Interventional Oncology — Endovascular Treatments Offer Survival Benefit and Palliation
By Shaun Samuels, MD
Vol. 14 No. 2 P. 30
More than 1.6 million Americans are diagnosed with cancer every year, and the five-year survival rate has grown in 30 years from 49% to 67% because of earlier detection as well as improvement in treatments, according to the American Cancer Society.
Although surgery, chemotherapy, and radiation are the standard first-line therapies, interventional oncology (IO) treatments hold promise as alternative therapies. These interventional treatments include radio-frequency ablation, cryoablation, microwave ablation, and arterial embolization (with or without chemotherapy or radioactive particles) of primary and metastatic cancerous lesions, predominantly in the liver, kidneys, lungs, and bones.
Anxious for options, cancer patients often are ahead of the oncology community in reading about these procedures and proactively ask their doctors about these therapies or approach interventional radiology departments.
The current cancer treatment environment is a political and economic minefield that sometimes prevents patients from knowing all their options or receiving what may be the optimal therapy for them. There are several reasons for this, not the least of which is oncologists often are unaware of the myriad IO alternatives available. They also may be skeptical because of the paucity of level 1 evidence for IO treatments or are concerned about losing control of their patients’ care.
Oncologists who send patients for IO treatment often do so only after standard chemotherapy has failed, which is reasonable based on the evidence available but still potentially deprives patients of what may be a better first-line interventional treatment for liver dominant disease.
Those of us who work in IO are confident that, used as primary or adjunct therapy, IO options can provide a survival benefit. IO treatments also can be used as a bridge to transplantation and have significant palliative value. We will continue to work to coordinate optimal care with oncologists, apprise them of the latest data regarding IO options, assure them that we as a group understand that the medical oncologist ought to be the primary director of each patient’s cancer care, and spread the word about the wealth of non-level 1 evidence for IO therapies.
Members of the IO field are not oncologists, and we shouldn’t pretend to be oncologists. Our expertise is IO, or the provision of percutaneous or transcatheter ablation or embolization treatment in cancer patients. For those practicing IO exclusively, their knowledge base in medical oncology often is prodigious, and they clearly are conversant with the medical oncologists on the minutiae of chemotherapeutics.
In my office at the Baptist Cardiac & Vascular Institute in Miami, perhaps 20% to 30% of patients come to the office directly rather than through referrals from their primary care physicians or oncologists. My colleagues and I educate them regarding what we can do for them but insist that their medical oncologists quarterback. Frustrated that their oncologists did not offer IO options, some patients do not want to go back to them. In these cases, we refer patients to a different medical oncologist.
Although the bulk of IO therapy focuses on the liver, various interventional treatments have been used to treat kidney, lung, and bone cancer, often when other treatments have failed, or for palliative benefit.
• Liver cancer: More than one-half of all treatments for primary and metastatic liver cancer come from the IO arsenal. The most common type of liver cancer, hepatocellular carcinomas, which frequently occur in the cirrhotic liver (and are on the rise because of an increase in hepatitis C cases), typically are unresectable and do not respond well to systemic chemotherapy.
The liver also is a common site for metastatic lesions, particularly because of colon and rectal cancer. Treatment options include chemoembolization (as an adjunctive or palliative therapy), Yttrium-90 radioembolization (which, although not curative, can extend survival), radio-frequency ablation, chemosaturation, and cryoablation.
• Kidney cancer: Renal cell carcinoma is the most common cancer of the kidneys and while the standard of care is either total or partial nephrectomy, IO offers several nephron-sparing options. These include radio-frequency ablation, cryoablation, and embolization. Patients who are not good candidates for surgery or have only one kidney may benefit from IO treatments. For certain patients with small lesions, cryoablation may be considered as a first-line therapy.
• Lung cancer: Interventional treatments for lung cancer include microwave ablation, radio-frequency ablation, and cryoablation and are most effective when lesions are local, focal, small, and haven’t spread to the mediastinum. Transcatheter embolization occasionally is used in lung tumors as well but reserved primarily for the control of tumors that have bled.
Typically, IO treatments are employed to treat pulmonary malignancies when patients are not surgical candidates. Because there are a wide variety of treatment modalities available, and 80% to 90% of lung cancers, once discovered, have become invasive, most IO operators treat a small percentage of these patients.
• Bone cancer: The bones are a common site for metastases, leading to severe bone pain and reduced quality of life. Radio-frequency ablation, cryoablation, and vertebroplasty have been shown to cause tumor necrosis, stabilize the bone, and alleviate pain. While oncologists typically refer patients to radiation oncologists to treat bone pain, ablation is an excellent option for palliation. Several extensive studies have demonstrated these palliative benefits.
Further, several newer interventional treatments hold promise, including gene therapy and magnetic chemotherapy.
There are many reasons for the scarcity of level 1 evidence for IO treatments. Because IO therapies are relatively new, researchers don’t have the numbers or even the potential to gather data to undertake a randomized controlled trial. Because new generations of treatments—or entirely new therapies—are continually being introduced, it’s difficult to know what to randomize against. Technologies improve quickly, making others obsolete just as quickly.
In the current environment, there is an overemphasis on randomized controlled trials as the only acceptance of proof. Reasonable experts in the medical community understand that this is irrational and impractical. Oncologists must realize that it is the difficulty in obtaining level 1 evidence, not the lack of value of interventional procedures, that has led to the lack of randomized controlled trials.
However, there is a variety of valuable evidence that, although not level 1, suggests IO is beneficial. Years and years of accumulated evidence—from single institution experiences to meta-analyses—proves IO is not experimental. Perhaps even more compelling, the Centers for Medicare & Medicaid Services has CPT codes for most IO therapies.
For the patients’ sake, interventional radiologists need to continue to push for wider understanding and consideration of IO therapies when arriving at a cancer treatment plan.
— Shaun Samuels, MD, is an interventional radiologist at Baptist Cardiac & Vascular Institute and an affiliate assistant professor at the University of South Florida at Tampa.