By David N. Leff
One out of eight women in the U.S. will incur breast cancer before the age of 95, and 3.6 percent of them will die of the disease.
For the year 2001, the total number of new mammary carcinomas diagnosed is estimated at 192,700 ¿ including 500 men. Deaths are expected to reach 40,600 ¿ 400 of them males.
The key word is ¿diagnosed.¿ Most breast cancers can be cured if caught early enough. Curiously, four out of five mammary tumors are detected by the woman herself ¿ by self-palpation. This practice, the experts say, should start at age 18, and go on monthly for life.
Mammography ¿ X-raying the breasts ¿ should be done once a year for woman over 50, and every year or two for those between 40 and 49. Both these diagnostic techniques leave plenty of room for error.
A research letter in The Lancet, dated April 28, 2001, purports to open a new chapter in nabbing these malignancies in time. It¿s titled: ¿Detection of breast cancer cells in ductal lavage fluid by methylation-specific PCR.¿ The article¿s senior author is molecular and cell biologist Saraswati Sukumar, at Johns Hopkins School of Medicine in Baltimore. David Hung, CEO of Pro-Duct Health Inc. in Menlo Park, Calif., is a co-author.
Just as Pap smears collect exfoliated cells from the margins of the vaginal cervix, and scraping the inner cheek harvests cells for DNA testing, cells lining the inner walls of the breast¿s milk ducts furnish cytological evidence of precancerous cells. They represent precursors of invasive tumors, but while still in situ can be treated medically with anti-estrogen therapy.
This outlook motivated Sukumar and her co-authors to develop dual approaches for such timely detection ¿ cytological and molecular. ¿In ductal cells,¿ she told BioWorld Today, ¿this is the first time anything has been done about applying a molecular test of ductal lavage fluid and its detection. That test is MSP ¿ methylation-specific PCR. The cells that line the ducts can be accessed and pulled out of the duct by a device called the ductal lavage catheter. Once these cells are obtained, we can test them cytologically ¿ that is, how do they look under the microscope ¿ and also by PCR to search for methylated genes.¿
Ducts Are Precancer Hot Spots
¿Practically all breast carcinomas,¿ she pointed out, ¿arise in the epithelium lining the milk ducts. So it is logical to flush the cells from there to see if any early cancers or established cancers exist, but are invisible to mammographic detection, or palpation. We found that in 17 out of 20 women who had cancer, their cells were detectable by our molecular test.
¿Then we tested another cohort of high-risk women, who had ¿ among other risk factors ¿ previous cancer in the other breast, or relatives with breast cancer, or the familial BRCA1 or BRCA2 gene ¿ and obtained fluid from both their breasts,¿ she said. ¿When we tested the cells from that fluid,¿ Sukumar recounted, ¿we found that five of them had positive cytology, and three of them were also positive by our molecular marker test. Two of those three have been newly diagnosed with breast cancer, and the third one is undergoing evaluation.
¿All of these high-risk individuals,¿ she pointed out, ¿were completely tumor-free when we tested them. Their mammograms were negative and their clinical examination showed that they had no tumor in their breasts, yet two of them had tumors detected by these devices.¿
Sukumar explained her rationale for determining abnormality in these cells: ¿In our laboratory, we have discovered several dozen genes that are abnormal in breast cancer as compared to normal. One of these abnormalities that those genes undergo is methylation of their promoter sequences. When these promoters contain islands of C-G ¿ cytosine-guanosine dinucleotide pairs ¿ the cytosines can acquire methyl groups. This brings down a cloud of repression on the promoter, which becomes unable to make any message, and therefore no protein. When that takes place, the cells may acquire a cancerous change.
¿As with any other endocrine organ, the cells that are lining these ducts, in normal circumstances, are there to produce milk,¿ she said. ¿As this is produced, it is squeezed and passes through a network of ductal branches, ultimately coming out at the nipple as milk.¿
Pro-Duct¿s Hung supplied Sukumar¿s lab ex gratia with the catheters his company manufactures. ¿The fluid is flushed in from one end and pulled out at the other end of this microcatheter,¿ he told BioWorld Today. ¿It¿s hair-like thickness of needle is inserted into a pore of the nipple ¿ the ductal opening. A syringe attached to one end introduces saline solution; another tube removes it.
¿There are five to eight pores in a typical nipple,¿ Hung explained, ¿but only one or two of them are usually secretory. When we aspirate and squeeze the breast gently, we can see a little bit of fluid come out through the ends of the ones that are being lavaged.¿
New Devices¿ Future Outlook
¿Ductal lavage is a very simple test,¿ Hung said. ¿Most people learn it at first shot. With a little bit of confidence and expertise, each duct should take not more than 10 to 20 minutes. It can be done in an outpatient setting, with just a local anesthetic, in conjunction with mammography. Over 100 cytologists have been trained nationwide so far to interpret ductal lavage cytology, which is performed and analyzed in a manner very similar to fine-needle aspiration cytology ¿ a very common procedure.
¿No one¿s ever had that catheter until this year,¿ he added. ¿They¿ve never gotten tubes of liquid containing cells before. But the cells are the same ones that have been analyzed for decades by standard cytology techniques. One of the microcatheter¿s future applications involves molecular studies on cells collected. One of those tests is the methylated-PCR analysis developed by Sukumar.
¿There are now over 70 high-risk breast centers and clinical practices in the U.S.,¿ Hung concluded, ¿which are already using it for risk stratification in high-risk women. These are out-of-study patients. That means that they are not in any clinical trials. They are applying it because they believe it is useful enough to do right now.¿