APT-weighted and Diffusion MRI for Characterizing Tumor Infiltration in High-Grade Gliomas

Characterization of Peri-tumoral Microenvironment in High-grade Gliomas Through the Combined Use of APT-weighted Imaging and Diffusion MRI

High-grade gliomas are the most common primary malignant brain tumors and are characterized by infiltration of the surrounding brain tissue beyond the visible tumor margins. This infiltrative growth represents a major challenge for treatment planning and contributes to tumor recurrence. Conventional magnetic resonance imaging (MRI) is limited in its ability to distinguish tumor infiltration from non-tumoral changes such as vasogenic edema in the peri-tumoral region.

This prospective single-center observational study aims to improve the characterization of the peri-tumoral microenvironment in patients with suspected high-grade gliomas using advanced MRI techniques, including amide proton transfer-weighted (APTw) imaging and diffusion tensor imaging (DTI). These techniques provide complementary information about tissue composition and microstructure and may help identify areas of tumor infiltration that are not visible on conventional imaging.

APTw- and DTI-derived maps will be combined to generate imaging-derived maps describing the likelihood of tumor infiltration within the peri-tumoral region. These maps will be compared with histopathological findings obtained from tissue samples collected during biopsy or tumor resection performed as part of standard clinical care. Histological analyses will include assessment of tumor cellularity using hematoxylin and eosin staining and additional immunohistochemical markers routinely used in neuropathological evaluation. Patients will undergo routine clinical follow-up and the prognostic significance of the imaging-derived map will be assessed.

The overall goal of the study is to develop and validate imaging-based biomarkers capable of identifying infiltrated tissue within the peri-tumoral region. These findings may contribute to improved diagnostic accuracy and support future treatment planning strategies in patients with high-grade gliomas.

High-grade gliomas (HGGs) are among the most aggressive primary brain tumors in adults and are characterized by diffuse infiltration into the surrounding brain tissue. This infiltrative behavior represents one of the main limitations to complete surgical removal and contributes to tumor recurrence.

Accurate identification of infiltrated tissue beyond the visible tumor margins remains a major challenge in neuro-oncology. Conventional magnetic resonance imaging (MRI) sequences, including contrast-enhanced T1-weighted imaging and fluid-attenuated inversion recovery (FLAIR), are routinely used to define tumor boundaries. However, non-contrast-enhancing regions often contain a mixture of tumor infiltration and vasogenic edema, which cannot be reliably distinguished using standard imaging alone. Improved imaging techniques capable of characterizing the biological properties of the peri-tumoral microenvironment are therefore needed to support more accurate assessment of tumor extent. Advanced MRI techniques provide complementary information about tissue composition and microstructure. Diffusion tensor imaging (DTI) provides information related to tissue organization and cellular architecture through the measurement of water diffusion properties. Amide proton transfer-weighted (APTw) imaging provides information related to endogenous mobile proteins and peptides, which are typically increased in tumor tissue and reflect metabolic and molecular changes. The combined use of these techniques may improve the identification of tumor-infiltrated tissue within regions that appear non-enhancing on conventional MRI.

This study is designed as a prospective, single-center observational study enrolling adult patients with radiologically suspected high-grade gliomas who are scheduled to undergo biopsy or tumor resection as part of standard clinical care. All enrolled participants will undergo a preoperative MRI examination that includes both standard clinical sequences and advanced imaging sequences, including diffusion tensor imaging (DTI) and amide proton transfer-weighted (APTw) imaging. Following imaging acquisition, patients will undergo neurosurgical procedures according to clinical indications. Tissue samples collected during biopsy or tumor resection will undergo standard histopathological evaluation as part of routine diagnostic care. Histological analyses will include assessment of tumor cellularity using hematoxylin and eosin staining and additional immunohistochemical markers.

Imaging data derived from APTw and DTI will be combined to generate maps describing the likelihood of tumor infiltration within the peri-tumoral region. These imaging-derived maps aim to represent spatial variations in tissue characteristics that reflect differences in tumor cellularity. A central objective of the study is the correlation between imaging-derived features and histopathological findings, to validate the maps. Tissue samples obtained during surgery will be spatially related to corresponding imaging locations, allowing comparison between imaging-derived measures and histological characteristics. This approach is intended to validate imaging-derived estimates of tumor infiltration against histological reference standards.

In addition to baseline imaging and histopathological correlation, patients will undergo routine postoperative follow-up according to clinical practice. Follow-up MRI examinations will be analyzed to evaluate patterns of tumor recurrence and to explore the spatial relationship between imaging-derived features identified at baseline and subsequent sites of tumor progression. Moreover the prognostic significance of the area of tumor infiltration described by the imaging-derived map will be evaluated.

The overall objective of this study is to develop and validate imaging-based biomarkers capable of identifying infiltrated tissue beyond the visible tumor margins through integration of advanced MRI techniques, histopathological correlation, and longitudinal follow-up. Improved identification of infiltrated tissue may contribute to a better understanding of tumor growth patterns and support future advances in surgical planning and treatment strategies in patients with high-grade gliomas.

Inclusion Criteria:

1. Adult patients (both male and female, >= 18 years old)
2. Previously acquired MRI suggestive for the presence of high-grade glioma
3. Treatment-naïve status, defined as no prior surgical, radiotherapeutic, or systemic oncological treatment for the index brain lesion.
4. Indication for biopsy or tumor resection
5. Willingness to participate to the study and ability to sign informed consent

Exclusion Criteria:

1. Pregnancy (to be excluded through a human chorionic gonadotropin pregnancy test performed on urine or serum when childbearing potential) and / or lactation.

2. Contraindications to MRI because of:

   I. Claustrophobia II. Presence of metallic objects or implanted medical devices in body (i.e., cardiac pacemaker, aneurysm clips, surgical clips, prostheses, artificial hearts, valves with steel parts, metal fragments, shrapnel, tattoos near the eye, or steel implants) III. Sickle cell disease IV. Renal failure or reduced renal function, as determined by Glomerular Filtration Rate (GFR) < 30 mL/min/1.73 m^2 based on a serum creatinine level obtained within 40 days prior to registration

3. Presence of any other co-existing condition (such as serious systemic illness, including uncontrolled intercurrent infection, uncontrolled malignancy, significant renal or hepatic disease, or psychiatric/social situations) which might, in the judgment of the investigator, increase the risks to the subject or limit compliance with study requirements

4. Inability to undergo surgical procedures

5. Severe hepatic impairment, defined as the presence of two or more of the following parameters (assessed within 40 days): bilirubin ≥3 mg/dL, albumin <2.8 g/dL, International normalized ratio >2.3 with no history of anticoagulant therapy, platelet count < 100 109/L, AST ≥ 400 U/L, ALT ≥400 U/L, presence of ascites.