Seeing Cancer Cells, Killing Cancer Cells

In some ways, theranostics works like other medical drugs by interacting with protein molecules, which are called receptors, on the walls of cells. These receptors can bind with outside molecules, such as hormones and drugs, which activate the receptors and generate a biochemical or electric signal that tells the cell what to do, such as to stop producing the chemicals that signal pain to the brain.

Different molecules are attracted to different types of receptors. By knowing which molecules go with which receptors, medicines can be created that link the right molecules with, for example, pain-blocking chemicals that the molecules then carry to the right cell receptors to, say, stop a headache.

This is the same with radiopharmaceuticals; radioactive materials are linked to molecules that have been selected based on how they interact with the body when certain cancers are present. The molecules then carry the radioactive materials to the target tumour for diagnostic imaging or treatment. As the healthy cells do not have the same receptors as the target cells, the radiopharmaceuticals bypass them and do not damage them.

“With an approach that focuses on the specific needs of each patient, theranostics provides a transition from conventional medicine to personalized and precision medicine; the result is the selection of the right therapy for the right patient,” said Diana Paez, Head of the IAEA’s Nuclear Medicine and Diagnostic Imaging Section.

For diagnostic imaging, radiopharmaceuticals with small amounts of radioactive material are either injected, ingested or inhaled, and then transported through the body to the target area. Once the drug gathers around or inside the target cells, the tiny amount of radiation emitted by the radiopharmaceutical is scanned and detected by a special camera. This then produces images of that area of the body.

Following the results of diagnostic imaging, the physician determines which course of treatment is best for the patient. If theranostics is suitable, a radiopharmaceutical is selected for that patient, and the exact amount of radiation needed for treatment is determined — the dose depends on the type and size of the tumour, as well as the patient’s age and gender, the severity of the case and the organ targeted. Once the radiopharmaceutical collects around or inside the cancer cells, the radiation it emits damages and kills the cancer cells, while harm to the surrounding healthy cells is minimized. Patients usually have several treatment sessions, and further diagnostic images are taken to monitor progress.

“We have seen responses to theranostic treatment that were nearly impossible with other kinds of treatment,” Haidar said. While for now they are only treating a handful of patients each year, Haidar and his team of 15 specialists in Lebanon have already begun seeing significant results.

“For example, I had an 82-year-old patient with prostate cancer that had spread to the lymph nodes and bones, and after failed treatment using other methods, we switched to theranostics,” he said. “After two doses with lutetium-177 prostatespecific membrane antigen (PSMA), we saw a significant drop in tumour lesions, and then, after an additional dose with another radiopharmaceutical, actinium-255 PSMA, near complete remission.”

These are just preliminary findings, explained Haidar, and there is still much work to be done in the field of theraonstics to more fully understand its impact and potential scope. He and his team plan to continue their work with the IAEA to advance their research, refine their skills and help train others in the region. The IAEA, through its technical cooperation programme, has provided training and donated equipment to Lebanon to support the development of its cancer care services.

“In the future, we could see an expansion of theranostics into use for breast and lung cancers,” he said. “If we can find a molecule that works specifically for these very common cancers, it could have a big impact on cancer survival rates and quality of life.”

This article was also featured in the IAEA Bulletin on Cancer Control published in September 2019.