Radiologists are performing a greater share of biopsies as image-guided and other less invasive techniques replace more aggressive procedures, according to a new study.

Radiologists went from performing close to a third of all biopsies nearly 10 years ago to now doing more than half, researchers said in an article appearing online Tuesday and in September in the print edition of Radiology.

The study also might help allay fears that the spread of advanced imaging modalities over the past decade has led to an increase in biopsies, as the researchers said the actual year-over-year growth rate for the potentially costly procedures was not large.

"There have been some people concerned with all these imaging studies we're doing, that it leads to all these unnecessary procedures," Dr. Sharon Kwan, lead author of the paper and a clinical fellow at the University of California San in Francisco, told DOTmed News. "It's really not a tremendously high growth rate."

In the study, the researchers examined Medicare claims from 1997 to 2008, covering 10 anatomic regions, including the abdomen, breast, kidney, liver and musculoskeletal soft tissue.

They found that radiologists' share of biopsies jumped from around 35 percent of all biopsies in 1997 to nearly 56 percent in 2008, with a compound annual growth rate of 8 percent. By contrast, during the same period, general surgeons saw a drop in their shares from around 21 to 15 percent, the researchers said.

The study suggests part of the jump in radiologists' involvement is the increasing reliance on less invasive percutaneous needle biopsies. Unlike open biopsies, this procedure uses a slender needle inserted through the skin to obtain tissue samples.

Although the first such biopsy, on the liver, was recorded in the medical literature as far back as 1923, in the past doctors lacked available technology to make the technique practical. While some used fluoroscopy, others palpated tissue, if they could find it, or just did it blind.

"[They] used landmarks, for example, by knowing where the liver is relative to the ribs, and directing their needle," Kwan said. "We don't do that anymore."

Thanks to the proliferation of MRI, CT and other high-tech scans over the last decade, the researchers suggest, percutaneous needle biopsies, or PNBs, are now a solid majority of all biopsies performed, having shot up from 59 percent of all biopsies in 1997 to around 67 percent in 2008, with a CAGR of 5 percent. Non-PNB biopsies fell a CAGR of around 3 percent in the same period.

But the spread of advanced imaging doesn't seem to have dramatically increased the number of biopsies performed - a concern in the medical community. Biopsy procedures rose from 1,380 to 1,945 biopsies per 100,000 Medicare enrollees between 1997 and 2008, the researchers found, at a CAGR of what the study's authors deemed a "modest" 3 percent.

TRACKING IMAGE-GUIDED BIOPSIES

Because the Medicare codes the researchers used didn't distinguish between percutaneous needle procedures performed with or without imaging guidance, the researchers could only track the growth of image-guided needle biopsies for breast and fine needle aspirations, both of which account for the majority of PNBs performed, the researchers said.

For breast core biopsies, image-guided ones rose from 85 percent to 95 percent between 2002 and 2008, the researchers said. For fine needle aspirations, the image-guided set rose from 54 percent to 77 percent during the same period.

Interestingly, as most fine needle aspirations, or FNAs, largely target the thyroid, the share of these procedures performed by endocrinologists has risen at the expense of radiologists, according to the researchers. As of 2008, endocrinologists performed one-fifth of image-guided FNAs, compared to about one-tenth in 2004. Radiologists performed close to half of FNAs in 2008, the researchers said, less than the 70 percent share they had six years ago.

Still, there are exceptions to the image-guided and PNB trend. A minority of biopsies for lymph nodes and musculoskeletal soft tissue are percutaneous needle biopsies, the researchers found, although the numbers do seem to be rising. In fact, lymph node biopsies saw one of the biggest jumps in radiologist involvement, up from around 12 percent close to a decade ago to 70 percent in 2008, for a CAGR of a whopping 22 percent.

But the reason these procedures are still minority PNB, the researchers suspect, is that these are mostly superficial tissues where targets are more easily got by feel or sight.

"If you have a lump in your forearm," Kwan said, "[you] may not need to have a CT or an ultrasound to guide the needle to that spot, versus if you had a lesion in the kidney, it'd be pretty difficult to guide the needle without imaging in the right spot."

For bone, strangely, the rate of PNBs declined over the past 10 years, although Kwan said this could be an artifact from having to rely on aggregated Medicare claims data. For instance, abdominal biopsy rates were probably slightly underestimated in the study, the researchers suspect, because these are usually coded as part of laparoscopic procedures.

"If you take a too granular look at these procedures, some potentially false trends [emerge]," Kwan said. "That's why we wanted to report things as a whole."