A 55-year-old woman presented to our center for restaging PET/CT. Her
history was significant for recurrent breast cancer in the mediastinum and
lungs. She initially underwent left mastectomy, adjuvant chemotherapy and
radiotherapy. She was started on palliative chemotherapy. Her initial staging
PET/CT showed subcentimeter medistinal lymph nodes (maximal SUV 8.4), right
lower lobe mass 1.4 × 1.2 cm (SUV 5.3), scattered subcentimeter nodules
in the lung. Her restaging scan with a PET/CT after chemotherapy showed
progressive disease with right axillary lymph nodes measuring 1 cm (SUV 2.0),
medistinal lymph nodes measuring 1 cm (SUV 3.6 to 10.1), right lower lobe mass
measuring 2.1 × 1.4 cm (SUV 7.1), relatively stable pulmonary nodules and
new left pleural effusion.
After a change in her chemotherapy regimen, her repeat PET/CT showed
increased AP window lymph nodes measuring up to 2.5 cm (however, SUV decreased
to 6.3 from 10.1), new subcarinal soft tissue measures 1.4 cm (SUV 5.5),
increase in size of epicardial lymph nodes to 1.1 cm (SUV 4.4), right lower
lobe mass increased in size to 2.3 × 1.7 cm (however, SUV decreased to
4.7 from 7.1), new pulmonary nodule, unchanged right axillary lymph nodes and
diffusely intense uptake of FDG activity in the bone marrow. This patient has
progressive disease based on the increasing size of the metastatic lesions. How
can we explain decreasing SUVs despite obvious progression of disease?
1: Axial CT (left column) and PET (right column) images demonstrating
progression of prevascular lymphadenopathy on anatomic images (second row is a
follow up imaging study). However, SUVs are declining despite visible increase
in intensity and extent of hypermetabolism. Note interval increased marrow
activity as depicted by increasing intensity of uptake in the ribs and thoracic
2: Axial CT (left column) and PET (right column) images demonstrating
progression of a lung lesion on anatomic images (second row is a follow up
imaging study). However, SUVs are declining despite visible increase in
intensity and extent of hypermetabolism.
Source: M. Ghesani
FDG-PET is shown to detect metastatic lesions and identify equivocal
lesions on conventional imaging. One of the limitations of PET/CT is the
sensitivity to detect malignant lesions decreases with low-grade tumors and
lesions <1 cm and in breast cancer, axillary metastasis.
A retrospective analysis in use of PET/CT in recurrent breast cancer
showed a sensitivity of 90%, specificity of 71% and accuracy of 83% with a
change in management being recorded in 51% of patients. In a prospective study
done by Souvatzoglou et al in recurrent breast cancer, PET/CT was positive in
67% of patients and negative in 10% of patients. Local recurrence was
identified in 12% of patients; metastatic sites were lymph nodes (36%), bone
(32%), liver (14%), lungs (10%), adrenal glands (3%) and pleura (2%). PET/CT
had changed the management in 33% of the patients.
Interval response to chemotherapy in nonosseous metastases can be in
the form of an increase in FDG avidity and increasing SUVs, indicating a
treatment failure. However, “steal phenomenon” occurs when an
increased uptake of FDG is noted in the bone marrow with relatively lower
available FDG activity to the nonosseous metastatic lesion. This steal
phenomenon could be due to the effect of chemotherapy or usage of growth
factors. This case illustrates steal phenomenon and importance of the need to
correlate overall interval change on both anatomic and functional imaging and
not solely rely on SUVs as a marker of either a favorable response or
progression of disease.
Vamsee Torri, MD, is a Fellow in Hematology/Oncology at St.
Luke’s-Roosevelt Hospital Center.
Iwao Tanaka, MD, is a Resident in Radiology at
St.Luke’s-Roosevelt Medical Center.
Rami Daya, MD, is a practicing oncologist in Brooklyn, N.Y.
Munir Ghesani, MD, is Associate Clinical Professor of Radiology at
Columbia University College of Physicians and Surgeons and Attending
Radiologist at St.Luke’s-Roosevelt Medical Center.
For more information:
- Radiographics. 2007;27:S215-S229.
- Cancer. 2006;107:2545-2551.
- J Nucl Med. Meeting Abstracts, 2008. 49:18P
- Informa Health Care. 2008. ISBN 0849380871,