Evaluation of a Hanging-Breast PET System for Primary Tumor Visualization in Patients With Stage I-III Breast Cancer: Comparison With Standard PET/CT.

OBJECTIVE: The purposes of this study were to evaluate the performance of a mammography with molecular imaging PET (MAMMI-PET) system for breast imaging in the hanging-breast position for the visualization of primary breast cancer lesions and to compare this method with whole-body PET/CT. SUBJECTS AND METHODS: Between March 2011 and March 2014, a prospective evaluation included women with one or more histologically confirmed primary breast cancer lesions (index lesions). After injection of 180-240 MBq of (18)F-FDG, whole-body PET/CT and MAMMI-PET acquisitions were performed, index lesions were scored 0, 1, or 2 for FDG uptake relative to background. Detection and FDG uptake were compared by breast length, maximal tumor diameter, affected breast quadrants, tumor grade, and histologic and immunologic sub-types. Finally, the two PET modalities were compared for detection of index lesions. RESULTS: For 234 index lesions (diameter, 5-170 mm), the overall sensitivity was 88.9% for MAMMI-PET and 91% for PET/CT (p = 0.61). Twenty-three (9.8%) index lesions located too close to the pectoral muscle were missed with MAMMI-PET, and 20 index lesions were missed with PET/CT. Lesion visibility on MAMMI-PET images was influenced by tumor grade (p = 0.034) but not by cancer subtype (p = 0.65). CONCLUSION: Although in an overall evaluation MAMMI-PET was not superior to PET/CT, MAMMI-PET does have higher sensitivity for primary breast cancer lesions within the scanning range of the device. Optimization of the positioning device may increase visualization of the most dorsal lesions.

Sequential (18)F-FDG PET/CT for early prediction of complete pathological response in breast and axilla during neoadjuvant chemotherapy.

PURPOSE: To investigate the value of response monitoring in both the primary tumour and axillary nodes on sequential PET/CT scans during neoadjuvant chemotherapy (NAC) for predicting complete pathological response (pCR), taking the breast cancer subtype into account. METHODS: In 107 consecutive patients 290 PET/CT scans were performed at baseline (PET/CT1, 107 patients), after 2 - 3 weeks of chemotherapy (PET/CT2, 85 patients), and after 6 - 8 weeks (PET/CT3, 98 patients). The relative changes in SUVmax (from baseline) of the tumour and the lymph nodes and in both combined (after logistic regression), and the changes in the highest SUVmax between scans (either tumour or lymph node) were determined and their associations with pCR of the tumour and lymph nodes after completion of NAC were assessed using receiver operating characteristic (ROC) analysis. RESULTS: A pCR was seen in 17 HER2-positive tumours (65 %), 1 ER-positive/HER2-negative tumour (2 %), and 16 triple-negative tumours (52 %). The areas under the ROC curves (ROC-AUC) for the prediction of pCR in HER2-positive tumours after 3 weeks were 0.61 for the relative change in tumours, 0.67 for the combined change in tumour and nodes, and 0.72 for the changes in the highest SUVmax between scans. After 8 weeks equivalent values were 0.59, 0.42 and 0.64, respectively. In triple-negative tumours the ROC-AUCs were 0.76, 0.84 and 0.76 after 2 weeks, and 0.87, 0.93 and 0.88 after 6 weeks, respectively. CONCLUSION: In triple-negative tumours a PET/CT scan after 6 weeks (three cycles) appears to be optimally predictive of pCR. In HER2-positive tumours neither a PET/CT scan after 3 weeks nor after 8 weeks seems to be useful. The changes in SUVmax of both the tumour and axillary nodes combined correlates best with pCR.

Combined use of ¹8F-FDG PET/CT and MRI for response monitoring of breast cancer during neoadjuvant chemotherapy.

PURPOSE: To explore the potential complementary value of PET/CT and dynamic contrast-enhanced MRI in predicting pathological response to neoadjuvant chemotherapy (NAC) of breast cancer and the dependency on breast cancer subtype. METHODS: We performed (18)F-FDG PET/CT and MRI examinations before and during NAC. The imaging features evaluated on both examinations included baseline and changes in (18)F-FDG maximum standardized uptake value (SUVmax) on PET/CT, and tumour morphology and contrast uptake kinetics on MRI. The outcome measure was a (near) pathological complete response ((near-)pCR) after surgery. Receiver operating characteristic curves with area under the curve (AUC) were used to evaluate the relationships between patient, tumour and imaging characteristics and tumour responses. RESULTS: Of 93 patients, 43 achieved a (near-)pCR. The responses varied among the different breast cancer subtypes. On univariate analysis the following variables were significantly associated with (near-)pCR: age (p = 0.033), breast cancer subtype (p < 0.001), relative change in SUVmax on PET/CT (p < 0.001) and relative change in largest tumour diameter on MRI (p < 0.001). The AUC for the relative reduction in SUVmax on PET/CT was 0.78 (95% CI 0.68-0.88), and for the relative reduction in tumour diameter at late enhancement on MRI was 0.79 (95% CI 0.70-0.89). The AUC increased to 0.90 (95% CI 0.83-0.96) in the final multivariate model with PET/CT, MRI and breast cancer subtype combined (p = 0.012). CONCLUSION: PET/CT and MRI showed comparable value for monitoring response during NAC. Combined use of PET/CT and MRI had complementary potential. Research with more patients is required to further elucidate the dependency on breast cancer subtype.

Accuracy of 18F-FDG PET/CT for primary tumor visualization and staging in T1 breast cancer.

BACKGROUND: The aim of this study was to assess the accuracy of 18F-FDG PET/CT in T1 breast cancer regarding visualization of the primary tumor and the detection of locoregional and distant metastases. METHODS: Sixty-two women with invasive T1 breast cancer underwent a PET/CT. Image acquisition of the thorax was done in prone position with hanging breasts, followed by whole-body scanning in supine position. Primary tumor FDG uptake was evaluated and compared with clinical and histopathological characteristics. Presence of locoregional and distant metastases was assessed and compared with conventional imaging procedures. RESULTS: The primary tumor was visible with PET/CT in 54 (87%) of 62 patients, increasing from 59% (10/17) in tumors ≤ 10 mm to 98% (44/45) in tumors over 10 mm. All triple negative and HER2-positive tumors and 40/48 (83%) ER-positive/HER2-negative tumors were visualized. Sensitivity and specificity of PET/CT in the detection of axillary metastases were 73% and 100%, respectively. PET/CT depicted periclavicular nodes in two patients. Of 12 distant lesions, one was confirmed to be a lung metastasis, three were false positive, and eight were new primary proliferative lesions. CONCLUSION: Using optimal imaging acquisition, the majority of T1 breast carcinomas can be visualized with PET/CT. Specificity in the detection of axillary metastases is excellent, but sensitivity appears to be limited. Additional whole body imaging has a low yield in this specific patient group.

Pre-chemotherapy 18F-FDG PET/CT upstages nodal stage in stage II-III breast cancer patients treated with neoadjuvant chemotherapy.

In breast cancer patients treated with neoadjuvant chemotherapy (NAC) the number of tumor-positive nodes can no longer reliably be determined. Furthermore, ultrasound (US) seems suboptimal for the detection of N3-disease. Therefore we assessed the proportion of breast cancer patients treated with NAC in which pre-chemotherapy 18F-FDG PET/CT detected ≥4 axillary nodes or occult N3-disease, upstaging nodal status and changing risk estimation for locoregional recurrence (LRR). Conventional regional staging consisted of US with fine needle aspiration and/or sentinel lymph node biopsy. Patients were classified as low-risk (cT2N0), intermediate-risk (cT0N1, cT1N1, cT2N1, cT3N0), or high-risk (cT3N1, cT4, cN2-3) for LRR. The presence and number of FDG-avid nodes were evaluated and the proportion of patients that would be upstaged by PET/CT, based on detection of ≥4 FDG-avid axillary nodes defined as cN2(4+) or occult N3-disease, was calculated. In total, 87 of 278 patients were considered high-risk based on conventional staging. PET/CT detected occult N3-disease in 5 (11 %) of 47 low-risk patients. In 144 intermediate-risk patients, PET/CT detected ≥4 FDG-avid nodes in 24 (17 %) patients and occult N3-disease in 22 (15 %) patients, thereby finally upstaging 38 (26 %) of intermediate-risk patients. Of 43 (23 %) upstaged patients, 18 were ypN0, 12 were ypN1, and 13 were ypN2-3. Pre-chemotherapy PET/CT is valuable for selection of breast cancer patients at high risk for LRR. In our population, 23 % of patients treated with NAC were upstaged to the high-risk group based on PET/CT information, potentially benefiting from regional radiotherapy.

Early assessment of axillary response with ¹8F-FDG PET/CT during neoadjuvant chemotherapy in stage II-III breast cancer: implications for surgical management of the axilla.

BACKGROUND: If all initially node-positive patients undergo axillary lymph node dissection (ALND) after neoadjuvant chemotherapy (NAC), overtreatment may occur in patients with complete response. Positron emission tomography-computed tomography (PET/CT) during NAC may predict axillary response and select patients appropriate for less invasive treatment after NAC. We evaluated the value of sequential (18)F fluorodeoxyglucose (FDG) PET/CTs during NAC for axillary response monitoring in stage II-III breast cancer. METHODS: A total of 219 PET/CTs were performed in 80 patients with cytology-proven, node-positive disease at baseline (PET/CT1, n = 80) and twice during NAC (PET/CT2 n = 62, PET/CT3, n = 77). The relative changes in maximum standardized uptake value (SUVmax) of axillary nodes were examined for their ability to assess pathological response. All patients underwent ALND after chemotherapy, and complete axillary response (pCR), defined as absence of isolated tumor cells and of micro- and macrometastases, served as the reference standard. RESULTS: A total of 32 (40 %) patients experienced axillary pCR. The relative decrease in SUVmax was significantly higher in patients with pCR than in those without, both on PET/CT2 (p < 0.001) and PET/CT3 (p = 0.025). The area under the receiver operating characteristic curve values for PET/CT2 and PET/CT3 were 0.80 (95 % confidence interval 0.68-0.92) and 0.65 (95 % confidence interval 0.52-0.79), respectively. A relative decrease of ≥60 % on PET/CT2 had an excellent specificity (35 of 37, 95 %), a high positive predictive value (12 of 14, 86 %), and a sensitivity of 48 %-that is, it accurately identified histologic pCR in 12 of 25 patients with disease that responded to therapy. CONCLUSIONS: (18)F-FDG PET/CT early during NAC is useful for axillary response monitoring in cytology-proven node-positive breast cancer because it identifies pathological response, thus permitting ALND to be spared.

Locoregional lymph node involvement on 18F-FDG PET/CT in breast cancer patients scheduled for neoadjuvant chemotherapy.

The optimal method for locoregional staging in patients treated with neoadjuvant chemotherapy (NAC), usually ultrasound (US) and pre- or post-chemotherapy sentinel lymph node biopsy (SLNB), remains subject of debate. The aim of this study was to assess the value of 18F-FDG PET/CT for detecting locoregional lymph node metastases in primary breast cancer patients scheduled for NAC. 311 breast cancer patients, scheduled for NAC, underwent PET/CT of the thorax in prone position with hanging breasts. A panel of four experienced reviewers examined PET/CT images, blinded for other diagnostic procedures. FDG uptake in locoregional nodes was determined qualitatively using a 4-point scale (0 = negative, 1 = questionable, 2 = moderately intense, and 3 = very intense). Results were compared with pathology obtained by US-guided fine needle aspiration or SLNB prior to NAC. All FDG-avid extra-axillary nodes were considered metastatic, based on the previously reported high positive predictive value of the technique. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG-avid nodes for the detection of axillary metastases (score 2 or 3) were 82, 92, 98, 53, and 84 %, respectively. Of 28 patients with questionable axillary FDG uptake (score 1), 23 (82 %) were node-positive. Occult lymph node metastases in the internal mammary chain and periclavicular area were detected in 26 (8 %) and 32 (10 %) patients, respectively, resulting in changed regional radiotherapy planning in 50 (16 %) patients. In breast cancer patients scheduled for NAC, PET/CT renders pre-chemotherapy SLNB unnecessary in case of an FDG-avid axillary node, enables axillary response monitoring during or after NAC, and leads to changes in radiotherapy for a substantial number of patients because of detection of occult N3-disease. Based on these results, we recommend a PET/CT as a standard staging procedure in breast cancer patients scheduled for NAC.

18F-FDG PET/CT as a staging procedure in primary stage II and III breast cancer: comparison with conventional imaging techniques.

The aim of the present study was to investigate if 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) outperforms conventional imaging techniques for excluding distant metastases prior to neoadjuvant chemotherapy (NAC) treatment in patients with stage II and III breast cancer. Second, we assessed the clinical importance of false positive findings. One hundred and fifty four patients with stage II or III breast cancer, scheduled to receive NAC, underwent an 18F-FDG PET/CT scan and conventional imaging, consisting of bone scintigraphy, ultrasound of the liver, and chest radiography. Suspect additional lesions at staging examination were confirmed by biopsy and histopathology and/or additional imaging. Metastases that were detected within 6 months after the PET/CT scan were considered evidence of occult metastasis, missed by staging examination. Forty-two additional distant lesions were seen in 25 patients with PET/CT and could be confirmed in 20 (13%) of 154 patients. PET/CT was false positive for 8 additional lesions (19%) and misclassified the presence of metastatic disease in 5 (3%) of 154 patients. In 16 (80%) of 20 patients, additional lesions were exclusively seen with PET/CT, leading to a change in treatment in 13 (8%) of 154 patients. In 129 patients with a negative staging PET/CT, no metastases developed during the follow-up of 9.0 months. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of PET/CT in the detection of additional distant lesions in patients with stage II or III breast cancer are 100, 96, 80, 100, and 97%, respectively. FDG PET/CT is superior to conventional imaging techniques in the detection of distant metastases in patients with untreated stage II or III breast cancer and is associated with a low false positive rate. PET/CT may be of additional value in the staging of breast cancer prior to NAC.

Additional value of 18F-FDG PET/CT response evaluation in axillary nodes during neoadjuvant therapy for triple-negative and HER2-positive breast cancer.

BACKGROUND: 18F-FDG PET/CT can monitor metabolic activity in early breast cancer during neoadjuvant systemic therapy (NST), but it is unknown if the metabolic breast and axillary response differ. We evaluated the correlation between metabolic breast and axillary response at various time points during NST. Furthermore, we analysed if the combined metabolic response improves pathologic complete response (pCR) prediction compared to using the metabolic breast response alone. METHODS: 18F-FDG PET/CT was performed at baseline (PET1), 2-3 weeks (PET2), and 6-8 weeks (PET3) of NST in patients with triple-negative (TN) and HER2-positive node-positive breast cancer. SUVmax and ∆SUVmax were determined separately for breast and axilla. Spearman's correlation coefficients (r) between both localisations were calculated. The accuracy of pCR total (ypT0/is,ypN0) prediction using the metabolic response in breast, axilla or both was examined using logistic regression analysis. RESULTS: Hundred-five patients were included: 45 TN and 60 HER2-positive tumours. The metabolic response in breast and axilla correlated moderately in TN tumours (r = 0.57) using ∆SUVmax between PET1-PET3 and poorly in HER2-positive tumours (r = 0.49) using SUVmax at PET2. In TN tumours, metabolic breast response predicted pCR well without improvement after adding axillary response (c-index 0.82 versus 0.85, p = 0.63). In HER2-positive tumours, metabolic breast response predicted pCR poorly with improvement after adding axillary response (c-index 0.64 versus 0.72, p = 0.06). CONCLUSIONS: 18F-FDG PET/CT response during NST differs between breast and axilla. In TN tumours, pCR total prediction can be made independent of metabolic axillary response. In HER2-positive tumours, axillary response may improve pCR total prediction. These findings may help guide PET/CT-response-based changes during NST. TRIAL REGISTRATION: NTR NTR1797 . Registered 29 May 2009, retrospectively registered.

Additional Prone 18F-FDG PET/CT Acquisition to Improve the Visualization of the Primary Tumor and Regional Lymph Node Metastases in Stage II/III Breast Cancer.

PURPOSE: To prospectively compare prone and supine acquired 18F-FDG PET/CT for visualization of primary tumors and regional lymph nodes in stage II/III breast cancer patients. MATERIALS AND METHODS: One hundred ninety-eight patients were included consecutively from August 2010 to April 2012. One hour after administration of 180-240 MBq 18F-FDG, PET/CT images of the thorax were firstly acquired in prone position. Subsequently, a standard PET/CT in supine position from skull base to thighs was made. Both sets of images were tested in a univariate and a multivariate analysis for the number of lesions per breast or lymph node (LN) region and anatomical mismatch between PET and CT images. RESULTS: Images in prone position showed less compression of breast tissue, more primary tumor (PT) multifocality (P < 0.001) and more avid axillary LNs (P < 0.001) compared with supine position. Anatomical mismatch of the axillary LN metastases was found more often on supine PET/CT images compared with prone (P = 0.004). Prone images showed a smaller PT functional volume compared with supine position (P < 0.001). CONCLUSIONS: Prone position PET/CT improved the visualization of PT multifocality and the number of detected axillary lymph nodes. Therefore, it is a valuable addition to standard supine PET/CT in the protocol for locoregional assessment in stage II/III breast cancer patients.

Evaluating heterogeneity of primary tumor (18)F-FDG uptake in breast cancer with a dedicated breast PET (MAMMI): a feasibility study based on correlation with PET/CT.

PURPOSE: The aim of the study was to evaluate the heterogeneity of primary tumor F-fluorodeoxyglucose ((18)F-FDG) uptake in breast cancer patients using a dedicated breast PET. PATIENTS AND METHODS: A positron emission tomography/computed tomography (PET/CT) of the thorax was performed 60 min after administration of 180-240 MBq of (18)F-FDG in patients with breast cancer. Subsequently, 110 min after injection, a scan was taken with a dedicated high-resolution breast PET [MAMmography with Molecular Imaging (MAMMI)]. Both procedures were performed with the patients in the prone position. Four-point scores were used to compare the intensity (0: none; 1: mild; 2: moderate; 3: high) and heterogeneity (0: none; 1: mild; 2: moderate; 3: high) of (18)F-FDG uptake between PET/CT and MAMMI images. RESULTS: Thirty-five patients in whom the primary tumor was visualized on both scans were included in this analysis. The mean primary tumor size was 35.1 mm (range 10-108 mm). The mean intensity score was similar on both devices (2.4 for PET/CT and 2.3 for MAMMI; P=0.439), but the mean heterogeneity score on MAMMI images was significantly higher (PET/CT 1.9 vs. MAMMI 2.3; P=0.005). MAMMI showed a higher heterogeneity score in 11 (31%) of 35 patients, especially in tumors with moderate or high intensity. Significantly higher heterogeneity scores on both PET/CT and MAMMI were seen in large tumors (P=0.005 and 0.014, respectively) and in tumors with high intensity scores (P=0.012 and P<0.001, respectively). CONCLUSION: Heterogeneous tumor (18)F-FDG uptake in breast cancer is frequently observed, particularly in large tumors with intense (18)F-FDG uptake. It is more often seen on MAMMI PET than on conventional PET/CT. Although the observed heterogeneity should be proven histopathologically, this finding offers a rationale for (18)F-FDG-guided biopsies.

Does the pretreatment tumor sampling location correspond with metabolic activity on 18F-FDG PET/CT in breast cancer patients scheduled for neoadjuvant chemotherapy?

PURPOSE: To define the correlation between the core biopsy location and the area with highest metabolic activity on 18F-FDG PET/CT in stage II-III breast cancer patients before neoadjuvant chemotherapy. Also, we would like to select a subgroup of patients in which PET/CT information may optimize tumor sampling. METHODS: A PET/CT in prone position was acquired in 199 patients with 203 tumors. The distance and relative difference in standardized uptake value (SUV) between core biopsy localization (indicated by a marker) and area with highest degree of FDG uptake were evaluated. A distance ≥ 2 cm and a relative difference in SUV ≥ 25% were considered clinically relevant and a combination of both was defined as non-correspondence. Non-correspondence for different tumor characteristics (TNM stage, lesion morphology on MRI and PET/CT, histology, subtype, grade, and Ki-67) was assessed. RESULTS: Non-correspondence was found in 28 (14%) of 203 tumors. Non-correspondence was significantly associated with T-stage, lesion morphology on MRI and PET/CT, tumor diameter, and histologic type. It was more often seen in tumors with a higher T-stage (p = 0.028), diffuse (non-mass) and multifocal tumors on MRI (p = 0.001), diffuse and multifocal tumors on PET/CT (p<0.001), tumors >3 cm (p<0.001), and lobular carcinomas (p<0.001). No association was found with other features. CONCLUSION: Non-correspondence between the core biopsy location and area with highest FDG uptake is regularly seen in stage II-III breast cancer patients. PET/CT information and possibly FDG-guided biopsies are most likely to improve pretreatment tumor sampling in tumors >3 cm, lobular carcinomas, and diffuse and multifocal tumors.

Association of perioperative troponin and atrial fibrillation after coronary artery bypass grafting.

OBJECTIVES: Prediction of atrial fibrillation (AF) after coronary artery bypass grafting (CABG) may lead to preventive or early treatment and improved outcome. We investigated the association of serial perioperative cardiac troponin T (cTNT) measurements with postoperative AF in patients undergoing CABG. METHODS: In a retrospective analysis of prospectively collected data, 3148 patients undergoing elective CABG were evaluated. cTNT values were routinely determined before the start of surgery (cTNT0), at arrival on the intensive care unit (cTNT1) and 8-12 h later (cTNT2). Measurement of cTNT was continued until the peak value was reached. The development of AF during hospital stay was scored. The association between cTNT (cTNT0, cTNT1, cTNT2 and cTNTmax in first 48 h) and AF was calculated in univariable and multivariable analysis. RESULTS: AF occurred in 1080 (34%) patients. cTNT0, cTNT2 and cTNTmax were significantly and positively associated with postoperative AF (P < 0.001) in a univariable analysis, whereas a trend was seen for cTNT1 (P = 0.051). Advanced age, inotropic support and postoperative infection were independently associated with postoperative AF after logistic regression analysis, but cTNT was not. Categorizing patients by inotropic support into categories of inotropic support duration (none, <48 h, >48 h), the mean cTNT values were significantly higher among patients with AF in each category (all P < 0.001). Perioperative cTNT was significantly higher in patients with postoperative complications, longer hospital stay and reduced in-hospital survival. CONCLUSIONS: Perioperative cTNT is univariably associated with postoperative AF after CABG, but not independently. Further, no clinically useful cut-off point for preventive or early treatment could be identified. Both perioperative cTNT and postoperative AF are associated with negative outcome and prolonged hospital stay.

FDG PET/CT during neoadjuvant chemotherapy may predict response in ER-positive/HER2-negative and triple negative, but not in HER2-positive breast cancer.

BACKGROUND: Response monitoring with MRI during neoadjuvant chemotherapy (NAC) in breast cancer is promising, but knowledge of breast cancer subtype is essential. The aim of the present study was to evaluate the relevance of breast cancer subtypes for monitoring of therapy response during NAC with 18F-FDG PET/CT. METHODS: Evaluation included 98 women with stages II and III breast cancer. PET/CTs were performed before and after six or eight weeks of NAC. FDG uptake was quantified using maximum standardized uptake values (SUVmax). Tumors were divided into three subtypes: HER2-positive, ER-positive/HER2-negative, and triple negative. Tumor response at surgery was assessed dichotomously (presence or absence of residual disease) and ordinally (breast response index, representing relative change in tumor stage). Multivariate regression and receiver operating characteristic (ROC) analyses were employed to determine associations with pathological response. RESULTS: A (near) complete pathological response was seen in 19 (76%) of 25 HER2-positive, 7 (16%) of 45 ER-positive/HER2-negative, and 20 (71%) of 28 triple negative tumors. Multivariate regression of pathological response indicated a significant interaction between change in FDG uptake and breast cancer subtype. The area under the ROC curve was 0.35 (0.12-0.64) for HER2-positive, 0.90 (0.76-1.00) for ER-positive/HER2-negative, and 0.96 (0.86-1.00) for triple negative tumors. We found no association between age, stage, histology, or baseline SUVmax and pathological response. CONCLUSION: Response monitoring with PET/CT during NAC in breast cancer seems feasible, but is dependent on the breast cancer subtype. PET/CT may predict response in ER-positive/HER2-negative and triple negative tumors, but seems less accurate in HER2-positive tumors.

FDG-avid sclerotic bone metastases in breast cancer patients: a PET/CT case series.

Distant metastases from breast cancer most frequently occur in the skeleton. Although 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET), with or without computed tomography (CT), is superior to bone scintigraphy for the detection of osteolytic bone metastases, it has been reported that sclerotic bone metastases frequently show no or only a low degree of FDG uptake on PET and PET/CT. Since both lytic and sclerotic metastases can occur in breast cancer patients, bone scintigraphy may remain of additional value in these patients. In this case series, we describe four breast cancer patients in whom FDG PET/CT has clearly visualized sclerotic bone metastases because of increased FDG uptake. Not so much the type of metastasis (sclerotic or lytic), but possibly the characteristics of the primary tumor or treatments prior to the FDG PET/CT scan might influence the degree of FDG uptake of bone metastases. The ability to detect sclerotic bone metastases based on increased FDG uptake supports the use of FDG PET/CT as a staging procedure in breast cancer patients, but knowledge of factors determining the visibility of bone metastases with FDG PET/CT is crucial.