WEB WATCH
Breast Cancer

- By Shirley Butler

The staff at My Handi-Capable Reporter considers the Internet the "window on the world" for people who are homebound. Because of this, we thought it would be a good idea to keep up with new research, new web sites and assorted items of interest cropping up on the WorldWide Web daily. We'll be bringing you items that we feel will be helpful, informative, or just plain fun! Any information we bring you will cite its source so you will be able to check it out and find more information on the subject. In other words, we won't be giving you our opinion, just data for you to use in your search for knowledge!

The Facts about Breast Cancer

Carcinoma of the breast is the most common solid-tumor malignancy among women in the U.S. with an estimated incidence of 183,000 and a mortality rate of 46,600 in 1996. Until 1994, the occurrence of breast cancer had been increasing at about 3% a year, but it is encouraging that the number of new cases per year has stabilized.

Efforts to control breast cancer in the U.S. have emphasized early detection of finding and treating tumors before they spread throughout the body. Mammography is a major component of these early detection efforts, but results are frequently false-positive and result in a high incidence of negative biopsies. The unique ability of Positron Emission Tomography (PET) to non-surgically identify regions of metabolic activity can be used to show the presence or absence of breast cancers. This and other potential uses of PET include

• discriminating between benign and malignant breast masses;
• locoregional staging of newly discovered breast cancer;
• detecting distant metastases; and
• evaluating tumor response to therapy.

PET is a relatively new imaging technique used to monitor biochemical processes such as metabolism. Since metabolism is generally greater in malignant tissue than in benign tissue, PET is sensitive to malignant masses. This characteristic can be exploited to detect breast cancer noninvasively. In addition to aiding in breast cancer diagnosis, PET can be used to screen breast cancer patients who may have axillary lymph node metastases. Similarly, PET is valuable in detecting distant metastases in patients who have advanced or recurrent breast cancer. Another potential application of PET is monitoring malignancy changes in chemotherapy patients in order to permit therapeutic regimens to be modified more judiciously. Effective chemotherapy is associated with a decrease in tumor size that is not generally apparent until late in the course or even following the conclusion of therapy. A technique that could be used early in the course of chemotherapy to determine the efficacy of a particular chemotherapeutic regimen would also allow early modifications of treatment, thereby sparing the patient the complications and costs of an ineffective chemotherapeutic regimen and avoiding delay in initiating a potentially more effective therapy. Since metabolic changes generally occur earlier than anatomic changes, it has been postulated that sequential PET imaging might be helpful in characterizing the response to treatment.

Screening For Distant Metastases

PET may also have a role in screening for distant metastases in patients with newly discovered, advanced stage breast cancer and in patients with possible recurrent breast cancer. Wahl and associates used PET to evaluate 12 patients with advanced primary or metastatic breast cancer. PET identified 10 of 10 bone metastases, 5 of 5 known soft-tissue metastases, and 4 previously unsuspected nodal lesions. Cook and colleagues evaluated 23 patients with known breast cancer using both PET and conventional skeletal scintigraphy. Overall, PET-FDG was more sensitive than skeletal scintigraphy in the detection of osseous metastases, but among patients with biastic metastases, scintigraphy was more sensitive than PET. Also, survival was significantly reduced in patients with pure osteolytic disease compared with patients with mixed or biastic disease. Further research is needed to determine if PET can routinely detect soft-tissue metastases prior to other imaging modalities or if PET can replace multiple-imaging modalities with a single whole-body scan.

PET has a number of promising applications among patients with known or suspected breast cancer. It can be used to discriminate between benign and malignant breast masses-this is most clinically relevant among patients whose breasts are difficult to evaluate with other modalities. Among patients with newly diagnosed breast cancer, PET can be used as a screening technique to select those patients who are at high risk for having ALNM and who should therefore undergo ALND. PET can detect distant metastases in patients with advanced or recurrent breast carcinoma, though further research is needed to determine the sensitivity and specificity of PET relative to other modalities. Finally, by detecting metabolic changes at an earlier stage than anatomic imaging modalities can, PET potentially allows for earlier modifications in therapeutic regimen for patients receiving chemotherapy.

A report by Lee P. Adler, MD, George Bakale, PhD, Kathryn C. Schnur, MD, and Robert R. Shenk, MD can be found on the Internet at the MedScape website (http://www.medscape.com).