Electron Donors Rather Than Reactive Oxygen Species Needed for Therapeutic Photochemical Reaction of Near-Infrared Photoimmunotherapy

Near-infrared photoimmunotherapy (NIR-PIT) employs molecularly targeted antibodies conjugated with a photoabsorbing silicon-phthalocyanine dye derivative which binds to cancer cells. Application of NIR light following binding of the antibody-photoabsorber conjugates (APCs) results in ligand release on the dye, dramatic changes in solubility of the APC-antigen complex, and rapid, irreversible cell membrane damage of cancer cells in a highly selective manner, resulting in a highly immunogenic cell death. Clinically, this process results in edema after treatment mediated by reactive oxygen species (ROS). Based on the chemical and biological mechanism of NIR-PIT cytotoxicity and edema formation, in order to minimize acute inflammatory edema without compromising therapeutic effects, l-sodium ascorbate (l-NaAA) was administered to quench harmful ROS and accelerate the ligand release reaction. l-NaAA suppressed acute edema by reducing ROS after NIR-PIT yet did not alter the therapeutic effects. NIR-PIT could be performed safely under existence of l-NaAA without side effects caused by unnecessary ROS production.

Near Infrared Photoimmunotherapy in a Transgenic Mouse Model of Spontaneous Epidermal Growth Factor Receptor (EGFR)-expressing Lung Cancer

Near infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by a sensitive photoabsorber following exposure to NIR light. Most studies of NIR-PIT have been performed in xenograft models of cancer. The purpose of this study was to evaluate the therapeutic effects of NIR-PIT in a transgenic model of spontaneous lung cancer expressing human EGFR (hEGFR-TL). Mice were separated into 3 groups for the following treatments: (1) no treatment (control); (2) 150 μg of photoabsorber, IR700, conjugated to panitumumab, an antibody targeting EGFR [antibody-photoabsorber conjugate (APC)] intravenously (i.v.) only; (3) 150 μg of APC i.v. with NIR light administration. Each treatment was performed every week up to three weeks. MRI was performed 1 day before and 3, 6, 13, 20, 27, and 34 days after first NIR-PIT. The relative volume of lung tumors was calculated from the tumor volume at each MRI time point divided by the initial volume. Steel test for multiple comparisons was used to compare the tumor volume ratio with that of control. Tumor volume ratio was inhibited significantly in the NIR-PIT group compared with control group (P < 0.01 at all time points). In conclusion, NIR-PIT effectively treated a spontaneous lung cancer in a hEGFR-TL transgenic mouse model. MRI successfully monitored the therapeutic effects of NIR-PIT. Mol Cancer Ther; 16(2); 408-14. ©2016 AACR.

Optimal high b-value for diffusion weighted MRI in diagnosing high risk prostate cancers in the peripheral zone

PURPOSE

To retrospectively determine the optimal b-value(s) of diffusion-weighted imaging (DWI) associated with intermediate-high risk cancer in the peripheral zone (PZ) of the prostate.

MATERIALS AND METHODS

Forty-two consecutive patients underwent multi b-value (16 evenly spaced b-values between 0 and 2000 s/mm² ) DWI along with multi-parametric MRI (MP-MRI) of the prostate at 3 Tesla followed by trans-rectal ultrasound/MRI fusion guided targeted biopsy of suspicious lesions detected at MP-MRI. Computed DWI images up to a simulated b-value of 4000 s/mm² were also obtained using a pair of b-values (b = 133 and 400 or 667 or 933 s/mm² ) from the multi b-value DWI. The contrast ratio of average intensity of the targeted lesions and the background PZ was determined. Receiver operator characteristic curves and the area under the curve (AUCs) were obtained for separating patients eligible for active surveillance with low risk prostate cancers from intermediate-high risk prostate cancers as per the cancer of the prostate risk assessment (CAPRA) scoring system.

RESULTS

The AUC first increased then decreased with the increase in b-values reaching maximum at b = 1600 s/mm² (0.74) with no statistically significant different AUC of DWI with b-values 1067-2000 s/mm² . The AUC of computed DWI increased then decreased with the increase in b-values reaching a maximum of 0.75 around b = 2000 s/mm² . There was no statistically significant difference between the AUC of optimal acquired DWI and either of optimal computed DWI.

CONCLUSION

The optimal b-value for acquired DWI in differentiating intermediate-high from low risk prostate cancers in the PZ is b = 1600 s/mm² . The computed DWI has similar performance as that of acquired DWI with the optimal performance around b = 2000 s/mm² .

LEVEL OF EVIDENCE

4 J. Magn. Reson. Imaging 2017;45:125-131.

Comparison of calculated and acquired high b value diffusion-weighted imaging in prostate cancer

PURPOSE

To determine whether the performance of calculated high b value diffusion-weighted images (DWI) derived from regular lower b value DWI using exponential diffusion decay models (intravoxel incoherent motion = IVIM and diffusional kurtosis = DK) is comparable to acquired high b value DWI in prostate cancer detection.

MATERIALS AND METHODS

One hundred six patients underwent diagnostic multiparametric prostate MRI at 3T using an endorectal coil. Five b value (b = 0, 188, 375, 563, 750 s/mm(2)) DWI and high b value (b = 0, 1000 and 2000 s/mm(2)) DWI were acquired. Calculated high b value (b = 1000 s/mm(2) and b = 2000 s/mm(2)) DWI were derived from the DWI dataset using DK and IVIM models. Calculated and acquired high b value DWI images were compared for lesion visibility and image quality by two experienced radiologists (1 and 6 years of experience). GEE with Wald test was used to compare the image quality among the four calculated high b value DWI by comparing the proportion of lesions in each model which were comparable to the acquired images. This comparison was done for all lesions and by lesion location (PZ or CG; low apical/anterior or apical/mid/base)

RESULTS

More lesions were visible on acquired b = 2000 s/mm(2) compared to b = 1000 s/mm(2) DWI. Calculated high b value DWI using the IVIM model had approximately the same number of lesions as acquired high b value DWI, whereas the DK model had fewer lesions than acquired images. The image quality of calculated high b value DWI was comparable to that of acquired images, and the highest quality images were obtained with b1000IVIM. The image quality of calculated b1000IVIM was the same as that of acquired DWI in apical/mid/base (98%) locations and comparable in low apical and anterior (95.4%) locations. The image quality of calculated b2000IVIM was inferior in both apical/mid/base (86.2%) locations and comparable in low apical and anterior (83.9%) locations.

CONCLUSION

Calculated high b value DWI obtained using IVIM model has same lesion visibility as that of acquired DWI. The image quality of calculated high b value DWI relative to corresponding acquired DWI decreases with increase in b value.

Abstract CT222: Ferumoxytol enhanced MRI for lymph node staging in genitourinary cancers

Background: Conventional imaging has limited accuracy in genitourinary (GU) cancer staging. This study examines the utility of ferumoxytol enhanced MRI in lymph node (LN) staging of GU cancers.

Methods: This ongoing IRB-approved phase II clinical trial enrolls patients with prostate cancer, renal cell carcinoma, or bladder cancer at high risk for LN metastases. Patients undergo baseline T2 and T2* weighted MRI scans followed by injection of 7.5mg/Kg ferumoxytol. Repeat scans are acquired at 24hr and 48hr post-injection. The criterion for positive LNs was preservation of hyper-intense signal indicating failure to take up ferumoxytol. Validation was by histopathology when available or on clinical grounds, for which LNs that changed size on routine imaging were considered true positives.

Results: To date, 13 patients have completed the study. Of 11 prostate cancer patients, one was studied pre-operatively while 10 had suspected therapy failure. Median age and PSA were 65yrs (36-75) and 5.6ng/mL (0.3-201). The other 2 patients had renal cell carcinoma and bladder cancer. Overall, 20 LNs were identified with mean size 1.9cm (0.7-3.8) long axis by 1.3cm (0.6-2.6) short axis. There were 14 true positive LNs, 1 false positive, 1 false negative, and 4 nodes pending validation. Validation was by histopathology for 7 LNs, with 2 nodes pending biopsy, and clinical grounds for 13 LNs, with 2 inconclusive nodes awaiting further validation. Ferumoxytol correctly identified LN status in 9 of 10 patients with validated nodes (Table 1).

Conclusions: Ferumoxytol enhanced MRI shows promise in detecting malignant LNs &gt;6mm in GU cancer patients. Since the method involves a conventional MRI unit with off-label use of an FDA-approved agent, it could be widely available. However, further validation is necessary before routine use.

Table 1: Preliminary results for LN staging in GU cancer patients using ferumoxytol enhanced MRI

SubjectStudy ArmGenderAge (yr)PSA at study initiation (ng/mL)LN numberLN locationsize/long axis (cm)size/short axis (cm)Ferumoxytol positive? 1 = yes, 0 = noResult1prostate cancerM6325.061R ext iliac3.02.61TP2L ext iliac1.30.81TP2prostate cancerM6573.961L RP1.61.41TP2L int iliac3.81.91TP3prostate cancerM6410.491R ext iliac3.00.91pending2L ext iliac1.91.10pending4prostate cancerM742.061L RP1.71.51TP5prostate cancerM642.891R ext iliac1.61.11TP6prostate cancerM650.281L int iliac1.50.81TP7prostate cancerM752.871R int iliac0.70.71TP8prostate cancerM6427.911R common iliac1.71.71inconclusive9prostate cancerM72201.21L RP2.31.70FN10prostate cancerM736.771L int iliac1.51.01TP11prostate cancerM361.351R femoral0.80.81FP2L ext iliac1.51.01inconclusive3R perirectal0.80.61TP12renal cell carcinomaF41N/A1aortocaval2.82.21TP2R RP3.62.31TP3R int iliac2.01.51TP13bladder cancerM59N/A1aortocaval1.51.01TPRP = retroperitoneal, TP = true positive, FN = false negative, FP = false positive, ext = external, int = internal

Citation Format: Anna M. Brown, Sandeep Sankineni, Marcelino Bernardo, Dagane Daar, Juanita Weaver, Yolanda McKinney, Anna Couvillon, James L. Gulley, Bradford J. Wood, Peter A. Pinto, William L. Dahut, Ravi Amrit Madan, Peter L. Choyke, Baris Turkbey. Ferumoxytol enhanced MRI for lymph node staging in genitourinary cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT222. doi:10.1158/1538-7445.AM2015-CT222

Ferumoxytol enhanced MRI for lymph node staging in prostate cancer

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Background: Conventional imaging methods of lymph node staging in prostate cancer are limited. The goal of this study is to determine the utility of ferumoxytol enhanced MRI in lymph node (LN) staging. Methods: This ongoing IRB-approved clinical trial enrolls prostate cancer patients at high risk for LN metastases. Patients first undergo baseline T2 and T2* weighted MRI scans followed by 7.5mg/Kg ferumoxytol injection. Repeat scans are acquired at 24 hr and 48 hr post-injection. The criterion for positive LNs was hyperintense signal indicating failure to take up ferumoxytol. Validation was determined on clinical grounds or by histopathology when available. Results: To date, 11 patients have completed the study. One patient was examined pre-operatively while the other 10 had suspected therapy failure. Median age and PSA were 65 yrs (36-75) and 5.6ng/dL (0.3-201). Of 16 LNs with median size 1.6 x 1.1cm, 10 were true positives, one was false positive and one was false negative with 4 nodes pending validation. The LN status was correctly identified in 8 of 11 patients [Table]. Conclusions: Ferumoxytol enhanced MRI shows promise in detecting malignant LNs with diameter >6mm in prostate cancer paients. This method is performed in a conventional MRI unit with off-label use of an FDA-approved agent and thus could be widely available. However, further validation is necessary before routine use. Clinical trial information: NCT02141490. [Table: see text]

Comparison of endorectal coil and nonendorectal coil T2W and diffusion-weighted MRI at 3 Tesla for localizing prostate cancer: correlation with whole-mount histopathology

PURPOSE

To compare utility of T2-weighted (T2W) MRI and diffusion-weighted MRI (DWI-MRI) obtained with and without an endorectal coil at 3 Tesla (T) for localizing prostate cancer.

MATERIALS AND METHODS

This Institutional Review Board-approved study included 20 patients (median prostate-specific antigen, 8.4 ng/mL). Patients underwent consecutive prostate MRIs at 3T, first with a surface coil alone, then with combination of surface, endorectal coils (dual coil) followed by robotic assisted radical prostatectomy. Lesions were mapped at time of acquisition on dual-coil T2W, DWI-MRI. To avoid bias, 6 months later nonendorectal coil T2W, DWI-MRI were mapped. Both MRI evaluations were performed by two readers blinded to pathology with differences resolved by consensus. A lesion-based correlation with whole-mount histopathology was performed.

RESULTS

At histopathology 51 cancer foci were present ranging in size from 2 to 60 mm. The sensitivity of the endorectal dual-coil, nonendorectal coil MRIs were 0.76, 0.45, respectively. PPVs for endorectal dual-coil, nonendorectal coil MRI were 0.80, 0.64, respectively. Mean size of detected lesions with nonendorectal coil MRI were larger than those detected by dual-coil MRI (22 mm versus 17.4 mm).

CONCLUSION

Dual-coil prostate MRI detected more cancer foci than nonendorectal coil MRI. While nonendorectal coil MRI is an attractive alternative, physicians performing prostate MRI should be aware of its limitations.

Prostate cancer: can multiparametric MR imaging help identify patients who are candidates for active surveillance?

PURPOSE

To determine whether multiparametric magnetic resonance (MR) imaging can help identify patients with prostate cancer who would most appropriately be candidates for active surveillance (AS) according to current guidelines and to compare the results with those of conventional clinical assessment scoring systems, including the D'Amico, Epstein, and Cancer of the Prostate Risk Assessment (CAPRA) systems, on the basis of findings at prostatectomy.

MATERIALS AND METHODS

This institutional review board-approved HIPAA-compliant retrospectively designed study included 133 patients (mean age, 59.3 years) with a mean prostate-specific antigen level of 6.73 ng/mL (median, 4.39 ng/mL) who underwent multiparametric MR imaging at 3.0 T before radical prostatectomy. Informed consent was obtained from all patients. Patients were then retrospectively classified as to whether they would have met AS eligibility criteria or were better served by surgery. AS eligibility criteria for prostatectomy specimens were a dominant tumor smaller than 0.5 mL without Gleason 4 or 5 patterns or extracapsular or seminal vesicle invasion. Conventional clinical assessment scores (the D'Amico, Epstein, and CAPRA scoring systems) were compared with multiparametric MR imaging findings for predicting AS candidates. The level of significance of difference between scoring systems was determined by using the χ(2) test for categoric variables with the level of significance set at P < .05.

RESULTS

Among 133 patients, 14 were eligible for AS on the basis of prostatectomy results. The sensitivity, positive predictive value (PPV), and overall accuracy, respectively, were 93%, 25%, and 70% for the D'Amico system, 64%, 45%, and 88% for the Epstein criteria, and 93%, 20%, and 59% for the CAPRA scoring system for predicting AS candidates (P < .005 for all, χ(2) test), while multiparametric MR imaging had a sensitivity of 93%, a PPV of 57%, and an overall accuracy of 92% (P < .005).

CONCLUSION

Multiparametric MR imaging provides useful additional information to existing clinicopathologic scoring systems of prostate cancer and improves the assignment of treatment (eg, AS or active treatment).

11C-Acetate PET/CT in localized prostate cancer: a study with MRI and histopathologic correlation

This work characterizes the uptake of (11)C-acetate in prostate cancer (PCa), benign prostate hyperplasia, and normal prostate tissue in comparison with multiparametric MRI, whole-mount histopathology, and clinical markers to evaluate the potential utility of (11)C-acetate for delineating intraprostatic tumors in a population of patients with localized PCa.

METHODS

Thirty-nine men with presumed localized PCa underwent dynamic-static abdominal-pelvic (11)C-acetate PET/CT for 30 min and 3-T multiparametric MRI before prostatectomy. PET/CT images were registered to MR images using pelvic bones for initial rotation-translation, followed by manual adjustments to account for prostate motion and deformation from the MRI endorectal coil. Whole-mount pathology specimens were sectioned using an MRI-based patient-specific mold resulting in improved registration between the MRI, PET, and pathology. (11)C-acetate PET standardized uptake values were compared with multiparametric MRI and pathology.

RESULTS

(11)C-acetate uptake was rapid but reversible, peaking at 3-5 min after injection and reaching a relative plateau at approximately 10 min. The average maximum standardized uptake value (10-12 min) of tumors was significantly higher than that of normal prostate tissue (4.4 ± 2.05 [range, 1.8-9.2] vs. 2.1 ± 0.94 [range, 0.7-3.4], respectively; P < 0.001); however, it was not significantly different from that of benign prostatic hyperplasia (4.8 ± 2.01 [range, 1.8-8.8]). A sector-based comparison with histopathology, including all tumors greater than 0.5 cm, revealed a sensitivity and specificity of 61.6% and 80.0%, respectively, for (11)C-acetate PET/CT and 82.3% and 95.1%, respectively, for MRI. The (11)C-acetate accuracy was comparable to that of MRI when only tumors greater than 0.9 cm were considered. In a small cohort (n = 9), (11)C-acetate uptake was independent of fatty acid synthase expression using immunohistochemistry.

CONCLUSION

(11)C-acetate PET/CT demonstrates higher uptake in tumor foci than in normal prostate tissue; however, (11)C-acetate uptake in tumors is similar to that in benign prostate hyperplasia nodules. Although (11)C-acetate PET/CT is not likely to have utility as an independent modality for evaluation of localized PCa, the high uptake in tumors may make it useful for monitoring focal therapy when tissue damage after therapy may limit anatomic imaging methods.

Multiparametric 3T prostate magnetic resonance imaging to detect cancer: histopathological correlation using prostatectomy specimens processed in customized magnetic resonance imaging based molds

PURPOSE

We determined the prostate cancer detection rate of multiparametric magnetic resonance imaging at 3T. Precise one-to-one histopathological correlation with magnetic resonance imaging was possible using prostate magnetic resonance imaging based custom printed specimen molds after radical prostatectomy.

MATERIALS AND METHODS

This institutional review board approved prospective study included 45 patients (mean age 60.2 years, range 49 to 75) with a mean prostate specific antigen of 6.37 ng/ml (range 2.3 to 23.7) who had biopsy proven prostate cancer (mean Gleason score of 6.7, range 6 to 9). Before prostatectomy all patients underwent prostate magnetic resonance imaging using endorectal and surface coils on a 3T scanner, which included triplane T2-weighted magnetic resonance imaging, apparent diffusion coefficient maps of diffusion weighted magnetic resonance imaging, dynamic contrast enhanced magnetic resonance imaging and spectroscopy. The prostate specimen was whole mount sectioned in a customized mold, allowing geometric alignment to magnetic resonance imaging. Tumors were mapped on magnetic resonance imaging and histopathology. Sensitivity, specificity, positive predictive value and negative predictive value of magnetic resonance imaging for cancer detection were calculated. In addition, the effects of tumor size and Gleason score on the sensitivity of multiparametric magnetic resonance imaging were evaluated.

RESULTS

The positive predictive value of multiparametric magnetic resonance imaging to detect prostate cancer was 98%, 98% and 100% in the overall prostate, peripheral zone and central gland, respectively. The sensitivity of magnetic resonance imaging sequences was higher for tumors larger than 5 mm in diameter as well as for those with higher Gleason scores (greater than 7, p <0.05).

CONCLUSIONS

Prostate magnetic resonance imaging at 3T allows for the detection of prostate cancer. A multiparametric approach increases the predictive power of magnetic resonance imaging for diagnosis. In this study accurate correlation between multiparametric magnetic resonance imaging and histopathology was obtained by the patient specific, magnetic resonance imaging based mold technique.