Assessment of tumour hypoxia, proliferation and glucose metabolism in head and neck cancer before and during treatment

Characterization of Mediastinal Bulky Lymphomas with FDG-PET-Based Radiomics and Machine Learning Techniques

BACKGROUND

This study tested the diagnostic value of 18F-FDG PET/CT (FDG-PET) volumetric and texture parameters in the histological differentiation of mediastinal bulky disease due to classical Hodgkin lymphoma (cHL), primary mediastinal B-cell lymphoma (PMBCL) and grey zone lymphoma (GZL), using machine learning techniques.

METHODS

We reviewed 80 cHL, 29 PMBCL and 8 GZL adult patients with mediastinal bulky disease and histopathological diagnoses who underwent FDG-PET pre-treatment. Volumetric and radiomic parameters were measured using FDG-PET both for bulky lesions (BL) and for all lesions (AL) using LIFEx software (threshold SUV ≥ 2.5). Binary and multiclass classifications were performed with various machine learning techniques fed by a relevant subset of radiomic features.

RESULTS

The analysis showed significant differences between the lymphoma groups in terms of SUVmax, SUVmean, MTV, TLG and several textural features of both first- and second-order grey level. Among machine learning classifiers, the tree-based ensembles achieved the best performance both for binary and multiclass classifications in histological differentiation.

CONCLUSIONS

Our results support the value of metabolic heterogeneity as an imaging biomarker, and the use of radiomic features for early characterization of mediastinal bulky lymphoma.

Hypoxia in relationship to tumor volume using hypoxia PET-imaging in head & neck cancer - A scoping review

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Primary tumor volume and hypoxic volume has previously not been convincingly related.

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367 patients with head and neck squamous cell carcinoma from 21 different studies using hypoxia-PET

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The hypoxic volume increased significantly with primary tumor volume.

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In larger tumor the hypoxic fraction was significantly higher than in smaller tumors.

Background

Hypoxia and large tumor volumes are negative prognostic factors for patients with head and neck squamous cell carcinoma (HNSCC) treated with radiation therapy (RT). PET-scanning with specific hypoxia-tracers (hypoxia-PET) can be used to non-invasively assess hypoxic tumor volume. Primary tumor volume is readily available for patients undergoing RT. However, the relationship between hypoxic volume and primary tumor volume is yet an open question. The current study investigates the hypotheses that larger tumors contain both a larger hypoxic volume and a higher hypoxic fraction.

Methods

PubMed and Embase were systematically searched to identify articles fulfilling the predefined criteria. Individual tumor data (primary tumor volume and hypoxic volume/fraction) was extracted. Relationship between hypoxic volume and primary tumor volume was investigated by linear regression. The correlation between hypoxic fraction and log₂(primary tumor volume) was determined for each cohort and in a pooled analysis individual regression slopes and coefficients of determination (R²) were weighted according to cohort size.

Results

21 relevant articles were identified and individual data from 367 patients was extracted, out of which 323 patients from 17 studies had quantifiable volumes of interest. A correlation between primary tumor volume and PET-determined hypoxic volume was found (P <.001, R² = 0.46). Larger tumors had a significantly higher fraction of hypoxia compared with smaller tumors (P<.01). The weighted analysis of all studies revealed that for each doubling of the tumor volume, the hypoxic fraction increased by four percentage points.

Conclusion

This study shows correlations between primary tumor volume and hypoxic volume as well as primary tumor volume and the hypoxic fraction in patients with HNSCC. The findings suggest that not only do large tumors contain more cancer cells, they also have a higher proportion of potentially radioresistant hypoxic cells. This knowledge can be important when individualizing RT.

Synthesis and Biological Evaluation of 5'-O-Fatty Acyl Ester Derivatives of 3'-Fluoro-2',3'-dideoxythymidine as Potential Anti-HIV Microbicides

A number of 5′-O-fatty acyl derivatives of 3′-fluoro-2′,3′-dideoxythymidine (FLT, 1) were synthesized. These conjugates were evaluated for their potential as topical microbicides with anti-HIV activity against cell-free (X4 and R5), cell-associated, and multidrug-resistant viruses. Compared to FLT and 3′-azido-2′,3′-dideoxythymidine (AZT), 5′-O-(12-azidododecanoyl) (5), 5′-O-myristoyl (6), and 5′-O-(12-thioethyldodecanoyl) (8) derivatives of FLT were found to be more active against both cell-free viruses (lymphocytotropic and monocytotropic strains) with EC50 values of 0.4 μM, 1.1 μM, and <0.2 μM, respectively, as well as cell-associated virus with EC50 values of 12.6, 6.4, and 2.3 μM, respectively. Conjugates 5, 6, and 8 exhibited >4 and >30 times better antiviral index than FLT and AZT, respectively. Conjugates 5 and 8 were significantly more potent than FLT against many multidrug-resistant strains. A comparison of the anti-HIV activity with the corresponding non-hydrolyzable ether conjugates suggested that ester hydrolysis to FLT and fatty acids is critical to enable anti-HIV activity. Cellular uptake studies were conducted using fluorescent derivatives of FLT attached with 5(6)-carboxyfluorescein through either β-alanine (23) or 12-aminododecanoic acid (24) spacers. The lipophilic fluorescent analog with a long chain (24) showed more than 12 times higher cellular uptake profile than the fluorescent analog with a short chain (23). These studies further confirmed that the attachment of fatty acids improved the cellular uptake of nucleoside conjugates. In addition, 5, 6, and 8 were the least cytotoxic and did not alter vaginal cell and sperm viability compared to the positive control, a commercial topical spermicide (N-9), which significantly decreased sperm and vaginal cell viability inducing the generation of proinflammatory cytokines.

Dose escalation to hypoxic subvolumes in head and neck cancer: A randomized phase II study using dynamic [18F]FMISO PET/CT

BACKGROUND AND PURPOSE

Tumor hypoxia is a major cause of resistance to radiochemotherapy in locally advanced head-and-neck cancer (LASCCHN). We present results of a randomized phase II trial on hypoxia dose escalation (DE) in LASCCHN based on dynamic [¹⁸F]FMISO (dynFMISO) positron emission tomography (PET). The purpose was to confirm the prognostic value of hypoxia PET and assess feasibility, toxicity and efficacy of hypoxia-DE.

MATERIALS AND METHODS

Patients with LASCCHN underwent baseline dynFMISO PET/CT. Hypoxic volumes (HV) were derived from dynFMISO data. Patients with hypoxic tumors (HV>0) were randomized into standard radiotherapy (ST: 70Gy/35fx) or dose escalation (DE: 77Gy/35fx) to the HV. Patients with non-hypoxic tumors were treated with ST. After a minimum follow-up of 2 years, feasibility, acute/late toxicity and local control (LC) were analyzed.

RESULTS

The study was closed prematurely due to slow accrual. Between 2009 and 2017, 53 patients were enrolled, 39 (74%) had hypoxic tumors and were randomized into ST or DE. For non-hypoxic patients, 100% 5-year LC was observed compared to 74% in patients with hypoxic tumors (p=0.039). The difference in 5-year LC between DE (16/19) and ST (10/17) was 25%, p=0.150. No relevant differences related to acute and late toxicities between the groups were observed.

CONCLUSION

This study confirmed the prognostic value of hypoxia PET in LASCCHN for LC. Outcome after hypoxia DE appears promising and may support the concept of DE. Slow accrual and premature closure may partly be due to a high complexity of the study setup which needs to be considered for future multicenter trials.

Role of Non-FDG-PET/CT in Head and Neck Cancer

Head and neck cancers are commonly encountered malignancies in the United States, of which the majority are attributed to squamous cell carcinoma. ¹⁸F-FDG-PET/CT has been well established in the evaluation, treatment planning, prognostic implications of these tumors and is routinely applied for the management of patients with these cancers. Many alternative investigational PET radiotracers have been extensively studied in the evaluation of these tumors. Although these radiotracers have not been able to replace ¹⁸F-FDG-PET/CT in routine clinical practice currently, they may provide important additional information about the biological mechanisms of these tumors, such as foci of tumor hypoxia as seen on hypoxia specific PET radiotracers such as ¹⁸F-Fluoromisonidazole (¹⁸F-FMISO), which could be useful in targeting radioresistant hypoxic tumor foci when treatment planning. There are multiple other hypoxia-specific PET radiotracers such as ¹⁸F-Fluoroazomycinarabinoside (FAZA), ¹⁸F-Flortanidazole (HX4), which have been evaluated similarly, of which ¹⁸F-Fluoromisonidazole (¹⁸F-FMISO) has been the most investigated. Other radiotracers frequently studied in the evaluation of these tumors include radiolabeled amino acid PET radiotracers, which show increased uptake in tumor cells with limited uptake in inflammatory tissue, which can be useful especially in differentiating postradiation inflammation from residual and/or recurrent disease. ¹⁸F-Fluorothymidine (FLT) is localized intracellularly by nucleoside transport and undergoes phosphorylation thereby being retained within tumor cells and can serve as an indicator of tumor proliferation. Decrease in radiotracer activity following treatment can be an early indicator of treatment response. This review aims at synthesizing the available literature on the most studied non-FDG-PET/CT in head and neck cancer.