Prospective, multisite, international comparison of \u3csup\u3e18\u3c/sup\u3eF-fluoromethylcholine PET/CT, multiparametric MRI, and \u3csup\u3e68\u3c/sup\u3eGa-HBED-CC PSMA-11 PET/CT in men with high-risk features and biochemical failure after radical prostatectomy: Clinical performance and patient outcomes

A significant proportion of men with rising prostate-specific antigen (PSA) levels after radical prostatectomy (RP) fail prostate fossa (PF) salvage radiation treatment (SRT). This study was done to assess the ability of F-fluoromethylcholine ( F-FCH) PET/CT (hereafter referred to as F-FCH), Ga-HBED-CC PSMA-11 PET/CT (hereafter referred to as PSMA), and pelvic multiparametric MRI (hereafter referred to as pelvic MRI) to identify men who will best benefit from SRT. Methods: Prospective, multisite imaging studies were carried out in men who had rising PSA levels after RP, high-risk features, and negative/equivocal conventional imaging results and who were being considered for SRT. F-FCH (91/91), pelvic MRI (88/91), and PSMA (31/91) (Australia) were all performed within 2 wk. Imaging was interpreted by experienced local/central interpreters who were masked with regard to other imaging results, with consensus being reached for discordant interpretations. Expected management was documented before and after imaging, and data about all treatments and PSA levels were collected for 3 y. The treatment response to SRT was defined as a reduction in PSA levels of .50% without androgen deprivation therapy. Results: The median Gleason score, PSA level at imaging, and PSA doubling time were 8, 0.42 (interquartile range, 0.29–0.93) ng/mL, and 5.0 (interquartile range, 3.3–7.6) months. Recurrent prostate cancer was detected in 28% (25/88) by pelvic MRI, 32% (29/91) by F-FCH, and 42% (13/31) by PSMA. This recurrence was found within the PF in 21.5% (19/88), 13% (12/91), and 19% (6/31) and at sites outside the PF (extra-PF) in 8% (7/88), 19% (17/91), and 32% (10/31) by MRI, F-FCH, and PSMA, respectively (P, 0.004). A total of 94% (16/17) of extra-PF sites on F-FCH were within the pelvic MRI field. Intra-pelvic extra-PF disease was detected in 90% (9/10) by PSMA and in 31% (5/16) by MRI. F-FCH changed management in 46% (42/91), and MRI changed management in 24% (21/88). PSMA provided additional management changes over F-FCH in 23% (7/31). The treatment response to SRT was higher in men with negative results or disease confined to the PF than in men with extra-PF disease ( F-FCH 73% [32/44] versus 33% [3/9] [P, 0.02], pelvic MRI 70% [32/46] versus 50% [2/4] [P was not significant], and PSMA 88% [7/ 8] versus 14% [1/7] [P, 0.005]). Men with negative imaging results (MRI, F-FCH, or PSMA) had high (78%) SRT response rates. Conclusion: F-FCH and PSMA had high detection rates for extra-PF disease in men with negative/equivocal conventional imaging results and rising PSA levels after RP. These findings affected management and treatment responses, suggesting an important role for PET in triaging men being considered for curative SRT. 18 18 18 68 18 18 18 18 18 18 18 18 1

A cysteine-based molecular code informs collagen C-propeptide assembly

Fundamental questions regarding collagen biosynthesis, especially with respect to the molecular origins of homotrimeric versus heterotrimeric assembly, remain unanswered. Here, we demonstrate that the presence or absence of a single cysteine in type-I collagen’s C-propeptide domain is a key factor governing the ability of a given collagen polypeptide to stably homotrimerize. We also identify a critical role for Ca2+ in non-covalent collagen C-propeptide trimerization, thereby priming the protein for disulfide-mediated covalent immortalization. The resulting cysteine-based code for stable assembly provides a molecular model that can be used to predict, a priori, the identity of not just collagen homotrimers, but also naturally occurring 2:1 and 1:1:1 heterotrimers. Moreover, the code applies across all of the sequence-diverse fibrillar collagens. These results provide new insight into how evolution leverages disulfide networks to fine-tune protein assembly, and will inform the ongoing development of designer proteins that assemble into specific oligomeric forms.National Science Foundation (U.S.) (Grant NSF-0070319)National Science Foundation (U.S.). Center for Science of Information (Grant P30-ES002109)National Institutes of Health (U.S.) (Grant R03AR067503)National Institutes of Health (U.S.) (Grant 1R01AR071443)National Institutes of Health (U.S.). Ruth Kirschstein Predoctoral Fellowship (1F31AR067615

Dual targeting of the epidermal growth factor receptor using the combination of cetuximab and erlotinib: Preclinical evaluation and results of the Phase II DUX Study in chemotherapy-refractory, advanced colorectal cancer

PurposeThis preclinical and phase II study evaluated the efficacy and safety of the combination of cetuximab and erlotinib in metastatic colorectal cancer (mCRC).Patients and methodsThe activity and mechanism of action of the combination of cetuximab plus erlotinib were investigated in vitro in colorectal cancer cell lines. In the clinical study, patients with chemotherapy-refractory mCRC were treated with cetuximab 400 mg/m(2) as a loading dose and then weekly cetuximab 250 mg/m(2) with erlotinib 100 mg orally daily. The primary end point was response rate (RR), which was evaluated separately in KRAS wild-type (WT) versus KRAS mutant tumors. Secondary end points included toxicity, progression-free survival (PFS), and overall survival. Target accrual was 50 patients, with a one-stage design.ResultsPreclinical studies demonstrated synergistic activity of cetuximab and erlotinib cotreatment on growth inhibition of colon cancer cell lines both as a result of enhanced inhibition of the epidermal growth factor receptor pathway and differential effects on STAT3. In the clinical study, 50 patients were enrolled, with 48 patients evaluable for response. The overall RR was 31% (95% CI, 26% to 57%), with a median PFS of 4.6 months (95% CI, 2.8 to 5.6 months). RR was 41% (95% CI, 26% to 57%) in KRAS WT tumors, with a median PFS of 5.6 months (95% CI, 2.9 to 5.6 months). There was no response in 11 patients with KRAS mutations. Frequent grade 3 and 4 toxicities were rash (48%), hypomagnesaemia (18%), and fatigue (10%).ConclusionThe combination of cetuximab and erlotinib synergistically inhibits growth of colon cancer cell lines, achieves promising efficacy in patients with KRAS WT mCRC, and merits evaluation in further randomized studies.Andrew J. Weickhardt, Tim J. Price, Geoff Chong, Val Gebski, Nick Pavlakis, Terrance G. Johns, Arun Azad, Effie Skrinos, Kate Fluck, Alexander Dobrovic, Renato Salemi, Andrew M. Scott, John M. Mariadason, and Niall C. Tebbut

The contribution of multiparametric pelvic and whole-body MRI to interpretation of \u3csup\u3e18\u3c/sup\u3eF-fluoromethylcholine or \u3csup\u3e68\u3c/sup\u3eGa-HBED-CC PSMA-11 PET/CT in patients with biochemical failure after radical prostatectomy

Our purpose was to assess whether the addition of data from multiparametric pelvic MRI (mpMR) and whole-body MRI (wbMR) to the interpretation of F-fluoromethylcholine ( F-FCH) or Ga-HBED-CC PSMA-11 ( Ga-PSMA) PET/CT (5PET) improves the detection of local tumor recurrence or of nodal and distant metastases in patients after radical prostatectomy with biochemical failure. Methods: The current analysis was performed as part of a prospective, multicenter trial on F-FCH or Ga-PSMA PET, mpMR, and wbMR. Eligible men had an elevated level of prostate-specific antigen (PSA) (.0.2 ng/mL) and high-risk features (Gleason score . 7, PSA doubling time, 10 mo, or PSA . 1.0 ng/mL) with negative or equivocal conventional imaging results. PET was interpreted with mpMR and wbMR in consensus by 2 radiologists and compared with prospective interpretation of PET or MRI alone. Performance measures of each modality (PET, MRI, and PET/mpMR-wbMR) were compared for each radiotracer and each individual patient (for F-FCH, or Ga-PSMA for patients who had Ga-PSMA PET) and to a composite reference standard. Results: There were 86 patients with PET ( F-FCH [n 5 76] and/or Ga-PSMA [n 5 26]) who had mpMR and wbMR. Local tumor recurrence was detected in 20 of 76 (26.3%) on F-FCH PET/ mpMR, versus 11 of 76 (14.5%) on F-FCH PET (P 5 0.039), and in 11 of 26 (42.3%) on Ga-PSMA PET/mpMR, versus 6 of 26 (23.1%) on Ga-PSMA PET (P 5 0.074). Per patient, PET/ mpMR was more often positive for local tumor recurrence than PET (P 5 0.039) or mpMR (P 5 0.019). There were 20 of 86 patients (23.3%) with regional nodal metastases on both PET/wbMR and PET (P 5 1.0) but only 12 of 86 (14%) on wbMR (P 5 0.061). Similarly, there were more nonregional metastases detected on PET/wbMR than on PET (P 5 0.683) or wbMR (P 5 0.074), but these differences did not reach significance. Compared with the composite reference standard for the detection of disease beyond the prostatic fossa, PET/wbMR, PET, and wbMR had sensitivity of 50%, 50%, and 8.3%, respectively, and specificity of 97.1%, 97.1%, and 94.1%, respectively. Conclusion: Interpretation of PET/mpMR resulted in a higher detection rate for local tumor recurrence in the prostatic bed in men with biochemical failure after radical prostatectomy. However, the addition of wbMR to F-FCH or Ga-PSMA PET did not improve detection of regional or distant metastases. 18 18 68 68 18 68 18 68 68 18 68 18 18 68 68 18 6

Impact of KRAS and BRAF gene mutation status on outcomes from the phase III AGITG MAX Trial of capecitabine alone or in combination with Bevacizumab and Mitomycin in advanced colorectal cancer

Purpose: Mutations affecting the KRAS gene are established predictive markers of outcome with anti–epithelial growth factor receptor (EGFR) antibodies in advanced colorectal cancer (CRC). The relevance of these markers for anti–vascular endothelial growth factor (VEGF) therapy is controversial. This analysis was performed to assess the predictive and prognostic impact of KRAS and BRAF gene mutation status in patients receiving capecitabine with bevacizumab (CG) or capecitabine without bevacizumab in the phase III AGITG MAX (Australasian Gastrointestinal Trials Group MAX) study. Patients and Methods: Mutation status was determined for 315 (66.9%) of the original 471 patients. Mutation status was correlated with efficacy outcomes (response rate, progression-free survival [PFS], and overall survival [OS]), and a predictive analyses was undertaken. Results: Mutations in KRAS and BRAF genes were observed in 28.8% and 10.6% of patients, respectively. KRAS gene mutation status (wild type [WT] v mutated [MT]) had no prognostic impact for PFS (hazard ratio [HR], 0.89; CI, 0.69 to 1.14) or OS (HR, 0.97; CI, 0.73 to 1.28). BRAF mutation status (WT v MT) was not prognostic for PFS (HR, 0.80; CI, 0.54 to 1.18) but was prognostic for OS (HR, 0.49; CI, 0.33 to 0.73; P = .001). By using the comparison of capecitabine versus capecitabine and bevacizumab (CB) and CB plus mitomycin (CBM), KRAS gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .95 and 0.43, respectively). Similarly, BRAF gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .46 and 0.32, respectively). Conclusion: KRAS gene mutation status was neither prognostic for OS nor predictive of bevacizumab outcome in patients with advanced CRC. BRAF gene mutation status was prognostic for OS but was not predictive of outcome with bevacizumab.Timothy J. Price, Jennifer E. Hardingham, Chee K. Lee, Andrew Weickhardt, Amanda R. Townsend, Joseph W. Wrin, Ann Chua, Aravind Shivasami, Michelle M. Cummins, Carmel Murone and Niall C. Tebbut

Assessment of simplified methods for quantification of 18F-FDHT uptake in patients with metastatic castration-resistant prostate cancer

18F-fluorodihydrotestosterone (18F-FDHT) PET/CT potentially provides a noninvasive method for assessment of androgen receptor expression in patients with metastatic castration-resistant prostate cancer (mCRPC). The objective of this study was to assess simplified methods for quantifying 18F-FDHT uptake in mCRPC patients and to assess effects of tumor perfusion on these 18F-FDHT uptake metrics. Methods: Seventeen mCRPC patients were included in this prospective observational multicenter study. Test and retest 30-min dynamic 18F-FDHT PET/CT scans with venous blood sampling were performed in 14 patients. In addition, arterial blood sampling and dynamic 15O-H2O scans were obtained in a subset of 6 patients. Several simplified methods were assessed: Patlak plots; SUV normalized to body weight (SUVBW), lean body mass (SUVLBM), whole blood (SUVWB), parent plasma activity concentration (SUVPP), area under the parent plasma curve (SUVAUC,PP), and area under the whole-blood input curve (SUVAUC,WB); and SUVBW corrected for sex hormone-binding globulin levels (SUVSHBG). Results were correlated with parameters derived from full pharmacokinetic 18F-FDHT and 15O-H2O. Finally, the repeatability of individual quantitative uptake metrics was assessed. Results: Eighty-seven 18F-FDHT-avid lesions were evaluated. 18F-FDHT uptake was best described by an irreversible 2-tissue-compartment model. Replacing the continuous metabolite-corrected arterial plasma input function with an image-derived input function in combination with venous sample data provided similar Ki results (R2 5 0.98). Patlak Ki and SUVAUC,PP showed an excellent correlation (R2 . 0.9). SUVBW showed a moderate correlation to Ki (R2 5 0.70, presumably due to fast 18F-FDHT metabolism. When calculating SUVSHBG, correlation to Ki improved (R2 5 0.88). The repeatability of full kinetic modeling parameters was inferior to that of simplified methods (repeatability coefficients . 36% vs., 28%, respectively). 18F-FDHT uptake showed minimal blood flow dependency. Conclusion: 18F-FDHT kinetics in mCRPC patients are best described by an irreversible 2-tissue-compartment model with blood volume parameter. SUVAUC,PP showed a near-perfect correlation with the irreversible 2-tissue-compartment model analysis and can be used for accurate quantification of 18F-FDHT uptake in whole-body PET/CT scans. In addition, SUVSHBG could potentially be used as an even simpler method to quantify 18F-FDHT uptake when less complex scanning protocols and accuracy are required