Thursday, August 15, 2013
From Urology Times published online Aug 9, 2013:
Using genomic sequencing, researchers have confirmed a link between a plant compound contained in common herbal remedies and upper urinary tract cancer.
For their study, genomic sequencing experts at Johns Hopkins University, Baltimore partnered with pharmacologists at Stony Brook University, Stony Brook, NY to reveal a striking mutational signature of upper urinary tract cancers caused by aristolochic acid, a plant compound contained in herbal remedies used to treat a variety of ailments such as arthritis, gout, and inflammation.
Aristolochic acid is found in the plant family "Aristolochia," a vine known widely as birthwort, and while the FDA first warned of its cancer-causing potential in 2001, botanical products and herbal remedies containing it can still be purchased online. Moreover, the vine has been found to be an environmental carcinogen through the contamination of food supplies of farming villages in the Balkans, where Aristolochia grows wildly in the local wheat fields.
For years, scientists have known of some mutations in upper urinary tract cancer patients exposed to the plant toxin. But the genome-wide spectrum of mutations associated with aristolochic acid exposure remained largely unknown.
For the current study, which was published in Science Translational Medicine (2013; 5:197ra102), the authors used whole-exome sequencing on 19 Taiwanese upper urinary tract cancer patients exposed to aristolochic acid and seven patients with no suspected exposure to the toxin.
"Genome-wide sequencing has allowed us to tie aristolochic acid exposure directly to an individual getting cancer," said co-author Kenneth Kinzler, PhD, of the Johns Hopkins Kimmel Cancer Center. "The technology gives us the recognizable mutational signature to say with certainty that a specific toxin is responsible for causing a specific cancer. Our hope is that using the more targeted whole-exome-sequencing process will provide the necessary data to guide public health decisions related to cancer prevention."
Specifically, Dr. Kinzler and colleagues said they found an average of 753 mutations in each tumor from the toxin-exposed group compared with 91 in tumors from the non-exposed group. This level of mutation is more than that found in melanomas caused by ultraviolet radiation and lung cancer caused by smoking.
Members of the toxin-exposed group had a large number of a particular, rare type of mutational signature in the ATCG chemical code of their DNA. The predominant mutation type in the toxin-exposed tumors (72%) was an A substituted with a T. In one instance, the scientists used the mutational signature to uncover an artistolochic-related tumor in a patient who was unaware of prior exposure.
Posted by Matthew E. Karlovsky, M.D. at 1:02 PM
Saturday, February 2, 2013
The FDA is perceived and promoted as the guardian of public safety, but many are critical of the FDA approval and regulatory process for being either slow or broken. Some groups see the FDA as being too slow to approve new drugs or treatments that can extend for save lives, while others see the FDA as being reckless and approving drugs and devices that then get recalled after complaints or complications become known.
When it comes to mesh used for vaginal prolapse and incontinence surgery, there is a lack of knowledge about the FDA and the approval process and the necessary requirements that must be met prior to FDA allowing a manufacturer's device to come to market. Currently there are approximately 100 mesh kits or devices approved/cleared by the FDA to be used in vaginal surgery. Here is a brief synopsis.
Stemming from the 1970’s the FDA passed regulations related to the classification and safety of surgical devices that we still use today with little updating. The FDA’s Center for Devices and Radiological Health (CDRH) is vested with the responsibility of ensuring the safety and effectiveness of ALL medical devices marketed in the US. The Food Drug and Cosmetic Act outlines devices to be classified into three categories based on the risk it poses to the human body:
Class I Device: Low risk device, where clinical data is not needed for approval, but general manufacturing controls are needed. An example of this is simple surgical instruments
Class II Device: Intermediate risk device. Surgical mesh falls into this category, and it requires “special controls” and labeling, but clinical trials are not absolutely required prior to marketing. A device can be approved if it is “substantially equivalent” to a prior device that is used for the same purpose. Vaginal mesh was deemed “substantially equivalent” to prior approved hernia mesh. This is known as the 510(k) Pre-Market Notification Process. It is used a s “piggyback process” to bring devices to market without strict human trials.
Class III Device: Complex/High risk. (3-5% of all products.) Requires stringent Pre-Market Approval, known as the 522 Process, requires strict manufacturing inspections, trials, post-Approval study of data, annual reporting to the FDA. An example of this is hemostatic agents (surgical foam that prevents bleeding).
The FDA is currently forcing manufacturers to conduct “522 studies” on their mesh products for vaginal surgery to evaluate prolapse surgery done with and without mesh. There are more than a hundred studies reporting outcomes of mesh, and except for a few, there are lacking large comparative trials which are now underway. For the standard mesh slings (TVT or TVT-O, and similar slings), the FDA is not requiring these studies as ample outcome and safety data exist. Depending on the outcome of the prolapse mesh studies, mesh may or may not be reclassified as a Class III. This does not mean that mesh is off the market or cannot be used in the meantime. Mesh complications can and should be reported to the FDA, but exact percentage of complications from mesh is difficult to know because mesh complications are underreported and the total number of mesh cases are not known.
Posted by Matthew E. Karlovsky, M.D. at 6:18 PM