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Please note: This article is part of the Cancer Center's News Archive and is here for historical purposes. The information and links may no longer be up-to-date.

Michigan Oncology Journal Spring 98

Positron Emission Tomographic Imaging of Breast Cancer

Richard L. Wahl, M.D.,
Professor of Internal Medicine and Radiology
Director, General Nuclear Imaging
Director, Radiopharmaceuticals Program

The most common methods to detect and diagnose breast cancer are physical examination and mammography. These very important and useful methods detect cancer because a mass has developed in the breast - an anatomic change. While anatomic methods are extremely useful, they do not assess the more fundamental changes in tumor metabolism within the mass, nor do they tell us with certainty whether masses are malignant or benign.

PET Scanning
My research group has been studying the use of positron emission tomography (PET) scanning as a method to detect, characterize and follow the treatment of breast cancer. PET scanning is a very sensitive method in which changes in the molecular biology and physiology of tumors are assessed non-invasively by imaging. PET scanning involves the intravenous injection of a short-lived positron emitting radiotracer, which preferentially accumulates in cancers. As an example, FDG, a short-lived analog of glucose (sugar), will preferentially accumulate in breast cancers due to their increased glucose metabolism, allowing for their detection with a specialized scanning camera called a PET camera. This camera not only scans the breast, but can scan the entire body. A wide variety of other positron emitting radiotracers can be used to detect physiological alterations in breast cancer such as increased blood flow, increased protein synthesis, increased DNA synthesis, and decreased oxygen concentrations.

This ability to non-invasively look into the breast at molecular changes instead of just anatomy allows PET to be both a promising research tool and a useful clinical tool in a growing number of challenging cases.

Anterior PET scan view of 45-year-old woman with newly diagnosed
a: Anterior PET scan view of 45-year-old woman with newly diagnosed right breast cancer. Tumor has high FDG uptake.
Same patient after two cycles of chemotherapy
b: Same patient after two cycles of chemotherapy. Tumor uptake of FDG is nearly absent, consistent with excellent response to therapy. Tracer uptake in left chest is normal heart.
PET scan shows intense uptake in tumor in left bracial plexus.
Patient with past history of breast cancer who now has left arm pain and weakness. FDG PET scan shows intense uptake in tumor in left bracial plexus.

Progress in Understanding PET
We have made progress in answering many of these questions, but much remains to be accomplished.
To date, we have learned that PET:

  • can detect breast cancers throughout the entire body;
  • has excellent sensitivity for detecting soft tissue recurrences, such as in the nerves of the neck and thorax;
  • fails to detect small primary tumors due to limitations of current PET scanners, which are not of high enough resolution or designed specifically for breast imaging;
  • can predict treatment response, but studies are ongoing to determine how accurate these early predictions are;
  • can detect otherwise hidden tumors in the hard-to-visualize internal mammary nodal chain, which we believe will provide unique staging data to modify treatment regimens;
  • is more sensitive than MRI for finding soft tissue tumors;
  • can see through silicone implants.

The U-M currently is leading a multi-center trial in which >220 women have been entered to define the accuracy of PET in non-invasive staging of lymph nodes. In addition, newly developed PET biopsy and probe devices are under study.

Summary
Positron emission tomography scanning of the breast is one example of a growing family of tests that image the molecular alterations in tumors as alterations in tumor and organ function as opposed to simply the "form" of the lesion, or anatomy. While we have learned a good deal regarding the role of PET, much more study is necessary to refine the clinical role of the method.

Because of the cost of PET imaging (currently >$1500/scan), it is not a suitable screening test in most patients, particularly if high-resolution scanners are not available. However, the ability to non-invasively image and quantitate tumor physiology, on repeated instances, with a very low radiation dose, suggests that PET will have a growing and important role in breast cancer management, both in research and clinical studies over the coming years.

If you have a patient with newly diagnosed breast cancer scheduled for lymph node dissection, a patient scheduled for a bone marrow transplant for breast cancer, or a patient who will be receiving chemo-therapy for known tumor recurrence, they may be eligible for a PET research study. Please call 800-865-1125 for more information.

Current Investigation
Since describing the use of PET to image primary and metastatic breast cancer nearly a decade ago, we have been addressing a number of questions. The major questions currently under investigation include:

  • Can initial PET scan results predict out-come in patients with newly diagnosed breast cancer?
  • Can quantification of the PET scan metabolic rates in breast cancer before and during chemotherapy predict whether a specific tumor in a specific patient will respond to that specific therapy?
  • Can PET predict response to therapy for primary or metastatic tumors?
  • Can PET reliably assess treatment response in bone lesions?
  • Can PET detect cancer in radiodense breasts of younger women in which mammograms have problems?
  • Can PET detect breast cancer recurrence when mammograms are confusing?
  • Can PET measure changes in tumor blood flow to predict efficacy of treatment?
  • Can PET non-invasively stage the axilla for tumor involvement to eliminate the need for axillary dissection?
  • Can PET see through silicone implants?
  • Can PET detect metastatic disease?
  • What is the smallest tumor PET can detect, and can it reliably separate malignant from benign changes?
  • Can PET direct biopsies of lesions seen only with PET?
  • Can PET-sensitive probes guide the surgeon to remove only the cancer in the breast at the time of surgery, thus mini- mizing deformity?
  • Can the PET method work in multi-center trials?
  • What are the basic science correlates of the signal seen on PET imaging?
  • What is the best PET tracer for breast cancer?

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Additional References
Wahl RL. Overview of the current status of PET in breast cancer imaging. Quarterly Journal of Nuclear Medicine. 42(1):1-7, 1998.

Sugawara Y, Fisher SJ, Zasadny KR, Kison PV, Baker LH, Wahl RL. Preclinical and clinical studies of bone marrow uptake of fluorine-1-fluorodeoxyglucose with or without granulocyte colony-stimulating factor during chemotherapy. Journal of Clinical Oncology. 16(1):173-80, 1998.

Adler LP, Faulhaber PF, Schnur KC, Al-Kasi NL, Shenk RR. Axillary lymph node metastases: screening with [F-18]2-deoxy-2-fluoro-D-glucose (FDG) PET. Radiology. 203(2):323-7, 1997.

Wahl RL. "Clinical Oncology Update: The Emerging Role of PET." In: Principles & Practices of Oncology, 5th edition. DeVita VT, Hellman S, Rosenberg SA, (eds), Lippincott-Raven, Philadelphia, PA, 1997.

Avril N, Dose J, Janicke F, Ziegler S, Romer W, Weber W, Herz M, Nathrath W, Graeff H, Schwaiger M. Assessment of axillary lymph node involvement in breast cancer patients with positron emission tomography using radiolabeled 2-(fluorine-18)-fluoro-2-deoxy-D-glucose. Journal of the National Cancer Institute. 88(17):1204-9, 1996.

Avril N, Dose J, Janicke F, Bense S, Ziegler S, Laubenbacher C, Romer W, Pache H, Herz M, Allgayer B, Nathrath W, Graeff H, Schwaiger M. Metabolic characterization of breast tumors with positron emission tomography using F-18 fluorodeoxyglucose. Journal of Clinical Oncology. 14(6):1848-57, 1996.

Dehdashti F, Mortimer JE, Siegel BA, Griffeth LK, Bonasera TJ, Fusselman MJ, Detert DD, Cutler PD, Katzenellenbogen JA, Welch MJ. Positron tomographic assessment of estrogen receptors in breast cancer: comparison with FDG-PET and in vitro receptor assays. Journal of NuclearMedicine. 36(10):1766-74, 1995.

Wahl RL, Helvie MA, Chang AE, Andersson I. Detection of breast cancer in women after augmentation mammoplasty using fluorine-18-fluorodeoxyglucose-PET. Journal of Nuclear Medicine. 35(5):872-5, 1994.

Wahl RL, Zasadny KR, Helvie M, Hutchins GD,Weber B, Cody R. Metabolic monitoring of breast cancer chemohormonotherapy using positron emission tomography (PET): Initial evaluation. Journal of Clinical Oncology. 11(11):2101-2111, 1993.

Wahl RL, Cody R, Hutchins GD, Mudgett E. Primary and metastatic breast carcinoma: Initial clinical evaluation with PET with the radiolabeled glucose analog 2-[F-18]-fluoro-deoxy-2-D-glucose (FDG). Radiology. 179:765-770, 1991.

 

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Please note: The articles listed in the Cancer Center's News Archive are here for historical purposes. The information and links may no longer be up-to-date.