When it comes to treating cancer patients, clinicians prefer to get more out of less – killing as much of the cancer as possible, but in ways that reduce harmful side effects to patients.
A focused therapy called tumor ablation offers a high success rate for eradicating some solid tumors with a low chance of local recurrence – and it does so by killing cancer cells, typically with heat or cold, rather than removing them with surgery or targeting them with harmful chemicals or radiation. Since its inception in the 1990s, researchers at the UW Carbone Cancer Center, including Louis Hinshaw, MD and Paul Laeseke, MD, PhD, have been instrumental in the research, development and clinical application of ablation technology, specifically microwave ablation.
The Benefits of Ablation
“Tumor ablation is a versatile cancer treatment that uses special needles, or probes, to apply extreme heat or, less commonly, cold to a solid tumor to destroy the cancerous cells,” Hinshaw explained. “In microwave ablation, there is a specially designed antenna that’s built into the tip of the ablation needle, which is then placed into the tumor. It then delivers an electromagnetic field to the tumor, which heats the tissue to 140oF, a temperature at which no cells can survive.”
The tumors of interest – most typically small, solid tumors of the liver, kidney or lungs – are located using imaging methods, such as ultrasound and computed tomography (CT), which guide the placement of up to three ablation antennas, depending on the tumor. Imaging is also used to assess the success of the procedure afterwards. Doctors look to see if the area of tissue they have destroyed with ablation covers the area of the targeted tumor plus some surrounding tissue to ensure they have killed all of the cancerous cells. When eligible for the procedure, tumor ablation is often all that is needed to rid patients of their cancer.
With low risk of complications and local recurrence, and a quick recovery time, tumor ablation is an appealing treatment option. However, as a relatively new – and therefore still developing – technology, microwave ablation is not yet a widely-used treatment, and has limitations. For example, it is only effective at treating solid tumors, not blood malignancies. Additionally, the treatment only affects tumor cells that are in the ablation zone, so patients with multiple or large tumors are typically not good candidates for treatment.
“We’re very good at treating tumors under four centimeters. For tumors above four centimeters, we start to see our treatment failure rates creep up,” Laeseke said. “And the tumors have to be in tissues that can withstand the ablation process, as the extreme heat can damage adjacent structures.”
While these limitations mean that ablation serves a minority of cancer patients today, the benefits of ablation have made a significant impact on certain cancer types, and in some cases is the primary treatment option. For example, 80 percent of liver cancer patients are unable to have surgery, but most of those patients can be treated with microwave ablation. At UW Carbone, a majority of patients with liver cancers and a significant minority of patients with kidney cancer will receive ablation at some point during their treatment. The procedure also does not have to be a standalone treatment.
“There are certainly tumors that are not good candidates for ablation initially that might become good candidates after they are treated with another type of therapy, such as chemotherapy,” Laeseke said.
Building off of UW Carbone’s strengths in tumor ablation technology, Hinshaw, Laeseke and colleagues in radiology and biomedical engineering (including ablation expert and founder of the clinical ablation program at UW, Fred Lee, MD) are researching ways to make this treatment a viable option for even more patients. For example, they are developing new imaging methods to assess the treatment’s success more accurately, while also developing ways to treat larger tumors or more tumor types.
“We’re certainly not the right treatment for all patients, but there are certain patients where we are the best treatment, and we continue to expand what we can do,” Hinshaw said. “As the field advances, I think we will prove to be a very important player in the world of oncology.”