June 2011

Breast PET in Clinical Practice — A Florida Health System’s Experience With Positron Emission Mammography
By Rakesh Parbhu, MD, and Mary Hayes, MD
Radiology Today
Vol. 12 No. 6 P. 25

Positron emission mammography (PEM) is a 3D molecular breast imaging tool that uses high-resolution PET technology to help physicians diagnose and stage breast cancer using IV injectable FDG that accumulates in glucose-avid cells. It offers better spatial resolution than traditional PET systems and allows for biopsying lesions as small as 1.3 mm. (Whole-body PET typically offers spatial resolution between 5 and 6 mm.)

PEM has shown promise in our practice for the initial staging of breast cancer patients, evaluating their response to therapy, assessing recurrence, and restaging. Implementing this new technology into our large, busy mammography department required considerable investment and planning. The purpose of this article is to share the initial clinical experience of how we have integrated PEM into our clinical practice.

Steps to Integration
The steps required to integrate PEM into a clinical breast center were similar to those used when breast MRI was introduced a decade ago. At that time, breast MRI represented a crossover modality that brought together body and breast imagers as well as technologists from two areas. Similarly, PEM requires cooperation across disciplines.

Being part of a subspecialized radiology practice and Memorial Healthcare System, we take a team approach to patient care. Our preliminary experience with PEM and PEM-guided biopsy benefited from setting up a primary team that included a nuclear medicine technologist, a mammography technologist with experience in stereotactic procedures, a nurse, and a radiologist. In the beginning, these “team leaders” were chosen for applications training and working out any logistical issues during the learning phase. Additional staff members were trained as time went on. Having designated leaders helped us with quality assurance and problem-solving issues.

To maintain optimal workflow, PEM scans are scheduled for one day per week. The cases are protocolled as early as possible, so if there is a potential need for PEM-guided biopsy, it can be scheduled on the same day to expedite preoperative planning.

Integration
PEM was introduced to our referring physicians through recommendations by a radiologist when a patient met criteria, through education at tumor boards and multidisciplinary conferences, and via enrollment in a prospective neoadjuvant treatment clinical trial, which involved many of our oncologists. We introduced PEM to patients through their radiologists as an emerging technology that could be beneficial to them.

PEM procedures are currently reimbursed at our center for the following cancer indications:

• Staging patients preoperatively

• PEM or whole-body PET — cannot bill for both if done on the same day

• Can be reimbursed for both MRI and PEM

• Restaging patients with locoregional recurrence

• Monitoring response to treatment

PEM, Breast MRI, or Both?
Since both PEM and MRI are adjunct modalities used for similar indications, it is important to first identify which patients would benefit from each. We have developed guidelines, shown in Table 1, to help referring physicians decide which patients are better suited for PEM, MRI, or—in a few select cases—both.

To date, we have performed PEM scans on more than 100 patients and PEM-guided biopsy on approximately 10% of our PEM cases. We are also conducting a clinical trial on PEM for response to neoadjuvant chemotherapy that we believe may prove a valuable application of this technology.

The role of PET in monitoring the response to therapy has been well documented in the literature. With a higher resolution than whole-body PET systems, PEM is showing promise for assessing response earlier, both in clinical practice and ongoing research, at our center as well as at the University of Chicago and MD Anderson Cancer Center. Patients should ultimately benefit from learning whether a tumor responds to earlier neoadjuvant chemotherapy because medical oncologists could opt to change targeted therapy earlier than with MRI, where typically we wait until the second cycle of chemotherapy before changes in blood flow are apparent. Using PEM for this indication could ultimately reduce patient morbidity, speed up treatment, and save healthcare dollars.

PEM is another tool in the comprehensive exam of a breast cancer patient and is diagnostically helpful in the appropriate patients. In cases where a breast MRI demonstrates extensive background enhancement or multiple indeterminate lesions, PEM has been useful in directing us to the area(s) of concern. MRI can also be limited in restaging patients on neoadjuvant treatment because the treatment itself constricts blood flow, which is what this modality is based on. PEM is not limited by this factor.

In our initial clinical experience with PEM and PEM-guided biopsy and in ongoing research, this tool has shown promise in the diagnostic algorithm in breast imaging.

— Rakesh Parbhu, MD, is chief of the breast center at Memorial Hospital South in south Florida.

— Mary Hayes, MD, is medical director of women’s imaging for Memorial Healthcare System Hospitals.

Table 1 — Physician Guide to Referring for PEM or MRI

References
1. Shilling K, Narayanan D, Kalinyak JE, et al. Positron emission mammography in breast cancer presurgical planning: Comparisons with magnetic resonance imaging. Eur J Nucl Med Mol Imaging. 2011;38(1):23-36.

2. Berg WA, Madsen KS, Schilling K, et al. Breast cancer: Comparative effectiveness of positron emission mammography and MR imaging in presurgical planning for the ipsilateral breast. Radiology. 2011;258(1):59-72.

3. Adler L, Narayanan D, Gammage L, Beylin D, Keen R. Quantitative improvement in breast lesion detectability on delayed images using high resolution positron emission mammography. J Nuc Med. 2007;48(Supplement 2):369P.

4. Kalinyak JE, Schilling K, Berg WA, et al. PET-guided breast biopsy. Breast J. 2011;17(2):143-151.

5. Yang WT, Rohren E, Mawlawi O, et al. Functional evaluation of response to targeted therapy in HER2 over expressing inflammatory breast cancer (IBC) patients using positron emission mammography (PEM). Presented at: American Association of Cancer Research; April 2010; Washington, D.C.

6. Lehman CD, Gatsonis C, Kuhl CK, et al. MRI evaluation of the contralateral breast in women with recently diagnosed breast cancer. N Eng J Med. 2007;356(13):1295-1303.

7. Schilling K, Franc BL, Kalinyak JE. Pre-surgical detection of malignancies in the contralateral breast using positron emission mammography: Comparisons with magnetic resonance imaging. Presented at: National Consortium of Breast Centers 21st Annual National Interdisciplinary Breast Center Conference; March 2011; Las Vegas, Nev.