“Inter- and intra-tumoral heterogeneity in breast cancer poses challenges to the paradigm of precision medicine. Sampling errors in core biopsy may lead to erroneous decisions in treatment planning. A holistic approach for breast tumor characterization is therefore needed for accurate diagnosis, treatment and prognosis,” according to Dr. Jones. PET imaging offers a quantitative measure of molecular markers and can be used as an in vivo assay for whole tumor characterization.
The use of whole body PET (WB-PET) for staging and restaging of breast cancer has provided valuable information that often alters treatment planning and can improve clinical outcomes. However, WB-PET is not recommended for local staging of disease within the breast. This is due in part to the poor spatial resolution (~5-10 mm FWHM) and associated partial volume error in small lesions. Moreover, most PET exams are performed in the supine position, which is suboptimal due to collapse of the breast and blurring from respiratory motion.
Increasing interest in functional evaluation of the primary breast tumor has led to the development of a dedicated breast PET (dbPET) imaging scanner. MAMMI dbPET is specially tailored for imaging of the breast at high spatial resolution (2 mm). It has a ring structure with 12 detector modules containing lutetium yttrium silicate (LYSO) scintillators for improved timing resolution and sensitivity focused on imaging the breast volume. Patients are examined in the prone position. Images obtained are true 3D and are spatially analogous to breast MRI. Molecular information obtained from MAMMI dbPET may therefore complement the anatomic and enhancement kinetic information obtained from MRI.
At UCSF, researchers are using MAMMI dbPET as a companion diagnostic with MRI to characterize breast tumors in patients undergoing neoadjuvant chemotherapy. Their efforts focus on combining functional information from dbPET and anatomical information from MRI to assess early treatment-induced changes in primary breast tumors.
In the near future, when more subtype specific radiotracers become available for clinical use, MAMMI may play a key role in in vivo assay of the whole breast tumor, from which accurate diagnosis can be made to enable precision medicine effectively.