Abstract PD4-07: PET imaging of PARP-1 expression in breast cancer

18F-FluorThanatrace ([18F]-FTT) is a novel radiotracer shown to quantify Poly [ADP-ribose] polymerase 1 (PARP-1) expression in vitro and in vivo through a receptor-ligand interaction. A recent study at the University of Pennsylvania in women with ovarian cancer demonstrated in vivo visualization of PARP-1 expression in tumors using this radiotracer that closely correlated with an in vitro assay of PARP-1 in tumor tissue (Makvandi, M. J. Clin. Invest. 128:2116, 2018). A radioligand with PARP-1 specificity, [125I]-KX1, was also developed as a companion tool for ex vivo evaluation of PARP-1 expression and PARP inhibitor (PARPi) drug occupancy by radioligand binding assay (Makvandi, M. Cancer Res. 76:4516, 2016). As the first step in validating this biomarker in breast cancer, we performed a prospective clinical trial comparing in vivo [18F]-FTTuptake and ex vivo PARP-1 expression in women with primary breast cancer.

Methods: 24 patients with Stage I-IV primary breast cancer were imaged with [18F]-FTT prior to any therapy including surgery. We correlated in vivo uptake with ex vivo immunohistochemistry (IHC) for PARP-1 and [125I]-KX1 autoradiography in untreated surgical specimens. Tumors were analyzed for alterations in DNA repair genes, copy number-based as well as mutational signatures indicative of homologous recombination deficiency (HRD) and mutational burden, using our established protocol (Maxwell, KN, Nature Commun. 8:319, 2017).

Results: [18F]-FTT uptake was visualized above background in all primary breast tumors and known metastases. Two areas of unexpected uptake revealed an unknown contralateral breast cancer and an ovarian carcinoid, respectively. We expected that uptake might be highest in triple negative breast cancer (TNBC), where PARPi have been most heavily studied. However, a range of tracer uptake was observed in tumors independent of breast cancer subtype (hormone receptor positive/HER2 negative, TNBC, HER2+) and BRCA status. Uptake ratios (SUVmax tumor/SUV max opposite breast) ranged from 1.2-10.5 with a median 4.0. Ex vivo[125I]-KX1 autoradiography was performed on a subset of untreated primary tumors (n=5) and compared with IHC staining for PARP-1 on sequential sections. This revealed a close spatial correspondence between elevated PARP-1 expression by IHC and regions of elevated [125I]-KX1 binding radiographically. There was also a strong positive correlation between in vivo [18F]-FTT uptake and ex vivo quantitative [125I]-KX1 autoradiography (r=0.78). Genomic analysis of HRD in all tumors is pending and will be reported.

Conclusion: Initial analyses support the ability of [18F]-FTT to visualize and measure PARP-1 expression in breast cancer. This is the first step toward developing an imaging companion diagnostic to help guide PARP inhibitor treatment in breast cancer. Ongoing studies are expanding upon these results, testing the extent to which expression of PARP-1 by [18F]-FTT can predict response to PARP inhibitors and measure target engagement during therapy.

Citation Format: McDonald ES, Carlin S, Maxwell KN, Nayak A, Doot RK, Pantel AR, Farwell MD, Pryma DA, Clark AS, Shah P, DeMichele AM, Ziober A, Schubert EK, Palmer K, Lee HS, Matro J, de la Cruz L, Tchou J, Anderson DN, Feldman MD, Sheffer RE, Knollman H, Schnall MD, Makvandi M, Domchek S, Hubbard RA, Mach RH, Mankoff DA. PET imaging of PARP-1 expression in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD4-07.

Abstract PD4-11: [18F]Fluciclovine PET tracks cellular glutamine pool size in breast cancer and changes in response to metabolic inhibition

Background: Some forms of triple negative breast cancer (TNBC) rely on glutamine (Gln) metabolism for survival and growth (1), therefore, targeting this metabolic pathway provides a viable strategy for managing TNBC. Drugs that inhibit glutaminase (GLS), a key enzyme of glutaminolysis, are being developed (1,2). [18F]Fluciclovine is a PET imaging agent that enters/exits cells via glutamine transporters and undergoes minimal metabolism. Therefore, we hypothesize, that akin to our prior work with [18F]fluoroglutamine (3), the distribution volume (VT) of fluciclovine obtained from dynamic PET can be used to estimate the cellular glutamine level (pool size) and to mark the effect of pharmacological inhibitors of tumor glutaminase (GLS). We tested this hypothesis in human TNBC and ER+ breast cancer xenograft exhibiting a high and low GLS activity, respectively.

Methods: To make [18F]fluciclovine preparation suitable for mouse imaging, citrate in the formulation was removed and replaced with PBS by eluting through a column (Bio-Rad). Cellular uptake was performed in the presence and absence of Gln transporter inhibitors and GLS inhibitor. In vivo dynamic PET imaging were performed on mice bearing HCC1806 (TNBC) and MCF-7 (ER+ BC) xenografts. Dynamic PET images were analyzed by Logan Plot (PMOD) to estimate VT.

Results: Cellular uptake of [18F]fluciclovine in HCC1806 and MCF-7 cells were sensitively inhibited by cold glutamine (Gln) and GPNA (a pharmacologic inhibitor of ASCT-2), confirming that the uptake is mediated by Gln transporters. The peak uptake in MCF-7 cells was 5-fold higher than HCC1806. In mouse models, VT from in vivo [18F]Fluciclovine PET in MCF-7 tumor is 1.4-fold of HCC1806. These data are consistent with a higher cellular Gln pool size in MCF-7 as the result of its lower GLS activity. After inhibition of tumor GLS activity, VT of [18F]fluciclovine in HCC-1806 tumors was increased by 56% from baseline values (n=2), whereas VT in MCF-7 tumors decreased 1% after treatment (n=2). Only a small change of FDG PET signal (5% decrease, n=5) was detected in TNBC tumors after GLS inhibitor treatment.

Discussions: These data suggest that VT obtained from [18F]fluciclovine PET is sensitive to changes of the Gln pool size induced by GLS inhibition whereas FDG PET is not. Since the Gln pool size is inversely related to the GLS activity, increased VT is consistent with the increased intracellular Gln level when metabolic conversion of Gln to glutamate by GLS is inhibited. Our results suggest that [18F]fluciclovine, an imaging agent approved for prostate cancer imaging, may be useful for assessing glutamine pool size in breast cancer and changes in response to GLS inhibition

Support: R21CA198563, R01CA211337, and Komen SAC130060. We thank Blue Earth Diagnostics for supplies of [18F]fluciclovine.

1.Gross MI, Demo SD, Dennison JB, et al. Mol Cancer Ther 2014;13(4):890-901.

2.Le A, Lane AN, Hamaker M, et al. Cell Metab 2012;15(1):110-21.

3.Zhou R, Pantel AR, Li S, et al. Cancer Res 2017;77(6):1476-84.

Citation Format: Cao J, Choi H, Pantel A, Kranseler D, Lee H, Mankoff D, Zhou R. [18F]Fluciclovine PET tracks cellular glutamine pool size in breast cancer and changes in response to metabolic inhibition [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD4-11.

Abstract PD4-10: 18F-fluoroestradiol (FES) and 18F-fluorodeoxyglucose (FDG) PET imaging in staging extent of disease in metastatic lobular breast cancer

Background: The histology and pattern of spread in lobular breast cancer has presented challenges in estimating extent of disease and identifying treatment options. 18F-FES is an estrogen analogue PET imaging tracer which measures tumor ER expression at multiple tumor sites simultaneously and predicts response to endocrine therapy. We analyzed FES-PET and FDG-PET SUV uptake in patients with metastatic lobular and ductal carcinoma to identify sites of tumor and responsiveness to therapy.

Methods: We retrospectively reviewed FES and FDG SUV uptake between ER+ lobular (n = 36) and ductal (n= 173, including 6 men) metastatic breast cancer patients enrolled in various institutional studies. Up to 3 lesions in each patient were evaluated by FES SUVmax and/or FDG SUVmax for a total of 475 lesions in FES images and 462 lesions in FDG images. Classification into three categories (low FDG, high FDG/high FES, and high FDG/low FES) was generated using recursive portioning with 5-fold internal cross validation. Using a Pearson Chi-squared test, we compared degree of uptake in FES and FDG between lobular and ductal carcinomas. We used linear mixed effects model to assess association of FES SULmean3 (Lean body mass adjusted SUV) and FDG SULmean3 with histology. Overall survival (OS), from time of FES-PET scan to death, and progression free survival (PFS) was evaluated between classification groups in both histologies using Kaplan-Meier curves and Cox model.

Results: In patients with metastatic breast cancer, 72 patients had low FDG, 96 had high FES/high FDG, and 41 with high FES/low FDG. Lobular lesions tended to have a higher proportion of patients in the risk group with lower FDG (42% vs 33%) and a lower proportion in the risk group with high FDG/low FES (11% vs 21%) but the difference was not statistically significant (p = 0.32). Mean (range) FES SULmean3 and FDG SULmax3 respectively for ductal was 1.38 (0.10, 6.7) and 3.17 (0.88, 12.26) and for lobular was 1.42 (0.34, 3.43) and 3.13 (1.04, 13.87). There was no significant difference between in FES SULmean3 and FDG SULmax3 between histologies. Following FES-PET imaging, patients with lobular carcinomas and low FDG demonstrated a higher median survival time (7.7 years) compared to high FDG/low FES (4.3 years) and high FDG/high FES (2.6 years). Similarly, patients with ductal carcinomas and low FDG had an improved median survival time (5.6 years) compared to both high FDG/high FES (2.9 years) and high FDG/low FES (2.5 years). However, the interaction between histology and the FDG/FES classifications was not significant (p = 0.86). Across a variety of tumor sites, lobular histology can be detected by both FES and FDG with no difference between the imaging modalities.

Conclusions: In the metastatic setting, quantitative FES and FDG can be used to discriminate indolent and aggressive phenotypes in both lobular and ductal breast cancer. A greater proportion of lobular carcinoma lesions had higher FES/lower FDG and would be anticipated to be more sensitive to endocrine therapy. Further prospective trials are needed to confirm the utility of FES to stage extent of disease in metastatic breast cancer.

Citation Format: Manohar PM, Peterson LM, Wu V, Jenkins IC, Novakova-Jiresova A, Specht JM, Link JM, Krohn KA, Kinahan PE, Mankoff DA, Linden HM. 18F-fluoroestradiol (FES) and 18F-fluorodeoxyglucose (FDG) PET imaging in staging extent of disease in metastatic lobular breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD4-10.

Abstract OT1-06-04: [18F] fluoroestradiol (FES) PET as a predictive measure for endocrine therapy in women with newly diagnosed metastatic breast cancer

Background: The majority of metastatic breast cancer patients have estrogen-receptor positive (ER+) disease. Therapy options include cytotoxic chemotherapy and ER-directed therapy, including endocrine therapy with or without molecularly targeted agents such as CK4/6 inhibitors. ER-targeted therapy is most commonly given first-line due to improved tolerability. However, not all patients will respond to first-line endocrine therapy due to intrinsic endocrine-therapy resistance mechanisms as well as tumor heterogeneity. There are no current methods in standard practice to inform on either of these issues.

F-18 fluorestradiol (FES), an estrogen analogue has been considered the most promising ER imaging agent and is widely studied in breast cancer. FES positron emission tomography (PET) evaluates multiple tumor sites simultaneously and, thus, can inform on tumor heterogeneity of ER expression, and can measure ER binding in primary and metastatic sites (e.g., lymph nodes, lung, bone, and soft tissue). Like tissue ER expression, FES positivity, as measured by standardized uptake value (SUV), has been shown to predict response to endocrine therapy with selective ER modulators or aromatase inhibitors in first-line therapy or salvage settings in small studies. Typically, a significantly higher tumor SUV was noted in responders compared with non-responders. Since FES uptake can provide a better assessment of ER expression across all sites of metastatic disease, FES may provide more expansive information on ER expression.. Furthermore, preliminary studies examining FES-PET in metastatic breast cancer have suggested that baseline FES uptake may predict response to endocrine therapy.

Trial Design: This is a prospective trial for patients about to start first line endocrine therapy for advanced ER+ breast cancer. Participants will undergo an FDG-PET within six weeks of FES-PET. FES-PET and serum hormone level to be completed prior to endocrine therapy. Patients may opt to have a 2nd FES-PET for test-re-test of FES-PET.

Specific Aims: Primary Aim : To assess the relationship between ER expression measured by FES-PET/CT and clinical benefit (response plus stable disease) of newly diagnosed ER+ metastatic breast cancer to endocrine therapy.

Secondary Aim: To assess the correlation between FES uptake in ER+ metastatic breast cancer and tissue ER expression.

Eligibility: Patients must have confirmed ER+ HER2- metastatic breast cancer and planning to receive endocrine therapy with or without CK 4/6 inhibitors. Patient must NOT have a history of >1 line of administered chemotherapy for metastatic disease and may not have received endocrine therapy for advanced disease. Prior endocrine or chemotherapy in the adjuvant setting is allowed.

Methods: Participants will undergo a F-18 fluorodeoxyglucose (FDG)-PET/CT within six weeks of FES-PET/CT. FES-PET/CT will be completed prior to treatment initiation. Patients may opt to have a 2nd FES-PET for test-re-test of FES-PET/CT

Present and Target Accrual: A total of 13 out of 99 patients have been enrolled onto this imaging study.

Citation Format: Linden H, Clark A, Fowler A, Novakova A, Mankoff D, Dehdashti F. [18F] fluoroestradiol (FES) PET as a predictive measure for endocrine therapy in women with newly diagnosed metastatic breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-06-04.

Abstract P4-02-05: Test-retest fidelity of FDG SUVmax in bone and non-boney metastatic breast cancer lesions in local area network PET/CT scanners

Background: Metabolic activity in lesions, measured by FDG-PET, is often used for assessing tumor aggressiveness and response to therapy. Patients may be scanned on different machines, so quantitative measurements should be reproducible. Reducing SUV variability in PET machines throughout a local network can aid in monitoring patient response to therapy and increase access to clinical trials.

Methods: Eighteen female patients with advanced or metastatic breast cancer underwent paired FDG PET/CT test-retest studies with 1-15 days between scans, and without interim change in treatment. Ten patients were studied in the same scanner and 8 patients were studied in 2 different scanners. Five different PET/CT scanners were used (2 GE DSTE, 2 Siemens (BioGraph 6 and mCT), 1 Philips Ingenuity TF). Each PET/CT scanner was calibrated using NIST-traceable reference sources to characterize and reduce variability. All of the images were interpreted by two separate reviewers. SUVmax values in lesions, corresponding normal tissue, and normal liver were collected. Linear mixed models with random intercept (patient effects) were fitted to compare differences in log(|SUVmax % difference|+.01) in multiple lesions per patient.

Results: SUVmax was assessed in a total of 130 lesions (75 bone). The median number of lesions per patient was 5 (range 1-17). Average SUVmax ranged from 1.0 to 18.2 (mean±SD = 6.0±3.2). The median SUVmax difference was 0.4 (8%) for 47 lesions imaged twice in the same scanner, and was 0.6 (13%) for 83 lesions imaged in two different scanners. In a multivariable linear mixed effects model, SUVmax for different scanners within the same institution did not differ more than for the same scanner (p=0.39), but repeat scans with different scanners and site personnel at had an average of 78% greater percentage difference in SUVmax than for the same scanner (p=0.009). In the same model, the average percent difference in SUVmax for bone lesions was estimated as 30% lower than for other sites (p=0.06, 95% confidence interval 0-50%). Examining normal liver uptake, the median SUVmean was 2.5 (range 1.9-3.1) with an median 6.5% difference between measurements (range 1.1%-23.7%) that did not appear to differ based on scanners used for repeat measurements (p=0.47).

Conclusions: The variability in quantitative FDG SUVmax between scans is modest, suggesting reliable reproducibility in appropriately calibrated settings. In our study, bone lesions had somewhat higher fidelity than other tumor sites. Additional studies will address variability in other cancer types. Careful calibration and monitoring of PET/CT scanners, and consistent imaging protocols are necessary in clinical trials that utilize quantitative PET/CT imaging in order to confidently interpret results.

Research Support: NIH grant U01-CA148131 and NCI-SAIC Contract 24XS036-004.

Citation Format: Linden HM, Peterson LM, Kurland B, Roberts T, Specht J, Shields AT, Novakova A, Christopfel R, Byrd D, Muzi M, Mankoff DA, Kinahan P. Test-retest fidelity of FDG SUVmax in bone and non-boney metastatic breast cancer lesions in local area network PET/CT scanners [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-02-05.

Abstract P6-01-02: Flourine-18-fluorodeoxyglucose positron emission tomography for the evaluation of response to therapy in bone-dominant metastatic breast cancer: Examination in patients enrolled on UPCC 17113

Background: Response of bone-only (BO) and bone-dominant (BD) metastatic breast cancer (mBC) to therapy is difficult to assess by conventional imaging. UPCC 17113 is a single institution prospective cohort study evaluating FDG PET at early and conventional follow up intervals, 4 and 12 weeks respectively, in patients with hormone receptor (HR) positive mBC receiving endocrine therapy. The objective of this study is to assess the relationship between changes relative to baseline in standard uptake values (SUV) of specific bone lesions and progression free survival (PFS). We will also explore change in SUV as it relates to overall survival (OS) and skeletal related events (SRE). We present interim results.

Methods: Enrolled patients were ≥18 years with biopsy proven or documented clinically obvious HR-positive BD/BO mBC due to start new endocrine therapy. Any line endocrine therapy was allowed. FDG PET was performed at baseline, 4 and 12 weeks after initiation of new therapy. SUVmax for the 5 most metabolically active osseous lesions, excluding sites previously treated by radiation or surgery, were recorded at baseline, 4- and 12- week time-points. Average index lesion SUVmax (sum SUVmax/#lesions) and % change from baseline were calculated. Decline of ≥30% from baseline was defined as significant.

Results: As of 6/1/2015, 11 patients were enrolled. All patients have completed the 4-week scan and 8 have completed the 12-week scan. Five and 6 out of the 11 patients had BO and BD HR-positive mBC respectively. Detectable changes in SUV from baseline were noted in all patients at both 4 and 12 weeks, with a 37% overall decline in average index lesion SUVmax at 4 weeks. 8 of 11 patients had a ≥30% decline, in SUV at 4 weeks averaging 46%. Five of the 6 patients in this group who completed the 12-week scan had a sustained decline averaging 50% from the baseline. Of note, the average decline between 4 and 12 weeks in this group was only 8%. Despite having an overall decline from baseline of 44%, the sixth patient in this group had an increase between 4 and 12 weeks of 22%. Three of the 11 patients had a <30% decline at 4 weeks with an average decline of 12%. Of the two patients in this group with 12 week scans, both had average increase of 25% from 4 weeks to 12 weeks, and an average overall increase from baseline of 12%.

Conclusions: There are detectable changes in FDG SUV of osseous lesions at 4 and 12 weeks following initiation of endocrine therapy in patients with BO or BD HR positive mBC. Our interim results demonstrate the emergence of 3 groups of patients: (1) those who have a <30% decline at 4 weeks and increase of SUV at 12 weeks, (2) those who have a ≥30% decline in SUV at 4 weeks with sustained decline at 12 weeks, and (3) those who have a ≥30% reduction in SUV at 4 weeks but who do not have a sustained decline at 12 weeks. These interim results suggest that early FDG PET/CT may provide information on mBC response to endocrine therapy and insight into timing of response and progression. As more patients are enrolled and complete the studies, clearer patterns will emerge which will be correlated with PFS, OS and SRE.

Citation Format: Lynch MC, Mankoff D, Bradbury AR, Domchek S, Glick JH, Matro J, DeMichele A, Clark AS. Flourine-18-fluorodeoxyglucose positron emission tomography for the evaluation of response to therapy in bone-dominant metastatic breast cancer: Examination in patients enrolled on UPCC 17113. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-01-02.

Abstract P5-01-02: Multimodality molecular imaging with dynamic 18F-fluorodeoxyglucose positron emission tomography (FDG PET) and MRI to evaluate response and resistance to neoadjuvant chemotherapy (NAC)

Background: Using quantitative FDG PET to measure glucose metabolism and perfusion, and dynamic contrast-enhanced (DCE) MRI to measure perfusion, we previously identified a metabolic signature for breast cancer resistant to NAC. This imaging signature is (1) persistent or increased tumor perfusion despite treatment, (2) an altered pattern of glucose kinetics in response to therapy, and (3) pre-therapy mismatch between tumor metabolism (MRFDG) and glucose delivery (K1) (high ratio of MRFDG/K1). These patterns predict poor response, early relapse and death independent of established prognostic factors, including pathologic response. Identification of factors associated with resistance or response to therapy is the translational goal of "Quantitative Dynamic PET and MRI in Breast Cancer Therapy," part of the Seattle Breast SPORE (1P50CA138293).

Methods: Patients (Pts) undergoing NAC for histologically confirmed breast cancer (stage II-III) were approached for this trial (CCIRB# 7587). FDG PET and DCE-MRI were obtained pre-therapy, 2-12 weeks after start of NAC (mid-therapy) and after completion of NAC. Breast biopsies were obtained pre-therapy and post-NAC. FDG PET included a dynamic scan with kinetic analysis. PET measures included SUVmax, MRFDG, K1, Ki, and Patlak. 3T DCE-MRI measurements included semi-quantitative vascular parameters of peak enhancement (PE), signal enhancement ratio (SER), washout fraction, functional tumor volume, and apparent diffusion coefficient (ADC) from diffusion-weighted MRI (DWI). Breast biopsies were assayed by immunohistochemistry and gene expression profiling. NAC was per physician's choice with most pts receiving weekly paclitaxel (with trastuzumab if HER2+) followed by doxorubicin/cyclophosphamide.

Results: 32 pts have completed the study. Pathologic complete response (pCR), defined as absence of invasive cancer in the breast, was observed in 9 (28%); near pCR defined as only microscopic residual invasive cancer in 3 (9%) more pts. Mid-therapy decline in SUVmax and K1 was associated with near pCR; (p-value 0.06, 0.04, respectively). Pre-therapy PET measures of MRFDG and K1 were not predictive of pCR. On MRI, pre-therapy PE (p=0.009), SER (p=0.01), washout fraction (p=0.02), ADC (p=0.08, trend) and mid-therapy change in volume (p=0.05) were each predictive of pCR. Gene profiling of pre-therapy biopsies showed correlation between high MRFDG/K1 ratio in basal and luminal B tumors.

Conclusions: Assessment of serial changes in tumor metabolism and perfusion by FDG PET and DCE-MRI is feasible in the clinic. Mid-therapy decline in metabolism and glucose delivery was predictive of pCR; consistent with prior retrospective series. Baseline DCE-MRI and DWI measures show promise to predict response, and associations of mid-therapy change in MR functional tumor volume with pCR agree with findings of another multisite clinical trial (ISPY). These imaging parameters may serve as useful biomarkers to inform future neoadjuvant trials. Integration of imaging data with gene expression profiling revealed that the pattern of metabolism in luminal B tumors was closer to that of the basal subtype compared to other ER-positive tumors.

Citation Format: Specht JM, Partridge S, Chai X, Novakova A, Peterson L, Shields A, Guenthoer J, Linden HM, Gralow JR, Gadi V, Korde L, Hills D, Hsu L, Hockenbery DM, Kinahan P, Mankoff DA, Porter PL. Multimodality molecular imaging with dynamic 18F-fluorodeoxyglucose positron emission tomography (FDG PET) and MRI to evaluate response and resistance to neoadjuvant chemotherapy (NAC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-01-02.

Abstract P5-01-06: 18F-radiolabeled PARP-1 inhibitor uptake as a marker of PARP-1 activity in breast cancer

Objectives: The nuclear enzyme PARP-1 plays a central role in sensing DNA damage and facilitating repair. Tumors with BRCA1/2 mutations are highly dependent on PARP-1 as an alternative mechanism for DNA repair, and PARP inhibitors generate synthetic lethality in tumors with BRCA mutations, resulting in cell cycle arrest and apoptosis. Zhou et al. recently synthesized an 18F-labeled PARP-1 inhibitor (18F-FluorThanatrace) for PET, and demonstrated high specific tracer uptake in a xenograft model of breast cancer (Zhou, Bioorg Med Chem, 22:1700, 2014). The current study seeks to quantify the relationship between 18F-FluorThanatrace binding (both in vitro and on PET imaging of human tumor xenografts) and the level of constitutively active PARP-1, using multiple human breast cancer cell lines, including a BRCA1 defective line.

Methods: BRCA1 defective HCC1937, triple negative MDA-MB-231, and luminal A MCF-7 human breast cancer lines were assessed for constitutive PARP-1 activity via a chemiluminescent ELISA assay for PAR and by Western blot. The same cell lines were incubated with 18F-FluorThanatrace over various time increments, and tracer uptake was assayed via a gamma counter. Specificity of tracer binding was verified via co-incubation with competitive inhibitor Olaparib, and specific tracer uptake was calculated as the difference between uptake with and without Olaparib. Specific tracer uptake was compared to levels of constitutive PARP-1 activity in all cell lines. In addition, HCC1937 and MDA-MB-231 xenograft tumor models were imaged via 18F-FluorThanatrace-PET/CT, and PET uptake was correlated with PARP-1 activity.

Results: BRCA1-defective HCC1937 had higher constitutive PARP-1 activity than cell lines with intact BRCA1. In vitro levels of 18F-FluorThanatrace uptake correlated with constitutive PARP-1 activity across cell lines. In addition, 18F-FluorThanatrace measured by PET in xenograft breast cancer tumor models correlated with constitutive PARP-1 activity.

Conclusions: Tumor uptake of 18F-FluorThanatrace, both in vitro and on PET imaging of xenograft tumor models, quantitatively reflects differences in PARP-1 activity across different breast cancer cell lines, including BRCA1 defective. This motivates further studies of 18F-FluorThanatrace as an in vivo measure of PARP-1 activity and possibly as a predictive marker for PARP-1 therapy in patients, including those with BRCA1/2 mutations.

Citation Format: Edmonds CE, Lieberman BP, Xu K, Zeng C, Makvandi M, Li S, Hou C, Lee H, Greenberg RA, Mankoff DA, Mach RH. 18F-radiolabeled PARP-1 inhibitor uptake as a marker of PARP-1 activity in breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-01-06.

Use of Standardized Uptake Value Ratios Decreases Interreader Variability of [18F] Florbetapir PET Brain Scan Interpretation

BACKGROUND AND PURPOSE

Fluorine-18 florbetapir is a recently developed β-amyloid plaque positron-emission tomography imaging agent with high sensitivity, specificity, and accuracy in the detection of moderate-to-frequent cerebral cortical β-amyloid plaque. However, the FDA has expressed concerns about the consistency of interpretation of [(18)F] florbetapir PET brain scans. We hypothesized that incorporating automated cerebral-to-whole-cerebellar standardized uptake value ratios into [(18)F] florbetapir PET brain scan interpretation would reduce this interreader variability.

MATERIALS AND METHODS

This randomized, blinded-reader study used previously acquired [(18)F] florbetapir scans from 30 anonymized patients who were enrolled in the Alzheimer's Disease Neuroimaging Initiative 2. In 4 separate, blinded-reading sessions, 5 readers classified 30 cases as positive or negative for significant β-amyloid deposition either qualitatively alone or qualitatively with additional adjunct software that determined standardized uptake value ratios. A κ coefficient was used to calculate interreader agreement with and without the use of standardized uptake value ratios.

RESULTS

There was complete interreader agreement on 20/30 cases of [(18)F] florbetapir PET brain scans by using qualitative interpretation and on 27/30 scans interpreted with the adjunct use of standardized uptake value ratios. The κ coefficient for the studies read with standardized uptake value ratios (0.92) was significantly higher compared with the qualitatively read studies (0.69, P = .006).

CONCLUSIONS

Use of standardized uptake value ratios improves interreader agreement in the interpretation of [(18)F] florbetapir images.

Abstract ES08-2: Predicting tumor response by functional imaging, PET imaging as a functional predictive biomarker

The ability to measure biochemical and molecular processes to guide breast cancer treatment represents a significant advance in individualized breast cancer treatment. These assays have traditionally been performed by analysis of cell culture or tissue samples. More recently, functional and molecular imaging allows in vivo assay of biochemistry and molecular biology that is highly complementary to tissue-based assay. Molecular imaging can help inform drug trial of targeted breast cancer treatment and clinical decision making by (1) measuring regional expression of the therapeutic target, (2) testing the ability of drugs to interact with their intended targets, and (3) by measuring cancer response early in the course of treatment.

This talk will review basic principals of molecular imaging in breast cancer, with an emphasis on those methods that have been tested in patients. The talk will review the current state of molecular imaging in breast cancer patients, including methods in routine clinical use, those undergoing advanced clinical trials, and those in early-phase testing. Current trials and future directions will be highlighted.

The session is designed for a broad audience, ranging from breast cancer translational scientists to practicing physicians caring for breast cancer patients.

References

1. Mankoff DA. Molecular imaging as a tool for translating breast cancer science. Breast Cancer Res. 2008;10 Suppl 1:S3.

2. Specht JM, Mankoff DA. Advances in molecular imaging for breast cancer detection and characterization. Breast Cancer Res. 2012 Mar 16;14(2):206.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr ES08-2.

Abstract P4-01-03: HDACi (vorinostat) in metastatic breast cancer to restore sensitivity to ER-directed (AI) therapy: A phase II clinical trial with FES imaging correlates

Background: Histone deacetylase inhibitors (HDACi) have shown pre-clinical promise in estrogen receptor(ER)-modulation and restoring sensitivity to endocrine manipulation, suggesting potential clinical benefit (Sabnis 2011) (Huang 2000) in ER+ breast cancer. Vorinostat is an FDA-approved HDACi for CTCL, and could have a beneficial role in restoring ER-signaling in endocrine-resistant tumors (Munster 2011) (Yardley 2011). [F-18]fluoroestradiol (FES) PET imaging may be used to monitor regional tumor ER expression in patients with breast cancer (Linden 2011).

Methods: Patients with metastatic breast cancer with prior clinical benefit from endocrine manipulation who progressed on an AI therapy are eligible for this ongoing trial. In part A, patients were given vorinostat for 2 weeks, then resumed AI for 6 W. In part B (reflecting results of prior HDACi trials) patients are given vorinostat 400mg po daily 5/7 days 3/4 weeks while AI is given continuously. Paired FES and FDG PET are performed at baseline, week 2 and 8; clinical/radiologic assessment of disease is also performed at week 8. Patients with clinical benefit (response or stable disease) may continue on treatment until progressive disease or study withdrawal. Lesion-level analysis of the association between baseline FES uptake (logged) and FES/FDG ratio used generalized estimating equations (GEE) with small-sample adjustments to standard errors.

Results: 12/ 20 planned patients have accrued, and the treatment is well tolerated. Enrolled women were postmenopausal, the majority with primary infiltrating ductal tumors, bone/soft tissue dominant with longstanding metastatic disease, exposed to multiple endocrine and chemotherapy regimens. Five patients have had clinical benefit (2/4 on part B with greater HDACi exposure). One patient withdrew from the study due to toxicity. FES and FDG uptake was analyzed in 42 lesions in 11 patients. Average FES uptake was 2.0 (SULmean) for patients with clinical benefit, and 1.2 in patients with progressive disease by 8 weeks (p = 0.09). FES/FDG ratio at baseline was also associated with response (p = 0.04).

Conclusions: HDACi therapy is promising in relapsed ER+ breast cancer. Imaging of metabolic pathways in parallel with clinical trials may accelerate understanding of the underlying tumor biology and refine treatment selection.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-01-03.

Abstract P4-01-02: The role of FLT PET early assessment of response to endocrine therapy for early stage breast cancer

Background: In estrogen receptor positive (ER+) tumors, a low proliferative index (Ki-67) two weeks into endocrine therapy predicts response. FLT PET non-invasively measures tumor proliferation in vivo. The pre-operative window is an opportunity to assess impact of systemic therapies. We tested associations between FLT PET qualitative and quantitative measures and Ki-67 following two weeks of aromatase inhibitor (AI) therapy.

Methods: Women with clinical stage I-II ER+ HER2– breast cancer underwent “run-in” of AI monotherapy prior to definitive surgery. Premenopausal women were given GNRH agonist treatment 2 W prior to AI therapy. FLT PET was performed before AI therapy, and 1-7 days before surgery. Ki-67 was measured in baseline core biopsy and surgical specimens.

Results: Fourteen patients (8 postmenopausal, 6 premenopausal) have been enrolled. All have undergone baseline FLT PET imaging; 11 have completed imaging and surgery, including one premenopausal patient with no residual invasive carcinoma following 26 days of AI therapy. The majority harbored ductal carcinomas (n = 9, 5 with lobular histology) with the majority histologic grade ≥ 2 (n = 11). The median number of days exposed to AI was 19 (range, 9-42). Baseline SUVmax ranged from 1.2 to 3.9 (median 2.2), and post run-in SUV (6-64 days later) ranged from 1.2 to 2.8 (median 1.8). Baseline Ki-67 ranged from 6-26.2, median 11.6; surgical Ki-67 post AI therapy ranged from 0- 20.3 median 3.7, with seven below 5%. SUV and flux declined in most patients, as did Ki-67.

Quantitative FLT flux correlated with tumor response assessed by proliferative index (Ki-67) before the “run-in” period, with a stronger correlation at surgery, Pearson correlation coefficients = 0.41 and 0.82, respectively. FLT SUV and qualitative changes were not strongly associated with Ki-67.

Conclusions: Both pre and postmenopausal women with early stage breast cancer showed imaging and tissue response to endocrine therapy. Quantitative, but not qualitative FLT is a promising tool to assess tumor proliferation and response to therapy. Accrual is ongoing and updated results will be reported.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-01-02.

Abstract BS3-2: Molecular Imaging of Breast Cancer: Visualizing In Vivo Breast Cancer Biology

The ability to measure biochemical and molecular processes underlies progress in breast cancer biology and treatment. These assays have traditionally been performed by analysis of cell culture or tissue samples. More recently, functional and molecular imaging allows in vivo assay of biochemistry and molecular biology that is highly complementary to tissue-based assay. Molecular imaging can serve and number of roles, from characterization of pre-clinical models, to testing the ability of novel drugs to interact with their intended targets, to characterizing entire burden of disease for patients with breast cancer, to helping direct therapeutic choices and assign their efficacy.

This talk will review basic principals of molecular imaging, with an emphasis on those methods of greatest translational potential. The session will discuss the use of pre-clinical models of breast disease to help test and validate new molecular imaging methods, and in turn, the use of molecular imaging to characterize the disease process in the animal models. The session will then review the current state of molecular imaging in breast cancer patients, including methods in routine clinical use, those undergoing advanced clinical trials, and those in early-phase testing.

The session is designed for a broad audience, ranging from breast cancer translational scientists to practicing physicians caring for breast cancer patients.

References

1. Vernon AE, Bakewell SJ, Chodosh LA. Deciphering the molecular basis of breast cancer metastasis with mouse models. Rev Endocr Metab Disord. 2007 Sep;8(3):199–213. 2. Mankoff DA. Molecular imaging as a tool for translating breast cancer science. Breast Cancer Res. 2008;10 Suppl 1:S3. 3. Specht JM, Mankoff DA. Advances in molecular imaging for breast cancer detection and characterization. Breast Cancer Res. 2012 Mar 16;14(2):206.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr BS3-2.

P1-06-25: Changes in FDG PET SUV Correlates with Ki-67 Following 2 Weeks of Aromatase Inhibitor Therapy in ER+ Early Stage Breast Cancer, a Pilot Imaging Study

Background: In estrogen receptor positive (ER+) tumors, a low proliferative index (Ki-67) two weeks into endocrine therapy predicts response. FDG PET non-invasively measures tumor sites in vivo. The pre-operative window is an opportunity to assess impact of systemic therapies. We tested associations between FDG PET standardized uptake value (SUV) and Ki-67 after two weeks of aromatase inhibitor (AI) therapy in newly diagnosed, postmenopausal women.

Methods: Postmenopausal patients with clinical stage I-II ER+ HER2− primary tumors underwent a 9–35 day “run-in” of AI monotherapy prior to definitive surgery. FDG PET was performed before AI therapy, and 1–5 days before surgery. Ki-67 was measured in baseline core biopsy and surgical specimens.

Results: To date, 18 patients (median age 59) have been enrolled of whom 14 patients have undergone serial FDG PET imaging with 12 completed assessment of Ki-67 in surgical samples including one who had no residual invasive carcinoma. The majority harbored ductal carcinomas (n=16) with 10/18 having histologic grade ≥ 2. The median number of days exposed to AI was 18 (range, 9–35). Baseline SUV ranged from 1.8 to 10.9 (median 2.5), and post run-in SUV (7-34 days later) ranged from 1.0 to 10.7 (median 2.5). A median 14% decrease in SUV was observed between paired FDG PET studies (range, 44% decline to 13% increase). Five of 12 patients’ index lesion FDG SUV declined by 20% or more; all also had Ki-67 ≤5% at surgery. An additional 5 patients with Ki-67 ≤5% at surgery had percentage change in FDG PET SUV of 0% to 17% decline. Results will be updated as accrual is ongoing.

Conclusions: Substantial changes in FDG PET SUV in the breast tumor were appreciated early in AI therapy. SUV declined or was stable in all but one patient of 14, and all patients with ≥ 20% decrease in SUV had a low (≤5%) Ki-67 at surgery. Serial PET is a promising measure of early response to therapy.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-06-25.

OT2-05-03: ACRIN 6688 Phase II Study of Fluorine-18 3′-Deoxy-3′ Fluorothymidine (FLT) in Invasive Breast Cancer

Background

Neoadjuvant chemotherapy (NAC) prior to surgery provides enhanced options for locoregional management and has become an integral component of primary breast cancer management. Initial tumor response in patients receiving NAC is generally determined at therapy completion. This evaluation is determined by either the presence/absence of palpable tumor as a clinical response and/or presence/absence of invasive tumor cells in the breast and nodes as a pathological response. The ability to evaluate the effectiveness of neoadjuvant therapy early during treatment would be of significant importance. FDG PET imaging has been shown to be predictive of subsequent tumor response, but the tendency of FDG to accumulate in inflammatory tissues can complicate image interpretation. MRI changes have also been touted as predictors of response. Preliminary data suggest that early FLT PET is better able to predict response to therapy, as FLT uptake has been shown to correlate with cellular proliferation, and does not significantly accumulate in inflammatory tissue (Kenny et al, Eur J Nucl Med Mol Imaging 2007:1339–1347). The analysis of these data may provide a better understanding of early treatment response and improve the clinical management of breast cancer in the future.

Trial design and eligibility: In this phase II multi-institutional study, breast cancer patients with locally advanced disease with a tumor size ≥2cm (measured on imaging or estimated by physical exam) are eligible. Participants will receive standard of care NAC at their respective institutions. Participants will have 3 FLT imaging sessions to evaluate therapy response: at baseline, early-treatment (5-10 days after initiating treatment), and post-treatment prior to surgery.

Specific aims: The primary objective is to correlate the percentage change in the standardized uptake value between baseline and early therapy FLT in the primary tumor with pathologic response. Correlatively, FLT PET parameters will be compared with proliferative indices from the initial biopsy and residual tumor surgical samples using Ki-67 staining, mitotic index, and residual cancer burden. Potential safety issues and the physiologic effects associated with FLT administration will also be evaluated.

Statistical methods: To evaluate the relationship between an uptake parameter and pathologic complete response, a ROC curve will be estimated and the area under the curve, along with its 95% confidence interval, will be determined.

Accrual: Currently, 45/67 patients have accrued to the study.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT2-05-03.

OT2-05-02: ACRIN 6691 Monitoring and Predicting Breast Cancer Neoadjuvant Chemotherapy Response Using Diffuse Optical Spectroscopic Imaging (DOSI)

Background

Imaging technologies monitoring and predicting breast cancer response to neoadjuvant chemotherapy (NAC) are of increasing interest. The utility of conventional imaging approaches varies and identifies the need for alternate functional imaging strategies. The use of model-based photon migration methods to quantitatively separate light absorption from scattering in multiply-scattering tissues is a type of near-infrared spectroscopy (NIRS) broadly referred to as diffuse optical spectroscopy (DOS) [Bevilacqua, et al. Applied Optics, 2000; Jakubowski, et al., J of Applied Optics, 2009]. DOSI is a promising experimental technology that allows patients undergoing NAC to be followed with a “no significant risk” device meeting Food and Drug Administration criteria for exempt status. The current design is a mobile device which offers increased accessibility and is relatively simple to perform and interpret, as compared to mammography, magnetic resonance imaging, and positron emission tomography. Due to its size and portability, DOSI is a low barrier-to-access technology, creating new opportunities for patients to receive personalized treatment and for physicians to gain new insight into response mechanisms. The long-term goal is to provide oncologists with a relatively simple, risk-free bedside tool that can be used to help inform medical decisions on chemotherapy regimen, duration, and timing of surgery, thereby maximizing therapeutic response and minimizing unnecessary toxicity.

Trial design: In this phase I/II prospective single arm study, patients will receive SOC NAC at five (5) NCI Network for Translational Research in Optical Imaging (NTROI) clinical sites with identical DOSI instruments and procedures. Patients will receive four DOSI exams: at baseline before chemotherapy, at early therapy 5–10 days after NAC initiation, at mid therapy, and at post therapy prior to surgery. The protocol will evaluate a harmonized DOSI technology platform that has been standardized for NAC monitoring.

Eligibility: Women who have been diagnosed with breast cancer, have had confirmation by pre-treatment biopsy, and are scheduled to receive NAC followed by surgery are eligible for this trial.

Specific aims: The primary aim of this clinical trial is to determine whether the baseline to mid-therapy changes in the DOSI measurement of the quantitative tumor tissue optical index can predict final pathologic complete response in patients with breast cancer undergoing NAC. The secondary aims investigate the correlation between additional DOSI quantitative measurements of tumor biochemical composition obtained at other timepoints, the full range of pathologic response (i.e. complete, partial, and non-response), and any corresponding imaging measurements.

Statistical methods: Logistic regression models will be used to study the relationships between pathological complete response and percent change in tissue optical index tumor to normal ratio at different imaging time points.

Study size: A total of sixty (60) patients will be enrolled in this imaging study. Currently, one patient has accrued.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT2-05-02.

P2-09-09: Dynamic FDG PET and DCE-MRI To Assess Tumor Metabolism and Blood Flow in Response to Neoadjuvant Sunitinib and Paclitaxel Followed by AC + G-CSF in Patients with Locally-Advanced (LABC) and/or Inflammatory Breast Cancer (IBC)

Background

Kinetic analysis of FDG PET and DCE-MRI can identify patterns of breast tumor metabolism and perfusion that predict pathologic response, relapse, and survival in patients (pts) receiving neoadjuvant chemotherapy (NC). We are enrolling pts with LABC or IBC on a phase II trial of neoadjuvant sunitinib and metronomic chemotherapy. The addition of sunitinib, a tyrosine kinase inhibitor of VEGFR1-3, PDGFR, c-KIT, to NC is hypothesized to increase rate of pathologic complete response (pCR). Assessment of FDG PET measures of glucose metabolism (Ki), glucose delivery (K1) which approximates blood flow, and MRI measures of blood flow and vascularity (peak enhancement (PE), signal enhancement ratio (SER), and volume) during NC offers the opportunity to evaluate the in vivo pharmacodynamics of sunitinib.

Methods: Pts with HER2−negative LABC or IBC participated in a companion imaging trial with [18F]-FDG PET and DCE-MRI before NC (T0), after a 1 wk run-in of sunitinib 25 mg po daily (T1), after 12 wks of paclitaxel 80 mg/m2 IV Qwk and sunitinib 25 mg po daily (T2), and prior to breast surgery (T3) after 15 wks of doxorubicin 24 mg/m2 IV Qwk, cyclophosphamide 60 mg/m2 po daily with G-CSF 5 mcg/kg SC days 2–6 each wk. FDG metabolic rate (Ki), glucose delivery (K1), and MR indices (PE, SER, volume) were assessed. Imaging parameters were compared for groups defined by NC pathologic complete response (pCR) vs. non-pCR using a two-sample t-test.

Results: The imaging trial included 14 pts. Median age was 50 years (43-79). All had HER2−negative LABC (n=13, 93%) or IBC (n=1, 7%). Most tumors were ductal (n=12, 86%) and high grade (n=9, 64%). Seven (50%) tumors were ER negative. pCR was observed in 4/14 (29%) pts in this cohort. Changes in Ki, K1, and MRI volume were observed between baseline (T0) and the sunitinib run-in (T1). For example, 8/14 (57%) had a decrease in K1 of >20%, and 3 (21%) had an increase of ≥20%. These 1 week changes did not predict subsequent response to NC. However, declines in Ki and K1 between baseline (T0) and following sunitinib and paclitaxel (T2) did predict pCR. The average change in glucose metabolism (Ki) was a 95% decline with pCR and a 68% decline otherwise (p= 0.007). The average T0-T2 K1 change was 83% decline for pts with pCR and 47% decline otherwise (p= 0.029). In contrast to our previous studies in LABC pts treated with NC where decline in K1 was predictive of response, decline in Ki appears to be the more robust predictor of response in this cohort. Of 11 pts with PET scans at T2 and T3, 5 showed marked increase (>20%) in Ki and 6 showed marked increase in K1 after withdrawal of sunitinib.

Conclusion: Changes in breast tumor glucose metabolism (Ki), glucose delivery (K1), and blood flow (MR PE, SER, volume) can be detected after 1 wk of sunitinib, but are not predictive of response to NC. In the setting of anti-vascular therapy, measures of tumor glucose metabolism (Ki) are predictive and perhaps, more predictive of outcome than measures of glucose delivery (K1) which may be altered by sunitinib.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-09-09.

Positron emission tomography imaging of tissue P-glycoprotein activity during pregnancy in the non-human primate

BACKGROUND AND PURPOSE

Changes in tissue P-glycoprotein (P-gp) activity during pregnancy could affect the pharmacokinetics and thus the efficacy and toxicity of many drugs. Therefore, using positron emission tomography (PET) imaging, we tested whether gestational age affects tissue P-gp activity in the pregnant non-human primate, Macaca nemestrina.

EXPERIMENTAL APPROACH

Mid-gestational (day 75 +/- 13, n= 7) and late-gestational (day 150 +/- 10, n= 5) age macaques were imaged after administration of a prototypic P-gp substrate, (11)C-verapamil (13.7-75.4 MBq.kg(-1)), before and during intravenous infusion of a P-gp inhibitor, cyclosporin A (CsA) (12 or 24 mg.kg(-1).h(-1)). Accumulation of radioactivity in the fetal liver served as a reporter of placental P-gp activity. P-gp activity was expressed as CsA-induced percent change in the ratio of the area (0-9 min) under the (11)C-radioactivity concentration-time curve in the tissue (AUC(tissue)) to that in the maternal plasma (AUC(plasma)).

KEY RESULTS

The CsA-induced change in AUC(fetal liver)/AUC(maternal)(plasma) of (11)C-radioactivity significantly increased from mid- (35 +/- 25%) to late gestation (125 +/- 66%). Likewise, the CsA-induced change in AUC(maternal brain)/AUC(plasma) increased from mid- (172 +/- 80%) to late gestation (337 +/- 148%). The AUC ratio for the other maternal tissues was not significantly affected. Neither the CsA blood concentrations nor the level of circulating (11)C-verapamil metabolites were significantly affected by gestational age.

CONCLUSIONS AND IMPLICATIONS

P-gp activity at the blood-brain barrier and the placental barrier in the macaque increased with gestational age. If replicated in humans, the exposure of the fetus and maternal brain to P-gp substrate drugs, and therefore their efficacy and toxicity, will change during pregnancy.

Phase II trial of continuous dosing of sunitinib in advanced, FDG-PET avid, medullary thyroid carcinoma (MTC) and well-differentiated thyroid cancer (WDTC)

6056

Background: Due to the low efficacy of chemotherapy in progressive, WDTC and MTC, novel treatment approaches are needed. Thyroid cancers have elevated levels of vascular endothelial growth factor and higher microvessel density than normal thyroid tissue. Sunitinib inhibits several tyrosine kinase receptors involved in angiogenesis as well as the RET kinase frequently mutated in thyroid cancer. Here we report the results of a phase II trial investigating the use of continuous dosing sunitinib in patients with metastatic WDTC and MTC. Methods: Patients were eligible for enrollment if they had metastatic, iodine-refractory WDTC or MTC. To target those patients with more aggressive thyroid cancer, enrollment was limited to FDG-PET avid disease. Sunitinib was administered at 37.5 mg po qday on a continuous basis. Planned sample size is 35 patients. The primary end-point is response rate per RECIST criteria. Secondary end-points include FDG-PET response rate (defined as 20% reduction from baseline SUV) after 7 days of treatment, toxicity, overall survival, duration of response, and time to progression. Results: To date 33 patients have been enrolled (7 MTC:26 WDTC), and 29 patients have been evaluated for disease response. Median time on study is 7.5 months. Response rates to date: CR 7% (2/29), duration of response (9m+ and 14m+), PR 25% (8/29) (median 12 months), SD 48% (14/29) (median 6 months). Rate of disease control at 3 months (SD+PR+CR) 83% (24/29). 15 patients remain on study. Among those who have progressed the median time to progression is 6.5 months. FDG-PET was performed on 22 patients following 7 days of treatment, 36% (8/22) have a PET response. Of these patients 7 have disease control per RECIST criteria. Grade 3 toxicities seen in more than one patient include: anemia (2/33), fatigue (4/33), neutropenia (12/33), hand/foot syndrome (4/33), diarrhea (5/33), and leukopenia (11/33). One patient on lovenox therapy died of gastrointestinal bleeding. Conclusions: Continuous dosing of sunitinib is active (disease control rate 83%) in patients with high risk, metatstatic WDTC and MTC, as defined by FDG-PET avid disease.

[Table: see text]

Molecular imaging to select cancer therapy and evaluate treatment response

The ability to assay in vivo biologic processes non-invasively and quantitatively makes molecular imaging a particularly attractive tool for clinical trials of new drugs and for clinical cancer practice. This review highlights the emerging application of molecular imaging to cancer drug testing and clinical cancer treatment. The potential roles that imaging can play in the approach to cancer drug trials and clinical treatment are first highlighted, including applications to early drug testing, Phase II and III clinical trials, and clinical practice. The use of molecular imaging to select cancer therapy is then discussed, citing examples where molecular imaging can be used to measure the expression of therapeutic targets and factors mediating therapeutic resistance. The use of imaging to measure early pharmacodynamic changes and subsequent response to cancer treatment is then reviewed. Finally, the need for standardization and reproducible quantitative imaging analysis is reviewed.

DCE-MRI and dynamic FDG PET to monitor breast cancer response to neoadjuvant sunitinib in patients with locally-advanced breast cancer

Abstract #6006

Background: We are enrolling patients with locally-advanced (LABC) or inflammatory breast cancer on a phase II trial of neoadjuvant sunitinib and metronomic chemotherapy. The addition of sunitinib is hypothesized to increase rate of pathologic complete response (pCR) via its effect on tumor vasculature. Measurement of FDG PET and MRI parameters of metabolism and blood flow (BF) after a one week run-in of sunitinib alone provides an opportunity to evaluate in vivo pharmacodynamics of sunitinib which may be predictive of response and provide insight into mechanism of sunitinib activity. Materials and Methods: Patients with HER2 negative LABC participated in an imaging trial with pre-therapy [18F]-FDG PET and DCE-MRI (T0) followed by a one-week run-in of sunitinib 37.5 mg orally daily with a second PET and MRI on day 7 (T1). FDG metabolic rate (MRFDG), transport (FDG K1) and MR indices of tumor perfusion (peak enhancement (PE), signal enhancement ratio (SER), and washout volume(WV)) were assessed. Results: Metabolism and perfusion parameters are available for the first 3 patients treated on this trial. All patients presented with grade 3, HER2 negative LABC. DCI-MRI (left) and PET images (right) pre-therapy (T0, top) and after one week sunitinib (T1, bottom) are illustrated in Figure 1. DCE-MRI studies show gray-scale images with color-coded regional perfusion (SER) superimposed; red indicates high levels of perfusion and blue lower levels. Three different responses were observed and expressed as percent change T0 to T1: patient 1 had no significant change in metabolism (MRFDG) or perfusion (K1,SER, PE); patient 2 showed a decline in perfusion with decreases in K1 (-55%), SER (-19%), PE (-10%), and WV (-56%), but minimal change in MRFDG (+ 5.9%); while patient 3 had marked declines in perfusion K1 (-41%), SER (-25%), WV (-78%) and MRFDG (-59%). Discussion: These early data demonstrate the ability to measure changes in tumor metabolism and blood flow by PET and MRI and illustrate heterogeneity in tumor response to sunitinib. As patients complete neoadjuvant chemotherapy (NC), metabolism and perfusion parameters from mid-therapy (T2) and end-therapy (T3) imaging will be evaluated in the context of pCR versus other with the goal of exploiting functional imaging parameters to predict response to NC and elucidate mechanism of response to sunitinib and metronomic chemotherapy. Supported by grant from NCCN, SI11.
 


Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6006.

Metabolism-perfusion mismatch as assessed by PET varies with breast cancer phenotype and predicts response to neoadjuvant chemotherapy

Abstract #6005

Background: Kinetic analysis of FDG and water PET can identify patterns of breast cancer metabolism and perfusion in patients receiving neoadjuvant chemotherapy (NC). Previously, we found that high pre-therapy glucose tumor metabolism relative to perfusion was associated with poor tumor pathologic response, early relapse, and death in patients with locally advanced breast cancer (LABC) treated with NC. This analysis examines tumor metabolism and perfusion as a function of tumor phenotype. Material and Methods: Tumor phenotype, defined by immunohistochemistry (IHC), was determined in 51 patients undergoing NC between 1995 and 2005. Luminal tumors were defined as those expressing either estrogen receptor (ER) or progesterone receptor (PR). The triple-negative (TN) phenotype was defined as ER and PR negative without HER2 overexpression by IHC or amplification by FISH. HER2 phenotype showed HER2 overexpression or amplification but were ER/PR negative. Women with LABC underwent dynamic [18F]-FDG and [15O]-water PET scans prior to NC. The FDG metabolic rate (MRFDG) and transport (FDG K1) parameters were calculated; blood flow (BF) was estimated from the water PET scan. Response to NC was determined from surgical specimens with pathologic complete response (pCR) defined as eradication of invasive tumor in the breast vs. other. Results: Of the tumors studied, 16 (31%) were TN, 30 (59%) were luminal, and 5 (10%) were HER2. pCR was observed in 4/16 (25%) TN tumors (95% CI: 0.10-0.50) compared to only 4/30 (13%) of luminal tumors (95% CI: 0.05-0.30) and 3/5 HER2 tumors. Linear regression of the association between PET parameters and phenotype (TN vs. luminal) found that TN was associated with higher MRFDG (p=0.007) and MRFDG/BF ratio (p=0.02), but not with BF (p=0.27). Only patients with low pre-therapy MRFDG/BF ratio (<35 umol/mL) achieved a pCR. Using this value as an ad-hoc cutoff, 4/7 (57%) of TN patients with low ratios had a pCR, while 0/9 with higher ratios had pCR. In contrast, only 4/21 (19%) of the luminal patients with low ratios had a pCR (one-sided mid-p=0.04 for TN vs. luminal pCR rate for patients with MRFDG/BF < 35 umol/mL). Discussion: These results demonstrate heterogeneity in breast tumor metabolism and perfusion as assessed by PET, and suggest a clinically relevant association between PET parameters and tumor phenotypes. The high MRFDG/BF ratio that predicts poor response to NC is more common in TN tumors; whereas in luminal or HER2 tumors, high MRFDG is generally matched with higher BF. Measurement of tumor metabolism and perfusion may identify a subset of tumors which are unlikely to respond to NC. Identification of such tumors may direct therapy toward those biologic targets most likely to overcome resistance.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6005.

Tumor metabolism, blood flow changes, and prognosis by positron emission tomography: A prospective cohort of locally advanced breast cancer patients

506

Background: Breast cancer patients with locally advanced tumors receive preoperative chemotherapy to provide early systemic treatment and assess in-vivo tumor response. Positron emission tomography (PET) has been used to follow tumor response to therapy, as pathologic response is predictive of patient outcome. We evaluated the prognostic utility of serial quantitative PET tumor blood flow (BF) and metabolism measurements. Methods: Fifty-five women with a primary diagnosis of locally advanced breast carcinoma (LABC) underwent dynamic [18F]-FDG and [15O]-water PET scans prior to and at midpoint of neoadjuvant chemotherapy. The FDG metabolic rate (MRFDG), transport (K1), and flux (Ki) parameters were calculated, and tumor blood flow was estimated from the [15O]-water study. Associations between tumor BF and MRFDG measurements and disease-free survival (DFS) and overall survival (OS) were evaluated using the Cox proportional hazards model. Results: Patients that had an increase in BF and K1, from baseline to mid-therapy measurements, had elevated recurrence and mortality risks compared to patients that had reductions in BF and MRFDG values. In multivariate analysis, changes in BF and K1 remained independent prognostic indicators of DFS and OS survival. Conclusions: PET measurements of tumor response prior to completion of neoadjuvant chemotherapy were predictive of patient outcome. Patients that failed to have a decline in BF and K1 experienced higher risks of recurrence and mortality that was largely independent of clinical tumor characteristics assessed in this study. These results suggest that tumor perfusion, measured directly by [15O]-water or indirectly by dynamic FDG PET, is highly predictive of outcome in neoadjuvantly treated breast cancer.

No significant financial relationships to disclose.

Risk assessment in high grade sarcoma patients during neoadjuvant chemotherapy using multiple tracer PET

20006

Background: Patients with high grade soft tissue sarcomas are treated with neoadjuvant chemotherapy. Sarcomas have biological features that may predict for poor outcome. Some of these features are tumor proliferation rate, level of tumor hypoxia, and upregulation of tumor drug resistance mechanisms. Methods: We have a group of specific PET imaging agents to quantify the level of activity of these tumor processes. Patients with soft tissue sarcomas receive [C-11]Thymidine (TdR) to assess cellular proliferation, [O-15] Water to quantify tumor blood flow and to serve as the input function for quantification of the other tracers, [C-11]Verapamil to assess drug resistance mechanism activity, and [F-18]Fluoromisonidazole) FMISO to quantify changes in tumor hypoxic volume in response to treatment. These studies are performed in a single PET imaging session prior to neoadjuvant chemotherapy, after the second of four cycles of therapy and in the week prior to resection. Results: An example of this complex study result, is demonstrated by a recent patient with a high grade soft tissue sarcoma. The tumor showed increased TdR uptake, a moderate hypoxic volume, and [C-11] verapamil uptake prior to initiation of neoadjuvant adriamycin based chemotherapy. After 2 cycles of therapy, there was a significant decrease in the maximum level and volume of TdR uptake and a large reduction in tumor hypoxic volume. Conclusions: These data would imply a high risk soft tissue sarcoma due the presence of increased cellular proliferation, a significant hypoxic volume and the absence of p-glycoprotein activity determined by the presence of [C-11]Verapamil uptake. However, early response is also suggested by the findings above. Patient outcome will be assessed and correlated with these tumor parameters to further understand what tumor biological risk factors can be quantified non-invasively and repeated throughout the clinical course in soft tissue sarcoma patients. Supported by NIH NCI PO1 42045–18 and S10 RR017229–01

[Table: see text]

No significant financial relationships to disclose.

Hypoxia imaging-directed radiation treatment planning

Increasing evidence supports the role of the tumor microenvironment in modulating cancer behavior. Tissue hypoxia, an important and common condition affecting the tumor microenvironment, is well established as a resistance factor in radiotherapy. Increasing evidence points to the ability of hypoxia to induce the expression of gene products, which confer aggressive tumor behavior and promote broad resistance to therapy. These factors suggest that determining the presence or absence of tumor hypoxia is important in planning cancer therapy. Recent advances in PET hypoxia imaging, conformal radiotherapy, and imaging-directed radiotherapy treatment planning now make it possible to perform hypoxia-directed radiotherapy. We review the biological aspects of tumor hypoxia and PET imaging approaches for measuring tumor hypoxia, along with methods for conformal radiotherapy and image-guided treatment, all of which provide the underpinnings for hypoxia-directed therapy. As a case example, we review emerging data on PET imaging of hypoxia to direct radiotherapy.

18fluorodeoxyglucose positron emission tomography to detect mediastinal or internal mammary metastases in breast cancer

PURPOSE

To determine the prevalence of suspected disease in the mediastinum and internal mammary (IM) node chain by 18fluorodeoxyglucose (FDG) positron emission tomography (PET), compared with conventional staging by computed tomography (CT) in patients with recurrent or metastatic breast cancer.

PATIENTS AND METHODS

We retrospectively evaluated intrathoracic lymph nodes using FDG PET and CT data in 73 consecutive patients with recurrent or metastatic breast cancer who had both CT and FDG PET within 30 days of each other. In reviews of CT scans, mediastinal nodes measuring 1 cm or greater in the short axis were considered positive. PET was considered positive when there were one or more mediastinal foci of FDG uptake greater than the mediastinal blood pool.

RESULTS

Overall, 40% of patients had abnormal mediastinal or IM FDG uptake consistent with metastases, compared with 23% of patients who had suspiciously enlarged mediastinal or IM nodes by CT. Both FDG PET and CT were positive in 22%. In the subset of 33 patients with assessable follow-up by CT or biopsy, the sensitivity, specificity, and accuracy for nodal disease was 85%, 90%, and 88%, respectively, by FDG PET; 54%, 85%, and 73%, respectively, by prospective interpretation of CT; and 50%, 83%, and 70%, respectively, by blinded observer interpretation of CT. Among patients suspected of having only locoregional disease recurrence (n = 33), 10 had unsuspected mediastinal or IM disease by FDG PET.

CONCLUSION

FDG PET may uncover disease in these nodal regions not recognized by conventional staging methods. Future prospective studies using histopathology for confirmation are needed to validate the preliminary findings of this retrospective study.

Imaging cellular proliferation as a measure of response to therapy

Cell proliferation imaging is based on extensive laboratory investigations of labeled thymidine being selectively incorporated into DNA. [11C]-Thymidine labeled in the ring-2 or the methyl position is the natural extension of earlier work using tritiated thymidine. Proliferation imaging using [11C]-thymidine requires correction for labeled metabolites; however, quantitative approaches can provide reliable estimates of cellular proliferation by measuring thymidine flux from the blood into DNA in tumors. 18F-labeled thymidine analogs that are resistant to catabolism in vivo, [18F]-FLT and [18F]-FMAU, may simplify quantitative analysis and may be more suitable for clinical studies but will require careful validation to determine how their uptake is quantitatively related to cell growth. Clinical studies using [11C]-thymidine have demonstrated the power of cellular proliferation imaging to characterize tumors and monitor response early in the course of therapy. Patient imaging using the PET thymidine analogs is at an earlier stage but appears promising as a clinically feasible approach to cellular proliferation imaging.

[18F]fluoroestradiol radiation dosimetry in human PET studies

[18F]16alpha-fluoroestradiol (FES) is a PET imaging agent useful for the study of estrogen receptors in breast cancer. We estimated the radiation dosimetry for this tracer using data obtained in patient studies.

METHODS

Time-dependent tissue concentrations of radioactivity were determined from blood samples and PET images in 49 patients (52 studies) after intravenous injection of FES. Radiation absorbed doses were calculated using the procedures of the MIRD committee, taking into account the variation in dose based on the distribution of activities observed in the individual patients. Effective dose equivalent was calculated using International Commission on Radiological Protection Publication 60 weights for the standard woman.

RESULTS

The effective dose equivalent was 0.022 mSv/MBq (80 mrem/mCi). The organ that received the highest dose was the liver (0.13 mGy/MBq [470 mrad/mCi]), followed by the gallbladder (0.10 mGy/MBq [380 mrad/mCi]) and the urinary bladder (0.05 mGy/MBq [190 mrad/mCi]).

CONCLUSION

The organ doses are comparable to those associated with other commonly performed nuclear medicine tests. FES is a useful estrogen receptor-imaging agent, and the potential radiation risks associated with this study are well within accepted limits.

Internal mammary lymph node drainage patterns in patients with breast cancer documented by breast lymphoscintigraphy

BACKGROUND

Metastases to internal mammary lymph nodes (IMN) may occur in patients with breast cancer and may alter treatment recommendations. The purpose of this study was to identify the frequency of IMN drainage in patients undergoing breast lymphoscintigraphy and sentinel lymph node dissection (SLND).

METHODS

The combined technique of peritumoral injection of radiocolloid and Lymphazurin blue for SLND was performed on 220 patients. All patients underwent preoperative lymphoscintigraphy before SLND. Lesion location by quadrant included: 110 upper outer (UOQ), 49 lower outer (LOQ), 30 upper inner (UIQ), 24 lower inner (LIQ), and 7 central.

RESULTS

Drainage to any nodal basin was observed in 184 of 220 patients (84%). IMN drainage was documented in 37 of 220 (17%) of patients. IMN drainage without evidence of axillary drainage occurred in 2 of 220 patients(1%). Drainage to the IMN based on quadrant location of the lesion was as follows: UOQ, 10%; LOQ, 27%; UIQ, 17%; LIQ, 25%; and central, 29%.

CONCLUSIONS

Internal mammary lymph node drainage shown by breast lymphoscintigraphy is common. Tumors in all quadrants may drain to IMNs, although drainage is significantly more common from quadrants other than the UOQ. Further studies are needed to determine whether lymphoscintigraphy drainage patterns identify patients at the highest risk for IMN metastases who may benefit from radiotherapy.

Positron-emission tomographic imaging of cancer: glucose metabolism and beyond

Positron emission tomography (PET) has become an important diagnostic tool in oncology. We briefly review the physics of PET, instrumentation for imaging, and approaches to radiopharmaceutical production. The principles underlying the use of [(18)F]-fluorodeoxyglucose (FDG) are described, and the clinical experience with FDG pertinent to radiation oncology is reviewed. Finally, preliminary studies using PET tracers with greater specificity than FDG for tumor imaging are discussed. Emphasis is placed on underlying principles and those aspects of oncologic PET most applicable to radiation oncology.

Increased false negative sentinel node biopsy rates after preoperative chemotherapy for invasive breast carcinoma

BACKGROUND

Sentinel lymph node dissection (SLND) has been a promising new technique in breast carcinoma staging, but could be unreliable in certain patient subsets. The current study assessed whether age, preoperative chemotherapy, tumor size, and/or previous excisional biopsy influenced the identification of sentinel nodes (SLNs) or the reliability of a node-negative SLND in predicting a node negative axilla.

METHODS

Eighty-two patients who had clinically negative axillae underwent SLND followed by Level I/II axillary lymph node dissection (ALND). SLNDs were performed using both technetium-99m (Tc-99m) labeled colloid and isosulfan blue dye. SLNs were analyzed by hematoxlyin and eosin and immunocytochemical techniques.

RESULTS

SLNs were successfully identified in 80% of patients. Mapping success was decreased among postmenopausal women but was not influenced by preoperative chemotherapy, large tumor size, or previous excisional biopsy. Of the 31 successfully mapped, node positive patients, 5 had false negative (FN) SLNDs (overall FN rate = 16%). Of the 9 successfully mapped patients who had received preoperative chemotherapy and had positive axillary nodes, 3 had FN SLND (FN rate = 33%). The presence of clinically positive lymph nodes before chemotherapy did not predict which patients would have a subsequent FN SLND. T3 tumor size, but not previous excision, was associated significantly with increased FN rate, although the FN rate for previous excision was 11%. No FN SLND occurred with T1/T2 tumors that were not excised previously and had not received preoperative chemotherapy.

CONCLUSIONS

Preoperative chemotherapy was associated with an unacceptably high FN rate for SLND. While larger tumor size also was associated with FN SLND, this effect might have been due to preoperative chemotherapy use in these patients. Small sample size precluded determining whether excisional biopsy before mapping increased FN SLND rates independently.

Characterizing tumors using metabolic imaging: PET imaging of cellular proliferation and steroid receptors

Treatment decisions in oncology are increasingly guided by information on the biologic characteristics of tumors. Currently, patient-specific information on tumor biology is obtained from the analysis of biopsy material. Positron emission tomography (PET) provides quantitative estimates of regional biochemistry and receptor status and can overcome the sampling error and difficulty in performing serial studies inherent with biopsy. Imaging using the glucose metabolism tracer, 2 -deoxy-2- fluoro-D-glucose (FDG), has demonstrated PET's ability to guide therapy in clinical oncology. In this review, we highlight PET approaches to imaging two other aspects of tumor biology: cellular proliferation and tumor steroid receptors. We review the biochemical and biologic processes underlying the imaging, positron-emitting radiopharmaceuticals that have been developed, quantitative image-analysis considerations, and clinical studies to date. This provides a basis for evaluating future developments in these promising applications of PET metabolic imaging.

Interactions of 16alpha-[18F]-fluoroestradiol (FES) with sex steroid binding protein (SBP)

Fluorine-18 16alpha-Fluoroestradiol ([18F]-FES) is a positron-emitting tracer for the estrogen receptor that is used for positron emission tomography (PET) studies of tumor tissues rich in the estrogen receptor. The role of the sex steroid binding protein (SBP or SHBG) in the transport of the [18F]-FES to the estrogen-receptor-rich tissue in breast cancer patients in vivo was investigated. To determine the extent to which [18F]-FES is bound to SBP in the blood, we performed a series of studies using blood samples obtained from patients undergoing [18F]-FES PET scans. The binding of [18F]-FES to the SBP was measured using a simple protein precipitation assay. The binding of [18F]-FES metabolites to SBP was also measured. These measurements showed that the tracer was distributed between albumin and SBP, and the binding capacity of SBP was sufficient to ensure that the protein was not saturated when the tracer was fully mixed with the plasma; however, local saturation of SBP may occur when [18F]-FES is administered intravenously. Typically about 45% of [18F]-FES in circulating plasma was bound to SBP, but this fraction was dependent on the concentration of SBP in plasma. The transfer of the tracer between the two proteins was rapid, complete in less than 20 s at 0 degrees C, suggesting that the equilibrium was maintained under most circumstances and that local saturation resolved quickly when blood from the injection site entered the central circulation. These data suggest that SBP binding of [18F]-FES is significant and will affect the input function of the tracer for any model that is used for the quantitative evaluation of [18F]-FES uptake in PET studies. Estimates of equilibrium binding in blood samples are sufficient to characterize [18F]-FES binding to SBP in the circulation.

Sentinel lymph node mapping for breast cancer: analysis in a diverse patient group

PURPOSE

To evaluate sentinel lymph node mapping in patients with breast cancer.

MATERIALS AND METHODS

Sixty-two patients with breast cancer scheduled to undergo axillary nodal dissection underwent scintigraphic localization of sentinel lymph nodes with filtered technetium 99m sulfur colloid. At surgery, isosulfan blue was injected. Sentinel nodes were identifiable by blue color and by radioactivity with hand-held gamma probe. Results were analyzed statistically.

RESULTS

A sentinel lymph node was identified in 49 patients (79%). Lymph nodes were positive for metastatic disease in 26 patients (42%). The mapping success rate was 78% (n = 21) in the 27 patients with no prior surgery, 78% (n = 18) in the 23 patients with prior surgery, and 86% (n = 12) in the 14 patients with prior chemotherapy. Axillary nodes were positive in 11 (41%) of the 27 patients with no prior intervention, six (26%) of the 23 patients with prior surgery, and 10 (71%) of the 14 patients with prior chemotherapy. There were no false-negative findings in patients without prior intervention. Four patients with positive nodes had false-negative sentinel nodes.

CONCLUSION

Sentinel lymph node mapping and biopsy without axillary dissection is appropriate in patients with breast cancer who have not undergone prior intervention. Further study is necessary to ascertain the accuracy of the procedure for patients who have undergone presurgical chemotherapy or previous excisional biopsy.

Monitoring the response of patients with locally advanced breast carcinoma to neoadjuvant chemotherapy using [technetium 99m]-sestamibi scintimammography

BACKGROUND

Mammographic and physical examination assessments of the response of locally advanced breast carcinoma (LABC) to neoadjuvant therapy have been shown to be inaccurate. The authors studied the feasibility and accuracy of [technetium 99m]-sestamibi (MIBI) for monitoring the response of patients with LABC to neoadjuvant chemotherapy.

METHODS

Patients receiving neoadjuvant chemotherapy for LABC underwent prone lateral scintimammography before therapy, after 2 months of therapy, and close to the completion of chemotherapy (presurgery) if chemotherapy continued for >3 months. Images were analyzed both qualitatively and quantitatively using the lesion-to-normal breast MIBI uptake ratio (L:N). Imaging results were compared with the clinical response and the pathologic response as determined from the posttherapy surgical specimen.

RESULTS

A total of 32 patients (29 who were assessable for primary tumor response and 28 who were assessable for lymph node response) were included in the study. The mean change in the primary tumor L:N MIBI uptake ratio after 2 months of chemotherapy was -35% for clinical responders and +17% for nonresponders (P<0.001). Patients achieving a pathologic primary tumor macroscopic complete response (CR) had a mean change in uptake on the presurgical scan of -58% versus -18% for patients with a partial response (P<0.005). A decrease of > or =40% in the MIBI uptake ratio identified CRs with 100% sensitivity and 89% specificity. Pretherapy imaging predicted axillary lymph node metastases in 85% of patients ultimately found to have > or =1 positive lymph nodes at surgery, but was less accurate in identifying residual lymph node disease after therapy (55% sensitivity and 75% specificity).

CONCLUSIONS

MIBI imaging accurately assessed the response to neoadjuvant chemotherapy in patients with LABC. Further studies are needed to determine the role of MIBI in this group of patients.

Technical aspects of sentinel node lymphoscintigraphy for breast cancer

OBJECTIVE

A significant morbidity risk is associated with axillary nodal dissections for breast cancer. Many treatment decisions are based on axillary nodal status. Lymphatic mapping and sentinel node biopsy have been investigated to determine if the histology of the sentinel node reflects the remaining lymph node basin. We describe the technical aspects of sentinel node lymphoscintigraphy for breast cancer.

METHODS

Ninety-three patients had lymphoscintigraphy for breast cancer. Patients with palpable lesions had 4 concentric injections around the site and lesions requiring localization had injections made through tubing connected to the localizing wire introducer needle. Immediate static images were acquired and the sentinel node was marked for surgery. Marks were reverified using a handheld gamma probe.

RESULTS

Lymph nodes were visualized by lymphoscintigraphy in 87% of cases. Time to visualization of lymph nodes ranged from 1-120 min with a mean of 28 min. An average of 1.5 nodes were visualized. The overall success rate for identifying the sentinel node at time of surgery was 85%.

CONCLUSION

We conclude that lymphoscintigraphy for breast cancer is a detailed procedure that requires coordination with radiology and surgery teams to ensure proper identification of sentinel lymph nodes.

Kinetic analysis of 2-[11C]thymidine PET imaging studies: validation studies

2-[11C]thymidine has been tested as a PET tracer of cellular proliferation. We have previously described a model of thymidine and labeled metabolite kinetics for use in quantifying the flux of thymidine into DNA as a measure of tumor proliferation. We describe here the results of studies to validate some of the model's assumptions and to test the model's ability to predict the time course of tracer incorporation into DNA in tumors.

METHODS

Three sets of studies were conducted: (a) The uptake of tracers in proliferative tissues of normal mice was measured early after injection to assess the relative delivery of thymidine and metabolites of thymidine catabolism (thymine and CO2) and calculate relative blood-tissue transfer rates (relative K1s). (b) By using sequential injections of [11C]thymidine and [11C]thymine in normal human volunteers, the kinetics of the first labeled metabolite were measured to determine whether it was trapped in proliferating tissue such as the bone marrow. (c) In a multitumor rat model, 2-[14C]thymidine injection, tumor sampling and quantitative DNA extraction were performed to measure the time course of label uptake into DNA for comparison with model predictions.

RESULTS

Studies in mice showed consistent relative delivery of thymidine and metabolites in somatic tissue but, as expected, showed reduced delivery of thymidine and thymine in the normal brain compared to CO2. Thymine studies in volunteers showed only minimal trapping of label in bone marrow in comparison to thymidine. This quantity of trapping could be explained by a small amount of fixation of labeled CO2 in tissue, a process that is included as part of the model. Uptake experiments in rats showed early incorporation of label into DNA, and the model was able to fit the time course of uptake.

CONCLUSION

These initial studies support the assumptions of the compartmental model and demonstrate its ability to quantify thymidine flux into DNA by using 2-[11C]thymidine and PET. Results suggest that further work will be necessary to investigate the effects of tumor heterogeneity and to compare PET measures of tumor proliferation to in vitro measures of proliferation and to clinical tumor behavior in patients undergoing therapy.

Value of combined FDG PET and MR imaging in the evaluation of suspected recurrent local-regional breast cancer: preliminary experience

PURPOSE

To assess the performance and potential clinical effects of combined 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) and magnetic resonance (MR) imaging of the axilla and brachial plexus in patients suspected of having local-regional breast cancer metastases.

MATERIALS AND METHODS

Upper-body FDG PET and axillary and supraclavicular MR imaging were performed in 10 patients (age range, 45-71 years) with clinical findings suggestive of breast cancer metastases. Medical records were reviewed retrospectively. Imaging findings were correlated with clinical data and follow-up findings in all patients. Surgical findings were available in four patients.

RESULTS

Nine patients had local-regional breast cancer metastases. MR imaging was diagnostic for tumor in five patients and was indeterminate in four patients with axillary or chest wall metastases. With FDG PET, metastatic tumor was positively identified in all nine patients. MR imaging was useful for determining the relationship of metastatic tumor to axillary and supraclavicular neurovascular structures. FDG PET helped confirm metastases in patients with indeterminate MR imaging findings and depicted unsuspected metastases outside the axilla.

CONCLUSION

MR imaging and FDG PET are complementary in detecting and characterizing local-regional breast cancer metastases. Combined FDG PET and MR imaging provide useful treatment-planning data for patients clinically suspected of having recurrent axillary or supraclavicular breast cancer.

2-[C-11]thymidine imaging of malignant brain tumors

Malignant brain tumors pose diagnostic and therapeutic problems. Despite the advent of new brain imaging modalities, including magnetic resonance imaging (MRI) and [F-18]fluorodeoxyglucose (FDG) positron emission tomography (PET), determination of tumor viability and response to treatment is often difficult. Blood-brain barrier disruption can be caused by tumor or nonspecific reactions to treatment, making MRI interpretation ambiguous. The high metabolic background of the normal brain and its regional variability makes it difficult to identify small or less active tumors by FDG imaging of cellular energetics. We have investigated 2-[C-11]thymidine (dThd) and PET to image the rate of brain tumor cellular proliferation. A series of 13 patients underwent closely spaced dThd PET, FDG PET, and MRI procedures, and the image results were compared by standardized visual analysis. The resulting dThd scans were qualitatively different from the other two scans in approximately 50% of the cases, which suggests that dThd provided information distinct from FDG PET and MRI. In two cases, recurrent tumor was more apparent on the dThd study than on FDG; in two other patients, tumor dThd uptake was less than FDG uptake, and these patients had slower tumor progression than the three patients with both high dThd and FDG uptake. To better characterize tumor proliferation, kinetic modeling was applied to dynamic dThd PET uptake data and metabolite-analyzed blood data in a subset of patients. Kinetic analysis was able to remove the confounding influence of [C-11]CO2, the principal labeled metabolite of 2-[C-11]dThd, and to estimate the flux of dThd incorporation into DNA. Sequential, same-day [C-11]CO2 and [C-11]dThd imaging demonstrated the ability of kinetic analysis to model both dThd and CO2 simultaneously. Images of dThd flux obtained using the model along with the mixture analysis method for pixel-by-pixel parametric imaging significantly enhanced the contrast of tumor compared with normal brain. Comparison of model estimates of dThd transport versus dThd flux was able to discern increased dThd uptake simply on the basis of blood-brain barrier disruption retention on the basis of increased cellular proliferation. This preliminary study demonstrates the potential for imaging brain tumor cellular proliferation to provide unique information for guiding patient treatment.

Imaging of oncologic patients: benefit of combined CT and FDG PET in the diagnosis of malignancy

OBJECTIVE

The purpose of this study was to assess the benefit of combined CT and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in diagnosing malignancy.

MATERIALS AND METHODS

The records of 26 patients with intraabdominal and intrathoracic neoplasms who underwent CT and FDG PET between January 1995 and September 1996 were retrospectively reviewed. Most of these patients had inconclusive findings on prior CT for the diagnosis of malignancy. Only sites of potential malignant disease were included in the data analysis. Presence or absence of malignancy was confirmed by histopathology or follow-up CT. Three observers experienced in abdominal imaging used CT findings alone to estimate level of suspicion (1 = definitely not malignant to 5 = definitely malignant) for primary or recurrent neoplasms (n = 21), distant metastases (n = 25), and neoplastic nodal involvement (n = 18). Six weeks later the three observers reviewed the same CT examinations supplemented with FDG PET and reestimated suspicion of malignancy. Receiver operating characteristic methodology was used to analyze the results. Sensitivity, specificity, positive and negative predictive values, and accuracy in diagnosis of malignant disease were calculated using level 4 (probable malignancy) as the cutoff for the presence of disease.

RESULTS

The mean area under the receiver operating characteristic curve, indicating successful diagnosis of malignancy, was .82 for CT alone and .92 for CT with FDG PET (p < .05). The accuracies for diagnosis of primary or recurrent neoplasms, distant metastases, and neoplastic nodal involvement were 62%, 68%, and 83%, respectively, for CT alone and 81% (p = .06), 88% (p = .03), and 89% (p > .25), respectively, for CT with FDG PET. Also, supplemental FDG PET imaging improved observer confidence and accuracy in diagnosing recurrent neoplasm in four (36%) of 11 patients who had undergone surgery or chemoradiation and in diagnosing four (29%) of 14 extrahepatic sites that had potential metastases.

CONCLUSION

Diagnosis of malignancy in oncologic patients is significantly improved when CT is supplemented with FDG PET. Combined imaging is particularly helpful in the evaluation of potential recurrence in previously treated patients and for diagnosing extrahepatic lesions that may be distant metastases.

Carbon-11-thymidine and FDG to measure therapy response

This study was performed to determine if PET imaging with 11C-thymidine could measure tumor response to chemotherapy early after the initiation of treatment. Imaging of deoxyriboneucleic acid biosynthesis, quantitated with 11C-thymidine, was compared with measurements of tumor energetics, obtained by imaging with 18F-fluorodeoxyglucose (FDG).

METHODS

We imaged four patients with small cell lung cancer and two with high-grade sarcoma both before and approximately 1 wk after the start of chemotherapy. Thymidine and FDG studies were done on the same day. Tumor uptake was quantified by standardized uptake values (SUVs) for both tracers by the metabolic rate of FDG and thymidine flux constant (K(TdR)) using regions of interest placed on the most active part of the tumor.

RESULTS

In the four patients with clinical response to treatment, both thymidine and FDG uptake markedly declined 1 wk after therapy. Thymidine measurements of SUV and K(TdR) declined by 64% +/- 15% and 84% +/- 33%, respectively. FDG SUV and the metabolic rate of FDG declined by 51% +/- 9% and 63% +/- 23%, respectively. In the patient with metastatic small cell lung cancer who had disease progression, the thymidine SUV decreased by only 8% (FDG not done). In a patient with abdominal sarcoma and progressive disease, thymidine SUV was essentially unchanged (declined by 3%), whereas FDG SUV increased by 69%.

CONCLUSION

Images show a decline in both cellular energetics and proliferative rate after successful chemotherapy. In the two patients with progressive disease, thymidine uptake was unchanged 1 wk after therapy. In our limited series, K(TdR) measurements showed a complete shutdown in tumor proliferation in patients in whom FDG showed a more limited decrease in glucose metabolism.