When prostate cancer metastasizes, doctors know that it most often will be found in bones, the lungs or the liver. But that doesn’t always mean it’s easy to find. Metastatic cancer cells often nest in different places in the body in numbers so small, or form tumors so tiny, they may not show up on some scans.
Recently, however, the U.S. Food and Drug Administration (FDA) approved two new imaging agents to help make metastatic prostate cancer easier to find. The radioactive agents—piflufolastat F-18 (Pylarify®) and lutetium Lu 177 vipivotide tetraxetan (Pluvicto™)—are designed to provide more complete information to doctors treating men diagnosed with recurrent or metastatic prostate cancer, giving them a clearer picture of whether their cancer has spread and where it may be found. They may also be used for some higher-risk patients with a primary prostate cancer diagnosis to see whether their cancer has already spread.
A study released in June found that treatment with lutetium Lu 177 vipivotide tetraxetan increased the lifespan of men with metastatic castration-resistant prostate cancer by an average of four months. While these advances don’t always directly affect health outcomes for men with prostate cancer, they’re pushing science forward as researchers look for new ways to identify and treat the disease. They may also help doctors and patients make more informed decisions on treatment options.
In this article, we'll explore:
- Prostate cancer facts
- How radioactive agents work
- How are these drugs used in patients?
- Comparing testing options
- Making informed decisions
If you’ve been diagnosed with prostate cancer and would like to get a second opinion on your diagnosis or treatment plan, call us or chat online with a member of our team.
Prostate cancer facts
Prostate cancer is the second most common cancer diagnosed in the United States—behind breast cancer—and the most common cancer diagnosed in men.
More than 34,000 men in the United States die each year from prostate cancer, making it the second leading cause of cancer deaths in U.S. men. It’s also expected to be the leading cause of new cancer diagnoses in U.S. men this year, with 248,530 cases predicted, according to the National Cancer Institute.
Prostate cancer is highly treatable, especially when detected early. The five-year survival rate for men diagnosed with the disease is 97.5 percent. That rate drops to 30 percent when the cancer is diagnosed after it’s metastasized.
How radioactive agents work
Radioactive tracer drugs used to diagnose and treat cancer work by seeking out and attaching themselves to specific proteins on cancer cells and illuminating the cells during imaging scans. They’re designed to latch onto prostate-specific membrane antigens (PSMAs found on prostate cancer cells, lighting them up during a PET/CT (positron emission tomography/computed tomography) scan. The drugs are injected intravenously prior to a PET/CT procedure. The PET scan illuminates cancer cells, while the CT shows the anatomic configuration of the part of the body being scanned.
Scientists are just beginning to scratch the surface on the potential of these agents, known as radiopharmaceuticals, which use radioactive particles called radioisotopes either as cancer imaging agents, as targeted treatments, or both.
Similar drugs have already been used extensively in Australia and several European countries.
“With conventional imaging, we’re waiting for the disease to look different or grow to a certain size before we think it’s abnormal,” says Jason Beland, MD, Medical Director of Imaging Services at Cancer Treatment Centers of America® (CTCA), Atlanta. “Now we can take the PET scan and the CT scan, and we overlay them. So, we’re seeing where things are, the lymph nodes and other things that may look normal on a regular CT scan, but now they’re lighting up. That’s telling us that there’s disease.”
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How are these drugs used in patients?
Radiopharmaceuticals may be used to detect prostate cancer in two types of patients:
- Those with a primary diagnosis, who may experience positive outcomes with surgery or other therapy, but have a high risk for the cancer spreading to other parts of the body
- Those whose cancer is suspected of having recurred based on elevated PSA (prostate-specific antigen) levels in their blood
“We need to understand how best to use this test and only employ it when it’s warranted, in these very specific situations,” Dr. Beland says. “We’re not talking about giving it to everyone who comes in off the street.”
Patients should talk to their doctor about potential side effects of these drugs and the risk of radiation exposure. There may also be some concern that false readings indicating metastatic disease could lead some doctors to forego standard treatments, such as surgery or radiation therapy, that may potentially extend the life of patients who only have a primary tumor. The FDA acknowledges that “there is a risk of misdiagnosis because piflufolastat F-18 binding may occur in other types of cancer as well as certain non-malignant conditions, which may lead to image interpretation errors.”
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Comparing testing options
Other tools being used to detect prostate cancer include CT scans (without the PET component), magnetic resonance imaging (MRI) scans and some nuclear medicine scans, such as bone scans. But unlike the PET scans using piflufolastat F-18, each of these imaging techniques is limited in its ability to detect prostate cancer lesions.
MRIs are better at characterizing localized disease, while using Gleason and PSA scores are recommended for determining patients most at risk.
CT scans, which use a form of X-ray, and bone scans are regularly used to check for evidence of metastatic cancer. “Neither is particularly good at finding individual prostate cancer cells, and thus can miss very small tumors,” the National Cancer Institute says in a May 2020 article. “And bone scans can detect bone damage or abnormalities that were caused by something other than cancer (e.g., arthritis), resulting in ‘false-positive’ findings that can lead to unnecessary additional testing.”
Making informed decisions
Unfortunately, for some patients, detecting and locating metastatic prostate cancer cells may confirm a diagnosis for which there are few treatment options. It may, however, help doctors and patients make more informed decisions on how to move forward.
Then again, a PET scan using a radiopharmaceutical that does not show the presence of metastatic cancer may make doctors more confident that a cancer recurrence—or a high-risk primary diagnosis—is indeed localized and proceed with treatment plans geared to that situation.
If you’ve been diagnosed with prostate cancer and want to explore your treatment options, or if you’re interested in a second opinion on your prostate cancer diagnosis and treatment plan, call us or chat online with a member of our team.
