MAMMOGRAM SCREENING INTERVAL AFTER LUMPECTOMY
How health policy can delay diagnosis.
“Local Recurrence” is the term used when cancer grows back in a woman’s breast after breast conserving treatment of breast cancer. Local recurrence means that surgery – usually combined with radiation therapy – did not permanently eliminate the cancer. Local recurrence is uncommon, but it can occur.
Experience has shown that if local recurrence is found early, it will not affect the survival of the majority of women. For this reason it is important to find local recurrences early.
MAMMOGRAMS IDENTIFY LOCAL RECURENCES
About two-thirds of local recurrences are found by mammograms. Most experts agree that a mammogram should be done six months after surgery to provide a new baseline that shows how the breast has changed after surgery.
There is debate as to whether the screening interval for follow-up mammograms after that first study should be every 6 months or every 12 months. A big reason for the disagreement is cost.
Mammograms are not very expensive, but there will be twice as many – costing twice as much – if mammograms are done every 6 rather than every 12 months. It is informative that in recent discussions about what timing interval to adopt, I was told that we should go to every 12 months because, “…the world is changing…we have to put costs in there…[and] we understand it’s arbitrary….”
ONLY AN OPINION
Until recently, information comparing 6 to 12 month follow up intervals was based on the opinion of experts (insurance companies, health policy researchers, oncologists, surgeons, and radiologists) who thought about this issue and made their best guess.
NOT PERFECT, BUT BETTER INFORMATION
A recent study from UCSF brings observational data to this debate.
In the 1980s, when I was doing most of the breast conservation surgery at UCSF – and Dr. Edward Sickles, Chief of Breast Imaging at UCSF, was setting up a program to follow these women with mammograms – he decided that 6 months was a good follow-up interval.
Admittedly, it was a guess, but it was also a decision that intentionally erred on the side of caution, trying to be extremely careful of the health of the women who were at risk.
Part of the reason 6 months was chosen was experience that if cancer was missed on a mammogram, changes on subsequent mammograms were unlikely to be recognized if the follow-up mammograms were less than 6 months apart. Not enough changed to be detectable if the interval was less than 6 months.
Other radiologists made the decision that they would do mammograms only every 12 months. In the mid 1980s, it would have been difficult to say that one doctor was right and the other was wrong.
LEARING FROM WOMEN WHO CHOSE NOT TO FOLLOW THE PROTOCOL
At UCSF, most women were advised to have follow-up mammograms every 6 months, and that is the protocol I have continued in my own personal practice. There have, however, been women who did not follow those recommendations.
Radiologists at UCSF have compared how the stage of locally recurrent cancer was affected by whether the woman had mammograms at the recommended 6 month intervals, or if they waited and had mammograms after a longer interval.
A SHORTER SCREENING INTERVAL MEANT RECURRENCES WERE FOUND EARLIER
As expected, not many women had local recurrence, but when recurrence did occur, there were differences in how advanced the cancer had become before detection.
If a woman had a local recurrence – and her breasts had been screened for recurrence using mammograms every 6 months (they included up to 9 months as the cutoff) – 94 percent of recurrent cancers were very early stage 0 or stage 1 compared to only 73 percent very early stage if the woman’s last mammogram was 9 to 15 months previously. [click here for the abstract] With the 6 month interval, when a cancer came back, it was found at a lower, more favorable stage.
This is not a perfect study – a perfect study would randomize women to mammograms either every 6 months or every 12 months – but data is always better than expert opinions.
Until better data is available, it seems prudent to have biannual, i.e. every 6 month mammograms for the first five years after breast conserving treatment of breast cancer. No matter what anyone may tell you to the contrary.