A team led by researchers from the Stanford University School of Medicine has demonstrated a way to diagnose cancer without resorting to surgery, raising the possibility of far fewer biopsies.
For this first-in-humans clinical trial, women with either breast or ovarian tumours were injected intravenously with microbubbles capable of binding to and identifying cancer.
Jurgen Willmann, MD, a professor of radiology at Stanford, is lead author, and Sanjiv ‘Sam’ Gambhir, MD, PhD, professor and chair of radiology, is the senior author of the study.
For the study, 24 women with ovarian tumours and 21 women with breast tumours were intravenously injected with the microbubbles. Clinicians used ordinary ultrasound to image the tumours for about a half-hour after injection. The high-tech bubbles clustered in the blood vessels of tumours that were malignant, but not in those that were benign.
The ultrasound imaging of patients’ bubble-labelled tumours was followed up with biopsies and pathology studies that confirmed the accuracy of the diagnostic microbubbles.
Medical microbubbles are spheres of phospholipids, the same material that makes up the membranes of living cells. The bubbles are 1 to 4 microns in diameter, a little smaller than a red blood cell, and filled with a harmless mixture of perfluorobutane and nitrogen gas.
Ordinary microbubbles have been approved by the Food and Drug Administration and in clinical use for several years now. But such microbubbles, a kind of ultrasound ‘contrast agent,’ have only been used to image organs like the liver by displaying the bubbles as they pass through blood vessels. Up to now, the bubbles couldn’t latch onto blood vessels of cancer in patients.
The microbubbles used in this study were designed to bind to a receptor called KDR found on the tumour blood vessels of cancer but not in healthy tissue. Noncancerous cells don’t have such a receptor. Under ultrasound imaging, the labelled microbubbles, called MBKDR, show up clearly when they cluster in a tumour. And since benign breast and ovarian tumours usually lack KDR, the labelled microbubbles mostly passed them by.
In this small, preliminary safety trial, the technique appeared to be both safe and very sensitive, said Willmann, who is chief of the Division of Body Imaging at Stanford. And it also works with ordinary ultrasound equipment. ‘So, there’s no new ultrasound equipment that needs to be built for that,’ he said. ‘You can just use your regular ultrasound and turn on the contrast mode – which all modern ultrasound equipment has.’