Stabin at SNMMI: It’s time to take on patient-specific dosimetry

The rally cry heard round the Society for Nuclear Medicine and Molecular Imaging (SNMMI) educational sessions, hallway discussions and exhibit floor pitches this week in Vancouver was the message of Hal Anger Lectureship & Award lecturer Michael G. Stabin, PhD, researcher at Vanderbilt University School of Medicine in Nashville, too: patient-specific dosimetry is a must in diagnosis and therapy. “Patients are different, they need different therapy,” he said.

“This is a pivotal time in radiation dosimetry and radiobiology,” Stabin told the audience of about 1,200 in the ballroom of the Canada Center. “We have a new generation of dose phantoms and selection of sophisticated [dose planning tools and] methods…and it’s time to incorporate dose calculations into clinical therapy planning…Our understanding of radiobiology is undergoing profound change. We will be rewriting history soon.”

In 2008, Stabin’s paper “The Case for Patient-Specific Dosimetry in Radionuclide Therapy” was published in Cancer Biotherapy and Radiopharmaceuticals. Its message was his dictum Monday: “Treating all nuclear medicine patients with a single, uniform method is consciously choosing that the patient be treated with a lower standard of care than patients who receive radiation therapy planning,” according to the paper.

Clinicians have the necessary tools to measure dose, he noted, detailing developments in phantoms, being more realistic and gender and age specific for males, females, pregnant females and children of different ages. Organ-specific phantoms now include the esophagus, prostate gland, salivary glands, eyes and a redefined gastrointestinal tract with new lower intestinal regions. Rat models have been similarly improved to add more precision to research. He also cited new software that allows easier dose tracking.

“With tools like these and others, it is time to increase dose calculation into clinical therapy planning,” Stabin said. “The tools and methods are mature and the evidence shows this…but [dose calculation] is not consulted much for diagnosis. In therapy, dosimetry should be used to optimize therapy to practice individualized medicine, but it is not consistently done. Perhaps the objectives are different. It can be expensive, there is a lack of standards and dose models don’t predict outcomes.”

Stabin detailed several studies showing the numerical benefits of patient-specific dose and patient survival. He cited several methods such as body size, 3D treatment planning, effective uniform dose, biologically effective dose and fractionated high dose rate treatment that can increase survival rates. In many situations, “data prove it works. But we are not using it,” he said, calling for more research to try new methods to bring about better patient results in diagnosis and treatment.

“We are tantalizingly close to a new understanding of radiation dose in terms of survival and terminal,” he noted. “New models permit the calculation of standardized dose for diagnostic radiopharmaceuticals and therapeutic agents. Tools exist for more sophisticated dose calculations and when done carefully accuracies are reasonable and show correlation with biological effects…But the challenge is getting acceptance in the clinic.”