The first x-ray picture was taken by the physicist Wilhelm Conrad Roentgen in 1895. He produced an image of his wife’s hand, clearly showing the bone structure. From the discovery of the x-ray and Marie Curie’s work on radiation in the early 1900s to the invention of ultrasound imaging in 1960, the widespread use of x-ray mammography in the 1970s and magnetic resonance imaging (MRI) in the 1980s – the past one hundred years, imaging technologies have significantly altered medical treatments and affected the lives of countless patients through medical imaging advances.
New imaging strategies for cancer are continuously being developed and Ontario is a world leader in research to develop these cutting edge imaging technologies. It is now possible to detect tiny cancer tumours at early stages of development and to pinpoint the exact size and location of a tumour. Advances in radiation technology are helping to make both chemotherapy and radiation therapy more effective.
Dr. Raymond Reilly is an Associate Professor of Pharmacy at the University of Toronto conducting research aimed at the discovery of new molecular imaging agents for cancer. He is also a scientist in the Division of Clinical Investigation and Human Physiology at the Toronto General Research Institute. Molecular imaging is a relatively new imaging technology, which involves tracking tumours by exploiting the biochemistry of cancer cells. Reilly’s approach combines radioisotopes with drugs used in standard cancer treatments, converting them into “radiopharmaceuticals”. These release gamma rays which can be imaged using a gamma camera making tumours and cancer cells spreading through the body easier to see, track and remove.
Reilly is conducting research using trastuzumab (Herceptin(r)), a relatively new drug used in the treatment of breast cancer. Fragments of the drug are labelled with indium-111 – a radioactive substance – and when the trastuzumab is administered intravenously it begins to home in on the cancer cells marking them for imaging and surgical removal. This technique, called radioimmunoguided surgery, is expected to be helpful to the surgeon who will use a specially-designed hand-held gamma probe to detect the “radioactively tagged” cancer cells during surgery, ensuring that as much cancerous tissue is removed as possible. “The margins of the disease are defined with the hope that the tumour can be completely removed with minimal disruption to the healthy breast tissue,” states Reilly. Reilly is also developing new molecular imaging agents that could predict more accurately than is now possible whether a patient will respond to treatment with Herceptin(r).
These new imaging techniques have several benefits, including their cost-effectiveness and ability to improve on standard treatments. “We expect that molecular imaging will provide the critical tools to appropriately select patients for new targeted cancer medicines, providing better patient care while minimizing costs to the health care system for treatments that do not provide benefit, but may pose risks,” says Reilly.
While Reilly’s imaging research builds on treatments already approved by Health Canada, three phases of clinical trials will be required to certify that the radiopharmaceuticals are safe and effective for future patients. He recently received approval from Health Canada to conduct trials, to be completed with Dr. Claire Holloway, a surgical oncologist at Sunnybrook Health Sciences Centre. Funding for the clinical trials was also awarded to Reilly and Holloway by the Ontario Institute for Cancer Research, through the Cancer Research Fund program. The Cancer Research Fund is also supporting the research on molecular imaging agents for predicting response to Herceptin(r).
Reilly has high hopes for his research and the future of molecular imaging. “Molecular imaging,” he says, “will offer unparalleled new opportunities in the next few years to identify targets on tumours anywhere in the body, track the delivery of drugs to these tumours using radiopharmaceuticals and determine much earlier than is now possible, whether a particular drug is working or not.”
Dr. David Jaffray, the Head of Radiation Physics at Princess Margaret Hospital, is an internationally recognized specialist in image-guided radiation therapy. He believes that imaging has begun to change the way cancer is treated. Jaffray says, “Imaging technologies are dramatically changing the way we think about cancer intervention. The development of molecular imaging technologies brings the promise of mapping the cancer.”
Jaffray’s research will enable radiation oncologists to deliver radiation therapy for cancer that targets the tumour more precisely. The images he produces account for the movement of the tumour within the body. For instance, if a patient drinks two cups of coffee prior to the treatment, a full bladder may cause the tumour to move from where it was at the time of the previous treatment. Jaffray would like to have images available to show the location of the tumour at the time of treatment so that it is focused only on the cancer cells and not on healthy tissue.Jaffray and his team have developed equipment constructed to provide the best images possible, including a cone-beam computed tomography (CT) machine to provide 3-D x-ray imaging. Jaffray’s design requires less x-ray exposure and the 3-D image is constructed in a computer program.
Improved imaging allows treatments for cancer to become more targeted, resulting in reduced side-effects for the patient. Jaffray says, “Rapid advances in manufacturing and computation are allowing us to integrate imaging systems directly into the treatment procedure, or alternatively, treatment systems into the imaging procedure. These image-guided therapy systems promise increased tumour control, fewer side effects, and are the key to capitalizing on the molecular imaging promise.” The legacy of Roentgen and Curie has enabled scientists and physicians to see inside the body and observe not only large structures like bones but small structures like tumour cells with amazing accuracy. The recent introduction of molecular imaging should now allow us to visualize the molecules that make up the cancer cell and the drug molecules used to treat it. 21st century imaging is creating a revolution in the treatment of cancer.