Prospective early response imaging biomarker for neoadjuvant breast cancer chemotherapy

Diffusion-Weighted MRI for Recurrent/Persistent Head and Neck Squamous-Cell Carcinoma After Radiotherapy: Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the accuracy of diffusion-weighted magnetic resonance imaging (DWI-MRI) in diagnosing persistent/recurrent head and neck squamous cell carcinomas (HNSCCs) after primary chemoradiotherapy (CRT).

DATA SOURCES

Scopus, PubMed/MEDLINE, and Cochrane Library databases were searched for relevant publications until April 18, 2023.

REVIEW METHODS

A systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses of Diagnostic Test Accuracy statement. The search was conducted independently by 2 investigators. Methodological quality of included studies was assessed using the Quality Assessment of Diagnostic Studies-2 questionnaire. Extracted data were used to calculate the pooled DWI-MRI sensitivity, specificity, diagnostic odds ratio, and positive and negative likelihood ratio.

RESULTS

A total of 618 patients from 10 studies were included for calculation of diagnostic accuracy parameters. At the level of the primary tumor, the pooled sensitivity and specificity were, respectively, 0.96 (95% confidence interval [CI]: 0.89-1.00) and 0.81 (95% CI: 0.54-0.98) in the case of qualitative analysis, and, respectively, 0.79 (95% CI: 0.66-0.89) and 0.88 (95% CI: 0.77-0.96) for quantitative analysis. At the level of the neck, the pooled sensitivity and specificity were, respectively, 0.87 (95% CI: 0.75-0.95) and 0.84 (95% CI: 0.74-0.93) when images were analyzed qualitatively, and 0.79 (95% CI: 0.60-0.94) and 0.90 (95% CI: 0.82-0.97) when analyzed quantitatively.

CONCLUSION

DWI-MRI showed high diagnostic accuracy and should be considered if persistent/recurrent HNSCCs is suspected after primary CRT. No significant differences were found between qualitative and quantitative imaging assessment.

Diffusion-weighted MRI to detect early response to chemoradiation in cervical cancer: A systematic review and meta-analysis

OBJECTIVE

Diffusion-weighted magnetic resonance imaging (DWI) has shown promise in predicting response to therapy in several malignancies. This systematic review and meta-analysis aimed to evaluate DWI in the prediction of response to treatment in patients with cervical cancer.

METHODS

A systematic search was conducted on PubMed, Web of Science, Cochrane and Google Scholar databases Studies that evaluated DWI and apparent diffusion coefficient (ADC) for response evaluation before, during and after treatment with a correlation to conventional response criteria were included. The primary endpoint was the mean ADC values of cervical cancer at these timepoints. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) was used to assess the quality of the studies.

RESULTS

Nine studies, comprising 270 patients, were included. Pre-treatment ADC values showed no correlation with eventual response. However, in our meta-analysis, there was a significant correlation with early treatment ADC values obtained within the first 3 weeks of therapy and response, as well as a significant correlation with the percentage change in ADC (ΔADC) and response. In addition, the pooled mean ΔADC percentage was also significantly higher in responders than in non-responders (49.7% vs 19.7%, respectively, p = 0.016).

CONCLUSION

DWI shows potential as a biomarker of early treatment response in patients with cervical carcinoma. Use of the change in ADC particularly within the first 3 weeks of therapy seems to be predictive of response and may serve as a suitable marker in the determination of early response.

Predictors of Neoadjuvant Chemotherapy Response in Breast Cancer: A Review

Neoadjuvant chemotherapy (NAC) largely increases operative chances and improves prognosis of the local advanced breast cancer patients. However, no specific means have been invented to predict the therapy responses of patients receiving NAC. Therefore, we focus on the alterations of tumor tissue-related microenvironments such as stromal tumor-infiltrating lymphocytes status, cyclin-dependent kinase expression, non-coding RNA transcription or other small molecular changes, in order to detect potentially predicted biomarkers which reflect the therapeutic efficacy of NAC in different subtypes of breast cancer. Further, possible mechanisms are also discussed to discover feasible treatment targets. Thus, these findings will be helpful to promote the prognosis of breast cancer patients who received NAC and summarized in this review.

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.

Apparent diffusion coefficient histogram in breast cancer brain metastases may predict their biological subtype and progression

Our aims for this study were to investigate the relationship between diffusion weighted image (DWI) parameters of brain metastases (BMs) and biological markers of breast cancer, and moreover, to assess whether DWI parameters accurately predict patient outcomes. DWI data for 34 patients with BMs from breast cancer were retrospectively reviewed. Apparent diffusion coefficient (ADC) histogram parameters were calculated from all measurable BMs. Two region of interest (ROI) methods are used for the analysis: from the largest BM or from all measurable BMs per one patient. ADC histogram parameters were compared between positive and negative groups depending on ER/PR and HER2 statuses. Overall survival analysis after BM (OSBM) and BM-specific progression-free survival (BMPFS) was analyzed with ADC parameters. Regardless of ROI methods, 25th percentile of ADC histogram was significantly lower in the ER/PR-positive group than in the ER/PR-negative group (P < 0.05). Using ROIs from all measurable BMs, Peak location, 50th percentile, 75th percentile, and mean value of ADC histogram were also significantly lower in the ER/PR-positive group than in the ER/PR-negative group (P < 0.05). However, there was no significant difference between HER2-postive and negative group. On univariate analysis, using ROIs from all measurable BMs, lower 25th percentile, 50th percentile and mean of ADC were significant predictors for poor BMPFS. ADC histogram analysis may have a prognostic value over ER/PR status as well as BMPFS.

A prospective study on neoadjuvant chemoradiotherapy plus anti-EGFR monoclonal antibody followed by surgery for locally advanced cervical cancer

Background

To investigate the efficacy and safety of neoadjuvant chemoradiotherapy plus anti-epidermal growth factor receptor monoclonal antibody followed by surgery for locally advanced cervical cancer (LACC).

Patients and methods

Patients with histologically proven LACC were enrolled into this prospective study. All patients received intensity-modulated radiation therapy with conventional fractionation. Weekly cisplatin or nedaplatin was administered concurrently with intensity-modulated radiation therapy. Nimotuzumab, a humanized anti-epidermal growth factor receptor monoclonal antibody, was given at a dose of 200 mg per week for 6 cycles. Approximately 1 month after the completion of neoadjuvant treatment, the patients were assessed for clinical tumor response and operability based on MRI and gynecological examination. For those who were considered to be candidates for surgery, radical hysterectomy, and pelvic lymph node dissection were performed 5–6 weeks after the completion of neoadjuvant therapy.

Results

Twenty-eight patients were enrolled. Clinical complete response and partial response were found in 8 (28.5%) and 20 (71.5%) patients, respectively. Four patients were not eligible for surgery and 2 patients refused surgery although they were assessed as surgical candidates. They were not included in this analysis. Radical hysterectomy and pelvic lymph node dissection were performed for the remaining 22 patients. Among them, 8 (36.4%) had complete pathology response, 9 (40.9%) presented with persistent atypical cells or cervical intraepithelial neoplasia, and 5 (22.7%) presented with macroscopic and/or microscopic residual disease, according to the pathological evaluation. Median follow-up time was 22 months (range, 5–39 months). The 2-year locoregional control rate, progression-free survival rate, distant metastasis-free survival rate, and overall survival rate were 95.0%, 85.2%, 84.0%, and 90.0%, respectively. Acute toxicities were mild in general and easily manageable. Chronic toxicities were mainly limited to grade 1. No severe late toxicities were observed.

Conclusion

Concurrent chemoradiotherapy plus nimotuzumab followed by surgery is highly effective and safe in LACC. Further studies are warranted to confirm the findings.

Ultrasonic histogram assessment of early response to concurrent chemo-radiotherapy in patients with locally advanced cervical cancer: a feasibility study

PURPOSE

To monitor early response for locally advanced cervical cancers undergoing concurrent chemo-radiotherapy (CCRT) by ultrasonic histogram.

METHODS

B-mode ultrasound examinations were performed at 4 time points in thirty-four patients during CCRT. Six ultrasonic histogram parameters were used to assess the echogenicity, homogeneity and heterogeneity of tumors.

RESULTS

I_peak increased rapidly since the first week after therapy initiation, whereas W_low, W_high and A_high changed significantly at the second week. The average ultrasonic histogram progressively moved toward the right and converted into more symmetrical shape.

CONCLUSION

Ultrasonic histogram could be served as a potential marker to monitor early response during CCRT.

Diffusion-Weighted Imaging of Brain Metastasis from Lung Cancer: Correlation of MRI Parameters with the Histologic Type and Gene Mutation Status

BACKGROUND AND PURPOSE

Development of noninvasive imaging biomarkers indicating the histology and the gene mutation status of brain metastasis from lung cancer is important. We aimed to investigate diffusion-weighted imaging parameters as predictors of the histology and gene mutations of brain metastasis from lung cancer.

MATERIALS AND METHODS

DWI data for 74 patients with brain metastasis from lung cancer were retrospectively reviewed. The patients were first grouped according to the primary tumor histology (adenocarcinoma, small-cell lung cancer, squamous cell carcinoma), and those with adenocarcinoma were further divided into epidermal growth factor receptor (EFGR) mutation-positive and wild type groups. Sex; age; number, size, and location of brain metastasis; DWI visual scores; the minimum ADC; and the normalized ADC ratio were compared among groups using χ² and ANOVA. Multiple logistic regression analysis was performed to determine independent predictors of the EGFR mutation.

RESULTS

The minimum ADC was lower in the small-cell lung cancer group than in the other 2 groups, though the difference was not significant. Furthermore, minimum ADC and the normalized ADC ratio were significantly lower in the EGFR mutation-positive group than in the wild type group (P = .021 and .014, respectively). Multivariate analysis revealed that minimum ADC and the normalized ADC ratio were independently associated with the EGFR mutation status (P = .028 and .021, respectively).

CONCLUSIONS

Our results suggest that DWI parameters (minimum ADC and normalized ADC ratio) for the solid components of brain metastasis from lung cancer are not correlated with their histology, whereas they can predict the EGFR mutation status in brain metastasis from lung adenocarcinoma.

Transport of drugs from blood vessels to tumour tissue

The effectiveness of anticancer drugs in treating a solid tumour is dependent on delivery of the drug to virtually all cancer cells in the tumour. The distribution of drug in tumour tissue depends on the plasma pharmacokinetics, the structure and function of the tumour vasculature and the transport properties of the drug as it moves through microvessel walls and in the extravascular tissue. The aim of this Review is to provide a broad, balanced perspective on the current understanding of drug transport to tumour cells and on the progress in developing methods to enhance drug delivery. First, the fundamental processes of solute transport in blood and tissue by convection and diffusion are reviewed, including the dependence of penetration distance from vessels into tissue on solute binding or uptake in tissue. The effects of the abnormal characteristics of tumour vasculature and extravascular tissue on these transport properties are then discussed. Finally, methods for overcoming limitations in drug transport and thereby achieving improved therapeutic results are surveyed.

Heterogeneity analysis of diffusion-weighted MRI for prediction and assessment of microstructural changes early after one cycle of induction chemotherapy in nasopharyngeal cancer patients

PURPOSE

To evaluate whether the pretreatment apparent diffusion coefficient (ADC) heterogeneity parameters and their alterations, after one cycle of induction chemotherapy, can be used as reliable markers of treatment response to induction chemotherapy in patients with nasopharyngeal cancer.

MATERIALS AND METHODS

Ten patients were recruited and received induction chemotherapy (IC). Diffusion-weighted imaging was performed prior to, during, and after IC. The first-order ADC histogram parameters at the intra-treatment time-point were compared to the baseline time-point in the metastatic lymph nodes (LNs). Some ADC pretreatment parameters were combined with each other, employing discriminant analysis to achieve a feasible model to separate the complete response (CR) from the partial response (PR) groups.

RESULTS

For ten patients, significant rise in Mean and Txt₁Mean (p = 0.048 and 0.015, respectively) was observed in the metastatic nodes following one cycle of IC. Txt₅Energy significantly decreased (p = 0.002). Discriminant analysis on pretreatment parameters illustrated that Txt₅Energy_pre was the best parameter to use to correctly classify CR and PR patients. This was followed by Txt₉Percentile75_pre, Txt₁Mean_pre, and Txt₂Standard Deviation_pre.

CONCLUSIONS

Our results suggest that heterogeneity metrics extracted from ADC-maps in metastatic lymph nodes, before and after IC, can be used as supplementary IC response indicators.

2-D and 3-D Ultrasound for Tumor Volume Analysis: A Prospective Study

Ultrasound (US) allows real-time tumor assessment. We evaluated the volumetric limits of 2-D and 3-D US, compared with magnetic resonance imaging (MRI), with a prospective institutional review board-approved clinical evaluation of US-to-MRI volumetric correlation. US images of pre- and post-neoadjuvant breast cancers were obtained. Volume discrepancy was evaluated with the non-parametric Wilcoxon signed-rank test. Expected inter-observer variability <14% was evaluated as relative paired difference (RPD); clinical relevance was gauged with the volumetric standard error of the mean (SEM). For 42 patients, 133 of 170 US examinations were evaluable. For tumors ≤20 cm³, both highly correlated to MRI with RPD within inter-observer variability and Pearson's correlation up to 0.86 (0.80 before and 0.86 after neoadjuvant chemotherapy, respectively). Lesions 20-40 cm³ had US-to-MRI discrepancy within inter-observer variability for 2-D (RPD: 13%), but not 3-D (RPD: 27%) US (SEM: 1.47 cm³ for 2-D, SEM: 2.28 cm³ for 3-D), suggesting clinical utility. Tumors >40 cm³ correlated poorly. Tumor volumes ≤20 cm³ exhibited a good correlation to MRI. Studies of clinical applications are warranted.

Predictive value of pre-treatment apparent diffusion coefficient (ADC) in radio-chemiotherapy treated head and neck squamous cell carcinoma

OBJECTIVE

This study aimed at evaluating the role of "baseline" apparent diffusion coefficent (ADC), in patients affected by head and neck cancer treated with radio-chemotherapy, as a potential marker of response to therapy.

METHODS

Fifty-seven patients underwent pretreatment ADC maps. Minimum, maximum, and medium ADC were computed. Age, dose, treatment time, and ADC values were compared between the two groups (Group 1: local control; Group 2: relapse/persistence of disease) using the Student t test two-tailed unpaired. Two-tailed Fischer exact test was used to compare T stage, N stage, grading and type of treatment between two groups. We have analyzed the receiver operating characteristic (ROC) of statistically significant variables.

RESULTS

In patients with local control, values of pre-treatment medium and minimum ADC were lower than ADC values of patients with persistent or recurrent disease, with values, respectively, of 0.83 ± 0.02 × 10^-3 mm²/s and 0.59 ± 0.02 × 10^-3 mm²/s (vs 0.94 ± 0.05 × 10^-3 mm²/s and 0.70 ± 0.05 × 10^-3 mm²/s). ROC curve analysis displayed statistical significance as regarding the medium ADC value, showing a sensitivity of 50% and a specificity of 84.8%. ROC analysis of the values minimum ADC showed a sensitivity of 42.9% and specificity of 87.9%.

CONCLUSION

The value of the ADC pre-treatment of patients with local control of the disease is lower than that of patients with persistent disease or recurrence.

Integrative analysis of diffusion-weighted MRI and genomic data to inform treatment of glioblastoma

Gene expression profiling from glioblastoma (GBM) patients enables characterization of cancer into subtypes that can be predictive of response to therapy. An integrative analysis of imaging and gene expression data can potentially be used to obtain novel biomarkers that are closely associated with the genetic subtype and gene signatures and thus provide a noninvasive approach to stratify GBM patients. In this retrospective study, we analyzed the expression of 12,042 genes for 558 patients from The Cancer Genome Atlas (TCGA). Among these patients, 50 patients had magnetic resonance imaging (MRI) studies including diffusion weighted (DW) MRI in The Cancer Imaging Archive (TCIA). We identified the contrast enhancing region of the tumors using the pre- and post-contrast T1-weighted MRI images and computed the apparent diffusion coefficient (ADC) histograms from the DW-MRI images. Using the gene expression data, we classified patients into four molecular subtypes, determined the number and composition of genes modules using the gap statistic, and computed gene signature scores. We used logistic regression to find significant predictors of GBM subtypes. We compared the predictors for different subtypes using Mann-Whitney U tests. We assessed detection power using area under the receiver operating characteristic (ROC) analysis. We computed Spearman correlations to determine the associations between ADC and each of the gene signatures. We performed gene enrichment analysis using Ingenuity Pathway Analysis (IPA). We adjusted all p values using the Benjamini and Hochberg method. The mean ADC was a significant predictor for the neural subtype. Neural tumors had a significantly lower mean ADC compared to non-neural tumors ([Formula: see text]), with mean ADC of [Formula: see text] and [Formula: see text] for neural and non-neural tumors, respectively. Mean ADC showed an area under the ROC of 0.75 for detecting neural tumors. We found eight gene modules in the GBM cohort. The mean ADC was significantly correlated with the gene signature related with dendritic cell maturation ([Formula: see text], [Formula: see text]). Mean ADC could be used as a biomarker of a gene signature associated with dendritic cell maturation and to assist in identifying patients with neural GBMs, known to be resistant to aggressive standard of care.

Diffusion-Weighted Imaging for Predicting and Monitoring Primary Central Nervous System Lymphoma Treatment Response

BACKGROUND AND PURPOSE

Whether ADC value predicts the therapy response and outcomes of primary central system lymphoma remains controversial. This study assessed the minimum ADC correlated with treatment response in patients with primary central nervous system lymphoma undergoing methotrexate-based chemotherapy.

MATERIALS AND METHODS

Thirty-five patients with primary central nervous system lymphoma underwent conventional MR imaging and DWI before chemotherapy and after 1 and 5 cycles of chemotherapy. Treatment response was determined according to the International PCNSL Collaborative Group criteria and was classified as a complete response, partial response, or progressive disease. Pretreatment minimum ADC, minimum ADC after 1 cycle, minimum ADC after 5 cycles, and change in minimum ADC were compared among the different response groups. The Pearson correlation test was calculated between these ADC parameters and tumor response.

RESULTS

The pretreatment minimum ADC of the progressive disease group was lower than that of the complete response and partial response groups, but there was no significant difference among them. The minimum ADC after 1 cycle and minimum ADC after 5 cycles were statistically significantly higher than the pretreatment minimum ADC. A comparison among groups showed that minimum ADC after 1 cycle, minimum ADC after 5 cycles, minimum ADC change, and the percentage of minimum ADC change were all significantly different among the 3 groups. A significant positive correlation was observed between the percentage of minimum ADC after 1 cycle of chemotherapy and the size reduction percentage after 5 cycles of chemotherapy. The minimum ADC change and the percentage of minimum ADC change performed better in the differentiation of the final treatment response, specifically in complete response and partial response from progressive disease.

CONCLUSIONS

The minimum ADC after 1 cycle and minimum ADC changes were better correlated with the treatment response than the pretreatment minimum ADC. Minimum ADC after early therapy may potentially to be used to predict and monitor the response of primary central nervous system lymphoma to chemotherapy.

Role of quantitative magnetic resonance imaging parameters in the evaluation of treatment response in malignant tumors

OBJECTIVE

To elaborate the role of quantitative magnetic resonance imaging (MRI) parameters in the evaluation of treatment response in malignant tumors.

DATA SOURCES

Data cited in this review were obtained mainly from PubMed in English from 1999 to 2014, with keywords "dynamic contrast-enhanced (DCE)-MRI," "diffusion-weighted imaging (DWI)," "microcirculation," "apparent diffusion coefficient (ADC)," "treatment response" and "oncology."

STUDY SELECTION

Articles regarding principles of DCE-MRI, principles of DWI, clinical applications as well as opportunity and aspiration were identified, retrieved and reviewed.

RESULTS

A significant correlation between ADC values and treatment response was reported in most DWI studies. Most quantitative DCE-MRI studies showed a significant correlation between K trans values and treatment response. However, in different tumors and studies, both high and low pretreatment ADC or K trans values were found to be associated with response rate. Both DCE-MRI and DWI demonstrated changes in their parameters hours to days after treatment, showing a decrease in K trans or an increase in ADC associated with response in most cases.

CONCLUSIONS

Combinations of quantitative MRI play an important role in the evaluation of treatment response of malignant tumors and hold promise for use as a cancer treatment response biomarker. However, validation is hampered by the lack of reproducibility and standardization. MRI acquisition protocols and quantitative image analysis approaches should be properly addressed prior to further testing the clinical use of quantitative MRI parameters in the assessment of treatments.

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.

Multi-site clinical evaluation of DW-MRI as a treatment response metric for breast cancer patients undergoing neoadjuvant chemotherapy

PURPOSE

To evaluate diffusion weighted MRI (DW-MR) as a response metric for assessment of neoadjuvant chemotherapy (NAC) in patients with primary breast cancer using prospective multi-center trials which provided MR scans along with clinical outcome information.

MATERIALS AND METHODS

A total of 39 patients with locally advanced breast cancer accrued from three different prospective clinical trials underwent DW-MR examination prior to and at 3-7 days (Hull University), 8-11 days (University of Michigan) and 35 days (NeoCOMICE) post-treatment initiation. Thirteen patients, 12 of which participated in treatment response study, from UM underwent short interval (<1hr) MRI examinations, referred to as "test-retest" for examination of repeatability. To further evaluate stability in ADC measurements, a thermally controlled diffusion phantom was used to assess repeatability of diffusion measurements. MRI sequences included contrast-enhanced T1-weighted, when appropriate, and DW images acquired at b-values of 0 and 800 s/mm2. Histogram analysis and a voxel-based analytical technique, the Parametric Response Map (PRM), were used to derive diffusion response metrics for assessment of treatment response prediction.

RESULTS

Mean tumor apparent diffusion coefficient (ADC) values generated from patient test-retest examinations were found to be very reproducible (|ΔADC|<0.1x10-3mm2/s). This data was used to calculate the 95% CI from the linear fit of tumor voxel ADC pairs of co-registered examinations (±0.45x10-3mm2/s) for PRM analysis of treatment response. Receiver operating characteristic analysis identified the PRM metric to be predictive of outcome at the 8-11 (AUC = 0.964, p = 0.01) and 35 day (AUC = 0.770, p = 0.05) time points (p<.05) while whole-tumor ADC changes where significant at the later 35 day time interval (AUC = 0.825, p = 0.02).

CONCLUSION

This study demonstrates the feasibility of performing a prospective analysis of DW-MRI as a predictive biomarker of NAC in breast cancer patients. In addition, we provide experimental evidence supporting the use of sensitive analytical tools, such as PRM, for evaluating ADC measurements.

Early treatment response in non-small cell lung cancer patients using diffusion-weighted imaging and functional diffusion maps--a feasibility study

OBJECTIVE

The aim of this study was to prospectively evaluate the feasibility of monitoring treatment response to chemotherapy in patients with non-small cell lung carcinoma using functional diffusion maps (fDMs).

MATERIALS AND METHODS

This study was approved by the Cantonal Research Ethics Committee and informed written consent was obtained from all patients. Nine patients (mean age = 66 years; range = 53-76 years, 5 females, 4 males) with overall 13 lesions were included. Imaging was performed within two weeks before initiation of chemotherapy and at one, two, and six weeks after initiation of chemotherapy. Imaging included a respiratory-triggered diffusion-weighted sequence including three b-factors (100, 600, and 800 s/mm2). Treatment response was defined by change in tumor diameter on computed tomography (CT) after two cycles of chemotherapy. Changes in the apparent diffusion coefficient (ADC) on a per-lesion basis and the percentages of voxel with significantly increased or decreased ADCs on fDMs were analyzed using repeated measures analysis of variance (ANOVA). Changes in tumor size were used as covariate to examine the ability of ADCs and fDM parameters to predict treatment response.

RESULTS

Repeated measures ANOVA revealed that the percentage of voxels with increased ADCs on fDMs (p = 0.002) as well as the mean ADC increase (p = 0.011) were significantly higher in good responders with a large reduction in tumor size on CT.

CONCLUSION

Our results indicate that the percentage of voxels with significantly increased ADCs on fDMs seems to be a promising biomarker for early prediction of treatment response in patients with non-small cell lung carcinoma. Contrary to averaged values, this approach allows the spatial heterogeneity of treatment response to be resolved.

The preliminary study of 18F-FLT micro-PET/CT in predicting radiosensitivity of human nasopharyngeal carcinoma xenografts

OBJECTIVE

The purpose of the preliminary study was to investigate the value of (18)F-FLT micro-PET/CT in predicting radiosensitivity of human nasopharyngeal carcinoma (NPC) xenografts in nude mice models.

METHODS

Twelve BALB/c-nu nude mice were randomly divided into two groups. They were subcutaneously injected with either CNE1 or CNE2 cell suspension. Xenograft volumes were measured after tumor formation. When the tumors reached nearly 10 mm in diameter, they received 15-Gy irradiation. Before and 24 h after irradiation, mice were performed with (18)F-FLT micro-PET/CT. The region of interest (ROI) was manually drawn, and the percent of injected dose per gram of the tumor and muscle in the ROIs was recorded. Tumor-to-muscle ratio (T/M) was calculated and compared with volume changes. Additionally, we also used ten untreated mice as control group.

RESULTS

After irradiation, CNE2 tumors decreased significantly while CNE1 tumors continuously grew and became stable after 1 week. However, in control group, CNE1 and CNE2 tumors continuously enlarged in the observed time. Therefore, we could regard CNE2 group as irradiation responder while CNE1 group as non-responder. In irradiation group, the value of T/M before irradiation (T/M 0) of CNE1 mice was statistically lower than CNE2 mice (1.62 ± 0.38 versus 5.57 ± 1.30; P = 0.004). Besides, T/M decreased significantly in CNE2 group after irradiation (5.57 ± 1.30 versus 3.59 ± 1.06; P < 0.001). By means of a receiver operating characteristic curve, the optimal cut value of T/M 0 and ∆T/M to predict responder was 2.38 and -0.15, respectively (both sensitivity and specificity = 100.0 %).

CONCLUSIONS

(18)F-FLT PET/CT has the potential to predict radiosensitivity in NPC xenografts nude mice models.

Image registration for quantitative parametric response mapping of cancer treatment response

Imaging biomarkers capable of early quantification of tumor response to therapy would provide an opportunity to individualize patient care. Image registration of longitudinal scans provides a method of detecting treatment associated changes within heterogeneous tumors by monitoring alterations in the quantitative value of individual voxels over time, which is unattainable by traditional volumetric-based histogram methods. The concepts involved in the use of image registration for tracking and quantifying breast cancer treatment response using parametric response mapping (PRM), a voxel-based analysis of diffusion-weighted magnetic resonance imaging (DW-MRI) scans, are presented. Application of PRM to breast tumor response detection is described, wherein robust registration solutions for tracking small changes in water diffusivity in breast tumors during therapy are required. Methodologies that employ simulations are presented for measuring expected statistical accuracy of PRM for response assessment. Test-retest clinical scans are used to yield estimates of system noise to indicate significant changes in voxel-based changes in water diffusivity. Overall, registration-based PRM image analysis provides significant opportunities for voxel-based image analysis to provide the required accuracy for early assessment of response to treatment in breast cancer patients receiving neoadjuvant chemotherapy.

The Role of (18) F-FDG PET/CT in Assessing Therapy Response in Cervix Cancer after Concurrent Chemoradiation Therapy

PURPOSE

To determine whether persisting cervical fluorodeoxyglucose (FDG) uptake after concurrent chemoradiotherapy (CCRT) for cervical cancer can reflect residual malignancy.

METHODS

F-FDG PET/CT was performed before and after CCRT in 136 patients with cervical cancer. The maximum and mean standardized uptake values (SUVmax and SUVmean) were recorded from PET/CT scans performed pre- and post-treatment. SUVs were correlated with treatment response after CCRT. Final treatment response was determined by MRI and further follow-up PET/CT. One hundred four of 136 patients underwent pelvic MRI, and 32 of 136 patients underwent further follow-up PET/CT. Patients were classified into two categories: patients with residual tumor or patients without residual tumor (complete responder). Pre- and post-treatment serum squamous cell carcinoma antigen (SCC) levels were also recorded for comparison. The optimal cutoff value of SUVmax for predicting residual cervical tumor was determined using receiver-operating characteristic (ROC) analysis.

RESULTS

Of 136 patients, 124 showed complete response on further follow-up studies and 12 were confirmed to have residual tumor. The post-treatment SUVmax and pre-/post-treatment SUVmean of complete responders were significantly lower than those of patients with residual tumor: 2.5 ± 0.8 and 7.2 ± 4.2/1.9 ± 0.7 for complete responders and 5.7 ± 2.6 and 12.8 ± 6.9/3.7 ± 0.7 for patients with residual tumor (p < 0.05). The pre-treatment SUVmax and pre-/post-treatment serum SCC levels of the complete responders tended to be lower than those of patients with residual tumor, but this did not have statistical significance. Using ROC analysis, an optimal cutoff SUVmax of 4.0 on the post-treatment PET/CT yielded a sensitivity, specificity, positive predictive value, and negative predictive value of 92 %, 94 %, 61 %, and 99 %, respectively (p < 0.001).

CONCLUSIONS

Persistent cervical FDG uptake in(18)F-FDG PET/CT after CCRT for cervical cancer may be caused by residual tumor or post-therapy inflammation. A higher cutoff SUVmax than conventional criteria for cervical cancer in post-CCRT PET/CT might help to detect residual tumor.

Comparison of different MRI sequences in lesion detection and early response evaluation of diffuse large B-cell lymphoma--a whole-body MRI and diffusion-weighted imaging study

To compare different MRI sequences for the detection of lesions and the evaluation of response to chemotherapy in patients with diffuse large B-cell lymphoma (DLBCL), 18 patients with histology-confirmed DLBCL underwent 3-T MRI scanning prior to and 1 week after chemotherapy. The MRI sequences included T1-weighted pre- and post-contrast, T2 -weighted with and without fat suppression, and a single-shot echo-planar diffusion-weighted imaging (DWI) with two b values (0 and 800 s/mm(2)). Conventional MRI sequence comparisons were performed using the contrast ratio between tumor and normal vertebral body instead of signal intensity. The apparent diffusion coefficient (ADC) of the tumor was measured directly on the parametric ADC map. The tumor volume was used as a reference for the evaluation of chemotherapy response. The mean tumor volume was 374 mL at baseline, and decreased by 65% 1 week after chemotherapy (p < 0.01). The T2 -weighted image with fat suppression showed a significantly higher contrast ratio compared with images from all other conventional MRI sequences, both before and after treatment (p < 0.01, respectively). The contrast ratio of the T2 -weighted image with fat suppression decreased significantly (p < 0.01), and that of the T1 -weighted pre-contrast image increased significantly (p < 0.01), after treatment. However, there was no correlation between the change in contrast ratio and tumor volume. The mean ADC value was 0.68 × 10(-3) mm(2)/s at baseline; it increased by 89% after chemotherapy (p < 0.001), and the change in ADC value correlated with the change in tumor volume (r = 0.66, p < 0.01). The baseline ADC value also correlated inversely with the percentage change in ADC after treatment (r = -0.62, p < 0.01). In conclusion, this study indicates that T2-weighted imaging with fat suppression is the best conventional sequence for the detection of lesions and evaluation of the efficacy of chemotherapy in DLBCL. DWI with ADC mapping is an imaging modality with both diagnostic and prognostic value that could complement conventional MRI.

Clinical application of magnetic resonance imaging in management of breast cancer patients receiving neoadjuvant chemotherapy

Neoadjuvant chemotherapy (NAC), also termed primary, induction, or preoperative chemotherapy, is traditionally used to downstage inoperable breast cancer. In recent years it has been increasingly used for patients who have operable cancers in order to facilitate breast-conserving surgery, achieve better cosmetic outcome, and improve prognosis by reaching pathologic complete response (pCR). Many studies have demonstrated that magnetic resonance imaging (MRI) can assess residual tumor size after NAC, and that provides critical information for planning of the optimal surgery. NAC also allows for timely adjustment of administered drugs based on response, so ineffective regimens could be terminated early to spare patients from unnecessary toxicity while allowing other effective regimens to work sooner. This review article summarizes the clinical application of MRI during NAC. The use of different MR imaging methods, including dynamic contrast-enhanced MRI, proton MR spectroscopy, and diffusion-weighted MRI, to monitor and evaluate the NAC response, as well as how changes of parameters measured at an early time after initiation of a drug regimen can predict final treatment outcome, are reviewed. MRI has been proven a valuable tool and will continue to provide important information facilitating individualized image-guided treatment and personalized management for breast cancer patients undergoing NAC.

Apparent diffusion coefficient modifications in assessing gastro-oesophageal cancer response to neoadjuvant treatment: comparison with tumour regression grade at histology

OBJECTIVES

To assess changes in apparent diffusion coefficient (ΔADC) and volume (ΔV) after neoadjuvant treatment (NT), and tumour regression grade (TRG) in gastro-oesophageal cancers (GEC), and to discriminate responders from non-responders.

METHODS

Thirty-two patients with biopsy-proven locally-advanced GEC underwent diffusion weighted magnetic resonance imaging (DWI) pre- and post-NT. Lesion ADC, volume, ΔADC and ΔV were calculated. TRG 1-2-3 patients were classified as R; TRG 4-5 as non-responders. ΔADC-TRG and ΔV-TRG correlations, pre-NT and post-NT ADC, ΔADC and ΔV cut-off values for responders and non-responders were calculated. Two readers measured mean tumour ADCs and interobserver variability was calculated. (Spearman's and intraclass correlation coefficient [ICC]).

RESULTS

The interobserver reproducibility was very good both for pre-NT (Spearman's rho = 0.8160; ICC = 0.8993) and post-NT (Spearman's rho = 0.8357; ICC = 0.8663). Responders showed lower pre-NT ADC (1.32 versus 1.63 × 10(-3) mm(2)/s; P = 0.002) and higher post-NT ADC (2.22 versus 1.51 × 10(-3) mm(2)/s; P = 0.001) than non-responders and ADC increased in responders (ΔADC, 85.45 versus -8.21 %; P = 0.00005). ΔADC inversely correlated with TRG (r = -0.71, P = 0.000004); no difference in ΔV between responders and non-responders (-50.92 % versus -14.12 %; P = 0.068) and no correlation ΔV-TRG (r = 0.02 P = 0.883) were observed.

CONCLUSIONS

The ADC can be used to assess gastro-oesophageal tumour response to neoadjuvant treatment as a reliable expression of tumour regression.

KEY POINTS

• DWI is now being used to assess many cancers. • Change in ADC measurements offer new information about oesophageal tumours. • ADC changes are more reliable than dimensional criteria in assessing neoadjuvant treatment. • Such ADC assessment could optimise management of locally advanced gastro-oesophageal cancers.

Serial diffusion MRI to monitor and model treatment response of the targeted nanotherapy CRLX101

PURPOSE

Targeted nanotherapies are being developed to improve tumor drug delivery and enhance therapeutic response. Techniques that can predict response will facilitate clinical translation and may help define optimal treatment strategies. We evaluated the efficacy of diffusion-weighted magnetic resonance imaging to monitor early response to CRLX101 (a cyclodextrin-based polymer particle containing the DNA topoisomerase I inhibitor camptothecin) nanotherapy (formerly IT-101), and explored its potential as a therapeutic response predictor using a mechanistic model of tumor cell proliferation.

EXPERIMENTAL DESIGN

Diffusion MRI was serially conducted following CRLX101 administration in a mouse lymphoma model. Apparent diffusion coefficients (ADCs) extracted from the data were used as treatment response biomarkers. Animals treated with irinotecan (CPT-11) and saline were imaged for comparison. ADC data were also input into a mathematical model of tumor growth. Histological analysis using cleaved-caspase 3, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, Ki-67, and hematoxylin and eosin (H&E) were conducted on tumor samples for correlation with imaging results.

RESULTS

CRLX101-treated tumors at day 2, 4, and 7 posttreatment exhibited changes in mean ADC = 16 ± 9%, 24 ± 10%, 49 ± 17%, and size (TV) = -5 ± 3%, -30 ± 4%, and -45 ± 13%, respectively. Both parameters were statistically greater than controls [p(ADC) ≤ 0.02, and p(TV) ≤ 0.01 at day 4 and 7], and noticeably greater than CPT-11-treated tumors (ADC = 5 ± 5%, 14 ± 7%, and 18 ± 6%; TV = -15 ± 5%, -22 ± 13%, and -26 ± 8%). Model-derived parameters for cell proliferation obtained using ADC data distinguished CRLX101-treated tumors from controls (P = 0.02).

CONCLUSIONS

Temporal changes in ADC specified early CRLX101 treatment response and could be used to model image-derived cell proliferation rates following treatment. Comparisons of targeted and nontargeted treatments highlight the utility of noninvasive imaging and modeling to evaluate, monitor, and predict responses to targeted nanotherapeutics.

Diffusion-weighted imaging reflects pathological therapeutic response and relapse in breast cancer

BACKGROUND

Conventional imaging does not always accurately depict the pathological response to neoadjuvant chemotherapy (NAC). Diffusion-weighted imaging (DWI) may provide additional insight into the chemotherapeutic effect. This study assessed whether the apparent diffusion coefficient (ADC) correlated with pathological outcome and prognosis in breast cancer patients receiving NAC.

METHODS

Fifty-six patients with locally advanced breast cancer received surgery after NAC. Dynamic contrast-enhanced (DCE) and DWI were performed before and after NAC. The pathological response was classified into five categories from no response to complete response according to amount of residual cancer. The correlation between ADC and postoperative pathologic and prognostic outcome was assessed.

RESULTS

The distribution of the pathological response classification was as follows: no response, 3 cases; mild response, 22 cases; moderate response, 12 cases; marked response, 11 cases; complete response, 8 cases. ADC after NAC correlated with pathological response, but ADC before NAC did not. The change in ADC after chemotherapy had better correlation coefficient (r = 0.67) than change in size (r = 0.58) and ADC after NAC (r = 0.64). Although the group with larger change of tumor size showed only marginal significance compared with the smaller change group (p = 0.089), the group with higher change of ADC showed significantly better prognosis than the lower one (p = 0.038).

CONCLUSIONS

Change in ADC after chemotherapy better correlated with pathological outcome and prognosis than change in tumor size. DWI has potential in evaluating the pathological outcome of NAC in breast cancer patients.

Prediction of pathologic response to neoadjuvant chemotherapy in patients with breast cancer using diffusion-weighted imaging and MRS

The aim of this study was to determine whether tumor size, MRS parameters and apparent diffusion coefficient (ADC) measurements could be applied to predict pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC). Ninety patients with breast cancer (median size, 4.5 cm; range, 1.6-9.5 cm) were evaluated with single-voxel ¹H MRS and dynamic contrast-enhanced MRI. Diffusion-weighted imaging was performed in 41 of these patients using a 1.5-T scanner before and after completion of NAC. Pre- and post-treatment measurements and changes in tumor size, MRS parameters [absolute and normalized total choline-containing compound (tCho) integral and tCho signal-to-noise ratio (SNR)] and ADCs in pCR versus non-pCR were compared using the nonparametric Mann-Whitney test. Receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic performance of each parameter. After NAC, 30 patients (33%) showed pCR and 60 (67%) showed non-pCR. At pretreatment, ADC was the only significant parameter in differentiating between pCR and non-pCR [(0.83 ± 0.05) × 10⁻³ versus (0.97 ± 0.14) × 10⁻³ mm²/s] (p = 0.014). Post-treatment measurements after completion of NAC and changes in tumor size (both p < 0.001), MRS parameters (p = 0.027 and p = 0.020 for absolute tCho integral, p = 0.036 and p = 0.023 for normalized tCho integral, and p = 0.032 and p = 0.061 for tCho SNR) and ADC (p = 0.003 and p < 0.001) were significantly different between the pCR and non-pCR groups, except for changes in tCho SNR. In ROC analysis, the areas under the ROC curve (AUCs) of 0.63-0.73 were obtained for tumor size and MRS parameters. AUCs for pre- and post-treatment ADC and changes in ADC were 0.75, 0.80 and 0.96, respectively. The optimal cut-off of the percentage change in ADC for predicting pCR was 40.7%, yielding 100% sensitivity and 91% specificity. Patients with pCR showed significantly lower pretreatment ADCs than those with non-pCR. The change in ADC after NAC was the most accurate predictor of pCR.

Evaluation of therapeutic response to concurrent chemoradiotherapy in patients with cervical cancer using diffusion-weighted MR imaging

PURPOSE

To investigate the changes in apparent diffusion coefficients (ADCs) in cervical cancer patients receiving concurrent chemoradiotherapy (CCRT), and to assess the relationship between tumor ADCs or changes in tumor ADCs and final tumor responses to therapy.

MATERIALS AND METHODS

Twenty-four patients with cervical cancer who received CCRT were examined with 3 Tesla (T) MRI including diffusion-weighted imaging (DWI). All patients had three serial MR examinations: before therapy (pre-Tx); at 4 weeks of therapy (mid-Tx); and 1 month after completion of therapy (post-Tx). At each examination, ADC was measured in tumors and normal gluteus muscles. Final tumor response as determined by change in tumor size or volume using MRI was correlated with tumor ADCs at each therapeutic time or changes in tumor ADCs at mid-Tx.

RESULTS

From pre-Tx to post-Tx, mean tumor ADCs were 0.88, 1.30, and 1.47 × 10(-3) mm(2)/s in sequence (P < 0.001), while those of normal gluteus muscles were 1.24, 1.29, and 1.21 × 10(-3) mm(2)/s in sequence (P > 0.05). At mid-Tx, tumor ADCs and changes in tumor ADCs had a significant correlation with final tumor size responses (P = 0.029 and 0.025, respectively). However, the tumor ADC values at pre-Tx were not associated with the final tumor size response (P = 0.47). The final tumor volume response was not associated with tumor ADC at pre-Tx or mid-Tx (P > 0.05) or changes in tumor ADCs at mid-Tx (P > 0.05).

CONCLUSION

DWI may have potentials in evaluating the therapeutic response to CCRT in patients with cervical cancer.

Head and neck high-field imaging: oncology applications

Head and neck imaging has benefited from 1.5 T magnetic resonance (MR) imaging, providing faster sequences, better soft tissue evaluation, and 3-axis imaging, with less radiation and iodine-based contrast injection. The US Food and Drug Administration has approved human MR imaging at high-field strength up to 4 T in clinical practice. 3 T MR imaging has become widely available, with the hope of significant advance in the evaluation of the head and neck region. This article reviews the benefits, disadvantages, and challenges of high-field imaging of the head and neck region, focusing on the imaging of head and neck cancer.

Immunochemotherapy with intensive consolidation for primary CNS lymphoma: a pilot study and prognostic assessment by diffusion-weighted MRI

PURPOSE

We evaluated a novel therapy for primary central nervous system lymphoma (PCNSL) with induction immunochemotherapy with high-dose methotrexate, temozolomide, and rituximab (MT-R) followed by intensive consolidation with infusional etoposide and high-dose cytarabine (EA). In addition, we evaluated the prognostic value of the minimum apparent diffusion coefficient (ADC(min)) derived from diffusion-weighted MRI (DW-MRI) in patients treated with this regimen.

EXPERIMENTAL DESIGN

Thirty-one patients (median age, 61 years; median Karnofsky performance score, 60) received induction with methotrexate every 14 days for 8 planned cycles. Rituximab was administered the first 6 cycles and temozolomide administered on odd-numbered cycles. Patients with responsive or stable central nervous system (CNS) disease received EA consolidation. Pretreatment DW-MRI was used to calculate the ADC(min) of contrast-enhancing lesions.

RESULTS

The complete response rate for MT-R induction was 52%. At a median follow-up of 79 months, the 2-year progression-free and overall survival were 45% and 58%, respectively. For patients receiving EA consolidation, the 2-year progression-free and overall survival were 78% and 93%, respectively. EA consolidation was also effective in an additional 3 patients who presented with synchronous CNS and systemic lymphoma. Tumor ADC(min) less than 384 × 10(-6) mm(2)/s was significantly associated with shorter progression-free and overall survival.

CONCLUSIONS

MT-R induction was effective and well tolerated. MT-R followed by EA consolidation yielded progression-free and overall survival outcomes comparable to regimens with chemotherapy followed by whole-brain radiotherapy consolidation but without evidence of neurotoxicity. Tumor ADC(min) derived from DW-MRI provided better prognostic information for PCNSL patients treated with the MTR-EA regimen than established clinical risk scores.

A finite difference method with periodic boundary conditions for simulations of diffusion-weighted magnetic resonance experiments in tissue

A new finite difference (FD) method for calculating the time evolution of complex transverse magnetization in diffusion-weighted magnetic resonance imaging and spectroscopy experiments is described that incorporates periodic boundary conditions. The new FD method relaxes restrictions on the allowable time step size employed in modeling which can significantly reduce computation time for simulations of large physical extent and allow for more complex, physiologically relevant, geometries to be simulated.

Motion correction in diffusion-weighted MRI of the breast at 3T

PURPOSE

To provide a quantitative assessment of motion and distortion correction of diffusion-weighted images (DWIs) of the breast and to evaluate the effects of registration on the mean apparent diffusion coefficient (mADC).

MATERIALS AND METHODS

Eight datasets from four patients with breast cancer and eight datasets from six healthy controls were acquired on a 3T scanner. A 3D affine registration was used to align each set of images and principal component analysis was used to assess the results. Variance in tumor ADC measurements, tumor mADC values, and voxel-wise tumor mADC values were compared before and after registration for each patient.

RESULTS

Image registration significantly (P = 0.008) improved image alignment for both groups and significantly (P < 0.001) reduced the variance across individual tumor ADC measurements. While misalignment led to potential under- and overestimation of mADC values for individual voxels, average tumor mADC values did not significantly change (P > 0.09) after registration.

CONCLUSION

3D affine registration improved the alignment of DWIs of the breast and reduced the variance between ADC measurements. Although the reduced variance did not significantly change tumor region-of-interest measures of mADC, it may have a significant impact on voxel-based analyses.

Applications of molecular imaging

Today molecular imaging technologies play a central role in clinical oncology. The use of imaging techniques in early cancer detection, treatment response, and new therapy development is steadily growing and has already significantly impacted on clinical management of cancer. In this chapter, we overview three different molecular imaging technologies used for the understanding of disease biomarkers, drug development, or monitoring therapeutic outcome. They are (1) optical imaging (bioluminescence and fluorescence imaging), (2) magnetic resonance imaging (MRI), and (3) nuclear imaging (e.g., single-photon emission computed tomography (SPECT) and positron emission tomography (PET)). We review the use of molecular reporters of biological processes (e.g., apoptosis and protein kinase activity) for high-throughput drug screening and new cancer therapies, diffusion MRI as a biomarker for early treatment response and PET and SPECT radioligands in oncology.

The assessment of breast cancer response to neoadjuvant chemotherapy: comparison of magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography

BACKGROUND

Neoadjuvant chemotherapy for locally advanced breast cancer is a widely accepted treatment. For assessment of the tumor response after chemotherapy, both magnetic resonance imaging (MRI) and (18)F-fluorodeoxyglucose positron emission tomography (PET) are promising methods.

PURPOSE

To retrospectively compare MRI and PET in the assessment of tumor response to neoadjuvant chemotherapy for primary breast cancer with the pathologic response as the reference standard.

MATERIAL AND METHODS

Between August 2006 and May 2008, 32 women with breast cancer underwent concurrent MRI and PET before and after neoadjuvant chemotherapy. For response assessment, we calculated the changes in the maximum diameters of the tumor (ΔD(max)) on MRI, and the changes in the standard uptake values (ΔSUV) on PET. The correlation between the ΔD(max) and ΔSUV was analyzed using Pearson's correlation coefficient. The correspondence rates between each imaging modality and pathologic assessment were calculated. For prediction of the pathologic complete response (pCR), the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were analyzed using the McNemar test.

RESULTS

The pathologic assessment of tumor response to neoadjuvant chemotherapy identified eight complete responses (25.0%), 10 partial responses (31.2%), and 14 non-responses (43.8%). The change in size on MRI was moderately correlated with the change in SUV on PET (r=0.574, p=0.001). The correspondence rate of response assessment was 75.0% (24/32) between MRI and pathologic response and 53.1% (17/32) between PET and pathologic response. For the pCR, specificity (95.8% vs. 62.5%) and PPV (83.3% vs. 47.1%) were statistically higher on MRI than PET (p < 0.05), while sensitivity (100.0% vs. 62.5%) and NPV (100.0% vs. 88.5%) on PET tended to be higher than MRI.

CONCLUSION

Before and after neoadjuvant chemotherapy for breast cancer, the ΔD(max) of MRI correlated moderately with the ΔSUV on PET. For prediction of the pCR, MRI proved to be a more specific modality than PET.

Predicting and monitoring cancer treatment response with diffusion-weighted MRI

An imaging biomarker that would provide for an early quantitative metric of clinical treatment response in cancer patients would provide for a paradigm shift in cancer care. Currently, nonimage based clinical outcome metrics include morphology, clinical, and laboratory parameters, however, these are obtained relatively late following treatment. Diffusion-weighted MRI (DW-MRI) holds promise for use as a cancer treatment response biomarker as it is sensitive to macromolecular and microstructural changes which can occur at the cellular level earlier than anatomical changes during therapy. Studies have shown that successful treatment of many tumor types can be detected using DW-MRI as an early increase in the apparent diffusion coefficient (ADC) values. Additionally, low pretreatment ADC values of various tumors are often predictive of better outcome. These capabilities, once validated, could provide for an important opportunity to individualize therapy thereby minimizing unnecessary systemic toxicity associated with ineffective therapies with the additional advantage of improving overall patient health care and associated costs. In this report, we provide a brief technical overview of DW-MRI acquisition protocols, quantitative image analysis approaches and review studies which have implemented DW-MRI for the purpose of early prediction of cancer treatment response.

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.

Assessment of multiexponential diffusion features as MRI cancer therapy response metrics

The aim of this study was to empirically test the effect of chemotherapy-induced tissue changes in a glioma model as measured by several diffusion indices calculated from nonmonoexponential formalisms over a wide range of b-values. We also compared these results to the conventional two-point apparent diffusion coefficient calculation using nominal b-values. Diffusion-weighted imaging was performed over an extended range of b-values (120-4000 sec/mm(2) ) on intracerebral rat 9L gliomas before and after a single dose of 1,3-bis(2-chloroethyl)-1-nitrosourea. Diffusion indices from three formalisms of diffusion-weighted signal decay [(a) two-point analytical calculation using either low or high b-values, (b) a stretched exponential formalism, and (c) a biexponential fit] were tested for responsiveness to therapy-induced differences between control and treated groups. Diffusion indices sensitive to "fast diffusion" produced the largest response to treatment, which resulted in significant differences between groups. These trends were not observed for "slow diffusion" indices. Although the highest rate of response was observed from the biexponential formalism, this was not found to be significantly different from the conventional monoexponential apparent diffusion coefficient method. In conclusion, parameters from the more complicated nonmonoexponential formalisms did not provide additional sensitivity to treatment response in this glioma model beyond that observed from the two-point conventional monoexponential apparent diffusion coefficient method.

Molecular and Functional Imaging of Breast Cancer

Background

Significant efforts have been directed toward developing and enhancing imaging methods for the early detection, diagnosis, and characterization of small breast tumors. Molecular and functional imaging sets the stage for enhancement of current methodology.

Methods

Current imaging modalities are described based on the molecular characteristics of normal and malignant tissue. New molecular imaging methods that have the potential for clinical use are also discussed.

Results:

Dynamic contrast-enhanced magnetic resonance imaging is more sensitive than mammography in BRCA1 carriers. It is used in screening and in the early evaluation of neoadjuvant therapy. Positron emission mammography is 91% sensitive and 93% specific in detecting primary breast cancers. Sentinel node scintigraphy is a key component of axillary lymph node evaluation. Other imaging modalities being studied include Tc99m sestamibi, radiolabeled thymidine or uridine, estrogen receptor imaging, magnetic resonance spectroscopy, and diffusion magnetic resonance imaging.

Conclusions

Molecular and functional imaging of the breast will likely alter clinical practice in diagnosing and staging primary breast cancer and assessing response to therapy since it will provide earlier information regarding the underlying biology of individual breast cancers, tumor stage, potential treatment strategies, and biomarkers for early evaluation of treatment effects.