Ryan S. Youland

Biopsy validation of 18F-DOPA PET and biodistribution in gliomas for neurosurgical planning and radiotherapy target delineation: results of a prospective pilot study

BACKGROUND Delineation of glioma extent for surgical or radiotherapy planning is routinely based on MRI. There is increasing awareness that contrast enhancement on T1-weighted images (T1-CE) may not reflect the entire extent of disease. The amino acid tracer (18)F-DOPA (3,4-dihydroxy-6-[18F] fluoro-l-phenylalanine) has a high tumor-to-background signal and high sensitivity for glioma imaging. This study compares (18)F-DOPA PET against conventional MRI for neurosurgical biopsy targeting, resection planning, and radiotherapy target volume delineation. METHODS Conventional MR and (18)F-DOPA PET/CT images were acquired in 10 patients with suspected malignant brain tumors. One to 3 biopsy locations per patient were chosen in regions of concordant and discordant (18)F-DOPA uptake and MR contrast enhancement. Histopathology was reviewed on 23 biopsies. (18)F-DOPA PET was quantified using standardized uptake values (SUV) and tumor-to-normal hemispheric tissue (T/N) ratios. RESULTS Pathologic review confirmed glioma in 22 of 23 biopsy specimens. Thirteen of 16 high-grade biopsy specimens were obtained from regions of elevated (18)F-DOPA uptake, while T1-CE was present in only 6 of those 16 samples. Optimal (18)F-DOPA PET thresholds corresponding to high-grade disease based on histopathology were calculated as T/N > 2.0. In every patient, (18)F-DOPA uptake regions with T/N > 2.0 extended beyond T1-CE up to a maximum of 3.5 cm. SUV was found to correlate with grade and cellularity. CONCLUSIONS (18)F-DOPA PET SUV(max) may more accurately identify regions of higher-grade/higher-density disease in patients with astrocytomas and will have utility in guiding stereotactic biopsy selection. Using SUV-based thresholds to define high-grade portions of disease may be valuable in delineating radiotherapy boost volumes.

Changes in presentation, treatment, and outcomes of adult low-grade gliomas over the past fifty years

BACKGROUND To identify changes in patient presentation, treatment, and outcomes of low-grade gliomas (LGGs) over the past 50 years. METHODS Records of 852 adults who received a diagnosis at Mayo Clinic from 1960 through 2011 with World Health Organization grade II LGGs were reviewed and grouped by those who received a diagnosis before (group I: 1960-1989) and after (group II: 1990-2011) the routine use of postoperative MRI. RESULTS Median follow-up was 23.3 and 8.7 years for groups I and II, respectively. Patients in group I more often presented with seizures, headaches, sensory/motor impairment, and astrocytoma histology. Over time, more gross total resections (GTRs) were achieved, fewer patients received postoperative radiotherapy (PORT), and more received chemotherapy. Median progression-free survival (PFS) and overall survival (OS) were 4.4 and 8.0 years, respectively. Although PFS was similar, 10-year OS was better in group II (47%) than in group I (33%; P < .0001). Improved PFS in multivariate analysis was associated with group I patients, nonastrocytoma histology, small tumor size, successful GTR, or radical subtotal resection (rSTR), PORT, and postoperative chemotherapy. Factors associated with improved OS in multivariate analysis were younger age, nonastrocytoma histology, small tumor size, and GTR/rSTR. CONCLUSIONS OS for LGG has improved over the past 50 years, despite similar rates of progression. In the modern cohort, more patients are receiving a diagnosis of oligodendroglioma and are undergoing extensive resections, both of which are associated with improvements in OS. Because of risk factor stratification by clinicians, the use of PORT has decreased and is primarily being used to treat high-risk tumors in modern patients.

Adult low-grade glioma: 19-year experience at a single institution.

Objectives:To determine prognostic factors and optimal timing of postoperative radiation therapy (RT) in adult low-grade gliomas. Methods:Records from 554 adults diagnosed with nonpilocytic low-grade gliomas at Mayo Clinic between 1992 and 2011 were retrospectively reviewed. Results:Median follow-up was 5.2 years. Histology revealed astrocytoma in 22%, oligoastrocytoma in 34%, and oligodendroglioma in 45%. Initial surgery achieved gross total resection in 31%, radical subtotal resection in 10%, subtotal resection (STR) in 21%, and biopsy only in 39%. Median overall survival (OS) and progression-free survival (PFS) were 11.4 and 4.1 years, respectively. On multivariate analysis, factors associated with lower OS included astrocytomas and use of postoperative RT. Adverse prognostic factors for PFS on multivariate analysis included tumor size, astrocytomas, STR/biopsy only and not receiving RT. Patients undergoing gross total resection/radical subtotal resection had the best OS and PFS. Comparing survival with the log-rank test demonstrated no association between RT and PFS (P=0.24), but RT was associated with lower OS (P<0.0001). In patients undergoing STR/biopsy only, RT was associated with improved PFS (P<0.0001) but lower OS (P=0.03). Postoperative RT was associated with adverse prognostic factors including age > 40 years, deep tumors, size≥5 cm, astrocytomas and STR/biopsy only. Patients delaying RT until recurrence experienced 10-year OS (71%) similar to patients never needing RT (74%; P=0.34). Conclusions:This study supports the association between aggressive surgical resection and better OS and PFS, and between postoperative RT and improved PFS in patients receiving STR/biopsy only. In addition, our findings suggest that delaying RT until progression is safe in patients who are eligible.

Prognostic Factors and Survival Patterns in Pediatric Low-grade Gliomas Over 4 Decades

Background: This study reports changes in long-term survival after the introduction of modern imaging in pediatric patients with low-grade gliomas (LGGs). Methods: Records from 351 consecutive pediatric patients diagnosed with LGG between 1970 and 2009 at Mayo Clinic Rochester were reviewed and divided into diagnosis before (group I: 1970 to 1989) and after (group II: 1990 to 2009) postoperative magnetic resonance imaging became regularly used in pediatric LGG. Results: Median progression-free survival (PFS) and overall survival (OS) were not reached. Overall, 10-year PFS was 62% and OS was 90%. On multivariate analysis, improved PFS was associated with gross total resection (GTR; P<0.0001) and postoperative radiation therapy (RT; P<0.0001). In those undergoing less than GTR, PFS was improved with RT, nearing rates of patients receiving GTR (P=0.12). On multivariate analysis, higher OS was associated with GTR (P<0.0001) and pilocytic histology (P=0.03). Group II had fewer headaches, fewer sensory/motor symptoms, less postoperative RT, and more GTRs. OS and PFS were not different between the groups. Conclusions: This large series of pediatric LGG patients with long-term follow-up found no significant changes in OS or PFS over time. Overall, GTR was associated with improved OS and PFS. RT was associated with an improvement in PFS, with the greatest benefit seen in patients undergoing less than GTR.

18F-FDG PET response and clinical outcomes after stereotactic body radiation therapy for metastatic melanoma

Background Clinical data that support stereotactic body radiation therapy (SBRT) metastatic malignant melanoma (MM) are limited. Furthermore, functional imaging with 18F-fludeoxyglucose positron emission tomography (PET) may offer a more accurate post-SBRT assessment. Therefore, we assessed the clinical outcomes and metabolic response of metastatic MM after SBRT. Methods and materials Patients with MM who were treated with SBRT and had pre- and post-PET scans (>1) were included in this study. A total of 390 pre- and post-SBRT PET/computed tomography (CT) scans for 80 metastases were analyzed. The PET metabolic response was evaluated per the PET Response Criteria in Solid Tumors (PERCIST), version 1.0, criteria. Single-fraction equivalent dose (SFED) was calculated as per the standard. The Kaplan-Meier method was used for estimates of overall survival (OS) and progression-free survival. The cumulative incidence method was used to estimate metastasis control (MC). A Wilcoxon test was used to compare survival estimates. The prognostic factors for MC and OS were assessed using the Cox proportional hazards model, and the Likelihood Ratio was also used for comparisons between groups. Results A median of 6 PET scans (range, 2-6 scans) was evaluated for each metastasis. The median SFED was 42.8 Gy (range, 18-56.4 Gy) and the median biologically effective dose was 254.4 Gy2.5 (range, 100.8-540 Gy2.5). Twenty percent of patients received chemotherapy and 59% received immunotherapy: granulocyte-macrophage colony-stimulating factor (64%) and ipilimumab (34%). MC was 94% and 90% at 1 year and 3 years, respectively. The OS was 74% and 27% and 1 year and 3 years, respectively. Complete response was achieved in 90% at a median of 2.8 months (range, 0.4-25.2 months). SFED >24 Gy correlated with improved MC (93% vs 75%, P = .01). Acute and late grade 3+ toxicities were 4% and 11%, respectively, with no grade 5 toxicity. Conclusions Post-SBRT PET/CT for extracranial metastatic MM resulted in high rates of complete response at a median of 2.8 months, and durable MC was achieved with SFED >24 Gy. SBRT, in addition to surgery and ablation, should be discussed with patients with MM, especially those with oligometastases.

Multi-isocenter hybrid electron and rapid arc photon treatment for reirradiation of extensive recurrent inflammatory breast cancer

Delivering an adequate and homogenous dose to a large volume of recurrent cutaneous disease can be challenging even with modern techniques. Here, the authors describe a 3-isocenter hybrid electron and rapid arc photon radiation treatment plan to provide optimal tumor coverage to an extensive recurrence of inflammatory breast carcinoma. This approach allowed for homogeneous treatment of a large volume while effectively modulating dose to previously irradiated tissue and minimizing dose to the underlying heart, lungs and brachial plexus.

Role of radiotherapy in extracranial metastatic malignant melanoma in the modern era

Background To assess the role of radiotherapy in metastatic malignant melanoma (MM) patients in modern era. Materials and methods This is a retrospective study of MM patients treated with radiotherapy at Mayo Clinic from 1999 to 2014. Patients with pre- and post-treatment imaging studies (CT, MRI, and/or PET/CT) were assessed for metastasis failure (MF), regional/distant failure, and overall survival (OS). Results In 75 MM patients, 56 and 68 lesions were treated with conventional/hypofractionated radiotherapy (CHRT) and stereotactic body radiotherapy (SBRT), respectively. The median doses for CHRT and SBRT were 30 Gy and 50 Gy, respectively. 1-year MF was 17% (SBRT 6% vs CHRT 31%, p < 0.01). 1-year regional (5% vs 29%, p < 0.01) and distant progression (75% vs 89%, p < 0.01) were improved with SBRT. Median OS was 15.6 months (CHRT 7.0 vs SBRT 22.9, p < 0.01). Prognostic factors for OS included age ≤55 years (RR 0.25), oligometastatic disease (RR 0.34), SBRT (RR 0.38) and treating all lesions (RR 0.28, all p < 0.01). Conclusions SBRT for extracranial MM exhibited improved MF compared with CHRT, consistent with intracranial radiosurgery data. Though these data are retrospective and subject to selection bias, our findings support the prudent use of SBRT in a select group of favorable, oligometastatic MM patients, and should be discussed as an alternative to surgery and ablation.

Abstract 4543: Uptake of 18F-FDOPA analogue 3H-L-DOPA is mediated by large neutral amino acid transporter LAT1 in human glioblastoma

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL INTRODUCTION: The L-Type amino acid transporter 1 (LAT1) transports large neutral amino acids across the plasma membrane in a variety of cells. Positron emission tomography (PET) imaging with the amino acid tracer 6-18F-fluoro-L-dopa (18F-FDOPA) provides useful histological information in human gliomas in addition to providing better localizing information then CT or MRI alone. This study is the first to correlate LAT1 expression with uptake of the 18F-FDOPA analog, 3H-L-DOPA in human glioblastomas. METHODS: Endogenous expression of LAT1 was evaluated in two established glioblastoma multiforme (GBM) cell lines and three primary GBM xenografts using Western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR). Uptake of FDOPA was assessed in vitro using 3H-L-DOPA as an analog to 18F-FDOPA. Knockdown of LAT1 expression was achieved by lentiviral expression of anti-LAT1 shRNA in GBM lines with high LAT1 expression. The effect of LAT1 knockdown on 3H-L-DOPA uptake was then quantified. RESULTS: Results from Western blotting and qRT-PCR demonstrate that LAT1 is variably expressed in GBM. Levels of 3H-L-DOPA uptake were directly related to LAT1 expression (p<0.001) across the 5 lines. Knockdown of LAT1 was achieved in T98 cells (knockdown efficiency = 82.8%) and xenograft GBM 28 (knockdown efficiency = 73.7%) as confirmed by qRT-PCR and Western blotting. Knockdown of LAT1 reduced 3H-L-DOPA uptake by 57.2% (p<0.0001) in T98 and 52.1% in GBM 28 (p<0.001). CONCLUSIONS: This is the first report of 3H-L-DOPA uptake being driven by LAT1 in human GBM. Our findings suggest LAT1 as a transporter of 18F-FDOPA in GBM. Additional studies are underway to correlate LAT1 expression with PET 18F-FDOPA uptake in patients with GBM. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4543. doi:1538-7445.AM2012-4543

Abstract B68: Differential gene expression associated with temozolomide resistance development in glioblastoma xenografts.

Purpose/Background: The first-line chemotherapeutic temozolomide (TMZ) does not offer any therapeutic benefit in some cases of glioblastoma (GBM) and emergence of resistance leads to tumor progression in almost all patients. While the expression of O-6-methylguanine-DNA-methyltransferase (MGMT) correlates well with TMZ resistance, its expression varies among GBM tumors. The goal of this study is to identify additional genes with potential roles in TMZ resistance. Materials and Methods: Five primary GBM xenografts were generated from patient samples, and subsequent secondary models for resistance were developed by subjecting tumor-bearing mice to escalating doses of TMZ. Triplicate samples from parental and TMZ-resistant xenografts were analyzed for gene expression using the Illumina BeadChip microarray platform. The top 100 differentially expressed genes for each line were considered candidates. Genes were selected for qRT-PCR validation after ontological and pathway analysis. A lentivirus-mediated shRNA knockdown was performed to validate the role of several candidate genes in TMZ resistance in U87 and primary GBM12 cell lines. Knockdown was confirmed with qRT-PCR and western blots. TMZ responsiveness was assessed using CyQUANT and Neurosphere assays. Results: Upregulated MGMT expression was found in 3 of the 5 xenografts (GBM12TMZ, GBM14TMZ and GBM28TMZ) and was mechanistically linked with TMZ resistance in these lines using O6-benzylguanine to reverse the resistance phenotype. Differential expression of other DNA damage response genes included CCND2, CDKN1A, GADD45B, UBB as well as apoptosis regulators NFKB2 and BIRC3. In lines with unchanged MGMT expression (GBM22TMZ and GBM39TMZ), changes in anti-apoptosis genes NFKB2 and MAP3K1, transcription factor SRF and signal transduction gene PRKCDBP were validated by qRT-PCR. In GBM12TMZ, in addition to MGMT upregulation, expression of Ubiquitin B (UBB) was found to be the most significantly down-regulated gene both on microarray (Log2FC = −4.55, Fold change = 0.043) and qRT-PCR (Log2RQ =-4.04, RQ = 0.061). To test a possible role of UBB in TMZ resistance, knockdown was achieved in U87 (knockdown efficiency=91.2%) and in primary xenograft line GBM12 (knockdown efficiency=84.4%). The CyQUANT assay for U87UBB-KD and U87NT treated with escalating doses of TMZ revealed no significant difference in cell survival (10 M TMZ relative survival= 89.7% for U87UBB-KD and 79.2% for U87NT; p-value=0.53). Similarly, a neurosphere assay for GBM12UBB-KD and GBM12NT also yielded no significant difference in cell survival (10 M TMZ relative survival= 25.13% for GBM12UBB-KD and 23.35% for GBM12NT; p-value=0.83). Conclusions: We have used a TMZ resistance xenograft model to identify candidate TMZ resistance genes. The current data provides evidence on the role of MGMT in the development of acquired TMZ resistance while ruling out UBB as potential TMZ resistance gene in GBM. Additional studies are underway to assess the functional significance of other candidate genes, particularly those with differential expression in the setting of constant MGMT expression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B68.