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Solitary sternal focus with FDG activity found on PET scan after treatment for recurrent breast cancer
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A 36-year-old woman originally presented in January 2007 with a palpable mass. She underwent bilateral mammogram and left breast ultrasound that revealed a 1.6 cm mass and a 0.8 cm left axillary lymph node. A subsequent ultrasound guided core biopsy of the left breast mass and an aspiration of the left axillary lymph node revealed invasive ductal carcinoma with the metastatic involvement of the left axillary lymph node.
The patient was started on neoadjuvant doxorubicin hydrochloride (Adriamycin, Pharmacia/UpJohn) and cyclophosphamide in an attempt for breast preservation; however, no significant change was noted on follow-up imaging.
The patient subsequently underwent sentinel lymph node biopsy and mastectomy in May 2007, at which time a 1.5 cm invasive ductal carcinoma was noted in the left breast with positive estrogen, progesterone, and HER2-neu receptors. Resection margins were negative. Two sentinel lymph nodes were without metastatic disease. No axillary dissection was performed at that time. Her postoperative course was uneventful, and she was subsequently initiated on weekly trastuzumab (Herceptin, Genentech) and docetaxel (Taxotere, Sanofi-Aventis).
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Photo by M Ghesani |
At the time of the initial radiation therapy consultation, axillary dissection was recommended. It was subsequently performed and showed no evidence of metastases in 12 axillary nodes. She went on to complete weekly docetaxel in October 2007 and eventually one year of trastuzumab treatment. She repeatedly declined adjuvant radiation and hormone therapy despite multiple recommendations because she was considering conceiving a child.
She noted a small, bead-like lump located adjacent to the left mastectomy scar at the beginning of 2009, but did not seek medical attention. In July, she saw a plastic surgeon to discuss reconstruction options.
Later, biopsy confirmed local recurrence demonstrating poorly differentiated infiltrating ductal carcinoma. The mass was resected with margins free of disease. The follow-up PET/CT scan one month later demonstrated no evidence of metastatic adenopathy at left mastectomy site, but revealed a tiny focus of FDG uptake in the sternum that was suspicious for a small osseous lesion.
A recommended follow-up bone scan showed no discrete focus of uptake as intense as seen on the PET/CT examination. However, subsequent MRI of the sternum (not shown) confirmed metastatic disease. She was again recommended for radiation therapy, which she accepted. She will soon start her treatment with the further plan to subsequently proceed with hormone therapy.
Discussion
The most common cause of the metastatic bone disease in women is breast cancer. It usually presents with the thoracic or lumbosacral involvement. Isolated metastases to the sternum, however, are less common. The management of the disease depends on the whether or not there is a control of the primary lesion.
A surgical approach is usually taken in the absence of clinical and radiographic evidence of systemic disease. A case of successful operative management of a solitary metastasis in the sternal body with reconstruction of the anterior chest wall was described by Nakamura et al. In this case, the patient had a left modified mastectomy. This approach was taken because the primary lesion was controlled and the sternal lesion was isolated. A subtotal sternotomy with the creation of an artificial chest wall from mesh was performed.
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Photo by M Ghesani |
Most importantly a solitary metastasis must be differentiated from other sternal disorders, such as necrotic tissue or benign lesions, as reported by Vriens et al. Vriens described a case series with three women. The bone scan for the evaluation of the sternal pain revealed a solitary hot spot in the sternum in all cases. In the final diagnosis, one patient had nonmalignant reactive changes, which require no further therapy; one patient had a bone metastasis, which was treated with radiation therapy and tamoxifen; and one patient had radionecrotic tissue, which was treated with hyperbaric therapy.
In the past, bone scan had been the most widely used modality to identify bone involvement in patients with breast cancer. With the development of PET, this modality became increasingly popular for the identifying bone metastasis. In a meta-analysis of six studies that compared PET (without CT) with skeletal scintigraphy, pooled patient-based sensitivity of PET was 81% and specificity was 93%. For bone scan, pooled patient-based sensitivity was 78% and specificity was 79%.
Cook et al have evaluated 23 patients with metastatic bone disease from breast cancer and found that PET was better overall for the detection of lytic metastases; however, sclerotic lesions were better seen by bone scan.
In current practice, PET is done on dual modality, integrating with CT. PET/CT is likely to improve accuracy, since CT can detect sclerotic lesions and PET can detect metabolic activity associated with lytic lesions. Thus, it appears that dual modality PET/CT imaging has an advantage over the bone scan.
Liana Makarian, MD, is an Oncology Fellow at St Luke’s-Roosevelt Hospital Center.
Andrew Evans, MD, is an Assistant Professor of Radiation Oncology, Albert Einstein College of Medicine and Attending in Radiation Oncology, St. Luke’s-Roosevelt Hospital Center.
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:
- Cook GJ. J Clin Oncol. 1998;16:3375-3379.
- Costelloe CM. Lancet Oncol. 2009;10:606-614
- Lee L. Curr Oncol. 2008;15:193-195
- Nakamura H. Surgery Today. 2007;37:1083-1086
- Shie P. Clin Nuc Med. 2008;33:97-101.
- Vriens BH. Ned Tijdschr Geneeskd (Dutch). 2007;151:1909-1914.