CASE REPORT 
Annals of Nuclear Medicine Vol. 12, No. 5, 293-296, 1998 
99mTc-tetrofosmin uptake in bone metastases from breast cancer 
Teruhiko TAKAYAMA,*1 Seigo KINUYA,*2 Makoto SUGIYAMA,*3 Atsushi HASHIBA,*4 Ryoyu TAKEDA *5 Masahisa ONOGUCHl,*1 Shiro TsUJI*1 and Norihisa TONAMI*2 
*lDepartment ofHealth Science and *2Department of Nuclear Medicine, School of Medicine, Kanazawa University 
*3Department ofRadiology, *4Department ofSurgery and *5Department oflnternal Medicme Hokunku Hospltal 
99mTc-tetrofosmin myocardial imaging was performed in a 62-year-old woman who had undergone standard radical mastectomy for right breast cancer 6 years ago. Although the result was negative for the ischemic heart disease, it showed abnormal accumulation corresponding to the bone metastases in the spine. We believe that 99mTc-tetrofosmin imaging is helpful in detecting bone metastases from breast cancer. 
Key words: 99mTc-tetrofosmin, breast cancer, bone metastasis, 99mTc-MDP 
INTRODUCTION 
MANY AUTHORS have reported that 99mTc-tetrofosmin is useful as tumor-seeking agent for lung,1-6 breast,7-10 thyroid11-14 and other malignant tumors.15-20 In some cases, not only the primary lesion but also its lymph node metastases were delineated in patients with lung cancer, thyroid cancer and breast cancer, but there is no report on the visualization of bone metastases from breast cancer. We present a case of high tracer uptake in bone metastasis from breast cancer. 
CASE REPORT 
A 62-year-old woman underwent standard radical mastectomy for right breast cancer (infiltrating ductal carcinoma) 6 years ago. In the follow-up, she complained of the left chest pain. Hematological examination revealed a gradual increase in serum carcinoembryonic antigen (CEA) and it reached 11.1 ng/ml (normal, <10 ng/ml). Physical examination, radiographic examination and electrocar-diogram (ECG) showed no significant finding. In order to rule out ischemic heart disease 99mTc-tetrofosmin myo-cardial imaging was performed with a gamma camera (Starcam 400AC/T, General Electric, Milwaukee, USA) 
Received May 21, 1998, revision accepted July l. 1998. For reprint contact: Teruhiko Takayama, M.D., Department of Health Science, School of Medicine. Kanazawa University, Kotatsuno 5-11-80, Kanazawa 920-0942, JAPAN. E-mail: teruhiko@kenroku.kanazawa-u.acjp 
equipped with a low-energy all purpose parallel-hole collimator. Fifteen minutes after the intravenous injection of 740 MBq 99mTc-tetrofosmin, an anterior thoracic planar image (512 x 512 matrix, 1500 kcounts) was acquired. The energy discriminator was centered on 140 keV with a 20% window. Subsequently single photon emission computed tomography (SPECT) data were acquired in thirty-two projections images of 15 sec each in an 180deg. arc extending a 30deg. right anterior oblique (RAO) to the left posterior oblique (LPO) projection (nearly 200 kcounts per pixel). All data were prefiltered with a Hanning filter with a cutoff frequency of 0.8 cycles/pixel. Myocardial SPECT images were reconstructed by means of a filtered backprojection algorithm and Ramp filter. No attenuation or scatter correction was performed. Since abnormal tracer accumulation was suspected in the middle lower chest on the anterior planar image, posterior planar images (256 x 1024 matrix, 1500 kcounts) and SPECT images with 360deg. rotation were repeatedly acquired (Fig. 1 ). The SPECT images clearly showed intense tracer activity in a location corresponding to the spine (Fig. 2). 99mTc-MDP scintigraphy showed increased uptake in the left first rib, the 7th and 8th thoracic vertebrae, the right 8th rib and the right sacroiliac joint, indicating multiple bone metastases from breast cancer (Fig. 3). X-ray CT, which was performed to exclude lung and lymph node metastases, delineated osteolytic changes in the right sacroiliac joint and the right rib with a surrounding small soft tissue density mass (Fig. 4). To our great surprise, the thoracic vertebral lesion was very faint on the CT image. No histological examination of the left first rib has been performed and a review of the CT image did not provide any useful information on this bone. 
DISCUSSION 
The tumor-seeking properties of 201Tl and 99mTc-methoxybutylisonitrile (MIBI) are well known. Com-pared with 201Tl. 99mTc has some advantages such as higher proton energy and a shorter half life, resulting in a smaller radiation dose, larger injected dose and better image quality. Furthermore, as an alternative to 99mTc-MIBI, 99mTc-tetrofosmin is currently used for myocardial perfusion imaging due to its rapid clearance from both the lungs and liver, resulting in earlier high-quality myocardial images. 99mTc-tetrofosmin uptake in malignant tumors has been demonstrated by various authors.1-20 Some authors re-ported that not only the primary lesion but also its lymph node metastases were delineated. Schillaci et al.5 reported 99mTc-tetrofosmin accumulation in a patient with lung cancer (adenocarcinoma) and its brain and mediastinal lymph node metastases. Kosuda et al.11  reported a case of follicular thyroid carcinoma in which lung, bone and lymph node metastases were delineated by both 99mTc-MIBI and 99mTc-tetrofosmin. Klain et al.12 reported that 99mTc-tetrofosmin imaging depicted the metastases in the lymph nodes of the neck and in the chest wall, skull and spine in patients with thyroid cancer. Lind et al.13 revealed that the overall sensitivity of 99mTc-tetrofosmin in detecting distant metastases from thyroid cancer was 86%. On the other hand, Rambaldi et al.7 firstly reported 99mTc-tetrofosmin uptake in breast cancer and its lymph node metastases. Mansi et al.8 demonstrated the sensitivity of 92.8% and 91.6% in 99mTc-tetrofosmin imaging for the detection of breast cancer and its axillary lymph node metastases, respectively. On the other hand, Akcay et al.10 reported 93% (13/17) and 60% (6/1 7) sensitivity in the detection of breast cancer and its axillary lymph node metastases, respectively. Although 99mTc-tetrofosmin uptake in lymph node metastases was reported, there is no report on 99mTc-tetrofosmin uptake in bone metastases from breast cancer. The precise mechanisms of uptake of 99mTc-tetrofosmin by tumor tissue has not been sufficiently elucidated, but its tumor localization may be explained on the basis of such factors as regional blood fiow and mitochondrial content.1,21 In addition, it was also reported that accumu-lation of this tracer in breast tumor cells in vitro is related to the P-glycoprotein similar to MIBI.22 99mTc-MDP scintigraphy is an excellent method for delineating tumor-bearing lesions in the whole body. It can be used not only in the follow-up of bone metastases from malignant tumors but also as scintimammography in detecting the primary breast cancer.23 In this case, 99mTc-MDP scintigraphy clearly demonstrated the location of increased tracer uptake: the left first rib, the 7th and 8th thoracic vertebrae, the right 8th rib and the right sacroiliac joint. On the other hand, 99mTc-tetrofosmin imaging showed indeterminate location of increased uptake. With the help of 99mTc-MDP scintigraphy, it was considered that 99mTc-tetrofosmin accumulated in the right 8th rib as well as the thoracic vertebral lesions. There was a discrepancy between 99mTc-MDP and 99mTc-tetrofosmin imaging on tracer uptake in the left first rib. 99mTc-tetrofosmin imaging showed no abnormality in the left first rib, whereas 99mTc-MDP scintigraphy showed greatly increased uptake. Review of the CT images did not provide any useful information on this bone. As no histological examination of the left first rib has been performed, we cannot explain the cause of the difference between the results for the two tracers. Further studies with both tracers are therefore required for assessing malignant tumors and their metastases. In conclusion 99mTc-tetrofosmin imaging would be helpful in detecting the bone metastases from breast cancer. Therefore, in the interpretation of 99mTc-tetro-fosmin myocardial imaging, attention should be paid to excluding the presence of bone metastases. 
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