Assessment of a statistical AIF extraction method for dynamic PET studies with 15O water and 18F fluorodeoxyglucose in locally advanced breast cancer patients.

Blood flow-metabolism mismatch from dynamic positron emission tomography (PET) studies with [Formula: see text]-labeled water ([Formula: see text]) and [Formula: see text]-labeled fluorodeoxyglucose (FDG) has been shown to be a promising diagnostic for locally advanced breast cancer (LABCa) patients. The mismatch measurement involves kinetic analysis with the arterial blood time course (AIF) as an input function. We evaluate the use of a statistical method for AIF extraction (SAIF) in these studies. Fifty three LABCa patients had dynamic PET studies with [Formula: see text] and FDG. For each PET study, two AIFs were recovered, an SAIF extraction and also a manual extraction based on a region of interest placed over the left ventricle (LV-ROI). Blood flow-metabolism mismatch was obtained with each AIF, and kinetic and prognostic reliability comparisons were made. Strong correlations were found between kinetic assessments produced by both AIFs. SAIF AIFs retained the full prognostic value, for pathologic response and overall survival, of LV-ROI AIFs.

Between-patient and within-patient (site-to-site) variability in estrogen receptor binding, measured in vivo by 18F-fluoroestradiol PET.

UNLABELLED: Heterogeneity of estrogen receptor (ER) expression may be an important predictor of breast cancer therapeutic response. (18)F-fluoroestradiol PET produces in vivo quantitative measurements of regional estrogen binding in breast cancer tumors. We describe within-patient (site-to-site) and between-patient heterogeneity of lesions in patients scheduled to receive endocrine therapy. METHODS: In 91 patients with a prior ER-positive biopsy, 505 lesions were analyzed for both (18)F-fluoroestradiol and (18)F-FDG uptake and the (18)F-fluoroestradiol/(18)F-FDG uptake ratio. Standardized uptake values (SUVs) were recorded for up to 16 lesions per patient, of 1.5 cm or more and visible on (18)F-FDG PET or conventional staging. Linear mixed-effects regression models examined associations between PET parameters and patient or lesion characteristics and estimated variance components. A reader study of SUV measurements for 9 scans further examined sources of within-patient variability. RESULTS: Average (18)F-fluoroestradiol uptake and (18)F-fluoroestradiol/(18)F-FDG ratio varied greatly across these patients, despite a history of ER-positive disease: about 37% had low or absent (18)F-fluoroestradiol uptake even with marked (18)F-FDG uptake. (18)F-fluoroestradiol SUV and (18)F-fluoroestradiol/(18)F-FDG ratio measurements within patients with multiple lesions were clustered around the patient's average value in most cases. Summarizing these findings, the intraclass correlation coefficient (proportion of total variation that is between-patient) was 0.60 (95% confidence interval, 0.50-0.69) for (18)F-fluoroestradiol SUV and 0.65 (95% confidence interval, 0.56-0.73) for the (18)F-fluoroestradiol/(18)F-FDG ratio. Some within-patient variation in PET measures (22%-44%) was attributable to interobserver variability as measured by the reader study. A subset of patients had mixed uptake, with widely disparate (18)F-fluoroestradiol SUV or (18)F-fluoroestradiol/(18)F-FDG ratio for lesions in the same scan. CONCLUSION: (18)F-fluoroestradiol uptake and the (18)F-fluoroestradiol/(18)F-FDG ratio varied greatly between patients but were usually consistent across lesions in the same scan. The average (18)F-fluoroestradiol SUV and (18)F-fluoroestradiol/(18)F-FDG ratio for a limited sample of lesions appear to provide a reasonable summary of synchronous ER expression for most patients. However, imaging the entire disease burden remains important to identify the subset of patients with mixed uptake, who may be at a critical point in their disease evolution.

PET tumor metabolism in locally advanced breast cancer patients undergoing neoadjuvant chemotherapy: value of static versus kinetic measures of fluorodeoxyglucose uptake.

PURPOSE: Changes in tumor metabolism from positron emission tomography (PET) in locally advanced breast cancer (LABC) patients treated with neoadjuvant chemotherapy (NC) are predictive of pathologic response. Serial dynamic [(18)F]-FDG (fluorodeoxyglucose) PET scans were used to compare kinetic parameters with the standardized uptake value (SUV) as predictors of pathologic response, disease-free survival (DFS), and overall survival (OS). EXPERIMENTAL DESIGN: Seventy-five LABC patients underwent FDG PET prior to and at midpoint of NC. FDG delivery (K(1)), FDG flux (K(i)), and SUV measures were calculated and compared by clinical and pathologic tumor characteristics using regression methods and area under the receiver operating characteristic curve (AUC). Associations between K(1), K(i), and SUV and DFS and OS were evaluated using the Cox proportional hazards model. RESULTS: Tumors that were hormone receptor negative, high grade, highly proliferative, or of ductal histology had higher FDG K(i) and SUV values; on an average, FDG K(1) did not differ systematically by tumor features. Predicting pathologic response in conjunction with estrogen receptor (ER) and axillary lymph node positivity, kinetic measures (AUC = 0.97) were more robust predictors than SUV (AUC = 0.84, P = 0.005). Changes in K(1) and K(i) predicted both DFS and OS, whereas changes in SUV predicted OS only. In multivariate modeling, only changes in K(1) remained an independent prognosticator of DFS and OS. CONCLUSION: Kinetic measures of FDG PET for LABC patients treated with NC accurately measured treatment response and predicted outcome compared with static SUV measures, suggesting that kinetic analysis may hold advantage of static uptake measures for response assessment.

Association between serial dynamic contrast-enhanced MRI and dynamic 18F-FDG PET measures in patients undergoing neoadjuvant chemotherapy for locally advanced breast cancer.

PURPOSE: To investigate the relationship between changes in vascularity and metabolic activity measured by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and dynamic (18)F-FDG-positron emission tomography (PET) in breast tumors undergoing neoadjuvant chemotherapy. MATERIALS AND METHODS: PET and MRI examinations were performed in 14 patients with locally advanced breast cancer (LABC) before and after chemotherapy. Dynamic (18)F-FDG PET measures included (18)F-FDG transport rate constant from blood to tissue (K(1)) and metabolism flux constant (Ki). DCE-MRI measures included initial peak enhancement (PE), signal enhancement ratio (SER), and tumor volume. Spearman rank-order correlations were assessed between changes in PET and MRI parameters, and measures were compared between patients with and without pathologic complete response (pCR) by Mann-Whitney U-test. RESULTS: Changes in glucose delivery (PET K(1)) were closely correlated with changes in tumor vascularity as reflected by DCE-MRI SER (r = 0.83, P < 0.001). Metabolic changes in PET Ki showed moderate correlations with vascularity changes as reflected by SER (r = 0.71) and PE (r = 0.76), and correlated closely with MRI tumor volume (r = 0.79, P < 0.001). Decreases in K(1), Ki, SER, and PE were greater for patients with pCR compared to those with residual disease (P < 0.05). CONCLUSION: Dynamic (18)F-FDG PET and DCE-MRI tumor measures of tumor metabolism, vascularity, and volume were well correlated for assessing LABC response to neoadjuvant chemotherapy and significantly discriminated pathologic complete responders. Further work is necessary to assess the value of combined PET and MRI for evaluating tumor pharmacodynamics in response to novel therapy.

Tumor metabolism and blood flow as assessed by positron emission tomography varies by tumor subtype in locally advanced breast cancer.

PURPOSE: Dynamic positron emission tomography (PET) imaging can identify patterns of breast cancer metabolism and perfusion in patients receiving neoadjuvant chemotherapy (NC) that are predictive of response. This analysis examines tumor metabolism and perfusion by tumor subtype. EXPERIMENTAL DESIGN: Tumor subtype was defined by immunohistochemistry in 71 patients with locally advanced breast cancer undergoing NC. Subtype was defined as luminal [estrogen receptor (ER)/progesterone receptor (PR) positive], triple negative [TN; ER/PR negative, human epidermal growth factor receptor 2 (HER2) negative], and HER2 (ER/PR negative, HER2 overexpressing). Metabolic rate (MRFDG) and blood flow (BF) were calculated from PET imaging before NC. Pathologic complete response (pCR) to NC was classified as pCR versus other. RESULTS: Twenty-five (35%) of 71 patients had TN tumors; 6 (8%) were HER2 and 40 (56%) were luminal. MRFDG for TN tumors was on average 67% greater than for luminal tumors (95% confidence interval, 9-156%) and average MRFDG/BF ratio was 53% greater in TN compared with luminal tumors (95% confidence interval, 9-114%; P<0.05 for both). Average BF levels did not differ by subtype (P=0.73). Most luminal tumors showed relatively low MRFDG and BF (and did not achieve pCR); high MRFDG was generally matched with high BF in luminal tumors and predicted pCR. This was not true in TN tumors. CONCLUSION: The relationship between breast tumor metabolism and perfusion differed by subtype. The high MRFDG/BF ratio that predicts poor response to NC was more common in TN tumors. Metabolism and perfusion measures may identify subsets of tumors susceptible and resistant to NC and may help direct targeted therapy.

Metabolic and vascular features of dynamic contrast-enhanced breast magnetic resonance imaging and (15)O-water positron emission tomography blood flow in breast cancer.

RATIONALE AND OBJECTIVES: We sought to (1) describe associations between measures of tumor perfusion by dynamic contrast-enhanced breast magnetic resonance imaging (DCE-MRI), blood flow by (15)O-water positron emission tomography (PET) and metabolism by (18)F-fluorodeoxyglucose ((18)F)-FDG PET and (2) improve our understanding of tumor enhancement on MRI through independent measures of tumor metabolism and blood flow. MATERIALS AND METHODS: We performed a retrospective analysis of the existing PET and MRI databases from the Departments of Nuclear Medicine and Radiology. We identified patients with locally advanced breast cancer who underwent (15)O-water/(18)F-FDG PET within 1 month of clinical DCE-MRI between February 2004 and August 2006. The (15)O-water PET blood flow and (18)F-FDG metabolic rate and tissue transport constant (K(1)) in the primary malignancy were calculated. DCE-MRI peak percent enhancement and peak signal enhancement ratio (SER) were measured for each tumor. Correlations and regression analysis of these variables were performed. RESULTS: Fifteen patients with complete PET and DCE-MRI data were included in the analysis cohort. Peak SER correlated significantly with blood flow (r = 0.73, P = .002) and K(1) (r = 0.76, P = .001). However, peak SER did not correlate significantly with FDG metabolic rate (r = 0.44, P = .101). There were no significant correlations between peak percent enhancement and any of the PET parameters. CONCLUSIONS: Our findings suggest that tumor perfusion, represented by (15)O-water PET blood flow, is an important factor in the MRI enhancement of locally advanced breast cancer. A lack of correlation of FDG metabolic rate with blood flow and DCE-MRI kinetics suggests that (18)F-FDG PET provides complementary metabolic information independent of vascular factors.

Tumor metabolism and blood flow changes by positron emission tomography: relation to survival in patients treated with neoadjuvant chemotherapy for locally advanced breast cancer.

PURPOSE: Patients with locally advanced breast carcinoma (LABC) receive preoperative chemotherapy to provide early systemic treatment and assess in vivo tumor response. Serial positron emission tomography (PET) has been shown to predict pathologic response in this setting. We evaluated serial quantitative PET tumor blood flow (BF) and metabolism as in vivo measurements to predict patient outcome. PATIENTS AND METHODS: Fifty-three women with primary LABC underwent dynamic [(18)F]fluorodeoxyglucose (FDG) and [(15)O]water PET scans before and at midpoint of neoadjuvant chemotherapy. The FDG metabolic rate (MRFDG) and transport (FDG K(1)) parameters were calculated; BF was estimated from the [(15)O]water study. Associations between BF, MRFDG, FDG K(1), and standardized uptake value and disease-free survival (DFS) and overall survival (OS) were evaluated using the Cox proportional hazards model. RESULTS: Patients with persistent or elevated BF and FDG K(1) from baseline to midtherapy had higher recurrence and mortality risks than patients with reductions. In multivariable analyses, BF and FDG K(1) changes remained independent prognosticators of DFS and OS. For example, in the association between BF and mortality, a patient with a 5% increase in tumor BF had a 67% higher mortality risk compared with a patient with a 5% decrease in tumor BF (hazard ratio = 1.67; 95% CI, 1.24 to 2.24; P < .001). CONCLUSION: LABC patients with limited or no decline in BF and FDG K(1) experienced higher recurrence and mortality risks that were greater than the effects of clinical tumor characteristics. Tumor perfusion changes over the course of neoadjuvant chemotherapy measured directly by [(15)O]water or indirectly by dynamic FDG predict DFS and OS.

Internal mammary nodal chain drainage is a prognostic indicator in axillary node-positive breast cancer.

BACKGROUND: Internal mammary (IM) nodes are a potential site of breast lymphatic drainage. We examined the relationship between lymphoscintigraphic evidence of IM drainage and survival in early-stage breast cancer patients (pts). METHODS: From a prospective database of 855 consecutive sentinel node mapping procedures using peritumoral radiocolloid injection from 1996-2004, we analyzed the 604 cases with stage I-III breast cancer. Overall survival and recurrence-free survival (OS, RFS) rates were compared in pts with (IM+) and without (IM-) IM drainage on lymphoscintigraphy using Kaplan-Meier plots and Cox proportional hazards models. RESULTS: 100 of 604 pts (17%) showed IM drainage. Five-year OS and RFS were 92% vs 88% and 88% vs 85% in IM- vs IM+ pts. In the 186 pts with axillary metastases (node+), 5-year OS and RFS were 91% vs 71% and 84% vs 69% in IM- vs IM+ pts. Univariate analysis of node+ pts estimated increased mortality risk for IM+ (hazard ratio, HR 2.9, P = .04), >or=4 positive nodes (HR 3.2, P = .02), tumors that were ER-negative (HR 3.4, P = .02), or had high Ki-67 (HR 6.8, P = .01). Multivariate analysis estimated similar increased risks [>or=4 nodes (HR 4.0, P = .02), IM+ (HR 3.3, P = .06), and ER negativity (HR 2.6, P = .09)]. CONCLUSIONS: IM nodal drainage predicted a nearly 3-fold increased mortality risk in node+ pts. Peritumoral radiocolloid injection provides a clinically relevant assessment of IM drainage and should be prospectively tested for its value in tailoring treatment strategies for axillary node-positive pts.

Dynamic and static approaches to quantifying 18F-FDG uptake for measuring cancer response to therapy, including the effect of granulocyte CSF.

UNLABELLED: The response of cancer to chemotherapy can be quantified using (18)F-FDG to indicate changes in tumor metabolism. Quantification using the standardized uptake value (SUV) is more feasible for clinical practice than is the metabolic rate of (18)F-FDG (MRFDG), which requires longer, dynamic scanning. The relationship between MRFDG and SUV depends in part on how each accounts for blood clearance of tracer. We tested whether chemotherapy and treatment with granulocyte colony-stimulating factor (CSF) changed the blood clearance curves and therefore affected the relationship between MRFDG and SUV. METHODS: Thirty-nine patients with locally advanced breast cancer underwent (18)F-FDG PET before and after chemotherapy, including granulocyte CSF. The area under the curve (AUC) for blood clearance was determined before and after therapy. MRFDGs were determined by graphical analyses, whereas SUVs were calculated using the standard formula normalized by body weight. MRFDG and SUVs were compared with each other and with tumor response. Paired percentage changes in MRFDG and SUV were also divided into tertiles based on pretherapy SUV to investigate differences in the relative sensitivity of SUV changes to MRFDG changes due to baseline tumor uptake. RESULTS: Despite a small but statistically significant 6% decrease in blood AUCs after therapy (P = 0.02), SUV and MRFDG did not differ significantly in slope (P = 0.53) or in correlation before and after therapy (r = 0.95 for both). Percentage changes in MRFDG and SUV between serial scans correlated with each other (r = 0.84) and with patient response (P

Serial 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) to monitor treatment of bone-dominant metastatic breast cancer predicts time to progression (TTP).

BACKGROUND: The response of bone-dominant (BD) breast cancer to therapy is difficult to assess by conventional imaging. Our preliminary studies have shown that quantitative serial 2-[(18)F] fluoro-2-deoxy-D: -glucose positron emission tomography (FDG PET) correlates with therapeutic response of BD breast cancer, but the relationship to long-term outcome measures is unknown. Our goal was to evaluate the prognostic power of serial FDG PET in BD breast cancer patients undergoing treatment. METHODS: We reviewed medical records of 405 consecutive breast cancer patients referred for FDG PET. Of these, 28 demonstrated metastatic BD breast cancer, were undergoing treatment, had at least 2 serial PET scans, and had abnormal FDG uptake on the first scan. Standardized uptake value (SUV) for the most conspicuous bone lesion at the initial scan, absolute change in SUV over an interval of 1-17 months, and percent change in SUV were considered as predictors of time-to-progression (TTP) and time to skeletal-related event (t-SRE). RESULTS: Using proportional hazards regression, smaller percentage decreases in SUV (or increases in SUV) were associated with a shorter TTP (P < 0.006). A patient with no change in SUV was twice as likely to progress compared to a patient with a 42% median decrease in SUV. A higher SUV on the initial FDG PET predicted a shorter t-SRE (hazard ratio = 1.30, P < 0.02). CONCLUSIONS: Changes in serial FDG PET may predict TTP in BD metastatic breast cancer patients. However, larger prospective trials are needed to validate changes in FDG PET as a surrogate endpoint for treatment response.

Hormone receptor status, tumor characteristics, and prognosis: a prospective cohort of breast cancer patients.

BACKGROUND: Breast cancer patients with tumors that are estrogen receptor (ER)-positive and/or progesterone receptor (PR)-positive have lower risks of mortality after their diagnosis compared to women with ER- and/or PR-negative disease. However, few studies have evaluated variations in the risks of breast cancer-specific mortality across ER/PR status by either demographic or clinical characteristics. METHODS: Using data from 11 population-based cancer registries that participate in the SEER (Surveillance, Epidemiology, and End Results) program, 155,175 women at least 30 years old with a primary diagnosis of invasive breast carcinoma from 1990 to 2001 were included in the study. Associations between joint hormone receptor status and breast cancer mortality risk within categories of diagnosis age, diagnosis year, race/ethnicity, histologic tumor type, stage, grade, size, and axillary lymph node status were evaluated using the Cox proportional hazards model. RESULTS: Compared to ER+/PR+ cases, elevations in risk of mortality were observed across all subcategories of age at diagnosis, ranging from 1.2- to 1.5-fold differences for ER+/PR- cases, 1.5- to 2.1-fold differences for ER-/PR+ cases, and 2.1- to 2.6-fold differences for ER-/PR- cases. Greater differences were observed in analyses stratified by grade; among women with low-grade lesions, ER-/PR- patients had a 2.6-fold (95% confidence interval [CI] 1.7 to 3.9) to 3.1-fold (95% CI 2.8 to 3.4) increased risk of mortality compared to ER+/PR+ patients, but among women with high-grade lesions, they had a 2.1-fold (95% CI 1.9 to 2.2) to 2.3-fold (95% CI 1.8 to 2.8) increased risk. CONCLUSION: Compared to women with ER+/PR+ tumors, women with ER+/PR-, ER-/PR+, or ER-/PR- tumors experienced higher risks of mortality, which were largely independent of the various demographic and clinical tumor characteristics assessed in this study. The higher relative mortality risks identified among ER-/PR- patients with small or low-grade tumors raise the question of whether there may be a beneficial role for adjuvant chemotherapy in this population.

Quantitative fluoroestradiol positron emission tomography imaging predicts response to endocrine treatment in breast cancer.

PURPOSE: In breast cancer, [(18)F]fluoroestradiol (FES) positron emission tomography (PET) correlates with estrogen receptors (ER) expression and predicts response to tamoxifen. We tested the ability of FES-PET imaging to predict response to salvage hormonal treatment in heavily pretreated metastatic breast cancer patients, predominantly treated with aromatase inhibitors. PATIENTS AND METHODS: Initial FES uptake measurements in 47 patients with ER-positive tumors were correlated with subsequent tumor response to 6 months of hormonal treatment. Most patients had bone dominant disease and prior tamoxifen exposure. Response was compared to initial FES-PET uptake, measured qualitatively and quantitatively using standardized uptake value (SUV) and estradiol-binding flux. RESULTS: Eleven of 47 patients (23%) had an objective response. While no patients with absent FES uptake had a response to treatment, the association between qualitative FES-PET results and response was not significant (P = .14). However, quantitative FES uptake and response were significantly associated; zero of 15 patients with initial SUV less than 1.5 responded to hormonal therapy, compared with 11 of 32 patients (34%) with SUV higher than 1.5 (P < .01). In the subset of patients whose tumors did not overexpress HER2/neu, 11 of 24 patients (46%) with SUV higher than 1.5 responded. CONCLUSION: Quantitative FES-PET can predict response to hormonal therapy and may help guide treatment selection. Treatment selection using quantitative FES-PET in our patient series would have increased the rate of response from 23% to 34% overall, and from 29% to 46% in the subset of patients lacking HER2/neu overexpression. A multi-institutional collaborative trial would permit definitive assessment of the value of FES-PET for therapeutic decision making.

Changes in Glucose Metabolism and Blood Flow Following Chemotherapy for Breast Cancer.

This article focuses on this application of positron emission tomography (PET) to breast cancer. The article first reviews the PET methodology used for breast cancer response assessment, with an emphasis on quantitative methods. This is followed by a review of results to date for neoadjuvant chemotherapy and therapy of metastatic breast cancer. Preliminary studies with tracers other than (18)F-fluordeoxyglucose are then reviewed. The article ends with a summary and a discussion of future directions.

Residual tumor uptake of [99mTc]-sestamibi after neoadjuvant chemotherapy for locally advanced breast carcinoma predicts survival.

BACKGROUND: Studies utilizing serial [99mTc]-sestamibi (MIBI) scintimammography have reported accurate prediction of tumor response in patients with locally advanced breast carcinoma (LABC) undergoing neoadjuvant chemotherapy. The pathologic response of LABC to presurgical treatment regimens is a prognostic indicator of survival. The authors tested whether MIBI uptake posttherapy predicted survival. METHODS: Sixty-two patients with LABC underwent MIBI scintimammography just before chemotherapy and 2 months after treatment initiation. An additional MIBI scan was performed if treatment lasted >3 months. The affected breast was imaged within 10 minutes after injection to reflect early uptake, which the authors have shown to be related to tumor blood flow. MIBI uptake was quantified using the lesion-to-normal breast (L:N) ratio. Most patients (93%) received weekly dose-intensive doxorubicin-based treatment. Disease-free survival (DFS) and overall survival (OS) were compared with posttherapy primary MIBI uptake and with other established prognostic factors for neoadjuvantly treated LABC, namely, primary tumor pathologic response and posttherapy axillary lymph node status. RESULTS: Patients with high uptake on the last observed MIBI scan (i.e., the L:N ratio was greater than the median value) had poorer DFS and OS (P<0.01 and P=0.01, respectively). Residual MIBI uptake retained independent prognostic significance in preliminary multivariate analysis that included other established prognostic markers. CONCLUSIONS: High primary breast tumor MIBI uptake after neoadjuvant chemotherapy predicted poor survival, suggesting serial MIBI imaging may provide a useful quantitative surrogate end point for neoadjuvant chemotherapy trials. Given the association between MIBI uptake and tumor blood flow, this prognostic capability may be related to retained tumor vascularity after treatment.

18F-FDG kinetics in locally advanced breast cancer: correlation with tumor blood flow and changes in response to neoadjuvant chemotherapy.

UNLABELLED: The aim of this study was to characterize the biologic response of locally advanced breast cancer (LABC) to chemotherapy using (15)O-water-derived blood flow measurements and (18)F-FDG-derived glucose metabolism rate parameters. METHODS: Thirty-five LABC patients underwent PET with (15)O-water and (18)F-FDG before neoadjuvant chemotherapy and 2 mo after the initiation of treatment. Kinetic analysis for (15)O-water was performed using a single tissue compartment model to calculate blood flow; a 2-tissue compartment model was used to estimate (18)F-FDG rate parameters K(1), k(2), k(3), and the flux constant, K(i). Correlations and ratios between blood flow and (18)F-FDG rate parameters were calculated and compared with pathologic tumor response. RESULTS: Although blood flow and (18)F-FDG transport (K(1)) were correlated before chemotherapy, there was relatively poor correlation between blood flow and the phosphorylation constant (k(3)) or the overall (18)F-FDG flux (K(i)). Blood flow and (18)F-FDG flux were more closely matched after chemotherapy, with changes in k(3) accounting for the increased correlation. These findings were consistent with a decline in both the K(i)/flow and k(3)/flow ratios with therapy. The ratio of (18)F-FDG flux to transport (K(i)/K(1)) after 2 mo of chemotherapy was predictive of ultimate response. CONCLUSION: The pattern of tumor glucose metabolism in LABC, as reflected by analysis of (18)F-FDG rate parameters, changes after therapy, even in patients with modest clinical responses. This may indicate a change in tumor "metabolic phenotype" in response to treatment. A low ratio of glucose metabolism (reflected by K(i)) to glucose delivery (reflected by K(1) and blood flow) after therapy is associated with a favorable response. Further work is needed to understand the tumor biology underlying these findings.

Evaluation of the internal mammary lymph nodes by FDG-PET in locally advanced breast cancer (LABC).

The presence of internal mammary (IM) lymph node metastases in breast cancer predicts outcome and may alter treatment. Standard imaging has limited usefulness for evaluation of the IM chain because of low sensitivity. Our preliminary studies suggested that [F-18]-2-fluoro-d-glucose positron emission tomography (FDG-PET) improves the detection of IM and mediastinal metastases. We therefore performed a retrospective review of women who underwent FDG-PET prior to treatment to determine the benefit of PET for imaging IM disease. The records of 28 consecutive patients undergoing FDG-PET prior to neoadjuvant chemotherapy for suspected locally advanced breast cancer (LABC) were reviewed. The presence of abnormal IM uptake on FDG-PET was noted. IM uptake on FDG PET was compared with standard radiographic imaging and was correlated with putative risk factors for IM involvement and with clinical patterns of failure. Patients did not undergo IM biopsy; however, patterns of failure were assessed to validate the FDG-PET findings. Clearly abnormal FDG uptake in the IM nodes was seen in 7 of 28 women (25%). Prospective conventional chest imaging failed to identify IM metastases in any patient. IM uptake on PET was associated with large size of the primary tumor (P = 0.03) and with inflammatory disease (P = 0.04). The presence of IM FDG uptake predicted failure by a pattern consistent with spread from IM lymph node metastasis. FDG-PET appears to be a useful noninvasive modality to detect IM metastases in LABC. Pathologic verification in a prospective study is necessary to confirm these findings.

Changes in blood flow and metabolism in locally advanced breast cancer treated with neoadjuvant chemotherapy.

UNLABELLED: Locally advanced breast cancer (LABC) is commonly treated with neoadjuvant chemotherapy followed by definitive surgery. The factors influencing the response of LABC to presurgical chemotherapy are incompletely understood. To characterize in vivo tumor biology in patients with LABC, we performed serial measurements of blood flow and glucose metabolism in LABC patients over the course of neoadjuvant chemotherapy and compared measurements with response. METHODS: Thirty-five patients with newly diagnosed LABC underwent (18)F-FDG and (15)O-water PET imaging before therapy and after 2 mo of chemotherapy. Tumor metabolism was estimated from graphical analysis of dynamic (18)F-FDG studies and was expressed as the metabolic rate of (18)F-FDG (MRFDG). Blood flow was estimated from dynamic images after bolus (15)O-water injection using a 1-compartment model. Metabolism and blood flow data were analyzed with and without partial-volume corrections to account for changes in tumor size over the course of therapy. Changes in tumor blood flow and metabolism were compared with response to chemotherapy and with patient survival. RESULTS: For all patients, the mean MRFDG after 2 mo of chemotherapy decreased by 54% and the mean blood flow by 21%. Responders showed a greater decline in MRFDG than did nonresponders; however, the difference was of borderline significance (P = 0.05) after correction for partial-volume effects. Patients who responded had a decline in tumor blood flow, whereas nonresponders had an average increase (-32% vs. +48%, P < 0.005); the difference between responders and nonresponders remained significant after partial-volume correction (P < 0.01). There was also a statistically significant association between the pathologic degree of response and the percentage change in blood flow at 2 mo with and without partial-volume correction; this was not the case for MRFDG. The change in blood flow after 2 mo of therapy predicted disease-free and overall survival. CONCLUSION: Although both resistant and responsive LABC tumors have an average decline in MRFDG over the course of chemotherapy, resistant tumors have an average increase in blood flow. Patients whose tumors fail to have a decline in blood flow after 2 mo of therapy have poorer disease-free and overall survival. Further investigations are needed to elucidate the tumor biology underlying these findings.

SUV varies with time after injection in (18)F-FDG PET of breast cancer: characterization and method to adjust for time differences.

UNLABELLED: The purpose of this study was to measure how (18)F-FDG PET standardized uptake values (SUVs) change over time in breast cancer and to examine the feasibility of a method to adjust for modest variations in the time of uptake measurement experienced in clinical practice. METHODS: (18)F-FDG PET was performed as 60-min dynamic imaging with an additional image acquired at approximately 75 min after injection. For 20 newly diagnosed, untreated, locally advanced breast cancer patients, both the maximum SUV and the average SUV within the lesion were calculated with and without correction for blood glucose concentration. A linear regression analysis of the portion of the time-activity curves starting at 27 min after injection was used to estimate the rate of SUV change per minute during the interval from 27 to 75 min. The rate of SUV change with time was compared with the instantaneous SUV obtained at different times from 27 to 75 min. RESULTS: In untreated breast cancer, (18)F-FDG SUV values changed approximately linearly after 27 min at a rate ranging from -0.02 to 0.15 per minute. In addition, the rate of SUV change was linearly correlated with the instantaneous SUV measured at different times after injection (r(2) ranged from 0.82 to 0.94; P < 0.001). Using this information, an empirical linear model of SUV variation with time from injection to uptake measurement was formulated. The comparison method was then applied prospectively to a second set of 20 locally advanced breast cancer lesions not included in the initial analysis. The average percent error using the method to adjust for time differences was 8% and 5% for maximum SUVs and average SUVs ranging from 2 to 12. CONCLUSION: In untreated breast cancer, the SUV at any time point approximately predicts the rate of change of SUV over time. A comparison method based on this finding appears feasible and may improve the usefulness of the SUV by providing a means of comparing SUV acquired at different times after injection.