Editorial

Abstract

Medicine, and oncology in particular, has always depended on the ability to visualize pathologic processes. The early discovery of x-rays in the 19th century and the subsequent development of the specialty of radiology and diagnostic imaging in the 20th century represent the essential basis for the vast majority of all therapeutic decision-making processes today. In oncology, therapeutic effects depend to a large extent on detecting pathological processes before tumor cells leave their initial site of origin and start to spread to distant organs or to form metastases that in many instances are no longer accessible to surgical intervention and curative treatment. Since most cancers usually remain asymptomatic until that stage or even longer, one of the most important technical challenges in oncology is to improve the techniques that help to visualize neoplastic processes long before symptoms appear. Techniques have even been developed with which preneoplastic lesions can be visualized, and when these methods have been applied for early detection of cancer and in cancer screening programs, an immediate and substantial impact on incidence and mortality rates has been observed. Hence, further technical improvement along these lines represents one of the most formidable tasks in clinical and translational cancer research. Based on the substantially improved knowledge of the major pathogenic processes of carcinogenesis and a sophisticated molecular understanding of the key biochemical pathways that lead to cellular transformation and outgrowth of cancers, groundbreaking novel concepts are now being developed to translate these achievements into clinical practice for the benefit of patients. In the special section of this issue of the International Journal of Cancer on molecular diagnostics and imaging, this novel concept is reviewed by three articles that each summarize the most recent developments at three diagnostic levels: a.) in vivo imaging of tumors or their precursor lesions, b.) the detection of disseminated tumor cells in compartments outside of the primary affected organ, such as bone marrow and peripheral blood, and c.) by novel concepts to identify biochemical parameters that allow indirect evidence to be gathered about tumor growth in an organism primarily based on proteins or derivatives thereof that are secreted or released by the emerging tumor cells into body fluids or secretions. Mark Pierce, David Javier and Rebecca Richards-Kortum describe in their article “Optical contrast agents and imaging systems for detection and diagnosis of cancer” the most recent developments and technical achievements in molecular imaging. They review the fundamental techniques and state-of-the-art optical molecular imaging with which the microscopic and macroscopic hallmarks of cancers and their precursor lesions can be visualized. They discuss novel approaches for the optical contrasting of cancers based on endogenous and exogenous parameters and review the most recent developments to exploit a tumor's own biological properties to help render these otherwise hidden processes visible to the human eye. Biochemical and molecular alterations of the tumor cells are being used to develop systems that help track their growth and spread in the body. Sabine Riethdorf, Harriet Wilkman and Klaus Pantel present the most recent developments in methods for monitoring the spread of single isolated tumor cells through the blood stream and bone marrow. They analyze the immunological and molecular techniques that are currently being used to detect disseminated tumor cells among the multitude of other non-neoplastic cells, particularly in peripheral blood or bone marrow samples. They also review recent evidence on the prognostic and clinical impact of these novel diagnostic strategies and discuss the pro's and con's of implementing these techniques into routine clinical practice, particularly so as to guide adjuvant therapy following surgical procedures. Finally, Vathany Kulasingam and Eleftherios Diamandis review novel approaches to identify protein biomarkers that could be used as serum parameters and hence could potentially constitute simple and highly cost-effective screening and surveillance tools. As they summarize in their paper, despite the many attempts to identify protein biomarkers by mass spectrometry and other methods from serum or other body samples, no novel clinically applicable biomarkers could be identified yet. To circumvent the technical difficulties, recent research focuses on “in vitro” model systems that may help to identify cancer biomarkers from cultured cancer cells. Particularly those proteins or protein fragments that are released by vital cancer cells into the respective culture medium are of special interest and systems to identify those markers for breast cancers are discussed in detail. Together with the guest editor of this special section, Manuel Perucho, I wish to thank the authors for their comprehensive and valuable reviews. I strongly believe that these contributions will stimulate further research in this fascinating area and, hopefully, we will be reading about this in forthcoming issues of the International Journal of Cancer.