The hand-in-glove role of the laboratory in managing the treatment of cancer patients is often overlooked. It’s understandable that so much emphasis is put on treatment, but without diagnostic tests there’s no sure way to know if treatments are having their intended effect.
For that reason, this month’s Disease Management section on Oncology looks at some exciting new diagnostic tests in the research pipeline.
Jonathan Briggs reports on promising research pointing toward the development of a serum or even saliva HER2test for breast cancer patients. Currently the gold standard for selecting patients for Herceptin therapy is an immuno-histochemistry test, which requires a biopsy. A serum test, which may be available within a year or so, would eliminate the risks associated with a biopsy and accomplish the same goal.
Prostate cancer — the most common form of cancer among U.S. men — is finally getting the recognition and research attention it deserves. Another refinement on the total PSA and free PSA test — complex PSA — is starting to garner attention for its specificity. “A single assay of complexed PSA provides the same enhancement of test specificity as determining free to total ratios that require two assays,“ according Michael Brawer, M.D., director of the Northwest Prostate Institute in Seattle.
In other news, a simple blood test to determine the spread of melanoma in the body is in clinical trial at the John Wayne Cancer Institute in Santa Monica, Calif. The test identified patients whose primary cutaneous melanoma had started to metastasize to nearby lymph nodes or distant sites. Of 57 such patients whose melanoma had metastasized without clinical signs, 43 had a positive assay.
With 1,220,000 Americans expected to be diagnosed with some form of cancer this year, these tests and procedures are welcome news for sure.
Prospect bright for serum or saliva HER2 test
Tumor characterization tests such as immuno histochemistry (IHC) or fluorescence in situ hybridization (FISH) make it possible for clinicians to use more disease-specific hormone and chemotherapy regimens. In addition to increasing the likelihood of successful treatment, therapies better targeted to specific tumor types also help patients avoid the side-effects of unneeded or ineffective treatment.
With breast cancer, for example, nearly one third of tumors over produce the growth promoting protein HER2/neu due to over expression of the HER2/neu (c-erB2) gene. These HER2/neu positive (HER2/neu+) cancers tend to grow and spread more aggressively than HER2/neu negative (HER2/neu-) breast cancers. Also, breast cancer patients whose tumors are HER2/neu+ tend to respond better to intensified adriamycin-based chemotherapy, whereas, breast cancer patients whose tumors are HER2/Neu– do not benefit from dose-intensified regimens. However, patients with HER2/Neu+ tumors can benefit from treatment with trastuzumab (Herceptin) in combination with other agents.
Herceptin is a monoclonal antibody that attaches to the growth promoting HER2/Neu protein and prevents it from stimulating breast cancer cell growth. Studies have shown that the combination of Herceptin and chemotherapy is more effective than chemotherapy alone. In addition, whether used alone or together with drugs such as paclitaxel (Taxol), Herceptin can both reduce tumor burden of some breast cancers and prolong patient survival.
Generally, Herceptin therapy is initiated after standard hormonal and/or chemotherapy is no longer effective, although clinical trials are underway to see if adding Herceptin to the first course of chemotherapy is beneficial too. Despite the value of Herceptin therapy, clinicians are hampered by the lack of an easy-to-perform test to help them select patients who would benefit from it. Perhaps more importantly, they need a simple test to help them monitor patpients during and after therapy.
The gold standard for selecting patients for Herceptin therapy is IHC, but there is concern that the accuracy and reliability of such tests, as currently performed, are questionable. Consequently, considerable effort is being put into reducing the inter-laboratory variability of these tests by enhancing them with computer-based analysis. But even an improved IHC test will still require a biopsied tissue sample. Serial biopsies are risky, impractical and potentially unreliable. For example, many patients receive Herceptin therapy because their cancer has metastasized to the liver. Open liver biopsies are very risky, and the chances of missing a diffuse tumor with a radiologically guided biopsy are high. What is needed is a practical, safe and reliable body-fluid test that can provide clinicians real-time HER2+ tumor status.
For some time, researchers have been aware that soluble fragments of the Her2/neu oncogene, released from the cell surface, are detectable in patients with breast cancer. Consequently, they have speculated that it could be possible to evaluate tumor status or response to therapy by determining the levels of Her2/neu protein in patients’ serum or saliva. In 1996, for example, investigators from Spain found that serum Her2/neu levels in patients were significantly higher in estrogen-negative and progesterone-negative tumors than in those with estrogen-positive and progesterone-positive tumors. These investigators also found that Her2/neu levels seemed to have some prognostic value. For example, patients with metastatic advanced disease had significantly higher levels than those with locoregional recurrence, and patients who did not do well postoperatively had unusually high levels prior to surgery.
A more recent study by Streckfus and colleagues at the University of Mississippi studied Her2/neu protein levels in both the saliva and serum of healthy women, women with benign breast lesions and women with diagnosed breast cancer, using the CA 15-3 as a gold standard. Although they found the protein in the saliva and serum of all three groups, the levels in the cancer patients were significantly higher than in the healthy patients or the patients with benign lesions. These and other studies encouraged researchers to continue to pursue a serum or saliva HER2 test.
Other biomarkers such as CEA or CA-15 are not specific for HER2+ tumors. A HER2-specific test would be particularly valuable because the primary method of evaluating a HER2+ breast cancer patient’s response to Herceptin therapy is with CT or other imaging modalities. Although most side effects associated with Herceptin treatment are relatively mild, there is some concern about potential cardiotoxicity. “The advantage of such a test,” according to Lyndsay Harris, M.D., at the Dana Farber Cancer Institute in Boston, “is that it not only would measure Her2/neu at the tumor level but what’s happening to the tumor expression of HER2/neu over time as treatment is given.”
“The hope is that a HER2-specific test could help us monitor patients with HER2+ tumors during and after treatment,” Harris said. “For example, in theory, if a HER2 test showed a patient had responded to Herceptin therapy, you could stop the Herceptin and avoid any potential side effects and reduce the cost of treatment. If her HER2 serum levels rose again, then you could restart Herceptin therapy.”
With the potential for more targeted treatment, it is no surprise that companies such as Bayer Diagnostics and Oncogen Science Diagnostics are working to develop a serum test for HER2. On the other hand, numerous questions about when and how such a test would be used remain to be answered. There is still a lot of work to do.
— Jonathan Briggs
PSA testing: Moving from the basic to the complex(ed)
Cancer of the prostate is the most common form of cancer in men in the United States. More than 300,000 men are diagnosed with the disease each year and of those approximately 40,000 die. Currently, the two best means of detecting prostate cancer are the digital rectal exam and the prostate specific antigen (PSA) test. The PSA test is based on the fact that levels of the antigen are elevated in about two-thirds of cancer cases. The first commercial PSA test came on the market in 1986. However, basic PSA tests are plagued by low sensitivity (as high as a 35 percent false negative rate). The specificity of PSA tests also is low because increases in PSA levels can occur with other conditions such as benign prostatic hyperplasia. Interpreting test results in the 4 ng/ml to 10 ng/ml range is particularly difficult.
In an effort to improve PSA testing, researchers have been investigating several possible variables including PSA density, PSA velocity, and age-specific reference ranges for PSA levels. Although each of these parameters provides useful information, each also has limitations. For example, determining PSA density (defined as the level [ng/ml] of PSA over the prostate volume [cc]) requires an ultrasound examination. PSA velocity requires serial testing. Furthermore, all these variables can be influenced and confounded by age and race. Age-ranges, for instance, can be used to improve the sensitivity of detection in younger men, whereas age-ranges improve specificity of detection in older men. As for race, age-range references differ between white, Asian and African-American men. So, interpreting test results can be complicated.
Another approach to improving PSA testing that many researchers are actively pursuing is to further refine the basic test by looking at differences in levels of PSA variants, of which there are several. “All variants of PSA have been shown to enhance PSA testing specificity,” said Michael Brawer, M.D., director of the Northwest Prostate Institute in Seattle. The first variants looked at were free PSA and PSA bound to other molecules. Studies have found that the free PSA to total PSA ratio (free/total PSA) is better than simple PSA levels for detecting prostate cancer in patients with intermediate PSA levels because the ratio is lower in patients with cancer than in those with benign prostatic hyperplasia. However, biopsy cutoff points vary between assays with this method. Moreover, determining the free to total PSA ratio requires two assays, one to determine the level of each form of the antigen. Consequently, testing costs are higher.
A refinement of this approach is to determine the percent of PSA complexed to other molecules (cPSA). PSA can be complexed to any of several enzyme inhibitors. There is considerable evidence that the percent of cPSA is higher in men with prostate cancer. “A single assay of complexed PSA provides the same enhancement of test specificity as determining free to total ratios that requires two assays, “ said Brawer. Thus, a single test using one of these complexes could be used to identify those patients and in fact, Bayer Diagnostics, Tarrytown, N.Y., recently received FDA approval for an alpha-1-antichymotrypsin-based assay. Meanwhile, other researchers are investigating alpha-2-macroglobulin (A2M), andalpha-1-antitrypsin complexes as potential means to improve PSA test specificity.
— Jonathan Briggs
|Blood test detecting melanoma metastasis in clinical trials at John Wayne Cancer Institute
A simple blood test to determine the spread of melanoma in the body is in clinical trial at the John Wayne Cancer Institute (JWCI) in Santa Monica, Calif.
“Surgical removal of a melanoma tumor on the skin can be curative, but only if tumor cells have not already spread from the melanoma,” said Rishab Gupta, M.D. director of immunodiagnosis at the Institute. Gupta, together with Donald L. Morton, M.D., medical director and surgeon-in-chief at JWCI, developed the test.
Tumor markers have been used with some success in prostate cancer, colorectal cancer and certain other cancers but until now have been disappointing for melanoma. This new test targets a tumor antigen produced by melanoma cells. The antigen has a molecular weight of 90 kilodaltons, hence its name TA-90.
TA-90 antigens on the surface of melanoma cells alert the patient’s immune system to produce anti-TA90 antibodies. The new ELISA test detects the presence of TA-90 as an immune complex of the antigen bound to anti-TA90 antibody.
“We found that the test could identify patients whose primary cutaneous melanoma had started to metastasize to nearby lymph nodes or distant sites. Of 57 such patients whose melanoma had metastasized without clinical signs, 43 had a positive TA-90 assay,” Gupta said.
The initial study had a sensitivity of 77 percent and a specificity of 76 percent for subclinical melanoma. Since then, more than 500 patients have participated in clinical trials of the TA-90 blood test, Gupta said.
Jennie Muglia, M.D., assistant professor of dermatology at Brown University Medical School in Providence, R.I., said that a test such as this would be very helpful in the treatment of melanoma. However, she expressed caution about the size of the initial study and its sensitivity rating of 77 percent. “Some metastatic disease could go undetected,” she said.
Muglia predicts that the TA-90 test will be most useful for treating patients in the “gray area” of prognosis. “Those patients with a thin melanoma are probably not going to have a spread of the disease, and those with a thick melanoma probably have metastasized already. It is the patients in the middle who could realize the most benefit.”
“For those patients, this test provides the physician with guidance on how aggressive to be in treating the disease,” Muglia said. TA-90 ELISA is considered a simple test because samples are obtained in the physician’s office. If commercialized, it should be no more expensive than existing diagnostic tumor marker tests such as CEA or CA 15-3, Gupta said.
The test has been carefully standardized with “standard operating procedures,” Gupta said. It also has been approved upon inspection by the Division of Laboratories and Acute Care Services in accordance with Clinical Laboratory Improvement Amendments (CLIA).
Clinicians who would like additional information on this investigational TA-90 test should contact Specialty Laboratories in Santa Monica, Calif., 800-421-4449. The test reference number is S48787.
— Cynthia W. DeMaio
Chemotherapy combined with numerous lab tests helps patients avoid nasty side effects
Until recently, patients undergoing cancer chemotherapy often required critical care due to both the disease and treatment side effects. Today, new medications and techniques that reduce side effects and quickly reverse the adverse effects of chemotherapy have increased its success and radically changed the treatment experience for both patients and caregivers. Prior to the introduction of these drugs, nadirs (or lowest points) in blood counts often resulted in complications such as infection, bleeding or anemia that caused patients to be hospitalized. Since complete treatment often requires multiple cycles of chemotherapy, multiple hospital stays were the norm.
“Present day chemotherapy is largely an ambulatory procedure that patients undergo during visits to cancer clinics,” said Leslie Simpson, a certified oncology nurse at Emerson Hospital in Concord, Mass. “Although they may have to return to the clinic frequently for laboratory follow-up and treatment of side-effects, most patients prefer that to hospitalization,” Simpson noted.
Despite these improvements, chemotherapy patients still must be monitored to avoid side effects such as bone marrow suppression, tumor lysis syndrome and severe nausea and vomiting.
Bone marrow suppression is the leading dose-limiting toxicity of chemotherapy for cancer patients. “In the past,” said Simpson “severe immunosuppression, which can result in infection, sepsis and even death, often resulted in reduced doses or canceled cycles of chemotherapy.” Many patients with leukemia and lymphoma die from infections, and infections are a source of significant complications in other cancers as well. Consequently, patients must be monitored and monitor themselves for any signs of infection. Some clinicians even give patients a supply of antibiotics, so that they can begin treatment immediately if they suspect an infection.
Of course, dose reductions and missed treatments can result in unwarranted progression of illness. The advent of colony-stimulating factors (CSFs) and drugs like epoetin allow patients to remain at home and still receive their optimal treatment dose.
“Blood counts are essential for patients undergoing chemotherapy,” Simpson said. They are done before, during and after treatment so that the appropriate drugs can be administered to bring counts back to normal. Patients who experience myelosuppression during chemotherapy are prescribed a regimen of CSF. Simpson
explained, “Following each cycle of chemotherapy, these patients should demonstrate a predictable pattern of chemotherapy nadir and recovery that spans an average of seven days to two weeks.” The development of CSFs and other drugs that stimulate blood component growth means that the critical complications of neutropenia and anemia can be prevented or treated.
Another potential side effect for chemotherapy patients is tumor lysis syndrome, a condition that commonly occurs in patients with a large tumor burden and rapidly dividing tumor cells. When these patients receive chemotherapy, there is large-scale rupture of tumor cell membranes, and the cell contents are spilled into the blood stream. “Symptoms of TLS include elevated potassium, uric acid and phosphate levels accompanied by decreased calcium levels and possibly other abnormal metabolic studies,” Simpson said. It is important to obtain baseline electrolytes and renal function values before beginning chemotherapy in patients who are at risk for TLS. These patients need to be monitored frequently throughout their treatment.
The most well-known side effects of chemotherapy are nausea and vomiting, which can be severe and debilitating. Fortunately, many drugs have become available to reduce this additional burden for cancer patients. The brain controls vomiting via the vomiting center and the chemoreceptor trigger zone. The vomiting center oversees the physical mechanism and can be stimulated by odors and visual stimuli. The chemoreceptor trigger zone is part of the body’s defense against toxins. The presence of toxins or certain drugs stimulates the release of neurotransmitters that stimulate the vomiting center.
Not all chemotherapeutic drugs are created equal when it comes to causing nausea and vomiting. The worst offenders are cisplatin, dacarbazine, doxorubicin and mechlorethamine. In contrast, methotrexate and fluorouracil tend to be less of a challenge.
“Patients receiving chemotherapy are treated prophylactically for nausea and vomiting rather than on an as-needed basis,” Simpson said. Antiemetic drugs are given before therapy begins and on a regular schedule thereafter. The drugs and the dosage used is determined by the emetogenic potential of the specific chemotherapeutic agents in the regimen.
To some extent, the degree of severity of nausea and vomiting caused by chemotherapy is related to the patient’s expectations. Thus, helping patients change their expectations can help reduce these side effects. There also are indications that the severity of nausea is reduced when patients used a portable transcutaneous electrical nerve stimulation device.
Perhaps understandably, some cancer patients are reluctant to take even more drugs to treat the effects of those they must take. Consequently they often try approaches, from other cultures and traditions to minimize side effects. For example, relaxation methods from Japan and acupressure from China are two areas that have been studied recently. Other techniques that have been or are being looked at include meditation, visualization and massage. “It’s not unusual for people in the oncology community to be open to alternative methods of care,” concluded Simpson.
— Jonathan Briggs
|RF ablation helps lung tumor patients
A new minimally invasive procedure to remove primary and metastatic lung tumors is under investigation in the United States and China. The procedure, pioneered by Patrick Sewell, M.D., assistant professor of radiology and surgery at the University of Mississippi Medical Center (UMC) in Jackson, uses radiofrequency energy to destroy tumor cells. “It will add a treatment choice for people who have run out of treatment choices, and it may replace some more invasive, and painful procedures currently used to treat lung cancer,” said Sewell.
Although radiofrequency ablation (RFA) has been used medically for several years, the focus on lung tumors is a relatively new application. RFA induces thermal-related cellular changes by passing a high frequency alternating current through tissue, resulting in coagulative necrosis. In Sewell’s procedure, an electrode array is placed percutaneously into the lung, and using image-guided, real-time CT, is advanced into the lesion. The tip of the electrode is fashioned with umbrella-like wire tines that feed current to the lesion and measure tissue impedance. Once the desired level of tissue impedance is reached, the probe is removed or repositioned to treat adjacent areas. The four-hour pro-cedure is usually performed under general anesthesia. Most patients also undergo chemo and radiation therapy. At UMC, Sewell has performed RFA of metastatic lung tumors in well over 100 patients. In March, he initiated a controlled study to determine its efficacy for treating primary lung tumors at several research hospitals in China.
According to Sewell, the eventual use of RFA will vary with regard to primary and metastatic lung tumors. Most U.S. patients with primary lung cancer undergo surgical excision of the tumor, often including lobes of the lung. For some patients, this radical surgery is not an option, and RFA may be used to destroy the tumor and prolong patient life. In cases of metastatic disease, however, where the patient may need multiple surgeries to remove multiple lesions, RFA has more promise and may eventually replace excision.“RFA is safer, less expensive, has a quicker recovery and is less painful. That’s why it is very appropriate for metastatic tumor,” Sewell said.
In China, RFA has already made an impact on the treatment of lung cancer. Because of limited resources and the high cost of medical care, many patients cannot afford traditional surgical techniques to treat lung cancer, and doctors there searched for alternatives.
Recognized as an expert in the field, Sewell was invited to China to teach the RFA technique to physicians and begin a collaborative effort to determine the effects of the procedure. Initial results from his second 16-day trip in March were quite promising: PET images of nine patients treated with primary lung tumors indicated that virtually all tumor tissue was eliminated with the technique. Sewell and his colleagues hope to publish preliminary data from the China study in the near future. Meanwhile, Sewell continues to research other interventional techniques, including cryosurgical ablation of renal tumors, using a new type of interventional MRI scanner.