Early response of prostate carcinoma xenografts to docetaxel chemotherapy monitored with diffusion MRI

Targeting prostate cancer with docetaxel-loaded peptide 563-conjugated PEtOx-co-PEI30%-b-PCL polymeric micelle nanocarriers

Prostate cancer is a global disease that negatively affects the quality of life. Although various strategies against prostate cancer have been developed, only a few achieved tumor-specific targeting. Therefore, a special emphasis has been placed on the treatment of cancer using nano-carrier-encapsulated chemotherapeutic agents conjugated with tumor-homing peptides. The targeting strategy coupling the drugs with nanotechnology helps to overcome the most common barriers, such as high toxicity and side effects. Prostate-specific membrane antigen has emerged as a promising target molecule for prostate cancer and shown to be targeted with high affinity by GRFLTGGTGRLLRIS peptide known as peptide 563 (P563). Here, we aimed to assess the in vitro and in vivo targeting efficiency, safety, and efficacy of P563-conjugated, docetaxel (DTX)-loaded polymeric micelle nanoparticles (P563-PEtOx-co-PEI30%-b-PCL-DTX) against prostate cancer. To this end, we analyzed the cytotoxic activity of P563-PEtOx-co-PEI30%-b-PCL and P563-PEtOx-co-PEI30%-b-PCL-DTX by a cell proliferation assay using PNT1A and 22Rv1 cells. We have also determined the targeting selectivity of P563-PEtOx-co-PEI30%-b-PCL-FITC by flow cytometry and assessed the induction of cell death by western blot and TUNEL assays for P563-PEtOx-co-PEI30%-b-PCL-DTX in 22Rv1 cells. To investigate the in vivo efficacy, we administered DTX in the free form or in polymeric micelle nanoparticles to athymic CD-1 nu/nu mice 22Rv1 xenograft models and performed histopathological analyses. Our study showed that targeting prostate cancer with P563-conjugated PEtOx-co-PEI30%-b-PCL polymeric micelles could exert a potent anti-cancer activity with low side effects.

Validation of the standardized index of shape tool to analyze DCE-MRI data in the assessment of neo-adjuvant therapy in locally advanced rectal cancer

PURPOSE

Standardized index of shape (SIS) tool validation to examine dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) in preoperative chemo-radiation therapy (pCRT) assessment of locally advanced rectal cancer (LARC) in order to guide the surgeon versus more or less conservative treatment.

MATERIALS AND METHODS

A total of 194 patients (January 2008-November 2020), with III-IV locally advanced rectal cancer and subjected to pCRT were included. Three expert radiologists performed DCE-MRI analysis using SIS tool. Degree of absolute agreement among measurements, degree of consistency among measurements, degree of reliability and level of variability were calculated. Patients with a pathological tumour regression grade (TRG) 1 or 2 were classified as major responders (complete responders have TRG 1).

RESULTS

Good significant correlation was obtained between SIS measurements (range 0.97-0.99). The degree of absolute agreement ranges from 0.93 to 0.99, the degree of consistency from 0.81 to 0.9 and the reliability from 0.98 to 1.00 (p value <  < 0.001). The variability coefficient ranges from 3.5% to 26%. SIS value obtained to discriminate responders by non-responders a sensitivity of 95.9%, a specificity of 84.7% and an accuracy of 91.8% while to detect complete responders, a sensitivity of 99.2%, a specificity of 63.9% and an accuracy of 86.1%.

CONCLUSION

SIS tool is suitable to assess pCRT response both to identify major responders and complete responders in order to guide the surgeon versus more or less conservative treatment.

Recent advances in iron oxide nanoparticles for brain cancer theranostics: from in vitro to clinical applications

Introduction: Today, the development of multifunctional nanoplatforms is more seriously considered in the field of cancer theranostics.Areas covered: In this respect, nanoparticles provide several advantages over the routine, conventional diagnostic methods, and treatments. Due to the expedient properties of iron oxide nanoparticles, such as being readily modified, great payload potential, intrinsic magnetic qualification, considerable biocompatibility, and overwhelming response to targeting strategies, these nanoparticles can be considered good candidates for application as diagnostic contrast agents and drug/gene delivery vehicles, while also being incorporated into hyperthermia-based approaches. Interestingly, these agents are detectable with routine imaging modalities such as magnetic resonance imaging.Expert opinion: Therefore, combining the traditional diagnostics and therapies with nanotechnological approaches may leave a positive impact on the survival rate of patients with cancer. This review summarizes the application of magnetic iron oxide nanoparticles in both in vitro and in vivo models of brain tumors.

[18F]-JK-PSMA-7 and [18F]-FDG tumour PET uptake in treated xenograft human prostate cancer model in mice

PURPOSE

This preclinical study aims to evaluate the extent to which a change in prostate-specific membrane antigen (PSMA) expression of castration-resistant prostate cancer (CRPC) following standard treatment is reflected in [¹⁸F]JK-PSMA-7 PET/CT.

METHODS

Castrated mice supplemented with testosterone implant were xenografted with human LNCaP CRPC. After appropriate tumour growth, androgen deprivation therapy (ADT) was carried out by the removal of the implant followed by a single injection of docetaxel (400 μg/20-g mouse) 2 weeks later. [¹⁸F]JK-PSMA-7 PET/CT were performed before ADT, then before and at days 12, 26, 47 and 69 after docetaxel administration. The [¹⁸F]JK-PSMA-7 PET data were compared to corresponding unspecific metabolic [¹⁸F]FDG PET/CT and ex vivo quantification of PSMA expression estimated by flow cytometry on repeated tumour biopsies.

RESULTS

ADT alone had no early effect on LNCaP tumours that pursued their progression. Until day 12 post-docetaxel, the [¹⁸F]JK-PSMA7 uptake was significantly higher than that of [¹⁸F]FDG, indicating the persistence of PSMA expression at those time points. From day 26 onwards when the tumours were rapidly expanding, both [¹⁸F]JK-PSMA7 and [¹⁸F]FDG uptake continuously decreased although the decrease in [¹⁸F]JK-PSMA uptake was markedly faster. The fraction of PSMA-positive cells in tumour biopsies decreased similarly over time to reach a non-specific level after the same time period.

CONCLUSION

Applying PSMA-based imaging for therapy monitoring in patients with CRPC should be considered with caution since a reduction in [¹⁸F]JK-PSMA-7 PET uptake after successive ADT and chemotherapy may be related to downregulation of PSMA expression in dedifferentiated and rapidly proliferating tumour cells.

Shear-wave velocity for colorectal cancer liver metastases as a potential prognostic factor after chemotherapy: a preliminary study

AIM

To evaluate whether shear-wave velocity (SWV) can be used for predicting the prognoses of patients with colorectal cancer liver metastases (CRLMs) after chemotherapy.

MATERIALS AND METHODS

Our institutional review board approved this prospective study, and written informed consent was obtained. SWV of CRLMs were obtained using point shear-wave elastography using acoustic radiation force impulse from 25 patients prior to and 2, 7, and 14 days after chemotherapy. Progression-free survival (PFS) after chemotherapy was estimated using the Kaplan-Meier method. The Cox proportional hazard regression model was used to determine significant predictive factors for PFS. For measurement reproducibility, an additional 37 patients with CRLMs were enrolled and assessed using intraclass correlation coefficients (ICCs).

RESULTS

After chemotherapy, 10 and 15 patients were classified into responder and non-responder groups, respectively. The estimated 1- and 3-year PFS values in the whole cohort were 36% and 8%, respectively. A decrease in the SWV value on day 2 relative to the initial value was a significant predictive factor for better PFS outcome (hazard ratio = 0.20, 95% confidence interval = 0.07-0.57, p=0.003). The estimated 1 and 3-year PFS rates were 66.7% and 22.2%, respectively, in nine patients with decreased SWV values on day 2 and significantly higher than 18.8% and 0% of 16 patients with increased SWV values on day 2. The ICC value of SWV of CRLMs in the additional 37 patients was 0.823 (95% CI = 0.685-0.905), indicating good agreement.

CONCLUSION

SWV values of CRLMs could provide prognostic information in patients with CRLMs treated with chemotherapy, as decreased SWV values on day 2 after chemotherapy was a significant predictive factor for better PFS.

Combined dynamic DCE-MRI and diffusion-weighted imaging to evaluate the effect of neoadjuvant chemotherapy in cervical cancer

PURPOSE

To prospectively investigate changes in quantitative parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and the apparent diffusion coefficient (ADC) of diffusion-weighted imaging (DWI) in patients with cervical cancer before and after neoadjuvant chemotherapy (NACT).

METHODS

Thirty-eight patients with cervical cancer underwent DCE-MRI and DWI 1 week before and 4 weeks after NACT. The patients were classified into 2 groups: significant reaction (sCR) group and the non-sCR group. DCE-MRI parameters and ADC values were measured and compared between the 2 groups.

RESULTS

Before NACT, the mean K^trans value was higher, but the mean V_e was lower, in the sCR group compared with the non-sCR group; these differences were statistically significant (p<0.05). After NACT, the mean K^trans value and the delta (i.e., changed) value of K^trans were significantly lower in the sCR group compared with the non-sCR group (p<0.05). However, the mean ADC and the delta value of the mean ADC between the 2 groups were slightly higher in the sCR group compared with the non-sCR group (p<0.05). The area under the curve of pre-mean K^trans, DK^trans, and pre-mean K^trans combined with post-mean ADC values were 0.801, 0.955, and 0.878, respectively (p<0.05). The optimal cutoff values for distinguishing sCR from non-sCR were pretreatment K^trans (0.7020 min^-1) and DK^trans (0.0437 min^-1).

CONCLUSIONS

Quantitative parameters (pre-mean K^trans, DK^trans, and pre-mean K^trans) combined with post-mean ADC could predict treatment efficacy more precisely. However, quantitative DCE-MRI combined with DWI could not significantly improve prognostic efficacy.

Magnetic Resonance Imaging for Translational Research in Oncology

The translation of results from the preclinical to the clinical setting is often anything other than straightforward. Indeed, ideas and even very intriguing results obtained at all levels of preclinical research, i.e., in vitro, on animal models, or even in clinical trials, often require much effort to validate, and sometimes, even useful data are lost or are demonstrated to be inapplicable in the clinic. In vivo, small-animal, preclinical imaging uses almost the same technologies in terms of hardware and software settings as for human patients, and hence, might result in a more rapid translation. In this perspective, magnetic resonance imaging might be the most translatable technique, since only in rare cases does it require the use of contrast agents, and when not, sequences developed in the lab can be readily applied to patients, thanks to their non-invasiveness. The wide range of sequences can give much useful information on the anatomy and pathophysiology of oncologic lesions in different body districts. This review aims to underline the versatility of this imaging technique and its various approaches, reporting the latest preclinical studies on thyroid, breast, and prostate cancers, both on small laboratory animals and on human patients, according to our previous and ongoing research lines.

Assessing response to neo-adjuvant therapy in locally advanced rectal cancer using Intra-voxel Incoherent Motion modelling by DWI data and Standardized Index of Shape from DCE-MRI

Background:

Our aim was to investigate preoperative chemoradiation therapy (pCRT) response in locally advanced rectal cancer (LARC) comparing standardized index of shape (SIS) obtained from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with intravoxel-incoherent-motion-modelling-derived parameters by diffusion-weighted imaging (DWI).

Materials and methods:

Eighty-eight patients with LARC were subjected to MRI before and after pCRT. Apparent diffusion coefficient (ADC), tissue diffusion (D_t), pseudodiffusion (D_p) and perfusion fraction (f) were calculated and percentage changes ∆ADC, ∆D_t, ∆D_p, ∆f were computed. SIS was derived comparing DCE-MRI pre- and post-pCRT. Nonparametric tests and receiver operating characteristic (ROC) curves were performed.

Results:

A total of 52 patients were classified as responders (tumour regression grade; TRG ⩽ 2) and 36 as not-responders (TRG > 3). Mann–Whitney U test showed statistically significant differences in SIS, ∆ADC and ∆D_t between responders and not-responders and between complete responders (19 patients with TRG = 1) versus incomplete responders. The best parameters to discriminate responders by nonresponders were SIS and ∆ADC, with an accuracy of 91% and 82% (cutoffs of −5.2% and 18.7%, respectively); the best parameters to detect pathological complete responders were SIS, ∆f and ∆D_p with an accuracy of 78% (cutoffs of 38.5%, 60.0% and 83.0%, respectively). No increase of performance was observed by combining linearly each possible couple of parameters or combining all parameters.

Conclusion:

SIS allows assessment of preoperative treatment response with high accuracy guiding the surgeon versus more or less conservative treatment. DWI-derived parameters reached less accuracy compared with SIS and combining linearly DCE- and DWI-derived parameters; no increase of accuracy was obtained.

Apparent diffusion coefficient as an effective index for the therapeutic efficiency of brain chemoradiotherapy for brain metastases from lung cancer

BACKGROUND

The potential of apparent diffusion coefficient (ADC) value alteration before and after chemoradiotherapy as a potential monitor for therapeutic efficiency of treatment for brain metastases from lung cancer were discussed.

METHOD

Thirty lung cancer patients with brain metastases, conventional magnetic resonance imaging (MRI) examination and diffusion weighted imaging (DWI) were performed one week before chemoradiotherapy and after one treatment cycle and two treatment cycles. 43 tumor lesions were divided into effective group and invalid group according to the changes of the tumor size. The differences in ADC values at different time points before and after treatment in each treatment group were analyzed.

RESULT

The maximum diameter of the tumor was no difference after one treatment cycle, but decreased after two treatment cycles. ADC values significantly increased after both one and two treatment cycles. In effective group, the ADC values were significantly increased after one and two treatment cycles. While, there are no difference in invalid group after one treatment cycle but decreased after two treatment cycles. ΔADC values in effective group after one and two treatment cycles were both significantly higher than those in the invalid group. ROC curve analysis then revealed that the area under the curve (AUC) of ΔADC after one treatment was 0.872.

CONCLUSION

ADC values in brain metastases from lung cancer can help monitor and dynamically observe the therapeutic efficiency of whole brain chemoradiotherapy.

The value of MRI in evaluating the efficacy and complications with the treatment of intra-arterial chemotherapy for retinoblastoma

Retinoblastoma is the most common intraocular malignant tumor of childhood. Intra-arterial chemotherapy (IAC) is a recently popularized technique used for the treatment of retinoblastoma, to decrease mortality, increase preservation of the eye, and prevent blindness. Along with the extensive use of IAC, it is important to apply noninvasive examination methods to assess the activity of the tumor and the risk factors for disease dissemination without histopathological confirmation. There are few studies that have assessed the value of magnetic resonance imaging (MRI) in evaluating the efficacy and complications of IAC for retinoblastoma. We retrospectively analyzed the MRI features of 60 patients with unilateral retinoblastoma given the primary treatment of IAC from January 2014 to February 2016 in our hospital. Our study showed that MRI could well assess the decreased activity of the tumor after IAC, presenting with diminished tumor size, increased apparent diffusion coefficient (ADC) values (from 0.94 ± 0.24 × 10-3 mm2/s to 2.24 ± 0.40 × 10-3 mm2/s), and a reduced degree of enhancement of the tumor. Our study also showed that MRI can monitor the risk factors of abnormal enhancement of the postlaminar optic nerve, to avoid unnecessary enucleation. Meanwhile, the results showed that the main late complications after IAC included affected eyeball volume reduction, subretinal hemorrhage, vitreous hemorrhage, vitreous opacity, cataractous len, and choroidal vascular ischemia.

Metronomic treatment in immunocompetent preclinical GL261 glioblastoma: effects of cyclophosphamide and temozolomide

Glioblastoma (GBM) causes poor survival in patients even when applying aggressive treatment. Temozolomide (TMZ) is the standard chemotherapeutic choice for GBM treatment, but resistance always ensues. In previous years, efforts have focused on new therapeutic regimens with conventional drugs to activate immune responses that may enhance tumor regression and prevent regrowth, for example the "metronomic" approaches. In metronomic scheduling studies, cyclophosphamide (CPA) in GL261 GBM growing subcutaneously in C57BL/6 mice was shown not only to activate antitumor CD8⁺ T-cell response, but also to induce long-term specific T-cell tumor memory. Accordingly, we have evaluated whether metronomic CPA or TMZ administration could increase survival in orthotopic GL261 in C57BL/6 mice, an immunocompetent model. Longitudinal in vivo studies with CPA (140 mg/kg) or TMZ (range 140-240 mg/kg) metronomic administration (every 6 days) were performed in tumor-bearing mice. Tumor evolution was monitored at 7 T with MRI (T₂ -weighted, diffusion-weighted imaging) and MRSI-based nosological images of response to therapy. Obtained results demonstrated that both treatments resulted in increased survival (38.6 ± 21.0 days, n = 30) compared with control (19.4 ± 2.4 days, n = 18). Best results were obtained with 140 mg/kg TMZ (treated, 44.9 ± 29.0 days, n = 12, versus control, 19.3 ± 2.3 days, n = 12), achieving a longer survival rate than previous group work using three cycles of TMZ therapy at 60 mg/kg (33.9 ± 11.7 days, n = 38). Additional interesting findings were, first, clear edema appearance during chemotherapeutic treatment, second, the ability to apply the semi-supervised source analysis previously developed in our group for non-invasive TMZ therapy response monitoring to detect CPA-induced response, and third, the necropsy findings in mice cured from GBM after high TMZ cumulative dosage (980-1400 mg/kg), which demonstrated lymphoma incidence. In summary, every 6 day administration schedule of TMZ or CPA improves survival in orthotopic GL261 GBM with respect to controls or non-metronomic therapy, in partial agreement with previous work on subcutaneous GL261.

Newer Imaging Modalities to Assess Tumor in the Prostate

Background

Several advances in the imaging of prostate cancer have been made in recent years. Diagnostic staging has become increasingly complex and confusing as newer technologies have developed more rapidly than research has been able to confirm or refute the accuracy of these technologies. By the time research has been performed, the technology used for a study has often become outdated and newer and more sophisticated imaging has become available.

Methods

We reviewed the literature on local and nodal staging of prostate cancer, as well as the role of magnetic resonance imaging (MRI), magnetic resonance spectroscopic imaging (MRSI), dynamic contrast-enhanced MRI, positron emission tomography (PET), endorectal power Doppler, lymphotropic MRI contrast agents, and future possibilities such as diffusion MRI. This review is not systematic, but rather focused on these imaging modalities.

Results

Advances in MRI, ultrasound, and lymphotropic contrast agents have improved our ability to differentiate between T2 and T3 prostate tumors. PET imaging has proven less successful at staging prostate cancer. A literature review suggests patients with moderate risk of extracapsular extension benefit most from endorectal MRI evaluation. Spectroscopy, dynamic imaging, and lymphotropic contrast agents are expected to continue to improve sensitivity and specificity of staging of prostate cancer. Power Doppler evaluation with endorectal ultrasound has proved useful for evaluation during endorectal biopsy for identifying hypervascular tumors for directed biopsy. Diffusion-weighted MRI remains untested clinically and represents a future direction for research.

Conclusions

Future studies using these new techniques are needed to demonstrate changes in outcomes in large patient populations.

Magnetically-actuated drug delivery device (MADDD) for minimally invasive treatment of prostate cancer: An in vivo animal pilot study

BACKGROUND

The vast majority of prostate cancer presents clinically localized to the prostate without evidence of metastasis. Currently, there are several modalities available to treat this particular disease. Despite radical prostatectomy demonstrating a modest prostate cancer specific mortality benefit in the PIVOT trial, several novel modalities have emerged to treat localized prostate cancer in patients that are either not eligible for surgery or that prefer an alternative approach.

METHODS

Athymic nude mice were subcutaneously inoculated with prostate cancer cells. The mice were divided into four cohorts, one cohort untreated, two cohorts received docetaxel (10 mg/kg) either subcutaneously (SC) or intravenously (IV) and the fourth cohort was treated using the magnetically-actuated docetaxel delivery device (MADDD), dispensing 1.5 μg of docetaxel per 30 min treatment session. Treatment in all three therapeutic arms (SC, IV, and MADDD) was administered once weekly for 6 weeks. Treatment efficacy was measured once a week according to tumor volume using ultrasound. In addition, calipers were used to assess tumor volume.

RESULTS

Animals implanted with the device demonstrated no signs of distress or discomfort, neither local nor systemic symptoms of inflammation and infection. Using an independent sample t-test, the tumor growth rate of the treated tumors was significant when compared to the control. Post hoc Tukey HSD test results showed that the mean tumor growth rate of our device cohort was significantly lower than SC and control cohorts. Moreover, IV cohort showed slight reduction in mean tumor growth rates than the ones from the device cohort, however, there was no statistical significance in tumor growth rate between these two cohorts. Furthermore, immunohistochemistry demonstrated an increased cellular apoptosis in the MADDD treated tumors and a decreased proliferation when compared to the other cohorts. In addition, IV cohort showed increased treatment side effects (weight loss) when compared to the device cohort. Finally, MADDD showed minimal expression of CD45 comparable to the control cohort, suggesting no signs of chronic inflammation.

CONCLUSIONS

In conclusion, this study showed for the first time that MADDD, clearly suppressed tumor growth in local prostate cancer tumors. This could potentially be a novel clinical treatment approach for localized prostate cancer.

The distribution of the apparent diffusion coefficient as an indicator of the response to chemotherapeutics in ovarian tumour xenografts

Diffusion-weighted magnetic resonance imaging (DW-MRI) was used to evaluate the effects of single-agent and combination treatment regimens in a spheroid-based animal model of ovarian cancer. Ovarian tumour xenografts grown in non-obese diabetic/severe-combined-immunodeficiency (NOD/SCID) mice were treated with carboplatin or paclitaxel, or combination carboplatin/paclitaxel chemotherapy regimens. After 4 weeks of treatment, tumours were extracted and underwent DW-MRI, mechanical testing, immunohistochemical and gene expression analyses. The distribution of the apparent diffusion coefficient (ADC) exhibited an upward shift as a result of each treatment regimen. The 99-th percentile of the ADC distribution (“maximum ADC”) exhibited a strong correlation with the tumour size (r² = 0.90) and with the inverse of the elastic modulus (r² = 0.96). Single-agent paclitaxel (n = 5) and combination carboplatin/paclitaxel (n = 2) treatment regimens were more effective in inducing changes in regions of higher cell density than single-agent carboplatin (n = 3) or the no-treatment control (n = 5). The maximum ADC was a good indicator of treatment-induced cell death and changes in the extracellular matrix (ECM). Comparative analysis of the tumours’ ADC distribution, mechanical properties and ECM constituents provides insights into the molecular and cellular response of the ovarian tumour xenografts to chemotherapy. Increased sample sizes are recommended for future studies. We propose experimental approaches to evaluation of the timeline of the tumour’s response to treatment.

Prognostic implications of diffusion-weighted magnetic resonance imaging in patients with superior sulcus tumors receiving induction chemoradiation therapy

OBJECTIVE

The aim of this study was to evaluate a diffusion-weighted magnetic resonance imaging to represent therapeutic response of induction chemoradiation and outcome in patients with non-small cell lung cancer of the superior sulcus.

METHODS

Seventeen patients with non-small cell lung cancer of the superior sulcus (median age, 57 years; range, 44-70 years) received induction chemoradiation, followed by surgery. Diffusion-weighted magnetic resonance imaging of the lesion using b values of 0 and 800 s/mm(2) was acquired before treatment and after induction chemoradiation. Changes in tumoral apparent diffusion coefficient were compared with clinical and histopathological response. Cumulative disease-free survival and proportion of surviving were estimated by the Kaplan-Meier method. Survival of diffusion responders and non-responders were compared by log-rank test.

RESULTS

A significant correlation was observed between changes of diffusion response after induction chemoradiation and overall survival. Using a defined threshold of percent increase in mean apparent diffusion coefficient, nine out of 17 patients (53%) were classified as diffusion responders and had a mean increase in mean apparent diffusion coefficient of 40.7 ± 11.2%, while eight diffusion non-responding patients (47%) had a mean increase of 11.0 ± 15.5% (P < 0.0001). Significant difference was found in overall survival between diffusion responders and diffusion non-responders (88.9 months versus 20.3 months, P = 0.002).

CONCLUSIONS

Diffusion-weighted magnetic resonance imaging represented therapeutic effect and prognosis after induction chemoradiation in patients with non-small cell lung cancer of the superior sulcus.

Whole body diffusion weighted MRI--a new view of myeloma

The recent consensus statement from the International Myeloma Working Group has introduced the role of whole body (WB) magnetic resonance imaging (MRI) into the management pathway for patients with multiple myeloma. The speed, coverage and high sensitivity of WB diffusion weighted (DW)-MRI and the unique capability to quantify both burden of disease and response to treatment has led to increasing implementation at leading centres worldwide for imaging malignant marrow disease, both primary and metastatic. WB DW-MRI is likely to have a significant impact on management decisions and pathways for patients with multiple myeloma. This review will introduce the basic principles of DW-MRI, present current evidence for patients with myeloma and will discuss practicalities and exciting future applications.

Preclinical imaging and translational animal models of cancer for accelerated clinical implementation of nanotechnologies and macromolecular agents

The majority of animal models of cancer have performed poorly in terms of predicting clinical performance of new therapeutics, which are most often first evaluated in patients with advanced, metastatic disease. The development and use of metastatic models of cancer may enhance clinical translatability of preclinical studies focused on the development of nanotechnology-based drug delivery systems and macromolecular therapeutics, potentially accelerating their clinical implementation. It is recognized that the development and use of such models are not without challenge. Preclinical imaging tools offer a solution by allowing temporal and spatial characterization of metastatic lesions. This paper provides a review of imaging methods applicable for evaluation of novel therapeutics in clinically relevant models of advanced cancer. An overview of currently utilized models of oncology in small animals is followed by image-based development and characterization of visceral metastatic cancer models. Examples of imaging tools employed for metastatic lesion detection, evaluation of anti-tumor and anti-metastatic potential and biodistribution of novel therapies, as well as the co-development and/or use of imageable surrogates of response, are also discussed. While the focus is on development of macromolecular and nanotechnology-based therapeutics, examples with small molecules are included in some cases to illustrate concepts and approaches that can be applied in the assessment of nanotechnologies or macromolecules.

MRI for Assessing Response to Neoadjuvant Therapy in Locally Advanced Rectal Cancer Using DCE-MR and DW-MR Data Sets: A Preliminary Report

To evaluate MRI for neoadjuvant therapy response assessment in locally advanced rectal cancer (LARC) using dynamic contrast enhanced-MRI (DCE-MRI) and diffusion weighted imaging (DWI), we have compared magnetic resonance volumetry based on DCE-MRI (V(DCE)) and on DWI (V(DWI)) scans with conventional T2-weighted volumetry (V(C)) in LARC patients after neoadjuvant therapy. Twenty-nine patients with LARC underwent MR examination before and after neoadjuvant therapy. A manual segmentation was performed on DCE-MR postcontrast images, on DWI (b-value 800 s/mm²), and on conventional T2-weighted images by two radiologists. DCE-MRI, DWI, and T2-weigthed volumetric changes before and after treatment were evaluated. Nonparametric sample tests, interobserver agreement, and receiver operating characteristic curve (ROC) were performed. Diagnostic performance linked to DCE-MRI volumetric change was superior to T2-w and DW-MRI volumetric changes performance (specificity 86%, sensitivity 93%, and accuracy 93%). Area Under ROC (AUC) of V(DCE) was greater than AUCs of V(C) and V(DWI) resulting in an increase of 15.6% and 11.1%, respectively. Interobserver agreement between two radiologists was 0.977, 0.864, and 0.756 for V(C), V(DCE), and V(DWI), respectively. V(DCE) seems to be a promising tool for therapy response assessment in LARC. Further studies on large series of patients are needed to refine technique and evaluate its potential value.

Diffusion MRI with Semi-Automated Segmentation Can Serve as a Restricted Predictive Biomarker of the Therapeutic Response of Liver Metastasis

PURPOSE

To assess the value of semi-automated segmentation applied to diffusion MRI for predicting the therapeutic response of liver metastasis.

METHODS

Conventional diffusion weighted magnetic resonance imaging (MRI) was performed using b-values of 0, 150, 300 and 450s/mm(2) at baseline and days 4, 11 and 39 following initiation of a new chemotherapy regimen in a pilot study with 18 women with 37 liver metastases from primary breast cancer. A semi-automated segmentation approach was used to identify liver metastases. Linear regression analysis was used to assess the relationship between baseline values of the apparent diffusion coefficient (ADC) and change in tumor size by day 39.

RESULTS

A semi-automated segmentation scheme was critical for obtaining the most reliable ADC measurements. A statistically significant relationship between baseline ADC values and change in tumor size at day 39 was observed for minimally treated patients with metastatic liver lesions measuring 2-5cm in size (p=0.002), but not for heavily treated patients with the same tumor size range (p=0.29), or for tumors of smaller or larger sizes. ROC analysis identified a baseline threshold ADC value of 1.33μm(2)/ms as 75% sensitive and 83% specific for identifying non-responding metastases in minimally treated patients with 2-5cm liver lesions.

CONCLUSION

Quantitative imaging can substantially benefit from a semi-automated segmentation scheme. Quantitative diffusion MRI results can be predictive of therapeutic outcome in selected patients with liver metastases, but not for all liver metastases, and therefore should be considered to be a restricted biomarker.

Diffusion-weighted magnetic resonance imaging in predicting the radiosensitivity of cervical cancer

This study investigates the application value of diffusion-weighted magnetic resonance imaging in predicting cervical cancer radiosensitivity. Twenty-five patients who were newly diagnosed as cervical cancer and accepted simple radiotherapy were included in this study. Before external irradiation, 20 GY and at the end of irradiation, routine 1.5 T MRI and diffusion-weighted magnetic resonance imaging scanning were carried. Apparent diffusion coefficient (ADC) value of primary tumor was measured. Its correlation with tumor regression rate was analyzed. ADC values of before irradiation, 20 GY and at the end of irradiation was (0.93 ± 0.14) × 10(-3) mm(2)/s, (1.25 ± 0.17) × 10(-3) mm(2)/s and (1.55 ± 0.13) × 10(-3) mm(2)/s, respectively. There were statistical significant differences (P< 0.01). D-value of ADC values between before and 20 GY external irradiation was (0.33 ± 0.16) mm(2)/s. The tumor volume before and at the end of external irradiation were (37.48 ± 26.83) cm(3) and (4.41 ± 3.72) cm(3) respectively, with tumor regression rate of before and after external irradiation of (0.86 ± 0.11). ADC values of before irradiation, 20 GY and at the end of irradiation did not correlate with tumor regression rate. D-value of ADC values between before and 20 GY external irradiation positively correlated with tumor regression rate (r = 0.423, P = 0.035). ADC value of cervical cancer increased after radiotherapy and early changes of ADC value was positively correlated with tumor regression rate, thus, ADC value could be used as a potential prediction factor for cervical cancer radiosensitivity.

Dose-response relationship in cisplatin-treated breast cancer xenografts monitored with dynamic contrast-enhanced ultrasound

Background

Exactly assessing tumor response to different dose of chemotherapy would help to tailor therapy for individual patients. This study was to determine the feasibility of dynamic contrast-enhanced ultrasound (CEUS) in the evaluation of tumor vascular response to different dose cisplatin.

Methods

MCF-7 breast cancer bearing mice were treated with different dose of cisplatin in group B (1 mg/kg) and group C (3 mg/kg). A control group A was given with saline. Sequential CEUS was performed on days 0, 3 and 7 of the treatment, in which time-signal intensity curves were obtained from the intratumoral and depth-matched liver parenchyma. Peak enhancement (PE), area under the curve of wash-in (WiAUC), wash-in rate (WiR) and wash-in perfusion index (WiPI) were calculated from perfusion time-intensity curves and normalized with respect to the adjacent liver parenchyma. Histopathological analysis was conducted to evaluate tumor cell density and microvascular density (MVD).

Results

Significant decreases in tumor normalized perfusion parameters were observed on day 3 in the high dose group and on day 7 in the low dose group. On day 7, nPE, nWiAUC, and nWiPI significantly decreased in group C and group B as compared with group A (P < 0.05), and further decreased in group C as compared with group B (P < 0.05). Significant decreases of tumor cell density and MVD were seen in treated group (group B and C) compared to control group (P < 0.05) and further decrease in group C compared to group B (P < 0.05).

Conclusions

Dynamic CEUS for quantification of tumor perfusion could be used to evaluate tumor vascular response to different dose of chemotherapy.

High-field small animal magnetic resonance oncology studies

This review focuses on the applications of high magnetic field magnetic resonance imaging (MRI) and spectroscopy (MRS) to cancer studies in small animals. High-field MRI can provide information about tumor physiology, the microenvironment, metabolism, vascularity and cellularity. Such studies are invaluable for understanding tumor growth and proliferation, response to treatment and drug development. The MR techniques reviewed here include (1)H, (31)P, chemical exchange saturation transfer imaging and hyperpolarized (13)C MRS as well as diffusion-weighted, blood oxygen level dependent contrast imaging and dynamic contrast-enhanced MRI. These methods have been proven effective in animal studies and are highly relevant to human clinical studies.

Diffusion MRI and novel texture analysis in osteosarcoma xenotransplants predicts response to anti-checkpoint therapy

Combinations of targeted drugs have been employed to treat sarcomas, however, response rates have not improved notably, therefore emphasizing the need for novel treatments. In addition, imaging approaches to assess therapeutic response is lacking, as currently measurable indices, such as volume and/or diameter, do not accurately correlate with changes in tumor biology. In this study, quantitative and profound analyses of magnetic resonance imaging (MRI) were developed to evaluate these as imaging biomarkers for MK1775 and Gem in an osteosarcoma xenotransplant model at early time-points following treatment. Notably, we showed that Gem and Gem+MK1775 groups had significantly inhibited tumor growth by day 4, which was presaged by elevations in mean ADC by 24 hours post treatment. Significant differences were also observed at later time points for the Gem+MK1775 combination and MK1775 therapy. ADC distribution and entropy (randomness of ADC values) were also elevated by 24 hours following therapy. Immunohistochemistry demonstrated that these treatment-related increases in ADC correlated with apoptosis and observed cell condensations (dense- and exploded bodies). These findings underline the role of ADC as a quantitative imaging biomarker for therapy-induced response and show promising clinical relevance in the sarcoma patient population.

The role of perfusion effects in monitoring of chemoradiotherapy of rectal carcinoma using diffusion-weighted imaging

PURPOSE

The aim of this study was to characterize and understand the therapy-induced changes in diffusion parameters in rectal carcinoma under chemoradiotherapy (CRT). The current literature shows conflicting results in this regard. We applied the intravoxel incoherent motion model, which allows for the differentiation between diffusion (D) and perfusion (f) effects, to further elucidate potential underlying causes for these divergent reports.

MATERIALS AND METHODS

Eighteen patients with primary rectal carcinoma undergoing preoperative CRT were examined before, during, and after neoadjuvant CRT using diffusion-weighted imaging. Using the intravoxel incoherent motion approach, f and D were extracted and compared with postoperative tumor downstaging and volume.

RESULTS

Initial diffusion-derived parameters were within a narrow range (D1 = 0.94 ± 0.12 × 10(-3) mm(2)/s). At follow-up, D rose significantly (D2 = 1.18 ± 0.13 × 10(-3) mm(2)/s; P < 0.0001) and continued to increase significantly after CRT (D3 = 1.24 ± 0.14 × 10(-3) mm(2)/s; P < 0.0001). The perfusion fraction f did not change significantly (f1 = 9.4 ± 2.0%, f2 = 9.4 ± 1.7%, f3 = 9.5 ± 2.7%). Mean volume (V) decreased significantly (V1 = 16,992 ± 13,083 mm(3); V2 = 12,793 ± 8317 mm(3), V3 = 9718 ± 6154 mm(3)). T-downstaging (10:18 patients) showed no significant correlation with diffusion-derived parameters.

CONCLUSIONS

Conflicting results in the literature considering apparent diffusion coefficient (ADC) changes in rectal carcinoma under CRT for patients showing T-downstaging are unlikely to be due to perfusion effects. Our data support the view that under effective therapy, an increase in D/ADC can be observed.

Islet cell liver metastases: assessment of volumetric early response with functional MR imaging after transarterial chemoembolization

PURPOSE

To assess early response to transarterial chemoembolization by using volumetric functional magnetic resonance (MR) imaging in patients with islet cell liver metastases (ICLMs).

MATERIALS AND METHODS

This retrospective institutional review board-approved HIPAA-compliant study included 215 ICLMs in 26 patients (15 men, 11 women; mean age, 59.7 years; age range, 37-79 years). Volumetric measurements were performed by an experienced radiologist on diffusion-weighted and contrast material-enhanced MR images at baseline and 1-month follow-up. Measurements included mean change (three-dimensional [3D] mean apparent diffusion coefficient [ADC], 3D mean enhancement) and percentage of tumor with change above a predetermined threshold (3D threshold ADC, 3D threshold enhancement). Response by volumetric measurements at 1-month follow-up was compared with Response Evaluation Criteria in Solid Tumors (RECIST) at 6-month follow-up. Lesions that had complete or partial response were considered responders, while those with stable or progressive disease were considered nonresponders. Statistical analysis included the t test, receiver operating characteristic (ROC) curve analysis, and logistic regression analysis.

RESULTS

RECIST criteria at 6-month follow-up indicated 78 (36.3%) lesions responded, while 137 (63.7%) did not. The increase in 3D mean ADC was significantly higher in responders than in nonresponders (median, 26.2% vs 10.9%; P<.001). The 3D threshold ADC was 71.1% in responders and 47.6% in nonresponders (P<.001). Decrease in 3D mean arterial enhancement (AE) was significantly higher in responders than in nonresponders (median, 40.5% vs 18.0%; P<.001). Decrease in 3D mean venous enhancement (VE) was significantly higher in responders than in nonresponders (median, 28.0% vs 10.0%; P<.001). The 3D threshold VE and 3D threshold AE did not differ between responders and nonresponders. In unadjusted logistic regression analyses, 3D mean ADC and 3D threshold ADC had the highest odds ratio (1.02 and 1.03, respectively) and the largest area under the ROC curve (0.698 and 0.695, respectively).

CONCLUSION

Volumetric functional MR imaging could be used to predict early response of hepatic ICLMs to therapy and to distinguish between responders and nonresponders.

Oncologic applications of diffusion-weighted MRI in the body

Diffusion-weighted MRI (DWI) allows the detection of malignancies in the abdomen and pelvis. Lesion detection and characterization using DWI largely depends on the increased cellularity of solid or cystic lesions compared with the surrounding tissue. This increased cellularity leads results in restricted diffusion as indicated by reduction in the apparent diffusion coefficient (ADC). Low pretreatment ADC values of several malignancies have been shown to be predictive of better outcome. DWI can assess response to systemic or regional treatment of cancer at a cellular level and will therefore detect successful treatment earlier than anatomical measures. In this review, we provide a brief technical overview of DWI, discuss quantitative image analysis approaches, and review studies which have used DWI for the purpose of detection and characterization of malignancies as well as the early prediction of treatment response.

Effect of implantation site and growth of hepatocellular carcinoma on apparent diffusion coefficient of water and sodium MRI

Hepatocellular carcinoma (HCC) and liver metastases are an increasing problem worldwide. Non-invasive methods for the early detection of HCC and understanding of the tumor growth mechanisms are highly desirable.  Both the diffusion-weighted (1)H (DWI) and (23)Na MRI reflect alterations in tissue compartment volumes in tumors, as well as physiological and metabolic transformation in cells. Effects of untreated growth on apparent diffusion coefficient of water (ADC), single quantum (SQ) and triple quantum-filtered (TQF) (23)Na MRI were compared in intrahepatically and subcutaneously implanted HCCs in rats. Animals were examined weekly for 4 weeks after injection of N1S1 cells. ADC of intrahepatic HCC was 1.5-times higher compared to the nearby liver tissue, and with growth, the ADC did not increase. ADC of subcutaneous HCC was lower compared to intrahepatic HCC and it increased with growth. Untreated growth of both intrahepatic and subcutaneous HCCs was associated with an increase in SQ and TQF (23)Na signal intensity suggesting an increase in tissue Na(+) and intracellular Na(+) (Na(+)(i)), respectively, most likely due to an increase in relative extracellular space and Na(+)(i) concentration as a result of changes in tissue structure and cellular metabolism. Thus, SQ and TQF (23)Na MRI may be complementary to diffusion imaging in areas susceptible to motion for characterizing hepatic tumors and for other applications, such as, predicting and monitoring therapy response.

Whole-body diffusion-weighted MR imaging in cancer: current status and research directions

Diffusion-weighted (DW) magnetic resonance (MR) imaging is emerging as a powerful clinical tool for directing the care of patients with cancer. Whole-body DW imaging is almost at the stage where it can enter widespread clinical investigations, because the technology is stable and protocols can be implemented for the majority of modern MR imaging systems. There is a continued need for further improvements in data acquisition and analysis and in display technologies. Priority areas for clinical research include clarification of histologic relationships between tissues of interest and DW MR imaging biomarkers at diagnosis and during therapy response. Because whole-body DW imaging excels at bone marrow assessments at diagnosis and for therapy response, it can potentially address a number of unmet clinical and pharmaceutical requirements. There are compelling needs to document and understand how common and novel treatments affect whole-body DW imaging results and to establish response criteria that can be tested in prospective clinical studies that incorporate measures of patient benefit.

Early evaluation of cancer response by a new functional biomarker: apparent diffusion coefficient

OBJECTIVE

The purpose of this article is to investigate whether apparent diffusion coefficient (ADC) might be used as a universal biomarker for response evaluation in different tumors.

SUBJECTS AND METHODS

Twenty-one patients with lung cancer, 12 patients with esophageal cancer, 19 patients with liver metastases, 24 patients with gastric cancer, and 26 patients with rectal cancer were recruited to the study. Percentage changes in the ADC and changes in the size of responding and nonresponding lesions of different tumors after treatment were analyzed using repeated measures analysis of variance.

RESULTS

There was no significant difference among the percentage ADC changes of different tumors (F = 1.57; p = 0.192). Clear differences were seen in the percentage ADC changes between responding and nonresponding tumors (F = 21.62; p < 0.001), which were significant at every time point after the start of treatment (early time point, F = 19.75 and p < 0.001; middle time point, F = 11.23 and p = 0.001; and later time point, F = 15.98 and p < 0.001). The percentage size changes after treatment between responding and nonresponding tumors were significantly different (F = 19.38; p < 0.001). However, at the early time point after treatment, the difference was not statistically significant (F = 0.02; p = 0.894).

CONCLUSION

The ADC changes correlated with treatment response in five types of body tumor but were independent of the tumor's location. Early increases in ADC during treatment indicate good response to treatment. ADC change is a promising biomarker for detecting therapeutic responses at an early stage that could be widely used.

Comparison of diffusion-weighted MRI and MR volumetry in the evaluation of early treatment outcomes after preoperative chemoradiotherapy for locally advanced rectal cancer

PURPOSE

To compare diffusion-weighted imaging (DWI) and magnetic resonance (MR) volumetry for predicting treatment outcomes of locally advanced rectal cancers with preoperative chemoradiotherapy (CRT).

MATERIALS AND METHODS

This prospective study was approved by our Institutional Review Board. Thirty-four patients underwent three MR examinations: pre-CRT (before CRT), early CRT (2 weeks after CRT initiation), and post-CRT (before surgery). The tumor apparent diffusion coefficient (ADC), ADC increase rate, and volume reduction rate were compared between responders and nonresponders using three reference standards: downstaging, modified Response Evaluation Criteria in Solid Tumors (mRECIST), and tumor regression grade (TRG). For DWI and volumetry, differences between responders and nonresponders were assessed by receiver operating characteristic analysis.

RESULTS

The median early tumor volume reduction rate of responders, subgrouped by downstaging and mRECIST (47.97% and 53.97%, respectively), was significantly higher than that of nonresponders (20.94% and 20.36%; P = 0.0024 and 0.0001, respectively), but there were no significant differences in pre-CRT ADC and early ADC increase rate using all references. When using the downstaging and mRECIST, the diagnostic performance of early tumor volume reduction rate (Az = 0.81 and 0.94, respectively) was higher than that of pre-CRT ADC (Az = 0.55 and 0.62; P = 0.033 and 0.007) and early ADC increase rate (Az = 0.58 and 0.64; P = 0.055 and 0.01) for predicting the treatment outcome. For TRG, there were no significant differences between DWI and volumetry.

CONCLUSION

Early tumor volume reduction rate at the second week after CRT initiation may be a better indicator than DWI based on the mean ADC measurements for predicting CRT treatment outcome.

Registration accuracy for MR images of the prostate using a subvolume based registration protocol

Background

In recent years, there has been a considerable research effort concerning the integration of magnetic resonance imaging (MRI) into the external radiotherapy workflow motivated by the superior soft tissue contrast as compared to computed tomography. Image registration is a necessary step in many applications, e.g. in patient positioning and therapy response assessment with repeated imaging. In this study, we investigate the dependence between the registration accuracy and the size of the registration volume for a subvolume based rigid registration protocol for MR images of the prostate.

Methods

Ten patients were imaged four times each over the course of radiotherapy treatment using a T2 weighted sequence. The images were registered to each other using a mean square distance metric and a step gradient optimizer for registration volumes of different sizes. The precision of the registrations was evaluated using the center of mass distance between the manually defined prostates in the registered images. The optimal size of the registration volume was determined by minimizing the standard deviation of these distances.

Results

We found that prostate position was most uncertain in the anterior-posterior (AP) direction using traditional full volume registration. The improvement in standard deviation of the mean center of mass distance between the prostate volumes using a registration volume optimized to the prostate was 3.9 mm (p < 0.001) in the AP direction. The optimum registration volume size was 0 mm margin added to the prostate gland as outlined in the first image series.

Conclusions

Repeated MR imaging of the prostate for therapy set-up or therapy assessment will both require high precision tissue registration. With a subvolume based registration the prostate registration uncertainty can be reduced down to the order of 1 mm (1 SD) compared to several millimeters for registration based on the whole pelvis.

Gastrointestinal stromal tumors treated with imatinib mesylate: apparent diffusion coefficient in the evaluation of therapy response in patients

PURPOSE

To prospectively investigate the use of the apparent diffusion coefficient (ADC) as an early response indicator in patients with gastrointestinal stromal tumors (GISTs) treated with imatinib mesylate.

MATERIALS AND METHODS

This study was approved by the institutional review board and written informed consent was obtained from all patients. Diffusion-weighted magnetic resonance (MR) imaging was performed in 32 patients with GISTs before and 1, 4, and 12 weeks after treatment with a tyrosine kinase inhibitor, imatinib mesylate. The measurable lesions were classified as having responded well or poorly according to size alterations at clinical evaluation following the first round of treatment (3 months). A linear mixed-effects model was applied to analyze changes in the ADCs of tumors during treatment and to compare the variation and slopes of the time-dependent ADC curves between the good- and poor-response groups.

RESULTS

There were 56 lesions in the good-response group and 35 in the poor-response group. An early (1 week after therapy) noticeable and statistically significant (P < .001) increase in the ADC was observed in the good-response group (median ADC increase, 44.8%) but not in the poor-response group (median ADC increase, 1.5%). The time-dependent ADC variation was significantly different between the good- and poor-response groups, with a sharper median ADC increase displayed in the former (week 1: 44.8% vs 1.5%; week 4: 80.4% vs 7.8%; week 12: 89.6% vs 16.7%; F = 25.78, P < .001). The largest difference in the weekly percentage increase in ADC between the good- and poor-response groups was observed at 1 week after therapy (week 0-1: 44.8% vs 1.5%; week 1-4: 7.0% vs 2.8%; week 4-12: 1.6% vs 0.7%). The pretherapy mean ADC (± standard deviation) of lesions in the good-response group (1.06 [×10(-3) mm(2)/sec] ± 0.27) was significantly lower than that in the poor-response group (1.24 [×10(-3) mm(2)/sec] ± 0.32) (F = 8.34, P = .005).

CONCLUSION

Comparatively low pretherapy ADC and marked ADC increase at 1 week after therapy is associated with good response to imatinib mesylate in patients with GISTs.

ADC response to radiation therapy correlates with induced changes in radiosensitivity

PURPOSE

Magnetic resonance imaging was used to compare the responses of human glioma tumor xenografts to a single fraction of radiation, where a change in radiosensitivity was induced by use of a suture-based ligature.

METHODS

Ischemia was induced by use of a suture-based ligature. Six mice were treated with 800 cGy of 200 kVp x rays while the ligature was applied. An additional six mice had the ligature applied for the same length of time but were not irradiated. Quantitative maps of each tumor were produced of water apparent diffusion coefficient (ADC) and transverse relaxation time (T2). Mice were imaged before and at multiple points after treatment. Volumetric, ADC, and T2 responses of the ligated groups were compared to previously measured responses of the same tumor model to the same radiation treatment, as well as those from an untreated control group.

RESULTS

Application of the ligature without irradiation did not affect tumor ADC values, but did produce a temporary decrease in tumor T2 values. Average tumor T2 was reduced by 6.2% 24 h after the ligature was applied. Average tumor ADC increased by 9.6% 7 days after irradiation with a ligature applied. This response was significantly less than that observed in the same tumor model when no ligature is present (21.8% at 7 days after irradiation).

CONCLUSIONS

These observations indicate that the response of ADC to radiation therapy is not determined entirely by physical dose deposition, but at least in part by radiosensitivity and resultant biological response.

Diffusion imaging for therapy response assessment of brain tumor

Advanced imaging provides insight into biophysical, physiologic, metabolic, or functional properties of tissues. Because water mobility is sensitive to cellular homeostasis, cellular density, and microstructural organization, it is considered a valuable tool in the advanced imaging arsenal. This article summarizes diffusion imaging concepts and highlights clinical applications of diffusion MR imaging for oncologic imaging. Diffusion tensor imaging and its derivative maps of diffusion anisotropy allow assessment of tumor compression or destruction of adjacent normal tissue anisotropy and may aid to assess tumor infiltration and aid presurgical planning.

Assessment of early docetaxel response in an experimental model of human breast cancer using DCE-MRI, ex vivo HR MAS, and in vivo 1H MRS

The purpose of this study was to evaluate the use of dynamic contrast-enhanced (DCE) MRI, in vivo (1)H MRS and ex vivo high resolution magic angle spinning (HR MAS) MRS of tissue samples as methods to detect early treatment effects of docetaxel in a breast cancer xenograft model (MCF-7) in mice. MCF-7 cells were implanted subcutaneously in athymic mice and treated with docetaxel (20, 30, and 40 mg/kg) or saline six weeks later. DCE-MRI and in vivo (1)H MRS were performed on a 7 T MR system three days after treatment. The dynamic images were used as input for a two-compartment model, yielding the vascular parameters K(trans) and v(e). HR MAS MRS, histology, and immunohistochemical staining for proliferation (Ki-67), apoptosis (M30 cytodeath), and vascular/endothelial cells (CD31) were performed on excised tumor tissue. Both in vivo spectra and HR MAS spectra were used as input for multivariate analysis (principal component analysis (PCA) and partial least squares regression analysis (PLS)) to compare controls to treated tumors. Tumor growth was suppressed in docetaxel-treated mice compared to the controls. The anti-tumor effect led to an increase in K(trans) and v(e) values in all the treated groups. Furthermore, in vivo MRS and HR MAS MRS revealed a significant decrease in choline metabolite levels for the treated groups, in accordance with reduced proliferative index as seen on Ki-67 stained sections. In this study DCE-MRI, in vivo MRS and ex vivo HR MAS MRS have been used to demonstrate that docetaxel treatment of a human breast cancer xenograft model results in changes in the vascular dynamics and metabolic profile of the tumors. This indicates that these MR methods could be used to monitor intra-tumoral treatment effects.

Locally advanced rectal carcinoma treated with preoperative chemotherapy and radiation therapy: preliminary analysis of diffusion-weighted MR imaging for early detection of tumor histopathologic downstaging

PURPOSE

To determine whether changes in apparent diffusion coefficients (ADCs) of rectal carcinoma obtained 1 week after the beginning of chemotherapy and radiation therapy (CRT) correlate with tumor histopathologic downstaging after preoperative CRT.

MATERIALS AND METHODS

This prospective study was approved by an institutional review board; informed consent was obtained from all patients. Thirty-seven patients (mean age, 54.7 years; 13 women, 24 men) with primary rectal carcinoma who were undergoing preoperative CRT were recruited for the study. Diffusion-weighted (DW) magnetic resonance (MR) imaging was performed with a 1.5-T MR imager in all patients before therapy, at the end of the 1st and 2nd week of therapy, and before surgery. Tumor ADCs were calculated. Linear mixed-effects modeling was applied to analyze change in ADCs and volumes following treatment.

RESULTS

Patients were assigned to the tumor downstaged group (n = 17) or the tumor nondownstaged group (n = 20) on the basis of histopathologic examination results following surgery. Before CRT, the mean tumor ADC in the downstaged group was lower than that in the nondownstaged group (1.07 x 10(-3) mm(2)/sec +/- 0.13 [standard deviation] vs 1.19 x 10(-3) mm(2)/sec +/- 0.15, F = 6.91, P = .013). At the end of the 1st week of CRT, the mean tumor ADC increased significantly from 1.07 x 10(-3) mm(2)/sec +/- 0.13 to 1.32 x 10(-3) mm(2)/sec +/- 0.16 (F = 37.63, P <.001) in the downstaged group, but there was no significant ADC increase in the nondownstaged group (F = 1.18, P = .291). The mean percentage of tumor ADC change in the downstaged group was significantly higher than that in the nondownstaged group at each time point (F = 18.39, P < .001).

CONCLUSION

Early increase of mean tumor ADC and low pretherapy mean ADC in rectal carcinoma correlate with good response to CRT. DW MR imaging is a promising noninvasive technique for helping predict and monitor early therapeutic response in patients with rectal carcinoma who are undergoing CRT.

Incremental value of magnetic resonance imaging in the advanced management of prostate cancer

Prostate cancer is a major public health burden throughout the world. The high incidence of prostate cancer, combined with earlier detection and downstaging at the time of diagnosis, and the slow natural progression and biological heterogeneity of the disease, has made its management a complex and controversial issue. There is growing demand for patient-specific therapies that can minimize treatment morbidity while maximizing treatment benefits. There are a number of clinical parameters and clinical nomograms to help with the choice of treatment. Magnetic resonance imaging (MRI) is a technique which makes safer, more individualized therapies possible due to high spatial resolution, superior contrast resolution, multiplanar capability, and a large field of view. Other MRI techniques such as MR spectroscopic imaging, dynamic contrast-enhanced MRI or perfusion MRI, and diffusion-weighted imaging complement MRI by reflecting tissue biochemistry, Brownian motion of water molecules, and capillary wall permeability, respectively. This editorial review highlights the incremental value of MRI in the advanced management of prostate cancer to non-invasively improve cancer staging, biologic potential, treatment planning, therapy response, local recurrence, and to guide target biopsy for clinical suspected cancer with previous negative biopsy. Finally, some future prospects for MRI in prostate cancer management are given.

Diffusion-weighted imaging in predicting and monitoring the response of uterine cervical cancer to combined chemoradiation

AIM

To investigate the ability of diffusion-weighted imaging (DWI) to predict and monitor the response of uterine cervical cancer to combined chemoradiation using apparent diffusion coefficients (ADCs).

MATERIALS AND METHODS

Seventeen women (mean age 48.5 years) with uterine cervical cancer received conventional magnetic resonance imaging (MRI) and DWI prior to chemoradiation and after 1 and 2 months of therapy. A subgroup of eight also had MRI and DWI repeated after 15 days of therapy. Treatment response was determined according to changes in tumour size after 2 months of therapy and was classified as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). Pretreatment ADCs were compared between the different disease response groups, and dynamic changes of ADCs in each group were observed. Pearson's correlation test was calculated between those ADC parameters and tumour response.

RESULTS

Pretreatment ADCs for CR were significantly lower than those of PR (p=0.005). Negative correlation was found between pretreatment ADCs and percentage size reduction after 2 months of chemoradiation (p=0.016). The percentage ADC change after 1 month correlated positively with percentage size reduction after 2 months of therapy (p=0.021). ADCs after 15 days of therapy increased significantly compared with pretreatment ones (p=0.001); however, the longest tumour diameter showed no statistically significant change (p=0.078).

CONCLUSION

ADCs may have the potential to be used to predict and monitor the response of uterine cervical cancer to therapy.

Significant temporal evolution of diffusion anisotropy for evaluating early response to radiosurgery in patients with vestibular schwannoma: findings from functional diffusion maps

BACKGROUND AND PURPOSE

Outcome evaluation in clinical oncology is conventionally based on long-term volumetric changes in the tumor size. The purpose of this study was to prospectively investigate the usefulness of fDMs in incorporating anisotropic diffusion in the evaluation of early response after radiosurgery in patients with vestibular schwannoma.

MATERIALS AND METHODS

The MD, FA, and IVDC were calculated by using simple averaging methods and fDMs. Six patients with vestibular schwannoma treated with stereotactic radiosurgery underwent longitudinal DTI studies on a 3T MR imaging scanner (maximum follow-up, 6 months). Posttreatment DTI data were spatially coregistered with pretreatment scans.

RESULTS

Tumors did not change significantly in size until 6 months after treatment. Diffusion indices changed significantly during the study period. There was a transient decrease in averaged MD followed by a significant increase. IVDC showed an opposite behavior compared with MD. FA decreased continuously throughout the study period. Functional diffusion maps showed a heterogeneous response of tumors to treatment, thereby providing complementary information to simple averaged values.

CONCLUSIONS

DTI allows early detection of therapeutic-induced changes in patients with vestibular schwannoma. Functional diffusion maps incorporating anisotropic diffusion may aid in assessing the heterogeneity of the therapeutic response in this patient group.

Molecular imaging in clinical trials

Imaging of biological processes using specific molecular probes allows exploration of the mechanism of action and efficacy for new therapies. This molecular imaging has made use of modalities including single photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance imaging (MRI), and optical techniques. Molecular imaging can be used to explore many of the hallmarks of cancer biology, including angiogenesis, proliferation, tissue invasion, evasion of apoptosis, and self-sufficiency in growth signals. Since many of these aspects of cancer biology are in turn the targets of novel therapies in development, molecular imaging techniques have great potential to inform trials of these new agents. The high cost of clinical drug development mandates the optimisation of early phase trial design to maximise the collection of evidence for efficacy and proof of mechanism, endpoints which have, in a number of examples, already been provided by molecular imaging. The variety provided by novel chemistry, and the availability of isotopes with varying physical properties, particularly suits PET imaging as a functional modality for application in clinical trials.

Temporal and dose dependence of T2 and ADC at 9.4 T in a mouse model following single fraction radiation therapy

The purpose of this study is to use magnetic resonance imaging to monitor the response of human glioma tumor xenografts to single fraction radiation therapy. Mice were divided into four treatment groups (n = 6 per group) that received 50, 200, 400, or 800 cGy of 200 kVp x rays. A fifth group (n = 6) received no radiation dose and served as the control. Quantitative maps of the treated tumor tissue were produced of water apparent diffusion coefficient (ADC) and transverse relaxation time (T2). Mice were imaged before and at multiple time points after treatment. There was a statistically significant difference in tumor growth relative to that of the control for all treatment groups. Only the highest dose group showed T2 values that were significantly different at all measured time points after treatment. In this group, there was an 8.3% increase in T2 relative to controls 2 days after treatment, but when measured 14 days after treatment, mean tumor T2 had dropped to 10.1% below the initial value. ADC showed statistically significant differences from the control at all dose points. A radiation dose dependence was observed. In the highest dose group, the fractional increases in ADC were higher than those observed for T2. ADC was sensitive to radiation-induced changes in lower dose groups that did not have significant T2 change. At all doses, elevation of mean tumor ADC preceded deviations in tumor growth from the control. These observations support the potential application of ADC as a time and dose sensitive marker of tumor response to radiation therapy.