -described "head to tail surgeon". Among his many talents were playing the trombone, refinishing furniture and painting beautiful landscapes, two of which were shown by Paul Greig during his thoughtful introduction of professor Michael A. Choti, this year’s Palmer lecturer.

A graduate of Yale, University of Pennsylvania and Memorial Sloan Kettering, Professor Choti joined the John Hopkins Faculty in 1992. He has served as director of the Hopkins’ Surgical Oncology Fellowship and Chief of the Surgical Oncology Program. His research is focused on ultrasound guided ablation techniques for liver tumours. He is the Jacob Handelsman Professor of Surgery, named for a gifted surgeon with interests and avocations similar to those of John Palmer.

Hepatic surgery is evolving in important ways. The mortality for ablation or resection of hepatic metastasis is now at 1% or lower and the five-year survival for hepatic resections for cancer exceeds 50%. Where resection was previously limited to one or two metastases, it is now common practice to resect even patients with many metastases. These dramatic advances are related to the improvements in preoperative therapy, imaging and surgical technique. The imaging requires a fusion of surgery and imaging techniques analogous to the work that is being done in urologic, cardiovascular, and neurosurgery. Unlike the brain or prostate, the liver moves with respiration and position, and the use of registered preoperative images in the operative theatre is more challenging. Additional metastases are found at exploration in 10% of cases. Another challenge is the disappearance of tumours that were imaged in the pretreatment interval, as they are often unfindable following chemotherapy. It is nevertheless important to resect the sites, as residual tumour cells are generally present despite their apparent disappearance on intra-operative imaging. The Hopkins group - comprised of engineers, surgeons, medical oncologists, and radiologists are actively exploring the use of more advanced techniques for imaging and resection. The group has patented a robotic ultrasound tool licensed to Intuitive Surgical. Such a device can be used to improve minimally invasive robotic procedures using image-guidance, including cancer ablation. Ablation techniques currently in use include chemical ablation (using ethanol or acetic acid), and thermal ablation using radiofrequency or microwave energy. The Choti team has developed a staging system based on the surgeons’ confidence in the completion of the ablation. In this way, this form of therapy may be able to achieve comparable results to that of more invasive resectional therapy. They are working with three dimensional ultrasound, motion tracking using video-gaming systems, and fusion of CT and MRI with operative ultrasound to resolve some of the imaging problems. Some metastases are isoechoic, i.e. they cannot easily be found by reason by their hypo or hyper echoicity, even if they are evident on CT. They are working with GE, Siemens, Phillips and other manufacturers to resolve these challenges. To improve conspicuity, they are adding elastography - a technique to visualize differences in stiffness that results from thermal destruction.

The current novel robotic probe works with high frequency therapeutic ultrasound to shape the ablation field.

Paul Grieg, Michael Choti and Ori Rotstein

John Trachtenberg asked about the use of magnetic resonance thermography, which he is employing successfully in prostate cancer ablation. Professor Choti felt that the system was more difficult in the hepatic application as the apparatus is awkward and expensive. Andy Smith asked about the drift of surgery toward radiology and radiology towards surgery. Choti answered that, indeed, the specialties are blending somewhat, as are the cultures. Radiology residents are getting more adept at patient care as interventional oncologists; they now see and follow patients. Hepatobiliary surgeons are learning radiology, though the specialties are clearly interdependent. Paul Greig asked about the use of ultrasound contrast to strengthen imaging. Choti answered that the Hopkins group is not exploring this at present, but the Europeans are very active in contrast ultrasonography. Ori Rotstein asked about the interaction of surgeons and engineers. Choti answered that it is hard to bring the mindsets together. "Surgeons are trained in mechanistic hypothesis testing, whereas the engineers’ thinking is based on system development and validation. They design robots and create software. The co-principal investigative model is in progress".

M.M.