Adaptability guides the evolution of cancer imaging

March 6, 2009

Prof. Hedvig Hricak told delegates during Friday’s opening lecture that they must learn from the words of Charles Darwin: embrace change and adapt.

Prof. Hedvig Hricak told delegates during Friday's opening lecture that they must learn from the words of Charles Darwin: embrace change and adapt.

Hricak, chairman of the department of radiology at New York's Memorial Sloan-Kettering Cancer Center, quoted directly from the 19th century naturalist, who caused a storm with his theory of natural selection. Darwin wrote in The Origin of Species that "it is not the strongest of the species that survives, nor the most intelligent that survives, it is the one that is most adaptable to change." He also observed: "In the long history of humankind, those who have learned to collaborate and improvise have prevailed."

Radiology has evolved considerably over the past 50 years, and one result of this evolution has been oncologic imaging, a field that has endless horizons, Hricak said. But as this process of evolution continues, radiologists must broaden their focus beyond gross anatomy.

"It is no longer enough to be knowledgeable about all the imaging modalities that we have," she said. "It is equally essential to understand that imaging is just one element in the integrated diagnostic approach to the management of cancer. We have no choice but to learn the importance of serum screening, proteomics, and molecular pathways."

Hricak outlined how molecular imaging and intervention are moving closer together in oncology with the emergence of a new field. Theranostics combines targeted imaging using a specific tracer with treatment that is directed at the same target.

To illustrate the power of targeted imaging, she showed three nuclear scans of a patient with metastatic prostate cancer. A standard bone scan showed few bony lesions, while FDG-PET imaging revealed lesions in different locations. Only PET imaging with the radiotracer FDHT (fluorodihydrotestosterone), which homes in on androgen receptors, picked up the full extent of metastatic disease.

"As we improve and we have targeted imaging, it is sometimes frightening to see how little we knew," Hricak said.

Targeted imaging could also have an important role in the management of breast cancer. Imaging with a tracer that targeted estrogen receptors, for example, would indicate which patients were likely to benefit from the drug Letrozole. Similarly, a method of imaging that highlighted HER2 receptors should show which patients would benefit from the drug Herceptin.

"Herceptin is an excellent drug, but 40% of patients do not have results because 40% of patients do not have HER2 receptors within their metastatic lesion," she said. "Is targeted imaging too expensive to use in cancer treatment, or is it more expensive to keep patients on a course of chemotherapy or androgen or hormonal therapy, and bring up their hopes while the cancer grows?"

Hricak also discussed the future evolution of contrast agents and imaging hardware. She raised the prospect of MRI/PET replacing CT and PET/CT in oncologic imaging -- if only a way could be found of making the technology cost-effective.

She concluded by setting out her "matrix for success" in oncologic imaging.

"We need to change from a technology-centered specialty to embrace physics, chemistry, and biology. We need to collaborate. An interdisciplinary and multidisciplinary team of clinicians and basic scientists is a must. And we need to continuously evolve, anticipate opportunities, love change, develop new procedures and applications, and adapt to new environments," she said.