Computer-aided Diagnosis of Breast Tumors
Computers may have a role in diagnosing breast tumors, according to a study published in the journal Archives of Surgery. Computer-aided diagnosis (CAD) may provide an immediate second opinion for physicians using digital ultrasound to examine breast lesions.
Researchers reviewed medical records for 243 patients who underwent digital ultrasound for the diagnosis of breast lumps. Biopsy had shown that 161 patients had benign (noncancerous) lumps, while 82 had cancerous tumors. A total of 153 of the ultrasounds were randomly selected to train the CAD system to distinguish benign from cancerous tumors; the other 90 ultrasounds (60 benign and 30 cancerous) were used to evaluate the system's performance. A physician selected the region of the ultrasound for the CAD system to evaluate, and an experienced radiologist independently classified each of the ultrasounds in the test set.
The CAD system had an accuracy of 90 percent, compared with the experienced radiologist's accuracy of 86.67 percent. In particular, the CAD system excelled at recognizing benign tumors, which could prevent unnecessary biopsies.
Source: Archives of Surgery. June 2000. Volume 135, pp. 696-699
Use of Electrical Appliances Does Not Increase Breast Cancer Risk
Electrical appliances typically used in the home--particularly electric blankets--are known to expose users to electromagnetic fields (EMFs). A number of studies have explored a proposed association between exposure to EMFs and breast cancer, with inconclusive results. A new study in the American Journal of Epidemiology finds no association between use of electrical appliances in the home and breast cancer risk.
A total of 608 breast cancer patients and 609 age-matched people in a control group were interviewed regarding their use of a number of home electrical appliances, including electric blankets, electrically heated waterbeds, hair dryers, and heating pads. Forty percent of the breast cancer patients and 43 percent of the people in the control group reported regular use of electric blankets in their lifetime.
Interviewers also collected information about a number of factors that are known to influence breast cancer risk, including menstrual and reproductive history, family history, and diet. Researchers took these factors into account when calculating breast cancer risk resulting from exposure to EMFs. The authors concluded that their study does not support an association between use of home electrical appliances and female breast cancer risk.
Source: American Journal of Epidemiology. June 1, 2000. Volume 151, No. 11, pp. 1103-1111
Risk for Breast Cancer in Women Born Prematurely
Women born before the 33rd gestational week appear to have an increased risk for breast cancer, according to a study in the Journal of the National Cancer Institute.
A total of 60,000 delivery charts were examined for the years 1925 to 1934 in Sweden. Researchers identified 273 girls born before the 35th gestational week or with a low birth weight (under 2000 grams) regardless of gestational age. Breast cancer was diagnosed in 12 of the women, seven of whom were younger than age 50 at diagnosis. Study authors calculated the expected number of breast cancer cases in the population.
Women born before the 31st gestational week had a 6.7-fold increased risk for breast cancer; the risk before age 50 was increased 12.2 times. Those born in the 31st or 32nd gestational week had a two- to four-fold increased risk. As gestational time increased, the risk for breast cancer decreased. The authors speculate that there may be a relationship between the hormonal environment in the uterus and the risk for breast cancer.
The number of babies born prematurely who survive has increased substantially since the women included in this study were born. The study authors estimate that in the next 10 to 20 years, women born prematurely will constitute close to 5 percent of all women with a new diagnosis of breast cancer.
Source: Journal of the National Cancer Institute. May 17, 2000. Volume 92, No. 10, pp. 840-841
Breast Cancer After a Negative Mammogram
A number of factors may account for the failure of a mammogram to detect breast cancer. These include the testing procedures used, the interpretation of the radiologist, and characteristics of the patient (for example, density of breast tissue). Another significant factor may be rapidly growing breast tumors, according to a study in the Journal of the National Cancer Institute.
Researchers studied the characteristics of interval breast cancers--cancers detected within 12 months of a mammogram that showed no evidence of tumor. They compared the records of 94 patients who had interval cancers with those of 87 patients (matched for age and ethnicity) who had breast cancer that was detected by mammography. They concluded: "Rapidly growing and aggressive tumors account for a substantial proportion of mammographic failure to detect breast cancer, especially among younger women, who have a higher proportion of aggressive cancers."
The study authors estimate that about 75 percent of interval cancers could be rapidly growing tumors that may have been too small to be detected during the last screening mammography.
Interval cancers tend to be diagnosed at a more advanced stage than cancers diagnosed by mammography. Further, women with interval cancers tend to have poorer survival than those with mammogram-detected cancers. The researchers suggest that more frequent screening mammograms may be appropriate to detect more interval cancers.
Source: Journal of the National Cancer Institute. May 3, 2000. Volume 92, No. 9, pp. 743-749
Effects of Radiation Therapy on Quality of Life
A study in the journal Cancer reports that radiation therapy has a significant, but temporary, impact on the quality of life of breast cancer patients who undergo lumpectomy.
Study participants were 837 women who had cancerous breast tumors but no cancer spread to the lymph nodes. They were randomly assigned to two groups: 416 received radiation therapy after surgery, and 421 did not. The two groups were similar in age, tumor size, and tumor characteristics. Each woman completed a questionnaire designed to assess her general quality of life at the start of the study, after one month, and after two months. Further, they were asked to answer three questions designed to assess the long-term effect on quality of life every three months for two years.
Women who did not receive radiation therapy reported an improvement in overall quality of life from the start of the study to two months, while those who received radiation therapy had little change in quality of life.
Results from the three items measuring long-term effects on quality of life suggested that skin irritation and breast pain attributed to radiation therapy may be reported three to six months after the start of treatment. However, the study authors point out that these symptoms were also present in some of the women who did not receive radiation. Two years after the start of the study, there was no difference between the groups in the rates of skin irritation, breast pain, and being upset by the appearance of the breast.
Results of studies have disagreed about whether or not patients receiving radiation therapy suffer from anxiety, depression, and fatigue in addition to breast symptoms. While the current study shows a difference in overall quality of life between patients receiving radiation and those who don't during the first few months of treatment, no differences were found in the areas of emotional and social well-being or attractiveness. The differences observed were in the areas of physical symptoms, inconvenience, and fatigue.
Both groups reported concern about the appearance of the breast, with concern decreasing over time. Those who received radiation did not report deterioration in cosmetic outcome after two years.
Source: Cancer. May 15, 2000. Volume 88, No. 10, pp. 2260-2266
Hormone Replacement Therapy and Lobular Breast Cancer
Combined estrogen and progestin hormone replacement therapy (HRT) may be associated with an increased risk for a certain type of breast cancer, according to a report in the journal Cancer.
Interviews were conducted with 537 white women aged 50 to 64 years who were diagnosed with breast cancer from 1998 to 1990 and 492 randomly selected women with no history of breast cancer. All study participants were asked about their medical history, use of hormones, family history, diet, and other factors that may affect breast cancer risk.
Of the 537 women with breast cancer, 370 had ductal carcinoma and 58 had lobular carcinoma; the remaining 109 had other types of cancer and were not included in the analysis.
Use of hormone replacement therapy--either estrogen alone or combined estrogen and progestin--for at least six months was reported by 73 percent of the women with lobular carcinoma, 51 percent of the women with ductal carcinoma, and 58 percent of the control women without cancer. Those who reported use of combined estrogen and progestin replacement therapy for at least six months had a 2.6-fold higher incidence of lobular carcinoma. They were not found to have an increased risk for ductal carcinoma.
Ductal carcinoma is cancer that occurs in the milk ducts of the breast. It accounts for 80 to 85 percent of all cases of breast cancer. Lobular carcinoma occurs in the lobules of the breast that produce milk and account for only 5 to 10 percent of all breast cancer cases.
The study authors caution that these results are based on a small number of cases of lobular carcinoma. Further, they point out that rates of ductal carcinoma are considerably higher than rates of lobular carcinoma. They conclude: "Therefore, with respect to absolute risk, even if combined hormone use is associated with an increased risk of this histologic type of breast carcinoma, only a small percentage of combined HRT users are likely to be affected."
Source: Cancer. June 1, 2000. Volume 88, No. 11, pp. 2570-2577
Tracking Breast Cancer Through the Sentinel Node
The lymph system is part of the body's immune system. It is made up of thin tubes that branch, like blood vessels, into all parts of the body, including the skin. Lymph vessels carry lymph, a colorless, watery fluid that contains lymphocytes. Lymphocytes are a type of white blood cell that helps the body fight infection.
Along this network of vessels are groups of small, bean-shaped organs called lymph nodes. Clusters of lymph nodes are found in the underarm (axillary), pelvis, neck, and abdomen.
Traditionally, when a woman underwent a mastectomy or lumpectomy, the surgeons took out a number of nearby axillary lymph nodes to see if the cancer had begun to spread through the lymph system. However, this often led to post-surgical complications such as pain, loss of arm movement, and a chronic condition called lymphedema in which fluid accumulates due to faulty lymphatic drainage.
Researchers began looking for a better way to test for the spread of cancer from tumors. The question was asked if there was a single node-a sentinel node-that would be the first lymph node to be affected by spreading cancer cells.
Interestingly, the concept of mapping the sentinel node was first reported in 1977 by a researcher studying cancer of the penis. The technique was later used to study drainage patterns of melanoma, and was first reported for breast cancer in 1993. Since then, researchers have improved methods for finding the sentinel node, and a growing number of studies are showing that when the sentinel node is "negative" (free of cancer), the remaining lymph nodes are also cancer free in a majority of cases.
A "sentinel node" is the first lymph node to which a tumor drains, and therefore is the first place to which cancer is likely to spread. (In some cases, it appears there can be more than one sentinel node.) In breast cancer, the sentinel node is usually located in the axillary nodes, the group of lymph nodes under the arm. However, in a small percentage of cases, the sentinel node is found elsewhere in the lymphatic system of the breast.
There are currently two standard methods for finding the sentinel node. One is to inject a blue dye near the breast tumor and track its path through the lymph nodes. The dye accumulates in the sentinel node. In a similar technique, doctors inject a safe, small amount of a radioactive solution near the tumor and then use a gamma detector to find the "hotspot," or the node in which the solution has accumulated.
Detecting Cancer Spread
A growing body of research is concluding that the sentinel node can be used to accurately determine if cancer cells have spread beyond the tumor to the lymph nodes. In a sentinel node biopsy, only one or a few lymph nodes are removed for laboratory analysis when a patient has a lumpectomy or mastectomy. Preliminary studies suggest that if lab tests find no cancer cells in the sentinel node, the patient is much less likely to have tumor cells in the remaining axillary nodes.
Along these lines, a recent study by researchers at the University of Vermont in Burlington concluded that many instances of "occult" (clinically undetectable) metastatic breast cancer can be identified in the sentinel lymph node but not in the other axillary lymph nodes.
Writing in the journal Cancer, Dr. Donald Weaver and colleagues evaluated sentinel and nonsentinel lymph node biopsies from 431 breast cancer patients at 11 hospitals across the country. "Overt" (identifiable) metastases were noted in 15.9 percent of the sentinel lymph nodes, but in only 4.2 percent of the nonsentinel lymph nodes.
"Occult" (clinically undetectable) metastases were discovered in 4.09 percent of the sentinel nodes but in only 0.35 percent of the nonsentinel nodes.
According to Weaver, these results further confirmed the value of the sentinel lymph node technique for mapping breast cancer spread, especially for discovering "occult" disease that might otherwise have gone undetected.
The recent annual Miami Breast Cancer Conference in March highlighted a trio of additional clinical trials which are examining the effectiveness of sentinel lymph node dissection in women with breast cancer.
One trial, dubbed Z0010, is examining how a breast cancer patient's prognosis differs if microscopic breast cancer cells (micrometastases) are found in the sentinel nodes and bone marrow, but not in the axillary lymph nodes.
A second trial, Z0011, is comparing axillary lymph node dissection with sentinel lymph node dissection in women with node-positive cancers (cancers in their lymph nodes). The researchers want to determine if axillary lymph node dissection is still a beneficial diagnostic tool.
In another presentation at the conference, Dr. Patrick Borgen, from the Memorial Sloan-Kettering Cancer Center in New York City, reported on a study evaluating 1,800 cases of lymphatic mapping for breast cancer. His group identified a median of two sentinel lymph nodes per patient, and the cancer was found in the second or third sentinel node 25 percent of the time. Borgen said his team's findings suggest that searching for additional sentinel nodes may be important for accurately determining the spread of the disease.
Fewer Side Effects
A recent study published in the journal Cancer, also noted that sentinel node biopsies result in fewer adverse side effects for women with breast cancer than traditional axillary node dissection.
Dr. Peter Schrenk and colleagues from the Ludwig Boltzmann Institute for Surgical Laparoscopy in Linz, Austria, compared 35 women who underwent sentinel lymph node biopsy with 35 women who underwent complete axillary lymph node dissection. They noted that arm stiffness and strength did not differ between the two groups. And neither surgery significantly affected the patients' activities of daily living.
However, they found that patients who had axillary lymph node dissections had more post-surgical complications than those who just had sentinel node biopsies. These complications included swelling of the upper arm and forearm, pain, numbness, motion restriction, and a significantly higher rate of lymphedema.
Confirming the Hypothesis
Borgen's success rate for identifying the spread of breast cancer via the sentinel node now ranges from 94 to 96 percent. He said this rate would probably be even higher except for some technical errors and variations in lymphatic flow. And Borgen's impressive results are typical of those from a growing number of studies focusing on the sentinel node.
Without question, as Borgen suggested during his presentation, the hypothesis that there is a sentinel lymph node (or nodes) most likely to be the first site(s) of breast cancer spread is a valid one. And because of the technique's remarkable success, other researchers involved with different cancers are now turning their attention toward the sentinel node.
Sources:
The National Cancer Institute (www.nci.nih.gov)
Cancer, Feb. 1, 2000; 88:608-614
Cancer, Mar. 1, 2000; 88:1099-1107
The 17th Annual Miami Breast Cancer Conference, March 3, 2000
Journal of the American College of Surgeons, 1999; 189:539-545
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