PET-guided breast cancer therapy targets specific hormones in individual patients

A new PET-guided method to monitoring tumor growth could help doctors identify the ways cancer avoids certain kinds of treatment. Researchers published the results of a trial studying this method in the Journal of Nuclear Medicine.

The study authors especially focused on ways that breast cancer tumors “learn” through feedback loops how to avoid inhibitors meant to block hormones such as epidermal growth factor receptor 1 (EGFR) and human epidermal growth factor receptor 3 (HER3) that allow a tumor to grow. Researchers used PET imaging to watch and anticipate how these tumors could develop new hormone pathways after adapting to treatment so that physicians can stay one step ahead of the tumors, anticipating where the new pathways might show up and waiting with new inhibitors at the ready.

And it worked, according to the researchers. They found that, in just a few days, they could see that resistance to inhibitors in those hormones was reduced, meaning tumor growth was slowed. The physicians used PET imaging to anticipate where the adapted hormone pathways might show up next and were able to get there first, an outcome that the researchers called “of sufficient magnitude as to allow reliable clinical interpretation.”

More specifically, the study authors reported the change in the receptor tyrosine kinases as related to the two studied hormones in different kinds of tumors. They said with the EGFR hormone, the PET probe PET/CT imaging of HCC70 tumors shows an SUV of 0.32 ± 0.03 for vehicle-, 0.50 ± 0.01 for GDC- 0941–, and 0.62 ± 0.01 for GDC-0068–treated tumors, respectively. For tumors dealing with the HER3 hormone, the PET probe PET/CT imaging of MDAMB468 tumors shows an SUV of 0.35 ± 0.02 for vehicle- and 0.73 ± 0.05 for GDC-0068–treated tumors.

The study authors touted this new method’s usefulness for its non-invasive nature and for the substantial changes physicians were able to make to treatment and outcome using the information gathered using the PET scans. This new method could fall under an increasing effort to personalize cancer treatment for individual patients, the study concluded.