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Introduction to the Special Issue on Medical Imaging in Oncology

Department of Radiology, University of Virginia, Charlottesville, VA

This special issue of the Journal of Clinical Oncology seeks to accomplish several goals:

• To educate the oncology community about what options imaging currently proffers in practice and in clinical trials;
  
• To provide a prospective on how imaging innovations will impact cancer care in the future;
  
• To explore why imaging bears such extraordinary potential to impel advances in cancer care.
  

Especially exciting is the development of "molecular imaging." Defined as, "the spatially localized and/or temporally resolved sensing of molecular and cellular processes in vivo,"¹ molecular imaging is simultaneously pulled along by and motivating the broader advance toward the future of molecular diagnosis and treatment of malignancies. Often pairing an image-receptor technology and a molecularly active agent, the potential of molecular imaging is typified by PET scanning using fluorodeoxyglucose (FDG), with which most oncologists are familiar. However, long-term, the potential of molecular imaging is much broader than this. Molecular imaging techniques provide real hope for the eventual development of disease-specific imaging methods. These methods might ultimately allow for the detection of cancer at a much earlier point in a tumor's development; the stratification of tumors according to their aggressiveness or susceptibility to specific treatment; and the rapid determination of the effectiveness of treatment.¹ Although still in its infancy, molecular imaging might be expected to develop into diverse clinical applications during the next decade or so, depending on such influences as clinician demand for molecular imaging information, problems confronting the regulatory approval of new molecular imaging technologies, and the aggressiveness of biologic, pharmaceutical, and imaging device manufacturers.² With time, it is not inconceivable that molecular imaging will supplant much of what oncologists request of anatomic imaging today.

Whether discussing anatomic or the new molecular imaging, it is useful to think of medical imaging as addressing four broad categories of applications: (1) screening and early detection; (2) diagnosis and staging; (3) guidance for less invasive treatments; and (4) monitoring of treatment response. Each of these has witnessed considerable technological innovation in recent years. With regard to screening, mammography for breast cancer remains the sole imaging screening technology effectively proven to reduce disease-specific mortality.³ There are, however, a number of other technology/disease pairs, like CT for lung cancer, CT colonography for colon cancer, and ultrasound and MRI for breast cancer, that are receiving considerable scrutiny. Indeed, the American College of Radiology Imaging Network (ACRIN; http://www.acrin.org), a National Cancer Institute–funded clinical trials cooperative group directed toward conducting multicenter clinical trials of diagnostic imaging and image-guided treatment, is currently sponsoring trials aimed at each of these applications.

Cancer diagnosis and staging have been the principal applications of imaging in the past, and they remain fruitful areas for the future. New imaging agents, combined with innovative image receptor technologies, and the fusion of already accepted technologies such as CT and PET, represent advances that could portend the discovery of tumors at an earlier stage. In addition, future imaging techniques will better detail the extent of disease, improving determination of whether cancer patients should undergo surgery or more conservative treatment.

Image-guided treatment has become a conventional therapeutic approach to cancer, with CT and ultrasound guidance being the staple technologies employed. Tumoricidal techniques, such as radiofrequency ablation, cryoablation, and catheter-directed chemotherapy or embolotherapy are now widely used. New technologies like MRI-guided focused energy (eg, ultrasound or microwave) transcutaneous ablation bear the potential to both further reduce invasiveness and better monitor the progress of treatment in real-time, minimizing the destruction of surrounding normal tissue.

It is in the area of monitoring of tumor response to treatment, however, that imaging is perhaps generating the greatest excitement. Today, both in daily practice and in clinical trials, anatomic measurement of tumor size on CT or MRI images is the principal means of determining whether a patient's treatment is working effectively. However, there are serious problems with this approach: lack of reliability of sequential measurements, often by different observers; difficulty measuring with some technologies and at some disease sites; the long duration over which observations must be collected before it is evident whether a treatment is efficacious; and the often poor relationship between changes in tumor size and significant health outcomes. New functional and metabolic imaging techniques have shown themselves in preliminary studies to perhaps be an improvement on the anatomic approach. These techniques have the potential to provide faster, more reliable, and more accurate information in the guidance of therapeutic decisions. What still needs to occur is research that optimizes and standardizes these modalities and validates that they can serve as biomarkers or even surrogate end points for various cancers and treatments across different types of clinical settings. Should this research verify the current preliminary impressions, enormous reductions in morbidity and improved survival could result. Moreover, the ability to employ functional/metabolic imaging as a surrogate marker for important health outcomes could drive considerable cost savings for patients and the health care system, as well as reduce the costs of bringing new therapeutic agents to clinical care.⁴

While no single journal issue can comprehensively survey all medical imaging applications to cancer, the Editors have endeavored to provide a sampling of what is most exciting in the field and portray it to JCO's readers. We recognize that most of JCO's readership comprises practicing physicians who are the constant end users of the information derived from imaging, but who are for the most part, not themselves involved in imaging practice. That being the case, we begin with an article that details basic principles of imaging that will be useful to those wishing to know more about how images are generated and how different imaging modalities are best employed. Subsequent articles address aspects of the four applications of imaging discussed earlier. For example, the article on screening guides the reader through some important concepts related to the considerably misunderstood field of imaging screening. There are writings on the applications of conventional and emerging technologies, image-guided treatment, how imaging is and might in the future be employed in new therapeutic drug development, and various new approaches to using imaging as a biomarker.

In laying out this issue, the Editors have asked the authors to impart to readers some of their own excitement over the potential of medical imaging to address our mutual goal of reducing the morbidity and death associated with cancer. We believe that the potential of imaging can best be realized through the collaboration of the entire cancer community, inclusive of government, cancer centers, cooperative clinical trials groups, patient advocates, and thousands of interested oncology practitioners. Education about the principles and capabilities of imaging is a good first step toward achieving this goal.

Author's Disclosures of Potential Conflicts of Interest

The author indicated no potential conflicts of interest.

REFERENCES

1. Thrall JH: ACR primer on molecular imaging. J Amer Coll Radiol 1:32, 2004

2. Hillman BJ, Neiman HL: Translating molecular imaging research into radiological practice: Proceedings of the American College of Radiology Colloquium. Radiology 222:19-24, 2002[Abstract/Free Full Text]

3. Hillman BJ, Amis ES, Weinreb JC, et al: The future of imaging screening: Proceedings of the Fourth Annual ACR FORUM. J Am Coll Radiol 2:43-50, 2005[CrossRef][Medline]

4. US Food and Drug Administration: Challenge and Opportunity on the Critical Path to New Medical Products. Washington, DC, Department of Health and Human Services, 2005

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