SATURDAY, March 31 (HealthDay News) — A noninvasive scan might someday help doctors track the progress of prostate cancer and help guide treatment, researchers report.
The imaging tool, known as a prostate cancer-specific radiotracer, has so far only been tested successfully in mice. But a team from Memorial Sloan-Kettering Cancer Center in New York City said the technology could help identify cases where prostate cancer has spread to the bone.
Radiotracers work by injecting a small amount of a compound tagged with a radionuclide into patients. Using positron emission tomography — also known as a PET scan — doctors are then able to better visualize tumors and tumor spread.
In studies involving mice with prostate cancer, the researchers had the radiotracer hone in on prostate-specific antigen (PSA), the same prostate cancer marker used in the PSA test. They found that the PSA gravitated to tissues containing prostate cancer that had already grown resistant to standard hormone-based therapies.
The study also revealed the radiotracer could help identify cases where prostate cancer had spread to the bone. The researchers pointed out traditional bone scans are unable to differentiate between malignant and nonmalignant lesions.
The findings were to be presented Saturday at the American Association for Cancer Research annual meeting in Chicago, and are also being published in Cancer Discovery.
If used on people, the researchers claimed that the radiotracer might someday help doctors “personalize” treatment strategies for prostate cancer and better manage the disease.
“The ultimate goal is to be able to predict the response of patients to new and existing therapies at an early stage, thereby personalizing their treatment and improving outcomes,” Michael J. Evans, research fellow in the Human Oncology and Pathogenesis Program at Memorial Sloan-Kettering Cancer Center, explained in meeting news release.
Encouraged by their findings, the study’s authors said they hope to begin a human trial next year.
Two prostate cancer experts said the tool, if borne out in patients, could prove very useful.
Dr. Michael Schwartz is director of laparoscopy and minimally invasive surgery at North Shore-LIJ Health System in Lake Success, N.Y. He noted that, as of now, doctors typically rely on results of the PSA blood test and/or standard diagnostic scans to help guide treatment decisions.
Both methods have their limits and, “while this study is very preliminary, if this radiotracer technology can prove to detect very early recurrence or metastasis in human patients, it could become extremely useful in either the pre- or post-treatment setting in selecting a treatment algorithm,” Schwartz said. “It also may help reduce the need for biopsy of possible metastatic lesions.”
Dr. Erik Goluboff, an attending urologist at Beth Israel Medical Center, New York City, agreed that, “this is an exciting study using a novel radiotracer to detect PSA-expressing tissues throughout the body.”
He believes that the new tool’s “greatest strength would be in monitoring changes in PSA expression in tissues as a result of various treatments. If a treatment showed a marked change, it could continue to be used in that patient, hence “personalized” medicine. If a specific change did not occur, that treatment could be abandoned and another tried instead. Since these changes could not be detected based on a PSA blood test alone, this new test would be very helpful in determining early on which therapy to choose in a given patient.”
However, Goluboff also noted that research from animal-based studies does not always pan out in humans and “further, larger studies are of course required to confirm these findings.”
The story conveyed a cheerleading tone throughout, starting with the the story’s opening words – “A noninvasive scan…” Non-invasive is usually an attribute of scanning technologies.
The true leap from mouse research to human application was only hinted at.
Don’t get us wrong: there’s nothing wrong with the topic. It’s the execution of the story that we question.
There’s a reason that Woloshin & Schwartz wrote, “Media Coverage of Scientific Meetings: Too Much, Too Soon?” This is an example.
Certainly an estimate of the cost of the radiotracer and PET scan could have been provided. PET scans are already in use in a number of applications – and their use is not inexpensive
The potential benefit wasn’t quantified – not even for the mice in question.
As with any test, questions about sensitivity and specificity should have been addressed.
The story said nothing about potential harms.
The amount of radiation used in a PET scan is low. It is about the same amount of radiation as in most CT scans. Also, the radiation doesn’t last for very long in your body.
It is possible, although very unlikely, to have an allergic reaction to the radioactive substance. Some people have pain, redness, or swelling at the injection site.
Harms also emerge from false positive and false negative test results – which could lead to unnecessary treatment or undertreatment.
The story reminded readers in several places that this work was only done in mice. So we’ll give the story the benefit of the doubt.
But the story also jumped the gun, reporting on the results even before they were presented at the American Association for Cancer Research annual meeting in Chicago.
We remind journalists and readers about the pitfalls of reporting on talks at scientific meetings.
Frankly, we think we’re being generous in giving this a satisfactory score on this criterion.
No disease mongering.
Perhaps the only thing that salvaged the story was the story-ending caveat from an independent expert:
…research from animal-based studies does not always pan out in humans and “further, larger studies are of course required to confirm these findings.”
Existing methods of looking for prostate cancer spread were waved off with a few words – “both methods have their limits.” In readers’ minds, that may automatically set up the newer idea as having the inside track on being better. Yet existing methods – by default – at least have proven track records. Such framing is imbalanced.
Bone scans are actually considered quite sensitive for metastatic disease. The pattern of abnormalities in combination with clinical data is often sufficient to make the diagnosis. The combination of bone scans and PSA already provides considerable information about tumor progression and hormone resistance. Biopsies are usually not necessary in the presence of suspicious bone scan abnormalities. It’s a huge leap to assume that using this test in humans would lead to improved outcomes (the goal of “personalized medicine”).
The story stated that the researchers “hope to begin a human trial next year.”
The relative novelty of the approach was not clearly established. How/why is this better than existing PET scans? Or how is it better (more accurate or useful or cheaper or safer) than using a bone scan and PSA results and clinically assessing the signs and symptoms of progression?
There were two independent experts quoted, but the only quote from the researcher came from a conference news release. That’s not good journalistic practice, and is another sign of the rush to publish – even before the data were presented at the conference.