Kathlyn Stone is an associate editor with HealthNewsReview.org. She tweets at @KatKStone.
The American College of Radiology recently issued a fairly terse 183-word news release on a new study published in its journal on the “natural history of untreated screen-detected breast cancer.” The report is subtitled “An argument against delayed screening or increasing the interval between screening” and is based on a small survey of Society of Breast Imaging members.
While no one questions that the release writers had the best interests of women in mind, the messages strike us as unnecessary fear-mongering built on very limited evidence, the drawbacks of which were not mentioned in the release. There is also a notable lack of context accompanying the release’s rather ominous take-home conclusion: “Medical science cannot yet determine which cancers will or will not advance to kill the person afflicted.”
Is the premise of the release – that all undetected and untreated breast cancers are a potential death sentence – a sound one? I asked some of our regular expert contributors to weigh in on the short document, paragraph by paragraph.
Paragraph 1: “Breast cancers detected by mammography screening do not spontaneously disappear or regress if left untreated, according to a new study published in the Journal of the American College of Radiology (JACR®). The scientific findings contradict claims that many cancers found via mammography may simply “go away” if left undiscovered or untreated.”
There are many who question the value of mammography performed at the intervals recommended by the American College of Radiology, but the basis for that skepticism is not primarily that cancers may simply “go away” — even though there is some evidence that this may occur. The bigger issue is whether some cancers might be so slow-growing (as with many prostate cancers) as to never cause symptoms of disease.
“There are several studies supporting spontaneous tumor regression,” says Deanna Attai. MD, a breast cancer surgeon and assistant clinical professor of surgery at UCLA, “and we know that DCIS [short for ductal carcinoma in-situ] may not develop into invasive disease. I think an important point to make is not whether or not tumors regress, but do they ever become clinically significant without treatment? It is clear that some tumors will not become clinically significant, but we do not yet have the ability to accurately predict this (with the 100 percent certainty that a patient and her physician would want) for an individual patient.”
It’s important to note that some experts are loath to even call DCIS a type of “cancer.” About 20 percent of mammography detected cancers are DCIS, and as we reported earlier this year: “Some experts estimate that up to 80% of women with DCIS found via screening may not need any treatment at all–and instead should just keep an eye on things.”
That brings us to Paragraph 2 and an incomplete discussion of the study itself:
“Among all practices involved in the study, 25,281 screen-detected invasive breast cancers and 9,360 cases of screen-detected ductal carcinoma in situ were reported over the 10-year study period. Among these cancers, there were 240 cases of untreated invasive breast cancer and 239 cases of untreated ductal carcinoma in situ. None were reported to have spontaneously disappeared or regressed at next mammography.”
The release doesn’t mention where those numbers come from. When we looked up the study, we learned it was based on a survey of 42 members of a society devoted to breast imaging and includes either audit data or “best estimates” from participants’ mammography practices. According to the “limitations” section of the study:
“Limitations of this study include those common to all surveys, including selection bias with respect to responses, the possibility of incorrect responses (especially when some survey respondents answered with best estimates instead of audit data), and that it depends upon the recollection of individual anecdotes. Related to the latter, no data were collected regarding patient demographics, tumor histology, or clinical progression of the disease; although these additional data would be pertinent to a better understanding of the frequency and clinical importance of overdiagnosis and would be helpful in providing guidance about who might be managed with “watchful waiting” and who should not, this was beyond the scope of our study.”
The study authors also note, “Furthermore we did not determine the exact reasons why some patients had no treatment.” In short, this study had serious and multiple limitations, and the release presented data from this very small survey, with some of the data based on guesses, and used it as a strong-arm message to women that they should “do this or risk dying.” That is not a helpful message.
Why did some patients forego treatment? Neither the release or study gives us that answer, but there are many reasons women may choose to watch and wait rather than be treated immediately. Mandy Stahre, PhD, an epidemiologist and breast cancer survivor, says “It’s not just patient demographics, but health of the patient and co-morbid conditions which could affect whether a patient seeks treatment. Age is also an important factor. If an 75 year old woman has a mammogram with a positive tumor, are you going to treat them or wait?”
When women are armed with good information and counsel from their physicians the best course for some might be to watch and wait, particularly if their screen suggests DCIS. The release should have acknowledged this.
Paragraph 3: “An unknown percentage of these 479 cases represent overdiagnosis, but because all untreated screen-detected cancers were visible and suspicious for malignancy at next mammographic examination, delaying the onset of screening (from age 40 to ages 45 or 50) or increasing the interval between screenings (biennial vs annual) should not reduce the frequency of overdiagnosis.”
Paragraph 4: “Medical science cannot yet determine which cancers will or will not advance to kill the person afflicted.”
Paragraphs 3 and 4 dismiss very real concerns about over-diagnosis. Over-diagnosis leads to over-treatment. The unnecessary surgery, radiation and chemotherapy that some women undergo for non-life-threatening cancer are a harm that should be discussed more openly. Estimates of over-diagnosis vary greatly, from 20 percent to more than 80 percent. These paragraphs both seem to suggest that there’s nothing to be done about over-diagnosis and that women must simply accept it as the cost of eliminating potentially deadly cancers. But the reality is there are trade-offs that fully informed women can and should be able to weigh before making any decision about breast screening and treatment. Active surveillance is an option that some women should discuss with their doctors. That’s what media messages should be encouraging — not ominous warnings that fail to give people the full picture.