Sunday, September 14, 2008
Does it make sense to screen asymptomatic breast implants with MRI?
One of the peculiarities of the USFDA process during silicone implant reintroduction in 2006 was the labeling on the devices recommending routine MRI surveillance of implants for rupture. When you step back and look at the proceedings and "unique" American history with breast implants, you can see that this was more a political concession to the anti-implant activist lobby then evidence-based medicine.
The FDA labeling currently suggests MRI's at 3 years post op and then every 2 years subsequently. It will be interesting with the coming form stable "gummy bear" implants whether or not this recomendation is still maintained.
Why 3 years for the first MRI?
That was the first data point with any ruptures reported in the FDA data during clinical trials. While there will be a certain failure rate associated with any manufactured device, it's likely that early failures of silicone devices were from missed trauma to the implant during insertion. Education courses on proper techniques for implant handling and insertion in recent years have emphasized ways to minimize this risk by suggesting larger incisions for gentler introduction and better visualization during closure.
But does it make sense to do this?
Clearly it does not. On this point, there's pretty much international agreement (USFDA excepted).
We've actually got a pretty good handle on rupture rates of 4th generation implants (conventional devices used for the last 15 years or so) up thru a decade, where it's pegged around 6-8% at 10 years based in two pretty solid studies on single devices by the two major implant makers Mentor & Allergan. If you take that and work backwards from the FDA recommendation, you're doing up to 4 MRI's during the first decade where the rupture rate is either almost nonexistent (years 3-7) or in the low single digits (year 9).
Whether you're screening an asymptomatic population for ruptured implants, colon cancer, breast cancer, or aortic aneurysms there's trade offs between costs and risk reduction. For tests to be effective for screening, they must satisfy both criteria. For a number of cancers, screening tests often fail this goal.
Take screening mammograms or breast self-exams for instance to detect breast cancer. In non-selected groups of women, both cancer detection modalities increase both cost and morbidity from unnecessary procedures without materially affecting death rates from breast cancer (arguably the whole point of screening). It's been persuasively argued when reviewing the data, that screening mammograms can be deferred to age 50 for low risk women (as opposed to the current recommendation for age 40) and perhaps discontinued altogether for women in their 70's with no affect whatsoever on breast cancer death rates. BTW, this same pattern of "dodgy logic" of routine screening also exists in regards to male prostate cancer and lung cancer screening in smokers.
Anyway, back to implants......
At the end of the day it's just hard to support screening implants for rupture in asymptomatic patients on either a cost basis or benefit basis. As it's been established that ruptured silicone implants (silent or otherwise) do not appear to correlate with systemic illness, the clear benefit of screening asymptomatic women is hard to establish. A team of doctor's from the world famous Sloan-Kettering Memorial Cancer Center agreed with this sentiment in a recent paper, Silicone Breast Implants and Magnetic Resonance Imaging Screening for Rupture: Do U.S. Food and Drug Administration Recommendations Reflect an Evidence-Based Practice Approach to Patient Care?