Predicting tumor responses and patient survival in chemoradiotherapy-treated patients with non-small-cell lung cancer using dynamic contrast-enhanced integrated magnetic resonance-positron-emission tomography

The prognostic value of positron emission tomography/magnetic resonance imaging in predicting survival in patients with adenocarcinoma of the esophagogastric junction

INTRODUCTION

In recent years, the utility of positron emission tomography/magnetic resonance imaging (PET/MRI) has become increasingly significant in diagnostic settings. This study provides a five-year follow-up on a previous pilot study that demonstrated the feasibility of PET/MRI in predicting the resectability of adenocarcinoma of the esophagogastric junction (AEG). We aimed to evaluate whether this imaging modality could further serve as a prognostic tool for survival in AEG patients.

METHODS

A total of 22 patients were included in the initial pilot study, with 17 of them undergoing surgery. All patients underwent three series of neo-adjuvant chemotherapy (NT). This follow-up study retrospectively analyzed the correlation between the apparent diffusion coefficient (ADC) and standard uptake value (SUV) measurements of the primary tumor from the original study with overall survival and recurrence. ADC and SUV values were measured prior to initiation of NT, and again 17-21 days into the first cycle of NT-administration, and the differences between the scans were calculated as ∆SUVmax, ∆ADCb0, and ∆ADCb50. Early treatment response was assessed using the Response Evaluation Criteria In Solid Tumors (RECIST). Binary logistic regression was employed to evaluate the predictive values of ADC and SUV parameters, and receiver operating characteristic (ROC) curves were generated to determine sensitivity, specificity, and area under the curve (AUC).

RESULTS

As of January 7, 2022, 8 of the 22 patients were still alive. The AUC was calculated to assess the association of imaging parameters with long-term survival: ∆SUVmax: AUC = 0.74, sensitivity, 87.5%, specificity 62.5% (p = 0.037). ∆ADCb0: AUC = 0.62, sensitivity 85.7%, specificity 57.1% (p = 0.400). ∆ADCb50: AUC = 0.78, sensitivity 78.6%, specificity 85.7% (p = 0.011). Combining all three parameters yielded an AUC of 0.81, with a sensitivity of 78.6% and a specificity of 85.7% (p = 0.002). The results for individual measurements were: SUVmax(pre-NT): AUC = 0.56, sensitivity 78.6%, specificity 50% (p = 0.646). SUVmax(post-NT): AUC = 0.81, sensitivity 85.7%, specificity 87.5% (p = 0.002). ADCb0(pre-NT): AUC = 0.55, sensitivity 71.4%, specificity 62.5% (p = 0.682). ADCb0(post-NT): AUC = 0.63, sensitivity 78.6%, specificity 57.1% (p = 0.339). ADCb50(pre-NT): AUC = 0.51, sensitivity 85.7%, specificity 37.5% (p = 0.952). ADCb50(post-NT): AUC = 0.63, sensitivity 42.9%, specificity 100% (p = 0.279). No significant correlation was found between RECIST group and survival status (p = 0.15).

CONCLUSION

Our results indicate that PET/MRI is feasible for predicting long-term survival in AEG patients. The highest AUCs were achieved when combining SUV and ADC parameters, and when using post-NT SUVmax alone.

Combination of ataxia telangiectasia and Rad3-related inhibition with ablative radiotherapy remodels the tumor microenvironment and enhances immunotherapy response in lung cancer

We investigated the combined effects of ataxia telangiectasia and Rad3-related (ATR) inhibition, ablative radiotherapy, and immune checkpoint inhibitor (ICI) therapy against lung cancer. ATR inhibitor was administered combined with ablative radiotherapy to assess its radiosensitizing effect on lung cancer cells. Treatment response and survival were evaluated in vivo using A549 xenograft flank tumor and synchronous LLC lung and flank tumor mouse models. Mice received ablative radiotherapy (12 Gy/d for 2 d), ATR inhibitor, and ICI. The tumor microenvironment was assessed in irradiated flank and non-irradiated lung tumors. Programmed death-ligand 1 expression was upregulated after irradiation. ATR inhibition attenuated this upregulation. ATR inhibitor pretreatment decreased cell survival after irradiation by inhibiting DNA double-strand break repair, inducing mitotic cell death, and altering cell cycle progression. ATR inhibition enhanced radiation-induced damage-associated molecular patterns determined by high mobility group box 1 quantification and activated the cyclic GMP-AMP synthase-stimulator of interferon genes pathway. Combined ATR inhibition and ablative radiotherapy inhibited tumor growth and improved survival in mice. Adding ICI therapy further enhanced local antitumor effects, reducing the metastatic lung tumor burden and remodeling the tumor microenvironment through immunogenic cell death induction and enhanced immune cell infiltration. Triple therapy increased immune cell infiltration in distant non-irradiated lung tumors and stimulated the generation of protective T-cell immunity in splenocytes. Safety analysis showed minimal toxicity. ATR inhibition enhanced the efficacy of ablative radiotherapy and immunotherapy in lung cancer. These findings underscore the importance of combination therapies for enhancing systemic antitumor immune responses and outcomes.

Predictive value of metabolic parameters and apparent diffusion coefficient derived from 18F-FDG PET/MR in patients with non-small cell lung cancer

BACKGROUND

Multiple models intravoxel incoherent motion (IVIM) based 18F-fluorodeoxyglucose positron emission tomography-magnetic resonance(18F-FDG PET/MR) could reflect the microscopic information of the tumor from multiple perspectives. However, its value in the prognostic assessment of non-small cell lung cancer (NSCLC) still needs to be further explored.

OBJECTIVE

To compare the value of 18F-FDG PET/MR metabolic parameters and diffusion parameters in the prognostic assessment of patients with NSCLC.

METERIAL AND METHODS

Chest PET and IVIM scans were performed on 61 NSCLC patients using PET/MR. The maximum standard uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), diffusion coefficient (D), perfusion fraction (f), pseudo diffusion coefficient (D*) and apparent diffusion coefficient (ADC) were calculated. The impact of SUVmax, MTV, TLG, D, f, D*and ADC on survival was measured in terms of the hazard ratio (HR) effect size. Overall survival time (OS) and progression-free survival time (PFS) were evaluated with the Kaplan-Meier and Cox proportional hazard models. Log-rank test was used to analyze the differences in parameters between groups.

RESULTS

61 NSCLC patients had an overall median OS of 18 months (14.75, 22.85) and a median PFS of 17 months (12.00, 21.75). Univariate analysis showed that pathological subtype, TNM stage, surgery, SUVmax, MTV, TLG, D, D* and ADC were both influential factors for OS and PFS in NSCLC patients. Multifactorial analysis showed that MTV, D* and ADC were independent predicting factors for OS and PFS in NSCLC patients.

CONCLUSION

MTV, D* and ADC are independent predicting factors affecting OS and PFS in NSCLC patients. 18F-FDG PET/MR-derived metabolic parameters and diffusion parameters have clinical value for prognostic assessment of NSCLC patients.

Clinical Variables and Radiomics Features for Predicting Pneumothorax in Patients Undergoing CT-guided Transthoracic Core Needle Biopsy

Purpose To develop a prediction model combining both clinical and CT texture analysis radiomics features for predicting pneumothorax complications in patients undergoing CT-guided core needle biopsy. Materials and Methods A total of 424 patients (mean age, 65.6 years ± 12.7 [SD]; 232 male, 192 female) who underwent CT-guided core needle biopsy between January 2021 and October 2022 were retrospectively included as the training data set. Clinical and procedure-related characteristics were documented. Texture analysis radiomics features were extracted from the subpleural lung parenchyma traversed by needle. Moderate pneumothorax was defined as a postprocedure air rim of 2 cm or greater. The prediction model was developed using logistic regression with backward elimination, presented by linear fusion of the selected features weighted by their coefficients. Model performance was assessed using the area under the receiver operating characteristic curve (AUC). Validation was conducted in an external cohort (n = 45; mean age, 58.2 years ± 12.7; 19 male, 26 female) from a different hospital. Results Moderate pneumothorax occurred in 12.0% (51 of 424) of the training cohort and 8.9% (four of 45) of the external test cohort. Patients with emphysema (P < .001) or a longer needle path length (P = .01) exhibited a higher incidence of moderate pneumothorax in the training cohort. Texture analysis features, including gray-level co-occurrence matrix cluster shade (P < .001), gray-level run-length matrix low gray-level run emphasis (P = .049), gray-level run-length matrix run entropy (P = .003), gray-level size-zone matrix gray-level variance (P < .001), and neighboring gray-tone difference matrix complexity (P < .001), showed higher values in patients with moderate pneumothorax. The combined clinical-radiomics model demonstrated satisfactory performance in both the training (AUC 0.78, accuracy = 71.9%) and external test cohorts (AUC 0.86, accuracy 73.3%). Conclusion The model integrating both clinical and radiomics features offered practical diagnostic performance and accuracy for predicting moderate pneumothorax in patients undergoing CT-guided core needle biopsy. Keywords: Biopsy/Needle Aspiration, Thorax, CT, Pneumothorax, Core Needle Biopsy, Texture Analysis, Radiomics, CT Supplemental material is available for this article. © RSNA, 2024.

Cisplatin and Albumin-Based Gold-Cisplatin Nanoparticles Enhance Ablative Radiation Therapy-Induced Antitumor Immunity in Local and Distant Tumor Microenvironment

PURPOSE

Ablative radiation therapy (RT) is an important strategy to eliminate primary tumor and can potentially induce the abscopal effect. Human serum albumin nanoparticle (NP) was used for controlled release of cisplatin to decrease cisplatin's systemic toxicity, and gold (Au) was added to increase RT-induced immunogenic cell death and potentiate the abscopal antitumor immunity.

METHODS AND MATERIALS

The designed albumin-based cisplatin-conjugated AuNPs were administered concurrently with ablative RT. C57BL/6 mice implanted with syngeneic murine Lewis lung carcinoma or murine MB49 tumor models were treated with ablative RT (12 Gy per fraction for 2 fractions, total 24 Gy), cisplatin, or Au-cisplatin NPs.

RESULTS

Combining ablative RT with cisplatin or Au-cisplatin NPs both destroyed the primary tumor effectively and elicited immunogenic cell death accompanied by release of danger-associated molecular patterns. This enhanced recruitment of effector tumor-infiltrating immune cells, including natural killer T cells and CD8+ T cells, and elicited an increased percentage of professional antigen-presenting CD11c+ dendritic cells. Transient weight loss, accompanying hepatotoxicity, nephrotoxicity, and hematopoietic suppression, was observed as a systemic adverse event in the cisplatin but not the Au-cisplatin NPs group. Cisplatin and Au-cisplatin NPs both showed equivalent ability to reduce metastatic potential when combined with ablative RT, confirmed by suppressed unirradiated flank tumor growth and decreased metastatic lung tumor burden, which translated to improved survival. Mobilization and abundance of effector tumor-infiltrating immune cells including CD8+ T cells and dendritic cells were observed in the distant lung tumor microenvironment after ablative RT with cisplatin or Au-cisplatin NPs, demonstrating increased antitumor immunotherapeutic activity as an abscopal effect.

CONCLUSIONS

Compared with cisplatin, the albumin-based Au-cisplatin NPs exhibited equivalent but no superior antitumor immunotherapeutic activity while reducing systemic adverse events and can be safely administered concurrently with ablative RT. Alternative NP formulations may be designed to further improve anticancer outcomes.

Xenon-Enhanced Ventilation Computed Tomography for Functional Lung Avoidance Radiation Therapy in Patients With Lung Cancer

PURPOSE

This phase 2 trial aimed to determine whether xenon-enhanced ventilation computed tomography (XeCT)-guided functional-lung-avoidance radiation therapy could reduce the radiation pneumonitis (RP) rate in patients with lung cancer undergoing definitive chemoradiation therapy.

METHODS AND MATERIALS

Functional lung ventilation was measured via pulmonary function testing (PFT) and XeCT. A standard plan (SP) without reference to XeCT and a functional-lung-avoidance plan (fAP) optimized for lowering the radiation dose to the functional lung at the guidance of XeCT were designed. Dosimetric parameters and predicted RP risks modeled by biological evaluation were compared between the 2 plans in a treatment planning system (TPS). All patients received the approved fAP. The primary endpoint was the rate of grade ≥2 RP, and the secondary endpoints were the survival outcomes. The study hypothesis was that fAP could reduce the rate of grade ≥2 RP to 12% compared with a 30% historical rate.

RESULTS

Thirty-six patients were evaluated. Xenon-enhanced total functional lung volumes positively correlated with PFT ventilation parameters (forced vital capacity, P = .012; forced expiratory volume in 1 second, P = .035), whereas they were not correlated with the diffusion capacity parameter. We observed a 17% rate of grade ≥2 RP (6 of 36 patients), which was significantly different (P = .040) compared with the historical control. Compared with the SP, the fAP significantly spared the total ventilated lung, leading to a reduction in predicted grade ≥2 RP (P = .001) by TPS biological evaluation. The median follow-up was 15.2 months. The 1-year local control (LC), disseminated failure-free survival (DFFS), and overall survival (OS) rates were 88%, 66%, and 91%, respectively. The median LC and OS were not reached, and the median DFFS was 24.0 months (95% confidence interval, 15.7-32.3 months).

CONCLUSIONS

This report of XeCT-guided functional-lung-avoidance radiation therapy provided evidence showing its feasibility in clinical practice. Its benefit should be assessed in a broader multicenter trial setting.

Therapeutic efficacy of cyclin-dependent kinase inhibition in combination with ionizing radiation for lung cancer

PURPOSE

To evaluate the therapeutic efficacy of cyclin-dependent kinase (CDK) inhibition in combination with ionizing radiation for lung cancer.

MATERIALS AND METHODS

Human lung adenocarcinoma (A549) and squamous cell carcinoma (H520) cells were used to evaluate the therapeutic efficacy of CDK inhibition in combination with ionizing radiation in vitro using colony formation assay, γH2AX immunofluorescence staining, western blotting, and cell cycle phase analysis. We also performed in vivo evaluations of ectopic tumor growth.

RESULTS

In vitro pretreatment with the CDK inhibitor, seliciclib, before irradiation significantly decreased the survival of A549 and H520 cells in a dose-dependent manner. Although CDK inhibition alone did not increase the intensity of γH2AX foci, its combination with ionizing radiation increased DNA double-strand breaks, as shown by γH2AX immunofluorescence staining and western blotting. The combination of CDK inhibition and ionizing radiation-induced G2/M arrest and increased apoptosis, as evidenced by the increased proportion of cells in G2/M arrest, subG1 apoptotic population, and expression of apoptotic markers (cleaved PARP-1 and cleaved caspase-3). Mechanistic studies showed reduced expression of cyclin A with combined treatment, indicating cell cycle shifting effects. An in vivo xenograft model showed that the combination of CDK inhibition and ionizing radiation delayed xenograft tumor growth, and increased the proportion of cleaved PARP-1- and cleaved caspase-3-positive cells, compared to either treatment alone.

CONCLUSIONS

We provide preclinical tumoricidal evidence that the combination of CDK inhibition and ionizing radiation is an efficacious treatment for lung cancer.

Preclinical evaluation of PEGylated liposomal doxorubicin as an effective radiosensitizer in chemoradiotherapy for lung cancer

PURPOSE

Development of a safe and effective systemic chemotherapeutic agent for concurrent administration with definitive thoracic radiotherapy remains a major goal of lung cancer management. The synergistic effect of PEGylated liposomal doxorubicin and irradiation was evaluated in lung cancer cell lines both in vitro and in vivo.

METHODS

In vitro radiosensitization of A549 and LLC cell lines was evaluated by colony formation assay, γH2AX fluorescent staining and western blot assay, and annexin V staining. A radiosensitization study with healthy human lung-derived cell line BEAS-2B was performed for comparative purposes. In vivo radiosensitization was evaluated by tumor ectopic growth, cell survival, pharmacokinetics, and biodistribution analyses. Cleaved caspase‑3, the marker for apoptosis, was assessed immunohistochemically in A549 xenograft tumors.

RESULTS

Treatment with PEGylated liposomal doxorubicin decreased A549 and LLC cell proliferation in a dose-dependent manner. In vitro studies revealed comparable radiosensitizer advantages of PEGylated liposomal doxorubicin and free doxorubicin, showing equivalent DNA double-strand breaks according to γH2AX fluorescent staining and western blot assays, similar numbers of apoptotic cells in the annexin‑V staining assay, and moderately decreased clonogenic survival. In vivo studies demonstrated markedly slow ectopic tumor growth with prolonged survival following treatment with PEGylated liposomal doxorubicin plus irradiation in both A549 and LLC mouse models, suggesting that PEGylated liposomal doxorubicin is more effective as a radiosensitizer than free doxorubicin in vivo. Pharmacokinetics evaluation showed a longer half-life of approximately 40 h for PEGylated liposomal doxorubicin, confirming that the liposomal carrier achieved controlled release. Biodistribution evaluation of PEGylated liposomal doxorubicin confirmed high accumulation of doxorubicin in tumors, indicating the promising drug delivery attributes of PEGylated liposomal doxorubicin. Although free doxorubicin caused histopathologic myocarditis with the cardiac muscle fibers showing varying degrees of damage, PEGylated liposomal doxorubicin caused no such effects. The immunohistochemical expression of cleaved caspase-3-positive cells was greatest expressed in the irradiation and PEGylated liposomal doxorubicin combined treatment group, indicating prolonged tumoricidal effects.

CONCLUSIONS

Our study provides preclinical in vitro and in vivo evidence of the effectiveness of PEGylated liposomal doxorubicin as a radiosensitizer, supporting its potential clinical development as a component of chemoradiotherapy.

Assessing tumor angiogenesis using dynamic contrast-enhanced integrated magnetic resonance-positron emission tomography in patients with non-small-cell lung cancer

Background

Angiogenesis assessment is important for personalized therapeutic intervention in patients with non-small-cell lung cancer (NSCLC). This study investigated whether radiologic parameters obtained by dynamic contrast-enhanced (DCE)-integrated magnetic resonance-positron emission tomography (MR-PET) could be used to quantitatively assess tumor angiogenesis in NSCLC.

Methods

This prospective cohort study included 75 patients with NSCLC who underwent DCE-integrated MR-PET at diagnosis. The following parameters were analyzed: metabolic tumor volume (MTV), maximum standardized uptake value (SUV_max), reverse reflux rate constant (k_ep), volume transfer constant (K^trans), blood plasma volume fraction (v_p), extracellular extravascular volume fraction (v_e), apparent diffusion coefficient (ADC), and initial area under the time-to-signal intensity curve at 60 s post enhancement (iAUC₆₀). Serum biomarkers of tumor angiogenesis, including vascular endothelial growth factor-A (VEGF-A), angiogenin, and angiopoietin-1, were measured by enzyme-linked immunosorbent assays simultaneously.

Results

Serum VEGF-A (p = 0.002), angiogenin (p = 0.023), and Ang-1 (p <  0.001) concentrations were significantly elevated in NSCLC patients compared with healthy individuals. MR-PET parameters, including MTV, K^trans, and k_ep, showed strong linear correlations (p <  0.001) with serum angiogenesis-related biomarkers. Serum VEGF-A concentrations (p = 0.004), MTV values (p <  0.001), and k_ep values (p = 0.029) were significantly higher in patients with advanced-stage disease (stage III or IV) than in those with early-stage disease (stage I or II). Patients with initial higher values of angiogenesis-related MR-PET parameters, including MTV > 30 cm³ (p = 0.046), K^trans > 200 10^− 3/min (p = 0.069), and k_ep > 900 10^− 3/min (p = 0.048), may have benefited from angiogenesis inhibitor therapy, which thus led to significantly longer overall survival.

Conclusions

The present findings suggest that DCE-integrated MR-PET provides a reliable, non-invasive, quantitative assessment of tumor angiogenesis; can guide the use of angiogenesis inhibitors toward longer survival; and will play an important role in the personalized treatment of NSCLC.

Combing MRI Perfusion and 18F-FDG PET/CT Metabolic Biomarkers Helps Predict Survival in Advanced Nasopharyngeal Carcinoma: A Prospective Multimodal Imaging Study

We prospectively investigated the prognostic value of imaging parameters for nasopharyngeal carcinoma (NPC) using dynamic contrast-enhanced MRI (DCE-MRI), diffusion-weighted imaging (DWI), and 2-deoxy-2-[fluorine-18]fluoro-D-glucose positron emission tomography (¹⁸F-FDG PET)/computed tomography (CT). Patients with stage III-IVb NPC underwent F-FDG PET/CT, DCE-MRI, and DWI before treatment. Kaplan-Meier and Cox-regression analyses were used to assess associations of PET and MRI imaging biomarkers with overall survival (OS) and recurrence-free survival (RFS). We used independent prognosticators to establish prognostic models; model performance was examined using Harrell's concordance index (c-index). Sixty-one patients were available for analysis, as 13 patients died and 20 experienced recurrence. Total lesion glycolysis (TLG) (p = 0.002) from PET/CT and the initial area under the curve (iAUC) (p = 0.036) from DCE-MRI were identified as independent prognosticators of OS; Epstein-Barr virus (EBV) DNA (p = 0.027), the extracellular volume fraction (V_e) (p = 0.027) from DCE-MRI, and TLG/iAUC (p = 0.025) were significant predictors of RFS. The c-indices of the prognostic models incorporating TLG + iAUC in predicting OS and incorporating EBV DNA + V_e + TLG/iAUC in predicting RFS were 0.79 and 0.76, respectively. These were significantly higher than the corresponding c-indices of the TNM staging system (p = 0.047 and 0.025, respectively); they were also higher than those of models with only MRI or PET biomarkers. In conclusion, the combination of pretreatment DCE-MRI and ¹⁸F-FDG PET/CT imaging biomarkers helps survival prediction in advanced NPC. Integrating MRI perfusion with PET metabolism and plasma EBV information may aid clinicians in planning the optimal personalized management strategy.

Chemoradiotherapy by intensity-modulated radiation therapy with simultaneous integrated boost in locally advanced or oligometastatic non-small-cell lung cancer-a two center experience

Purpose

Integrating moderate hypofractionation to the macroscopic tumor with elective nodal irradiation while sparing the organs at risk (OAR) in chemoradiotherapy of locally advanced non-small-cell lung cancer.

Methods

From 2010–2018, treatment, patient and tumor characteristics of 138 patients from two radiation therapy centers were assessed. Chemoradiotherapy by intensity-modulated radiation therapy (IMRT) with a simultaneous integrated boost (SIB) to the primary tumor and macroscopic lymph node metastases was used.

Results

A total of 124 (90%) patients received concurrent chemotherapy. 106 (76%) patients had UICC (Union for International Cancer Control) stage ≥IIIB and 21 (15%) patients had an oligometastatic disease (UICC stage IV). Median SIB and elective total dose was 61.6 and 50.4 Gy in 28 fractions, respectively. Furthermore, 64 patients (46%) had an additional sequential boost to the primary tumor after the SIB-IMRT main series: median 6.6 Gy in median 3 fractions. The median cumulative mean lung dose was 15.6 Gy (range 6.2–29.5 Gy). Median follow-up and radiological follow-up for all patients was 18.0 months (range 0.6–86.9) and 16.0 months (range 0.2–86.9), respectively. Actuarial local control rates at 1, 2 and 3 years were 80.4, 68.4 and 57.8%. Median overall survival and progression-free survival was 30.0 months (95% confidence interval [CI] 23.5–36.4) and 12.1 months (95% CI 8.2–16.0), respectively. Treatment-related toxicity was moderate. Radiation-induced pneumonitis grade 2 and grade 3 occurred in 13 (9.8%) and 3 (2.3%) patients.

Conclusions

Chemoradiotherapy using SIB-IMRT showed promising local tumor control rates and acceptable toxicity in patients with locally advanced and in part oligometastatic lung cancer. The SIB concept, resulting in a relatively low mean lung dose, was associated with low numbers of clinically relevant pneumonitis. The overall survival appears promising in the presence of a majority of patients with UICC stage ≥IIIB disease.

Trimodality PET/CT/MRI and Radiotherapy: A Mini-Review

Computed tomography (CT) has revolutionized external radiotherapy by making it possible to visualize and segment the tumors and the organs at risk in a three-dimensional way. However, if CT is a now a standard, it presents some limitations, notably concerning tumor characterization and delineation. Its association with functional and anatomical images, that are positron emission tomography (PET) and magnetic resonance imaging (MRI), surpasses its limits. This association can be in the form of a trimodality PET/CT/MRI. The objective of this mini-review is to describe the process of performing this PET/CT/MRI trimodality for radiotherapy and its potential clinical applications. Trimodality can be performed in two ways, either a PET/MRI fused to a planning CT (possibly with a pseudo-CT generated from the MRI for the planning), or a PET/CT fused to an MRI and then registered to a planning CT (possibly the CT of PET/CT if calibrated for radiotherapy). These examinations should be performed in the treatment position, and in the second case, a patient transfer system can be used between the PET/CT and MRI to limit movement. If trimodality requires adapted equipment, notably compatible MRI equipment with high-performance dedicated coils, it allows the advantages of the three techniques to be combined with a synergistic effect while limiting their disadvantages when carried out separately. Trimodality is already possible in clinical routine and can have a high clinical impact and good inter-observer agreement, notably for head and neck cancers, brain tumor, prostate cancer, cervical cancer.

Treatment-related changes in neuroendocrine tumors as assessed by textural features derived from 68Ga-DOTATOC PET/MRI with simultaneous acquisition of apparent diffusion coefficient

Background

Neuroendocrine tumors (NETs) frequently overexpress somatostatin receptors (SSTRs), which is the molecular basis for ⁶⁸Ga-DOTATOC positron-emission tomography (PET) and radiopeptide therapy (PRRT). However, SSTR expression fluctuates and can be subject to treatment-related changes. The aim of this retrospective study was to assess, which changes in PET and apparent diffusion coefficient (ADC) occur for different treatments and if pre-therapeutic ⁶⁸Ga-DOTATOC-PET/MRI was able to predict treatment response to PRRT.

Methods

Patients with histopathologically confirmed NET, at least one liver metastasis > 1 cm and at least two ⁶⁸Ga-DOTATOC-PET/MRI including ADC maps were eligible. ⁶⁸Ga-DOTATOC-PET/MRI of up to 5 liver lesions per patients was subsequently analyzed. Extracted features comprise conventional PET parameters, such as maximum and mean standardized uptake value (SUVmax and SUVmean) and ADC values. Furthermore, textural features (TFs) from both modalities were extracted. In patients with multiple ⁶⁸Ga-DOTATOC-PET/MRI a pair of 2 scans each was analyzed separately and the parameter changes between both scans calculated. The same image analysis was performed in patients with ⁶⁸Ga-DOTATOC-PET/MRI before PRRT. Differences in PET and ADC maps parameters between PRRT-responders and non-responders were compared using Mann-Whitney test to test differences among groups for statistical significance.

Results

29 pairs of ⁶⁸Ga-DOTATOC-PET/MRI scans of 18 patients were eligible for the assessment of treatment-related changes. In 12 cases patients were treated with somatostatin analogues between scans, in 9 cases with PRRT and in 2 cases each patients received local treatment, chemotherapy and sunitinib. Treatment responders showed a statistically significant decrease in lesion volume and a borderline significant decrease in entropy on ADC maps when compared to non-responders. Patients treated with standalone SSA showed a borderline significant decrease in mean and maximum ADC, compared to patients treated with PRRT. No parameters were able to predict treatment response to PRRT on pre-therapeutic ⁶⁸Ga-DOTATOC-PET/MRI.

Conclusions

Patients responding to current treatment showed a statistically significant decrease in lesion volume on ADC maps and a borderline significant decrease in entropy. No statistically significant changes in PET parameters were observed. No PET or ADC maps parameters predicted treatment response to PRRT. However, the sample size of this preliminary study is small and further research needed.

Proton MRI of the Lung: How to Tame Scarce Protons and Fast Signal Decay

Pulmonary proton MRI techniques offer the unique possibility of assessing lung function and structure without the requirement for hyperpolarization or dedicated hardware, which is mandatory for multinuclear acquisition. Five popular approaches are presented and discussed in this review: 1) oxygen enhanced (OE)-MRI; 2) arterial spin labeling (ASL); 3) Fourier decomposition (FD) MRI and other related methods including self-gated noncontrast-enhanced functional lung (SENCEFUL) MR and phase-resolved functional lung (PREFUL) imaging; 4) dynamic contrast-enhanced (DCE) MRI; and 5) ultrashort TE (UTE) MRI. While DCE MRI is the most established and well-studied perfusion measurement, FD MRI offers a free-breathing test without any contrast agent and is predestined for application in patients with renal failure or with low compliance. Additionally, FD MRI and related methods like PREFUL and SENCEFUL can act as an ionizing radiation-free V/Q scan, since ventilation and perfusion information is acquired simultaneously during one scan. For OE-MRI, different concentrations of oxygen are applied via a facemask to assess the regional change in T₁ , which is caused by the paramagnetic property of oxygen. Since this change is governed by a combination of ventilation, diffusion, and perfusion, a compound functional measurement can be achieved with OE-MRI. The known problem of fast T₂ * decay of the lung parenchyma leading to a low signal-to-noise ratio is bypassed by the UTE acquisition strategy. Computed tomography (CT)-like images allow the assessment of lung structure with high spatial resolution without ionizing radiation. Despite these different branches of proton MRI, common trends are evident among pulmonary proton MRI: 1) free-breathing acquisition with self-gating; 2) application of UTE to preserve a stronger parenchymal signal; and 3) transition from 2D to 3D acquisition. On that note, there is a visible convergence of the different methods and it is not difficult to imagine that future methods will combine different aspects of the presented methods.