[Update: A colleague pointed me to the NPR story by Richard Knox, which says, "Scientists have known for a while that breast cancer is really four different diseases…" And in the comments below, I added a link to a JAMA study that described the four types in 2006. So I'm now more confident saying that reporters who said researchers "identified four types of breast cancer" were incorrect.]
Sorting out what is new about the breast-cancer-genetics study published Sunday in Nature is proving to be a daunting task. Reading the coverage, however, it seems most of the press made a mistake.
Here's what I know from the press release issued by the National Institutes of Health:
One subtype of breast cancer shares many genetic features with high-grade serous ovarian cancer…The findings suggest that the two cancers are of similar molecular origin, which may facilitate the comparison of therapeutic data for subtypes of breast and ovarian cancers…Analyses of genomic data have confirmed that there are four primary subtypes of breast cancer, each with its own biology and survival outlooks.
The findings come from a detailed genetic analysis of breast cancer genes as part of what's called The Cancer Genome Atlas, a government project that has already analyzed the genes of certain ovarian, colorectal, lung, and brain cancers.
What I read in much of the copy, however, was not included in the release, nor could I find it in the study itself.
Gina Kolata at The New York Times reported that researchers "have identified four genetically distinct types" of breast cancer. But the press release says researchers "described new insights into the four standard molecular subtypes" of breast cancer. Kolata's lede is apparently wrong, and so is the headline that reflects the error. A Google search turned up many stories that talked about the identification of four types of breast cancer–all, apparently, incorrect. Victoria Colliver at The San Francisco Chronicle seems to make the same mistake, if it is a mistake, in a lede that says researchers "have redefined the disease into four main classes." So did the AP.
Liz Szabo at USA Today avoids that phrasing, writing that scientists "have finished mapping virtually all of the genetic mutations in breast cancer," which may be overreaching a bit. The press release says the researchers identified a lot of genetic mutations, but it doesn't say that the study covered "virtually all" of them. She also writes that the resarch "could soon change the way patients are treated." In contrast, Harold Varmus, the head of the National Cancer Institute, says in the release, "This treasure trove of genetic information will need to be examined in great detail to identify how we can use if functionally and clinically." In other words, I think, it will not affect the way patients are treated any time soon.
A lede that noted the similarity between ovarian cancer and one kind of breast cancer would have been safe. So would a lede that said resarchers made a major advance in understanding the genetics of breast cancer, which might one day lead to better care for patients.