Biomedical Business & Technology Contributing Editor

CHICAGO — After heart disease, cancer is the second leading cause of death. And for people under age 85, cancer is the leading cause of death in the U.S. (see Table 1, next page). While significant progress has been made in improving cancer survival rates — as evidenced by a drop in cancer deaths in the U.S., in both 2003 and 2004 — the number of new cases of this disease continues to climb. Coupled with improved survival rates, the continued increase in cancer incidence is resulting in rapid growth in the number of individuals alive with cancer, leading to greater demand for products and services for cancer diagnosis, treatment and on-going monitoring.

The 43rd annual meeting of the American Society of Clinical Oncology (ASCO, Alexandria, Virginia), held here in June, provided a window on recent developments in cancer diagnostics and treatment and highlighted the expanding role of molecular diagnostics and molecular imaging in the management of a wide range of cancers.

Genetic tests coupled with proteomic markers are increasingly being employed for therapy guidance, including both initial selection of therapy as well as monitoring of response. Molecular profiling of patients is being employed both to assess cancer risk and also to determine optimal drug treatment, and newer targeted drugs require the use of molecular testing to identify patients who will have a positive response to therapy.

Cancer screening was also an important topic at the ASCO meeting, with advances described in imaging for early detection of cancer as well as genomic testing to identify high-risk individuals. Advances in cancer prevention were described at the conference that could reduce the number of new patients in the future but create a new market for prevention products, along with advances in informatics to more efficiently manage the complex cancer diagnostic and therapeutic process.

Molecular technology guides therapy

The improvement in cancer survival is the result of both earlier detection of cancer using advanced screening and diagnostic methods, as well as improved therapies, particularly molecularly targeted treatments that provide effective ablation of cancer cells with minimal effects on normal tissue. Molecular diagnostics technology is playing a role in both applications, providing a new approach to identify individuals at increased risk for cancer so they can be more closely monitored or, in some cases, treated with preventive therapy, as well as providing a tool for guidance of targeted therapies.

For example, a new molecular diagnostic test under development by eXagen Diagnostics (Albuquerque, New Mexico), eXagenBC, is a DNA-based test that will allow prediction of breast cancer recurrence based on an analysis of three markers (CYO24, PDCD6IP, and Birc 5) via three-color fluorescence in-situ hybridization (FISH) analysis of a patient’s tumor. The test is designed for use in women with breast cancer who are estrogen and progesterone receptor positive or negative, and was developed using the company’s gene discovery method based on its Coperna computational engine technology. The company submitted a 510(k) application to the FDA for the eXagenBC test in April 2007, and expects marketing clearance this month. It expects most labs to employ an automated version of the test in order to take advantage of the higher reimbursement available for automated vs. manual analysis.

The test has been evaluated by Clarient (San Juan Capistrano, California), a provider of specialized cancer diagnostic services and cellular imaging technologies; NeoGenomics Laboratories (Ft. Myers, Florida), another laboratory specializing in cancer genetics and molecular diagnostic testing; the Cleveland Clinic (Cleveland, Ohio); and the Centre for Molecular Medicine and Therapeutics (Vancouver, British Columbia).

Other predictive tests employing a multi-marker molecular diagnostic strategy include the MammaPrint, a 70-gene microarray assay from Agendia BV (Amsterdam, The Netherlands); a Breast Cancer Profiling (BCP) assay from AviaraDx (Carlsbad, California); and the Oncotype DX breast cancer profiling test from Genomic Health (Redwood City, California). Another test, the MammaStrat assay from Applied Genomics (Huntsville, Alabama), employs immunohistochemistry technology to analyze expression of multiple markers to determine prognosis and response to therapy.

New tests in development

Additional new and development-stage cancer tests based on molecular technology are described in Table 2. Such tests are being used increasingly by oncologists to improve therapy selection in a variety of cancer types including breast, lung and colorectal cancer.

The expanding use of molecular diagnostics has spawned a rapidly growing market for diagnostic products used in cancer management. As shown in Table 3, the global market for cancer in vitro diagnostic and monitoring is estimated at almost $2 billion in 2006 and is forecast to grow at an 8.8% compound annual rate to approach $3 billion by 2011. These figures exclude testing service revenues for companies such as Genomic Health and Genzyme Genetics.

The highest-growth segment of the market is molecular testing products, used to determine the best drug treatment for patients as well as for initial diagnosis and risk assessment. A key factor driving growth in that segment is the ability of molecular testing to identify treatments that may be effective in particular patients but are not utilized when standard, un-guided therapy selection is employed.

For example, as discussed by Daniel Von Hoff, MD of the Translational Genomics Research Institute (Phoenix, Arizona) at the conference, there are many agents that prove effective for a small percentage of patients with a particular type of cancer, but in routine practice there is no effort to match those agents with patients who will respond. In the TargetNow study described by Von Hoff, comprehensive molecular profiling was shown to identify the presence of a target for an existing drug in all patients who had previously failed standard drug treatment. Patients treated with the newly identified drug all responded, although so far the evidence is anecdotal. Von Hoff and others have now established a new testing lab, U.S. Oncology Research, which will serve as a central resource to analyze patients’ tumors for multiple drug targets.

As discussed by Roy Herbst, MD, PhD, of the MD Anderson Cancer Center (Houston) and other presenters at a convention press conference, with the advent of molecular diagnostic techniques, cancer management is now evolving into the era of personalized medicine, in which the use of targeted anti-cancer agents is guided by tests capable of determining individual patient response.

Better targeting increases survival

In head and neck cancer, for example, a disease which afflicts 500,000 new patients worldwide each year and responsible for 300,000 deaths annually, the use of targeted therapy has been shown to result in a significant improvement in median survival. According to Jan Vermorken, MD, PhD, of Antwerp University Hospital (Antwerp, Belgium), who discussed results of the EXTREME trial at the conference, addition of the EGFR-targeted drug Erbitux, developed by ImClone Systems (New York) and marketed by Bristol-Myers Squibb (Princeton, New Jersey), to standard carboplatin or cisplatin chemotherapy resulted in a significant 2.7 month increase in survival, from 7.4 months to 10.1 months. A survival increase of that magnitude has never been seen before by addition of a second drug to the treatment regimen, according to Von Hoff.

Another example, discussed by Christian Manegold, MD, PhD, of the German Cancer Research Center (Heidelberg), is the 20%-30% increase in survival observed in the AVAiL study employing the targeted anti-angiogenic drug Avastin from Genentech (South San Francisco) in non-small cell lung cancer.

A potential limitation to the use of molecular testing to guide targeted therapy, described by Teresa Moran, MD, of the Catalan Institute of Oncology (Badalona, Spain), is the lack of tissue specimens needed for molecular analysis in later-stage cancers such as Stage IV non-small cell lung cancer (NSCLC). About 60% of NSCLC patients will respond to an EGFR-targeted agent, but only about 10% of NSCLC cases exhibit EGFR mutations.

New techniques for prediction...

Moran evaluated a new technique using the polymerase chain reaction (PCR) technology to obtain specimens of circulating tumor DNA from peripheral blood, and found that EGFR mutations could be detected with a sensitivity of 69.4%. Evaluation of another marker, PS2, showed a sensitivity of 100% using serum DNA analysis. While a tissue biopsy remains the preferred sample type for molecular analysis in cancer, serum is now believed to provide a viable alternative if tissue is unavailable.

Additional applications of molecular testing for therapy guidance were described at the conference for blood-borne cancers including leukemia and non-Hodgkin’s lymphoma. Asuragen (Austin, Texas) exhibited the Signature LTx leukemia translation panel, a multiplex RT-PCR assay that detects nine common leukemia-associated translocations. The assay is performed on the flow cytometry analyzer from Luminex Molecular Diagnostics (Austin), and provides a simplified approach to leukemia subtyping.Asuragen is also developing molecular assays for detection of minimal residual disease in cancer patients following chemotherapy.

PGx Health (Morrisville, North Carolina) is offering a new test called PGxPredict to predict response to the targeted agent Rituximab from Biogen Idec (Cambridge, Massachusetts) and Genentech in non-Hodgkin’s lymphoma (NHL). In about 20% of NHL patients who are CD-20 positive and are therefore responsive, a 90% response rate is achieved. The PGxPredict test can be performed before treatment begins to determine if Rituximab should be added to the therapeutic regimen, or used to evaluate the 50%-70% of patients who suffer relapse after first-line treatment to determine if the drug is a viable second line of therapy. Non-Hodgkin’s lymphoma affects 286,000 patients worldwide annually, with about 20% of cases in the U.S. Incidence is increasing at a rate of 4%-6% per year.

... and guiding treatment

MolecularMD (Portland, Oregon) offers molecular tests used in the guidance of treatment of chronic myelogenous leukemia (CML) and acute lymphoblastic leukemia (ALL), as well as molecular tests used in the management of solid tumors. In the case of CML and ALL, the company provides a $350 PCR test for quantitation of bcr-abl RNA, which is performed every three months and is more sensitive for detection of relapse in patients undergoing targeted antibody or stem cell therapy compared to flow cytometry or FISH assays. The company also provides sequencing services to help guide therapy for those patients who relapse.

Molecular profiling is also being evaluated for a role in the early detection of cancer and cancer risk prediction, as well as for characterization of population-related genetic predispositions that impact drug response in cancer.

David Gandara, MD, of UC Davis School of Medicine, described recent studies of single nucleotide polymorphism (SNP) distributions in Japanese vs. U.S. populations with advanced non-small cell lung cancer. It has previously been observed that therapeutic response rates to chemotherapy agents such as paclitaxel in such patients, as well as adverse drug response rates, differ markedly between populations, with Japanese populations exhibiting a better response (51% response rate vs. 37% for U.S. patients). Gandara’s team analyzed host DNA from the two populations, looking specifically at six SNPs in genes involved in paclitaxel metabolism. The analysis not only showed a correlation in SNP patterns between the patient groups, but also demonstrated a correlation between progression-free survival and genotype.

In cancer risk assessment, some researchers are focusing on microRNAs as potential useful tools to predict cancer susceptibility and allow early detection of oncogenesis. MicroRNAs are non-coding se-quences that regulate gene expression. Thousands of different microRNAs are produced by cells, some which act as tumor suppressors and other that act as oncogenes to promote tumor development.

As discussed by Frank Slack, PhD, of Yale University (New Haven, New Jersey), certain microRNAs have been identified that may serve as very early markers of cancer. In particular, in a study performed in collaboration with Asuragen, Slack has found two microRNAs, let-7 and LC56, that are altered in lung cancer patients.

Other microRNAs have been identified which are altered in lymphoma, as well as ones that are altered in colon, breast, pancreas, prostate and stomach cancer. According to George Calin, MD, PhD, of The Ohio State University (Columbus), microRNAs may be the primary causative factors in familial cancer, which accounts for 20%-30% of all cancer cases. Calin said that researchers have searched for genes that directly cause cancer (hereditary cancer) for over 35 years, but only 5%-10% of all cancers are attributable to such genes. Examples include the BRCA-1 and BRCA-2 genes involved in hereditary breast cancer.

In the case of familial cancer, Calin theorizes that microRNAs may play the dominant role, and studies have now shown that small variations in microRNAs can in principle cause most familial cancers. Some microRNA alternations are unique to cancer patients, and are not observed in disease-free individuals. Additional microRNAs that may eventually prove to be important markers for cancer predisposition assessment according to Calin include R15 and R16.

Stem cell research for cancer

Stem cells are another emerging focus for research in cancer development.

As discussed by Michael Clarke, MD, of Stanford University (Palo Alto, California) at the conference, cancer stem cells are increasingly becoming recognized as playing a key role in disease progression. Experience in treating certain cancers that are highly curable, such as testicular cancer, shows that stem cells in those cancer types are susceptible to chemotherapy or radiation and consequently can be eliminated along with the more mature tumor cells.

In most other cancers, however, stem cells prove highly resistant to chemotherapy and radiation. Treatment tends to kill mature tumor cells and results in enrichment for cancer stem cells, resulting in recurrence of a tumor that is more resistant to treatment than the original one. Consequently, progress in developing new cancer therapies may hinge on creating treatments, probably employing drug cocktails rather than single agents, which are effective in ablating resistant stem cells. A key limitation of research in this area is lack of analytical methods to identify and track stem cells in vivo, and methods to allow their isolation for studies of drug susceptibility.

One method that addresses the tracking of rare cells in cancer patients has been commercialized by Veridex (Warren, New Jersey), a unit of Johnson & Johnson (New Brunswick, New Jersey). The Veridex CellSearch system, developed by Immunicon (Huntingdon Valley, Pennsylvania), was introduced in 2004 for detection of circulating tumor cells in patients with metastatic breast cancer as an indicator of shorter progression-free survival. To date, 65 CellSearch systems have been installed and are in use worldwide. That level of sales is considerably lower than expected by Immunicon, which recently announced it is seeking to end its exclusive marketing agreement with Veridex..

Another technology for detection of specific cell populations in vivo with applications in cancer management is molecular imaging. As discussed by Peter Choyke, MD, of the National Cancer Institute (Bethesda, Maryland) at the sessions, new imaging technologies employing fluorescence labels are being developed that allow detection of tumor cells as well as surrounding anatomic landmarks, providing highly specific and sensitive identification and characterization of lesions as small as 50 microns.

The technology being developed by Choyke uses near-infrared light to give good penetration through body tissue while minimizing autofluorescence background, with potential uses both in cancer screening and also for intra-operative imaging, where use of conventional tumor imaging techniques such as CT scanning is impractical.

Choyke described the use of multiple wavelength imaging to characterize tumor tissue in-vivo, such as measuring the relative uptake of agents targeting the HER1 vs. the HER2 receptor, an important application for selection of targeted drug therapy. Molecular imaging technology also can serve as the basis for targeted therapy using light-activated cytotoxic drugs.

For example, molecular imaging probes can be used intra-operatively to guide a tumor debulking procedure by providing real-time identification of tumor tissue. Subsequently, light activation can be used to ablate any remaining tumor cells, allowing a more complete removal of the tumor tissue. The agents developed by Choyke have been shown to have a sensitivity and specificity of greater than 95% for the targeted cancers.

PET and ultrasound in development

Other technologies under development for molecular imaging of cancer include Positron Emission Tomography (PET) scanning and contrast-enhanced ultrasound. Shahriar Yaghoubi, MD, of Stanford University, described the use of PET to track the distribution of cancer gene therapy agents in vivo, and use of PET to image cytotoxic T cells used to treat brain cancer in studies performed at the City of Hope Cancer Center (Duarte, California).

The capabilities of PET are expanding with the development of high-resolution technology and advanced imaging software by suppliers such as Siemens Medical Solutions (SMS; Berlin, Germany) and GE Healthcare (Waukesha, Wisconsin).

SMS recently reported development of a prototype MRI/PET system that combines the high-resolution imaging capability of MRI with the metabolic imaging capability of PET. SMS also has introduced a new HD-PET system with 2 mm spatial resolution that is part of the Biograph TruePoint family of hybrid PET-CT systems that provides a doubling of PET image contrast. Siemens also introduced new Syngo software for improving workflow in molecular imaging.

GE introduced a new PET imaging software tool at the ASCO conference for monitoring tumor response to therapy. The company’s PET VCAR software, designed for use on GE’s line of PET/CT systems as well as other PET/CT platforms, provides quantitative PET measurements for the first time. This feature allows tracking of tumor size and activity over time, based on the capability of the software to automatically re-locate a lesion detected in a previous scan and perform a quantitative analysis of the PET signal. The VCAR software has received FDA clearance, but the product will not be marketed until later in 2007.

Contrast-enhanced ultrasound is another technology with expanding applications in cancer imaging. As described by Jonathan Lindner, MD, of Oregon Health & Sciences University (Portland), ultrasound contrast agents employing 2 micron diameter microbubbles can be targeted by attaching antibodies to their surface that bind to specific molecules associated with a tumor.

For example, Lindner has used targeted microbubble contrast agents targeting the vascular endothelial growth factor receptor (VEGF-R2) to image the angiogenic network of human melanomas. Contrast ultrasound has the advantage of rapid imaging time, since the microbubble agent distributes throughout the vascular network in five to 10 minutes, as well as lack of exposure to ionizing radiation and wide availability of ultrasound imaging systems.

Lindner is also investigating therapeutic applications of the technology, based on encapsulation of cytotoxic agents within the targeted microbubbles. Once the microbubbles have localized at the targeted tumor site, the ultrasound energy is increased, causing the bubbles to burst and release the agent.

MRI challenges mammography

Another area highlighted at the conference was improved methods for cancer screening, as well as emerging cancer prevention technologies that promise to significantly reduce incidence rates for certain cancers.

Breast cancer screening is being revolutionized by the use of advanced MRI technology, increasingly shown to be more sensitive in detecting early-stage breast lesions than mammography in high-risk women. At present, MRI screening is being used primarily for women who test positive for the BRCA1/2 oncogenes, putting them at elevated risk for breast cancer.

Improved screening methods are clearly needed, since studies presented at the ASCO sessions by Rosenberg et al. show that breast self-exam, not mammography, is the primary method by which breast cancer is found, accounting for 75% of cases.

GE Healthcare has developed new MRI software called BREASE-XV that is optimized specifically for breast imaging. MRI historically has been considered to have limited utility in breast cancer imaging because of its lower sensitivity compared to X-ray mammography in detection of calcification, such as that associated with ductal carcinoma in-situ (DCIS).

However, a study conducted by Kuhl et al. of the University of Bonn (Bonn, Germany) and presented at ASCO, found that MRI was able to detect DCIS more reliably than mammography and could detect a significant number of DCIS lesions that were not detected by mammography.

Another study presented at the conference by Laura Vallow, MD, of Mayo Clinic (Jacksonville, Florida), found that MRI can detect some cancers missed by mammography. The Mayo study involved a direct comparison of MRI and mammography for detection of new breast tumors in women who had already been diagnosed with breast cancer. MRI detected tumors in the same breast in which cancer had been diagnosed that were missed by mammography in 16% of 390 patients, and also detected tumors in the contra-lateral breast that were missed by mammography in 3.2% of 401 women.

Suppliers believe that MRI can detect all types of breast cancers with a sensitivity and specificity at least equal to that of mammography, and that it is generally a superior technology. The widespread adoption of MRI for breast cancer screening, as well as adoption of MRI for screening for other cancers including lung, could result in significant growth in the market, which totaled over $2.1 billion in the U.S. in 2006 as shown in Table 4.

Attacking cervical cancer

Other new developments in cancer prevention highlighted at the conference focused on prevention of cervical cancer. About 600,000 new cases of cervical cancer are diagnosed each year worldwide, including 9,700 in the U.S., with most associated with infection by certain subtypes of Human Papilloma Virus (HPV). HPV is also implicated as a causal factor to a varying extent in oropharynx, anal, vulval and penile cancer, and may possibly be associated with development of a number of other cancer types such as squamous cell carcinoma.

For example, as discussed by Maura Gillison, MD, PhD, of Johns Hopkins Kimmel Cancer Center (Baltimore), as many as 83,000 of the approximately 564,000 cases of head and neck cancer occurring worldwide each year may be due to HPV infection. There are multiple subtypes of HPV, only some of which have been associated with cancer. Gardasil, the new vaccine against HPV developed and marketed by Merck & Co. (Whitehouse Station, New Jersey) is targeted at HPV types 6, 11, 16 and 18, or more specifically against the E6 and E7 proteins produced by those HPV subtypes when the virus integrates into the host genome and becomes actively transcribed.

Adoption of the vaccine among the target population of girls and women between the ages of 9 and 26 has been limited, however, by social concerns and concerns about safety. Cost is another barrier, particularly in the less developed regions where most cases of cervical cancer occur, since the three-dose vaccination series of Gardasil has a wholesale acquisition cost of $360.

Nevertheless, sales of Gardasil totaled $365.4 million in 1Q07, and $234.8 million in 2006 following the product’s FDA approval in June 2006. Adoption of the vaccine is not expected to impact the cervical cancer screening market, however, since regular PAP smear testing is still recommended for women who have been vaccinated. As shown previously in Table 3, a significant market has developed for PAP screening products to detect cervical cancer, including molecular tests for the culprit HPV subtypes in cervical smear specimens. At present, Digene (Gaithersburg, Maryland) is the only supplier of FDA-approved test kits for use in HPV screening, but new products are expected on the market shortly from Roche Diagnostics (Indianapolis) as well as Third Wave Technologies (Madison, Wisconsin).

Third Wave is in clinical trials for FDA clearance of an HPV screening test based on its molecular Analyte Specific Reagents for HPV detection, and expects to achieve market penetration due to the greater ease of use of its test compared to the Digene assay. The new Third Wave HPV test requires hands-on time of only 20 minutes, a significant reduction compared to the Digene test according to Third Wave.

Another new cancer screening test was introduced in late May, just prior to the ASCO conference, by Panacea Pharmaceuticals (Gaithersburg, Maryland). The PC Detect test from Panacea Laboratories is a new prostate cancer screening assay that measures levels of Human Aspartyl beta-Hydroxylase (HAAH) in blood.

The new test is intended for use as an adjunct to PSA screening and digital rectal examination (DRE) for early detection of prostate cancer. It is particularly useful in those cases in which the PSA level is normal (less than or equal to 4 ng/mL) but cancer is still present, which can range from 24-27% of men with PSA levels between 2.1 and 4.0 ng/mL. At present, the test is available only from Panacea’s CLIA-registered laboratory, but Panacea plans to submit a PMA later in 2007 for a PC Detect kit that will be sold to clinical labs throughout the U.S.