Medical science’s approach to treating cancer has always been just that—providing treatment to patients after they’ve received a cancer diagnosis. Of course, preventing cancer before it occurs is a goal, but virtually all cancer-prevention strategies to date have been passive in nature—health-care providers offer advice about lifestyle changes that could reduce patients’ odds of later developing cancer, such as “stop smoking” or “use sunscreen.”
Exciting news: We’re on the cusp of a dramatic paradigm shift—human trials are underway to test medical treatments that could put a halt to certain cancers even before they become cancer. Elizabeth Blackburn, PhD, the Nobel Prize–winning past president of the American Association for Cancer Research, has coined the term “cancer interception” for these efforts, drawing a comparison with interceptions on the football field. While most cancer treatments don’t begin until the opposition has put points on the board—and the patient’s health has suffered—cancer interception would stop the opposition from advancing and potentially provide an opportunity to run the ball back in the other direction.
Treatments that can stop cancer before it becomes cancer already exist in a few very specific circumstances…
Vaccines are available that reduce the odds of developing a small number of cancers that have a known viral component. Examples: Vaccines that protect against human papillomavirus can reduce the odds of developing cervical cancer…and vaccines that protect against hepatitis B can reduce the odds of liver cancer.
Removal of precancerous lesions, also known as an intraepithelial neoplasia (IEN), routinely occurs when lesions are identified by imaging or exams. Examples: When a patient has a polyp removed from the colon during a colonoscopy, that polyp may be a precancerous growth removed to prevent cancer from developing. The same is true for certain types of precancerous skin moles.
But existing cancer preventions are the exceptions. Research underway could soon produce treatments that dramatically reduce the odds of developing a much wider range of cancers, including some of the most common…and deadly.
By the time someone is diagnosed with cancer, “precancerous cells” might have been lurking in his/her body for decades. These precancerous cells share gene mutations with cancer cells and could develop into cancer, but they are not themselves considered cancerous because they do not invade surrounding tissue or spread throughout the body. Most precancerous cells are eliminated by the immune system before they develop into cancer—and before patients and doctors even realize they exist—but some evade detection by the immune system. The goal of cancer-interception research is to target these precancerous cells with treatments that prevent them from becoming malignant.
Unfortunately, medical science currently has a very limited understanding of how precancers work on the molecular level, much less an ability to identify and treat them. For all of the time and money that has been spent on studying cancers over the years, very little has been devoted to studying precancers. Exception: Medical science does have a sufficiently strong understanding of the precancerous phase of leukemia and multiple myeloma that doctors can determine when these cancers might be developing based on blood and bone marrow tests.
Work currently is underway to develop a “precancer atlas”—an in-depth catalog of the biology of a range of precancerous cells and the paths those cells take to develop into cancer. Research teams involved with this project are studying not only the precancerous cells but also the healthy tissues and cells that surround them to understand how the precancerous cells develop and interact with their surroundings. Armed with that information, researchers should be able to identify aspects of the precancer that can be targeted using tools such as vaccines and “immune checkpoint inhibitors”—a type of immunotherapy that could encourage the immune system to continue battling precancerous cells until they are eradicated. Current projects are focused on the precancerous cells that lead to pancreatic cancer, lung cancer, colorectal and endometrial cancers, and head and neck cancers.
What’s especially exciting now is that cancer-interception clinical trials have already begun, including…
Colorectal cancer vaccine. The most common cause of hereditary colorectal cancer is Lynch syndrome—it causes about 3% to 5% of colorectal cancers. The gene defect that causes Lynch syndrome affects the body’s ability to repair DNA errors, leading to the accumulation of mutated proteins and increasing the odds of developing colorectal cancer and, to a lesser degree, increasing the risk for endometrial, ovarian, stomach and brain cancers. It’s estimated that one of every 288 people has Lynch syndrome, though most people who have it are not aware that they do.
A genetic counselor can review a patient’s family history and look for mutations in germline DNA—but this test currently cannot be self-ordered.
A clinical trial being conducted by Eduardo Vilar-Sanchez, MD, PhD, at The University of Texas MD Anderson Cancer Center is investigating a vaccine that could prevent Lynch syndrome cancers. This vaccine does not have the potential to prevent all colorectal cancers, because many are not linked to Lynch syndrome.
Pancreatic cancer vaccine. Pancreatic cancer is among the leading causes of cancer deaths because it often is not identified until it has reached its late stages. The five-year survival rate is well under 10%. A potential pancreatic cancer vaccine developed by Elizabeth Jaffee, MD, and Neeha Zaidi, MD, at Johns Hopkins currently is undergoing clinical trials. The hope is that this vaccine will train the immune system to track down and eliminate pancreatic cancer cells before they spread.
With clinical trials already underway and the FDA receptive to this area of research, cancer interception is racing forward—but treatments are unlikely to become widely available until the 2030s. Today’s clinical trials will have to be followed by large-scale studies to prove that these procedures are safe and effective, and those large-scale studies likely will have to be conducted over periods of five years or longer. When you test a new treatment for an existing cancer, it can be determined relatively quickly whether that treatment has caused the cancer to go into remission…but when you test a vaccine designed to prevent cancer, you have to track your test subjects for years to determine if they are indeed developing the cancer at a lower rate than would otherwise have been expected.
If you are at high risk for a particular cancer—based on family history…genetic mutations uncovered by DNA tests…and/or scans revealing high-risk lesions—follow the cancer-screening schedule and lifestyle advice suggested by your health-care providers. And in the years ahead, ask your doctors if they are aware of clinical trials of any new cancer-interception treatments related to the cancer you are at elevated risk of developing. Taking part in such a trial could get you access to the treatment years before it is widely available. If not, watch for these treatments themselves to become available, likely starting in the 2030s.
