[Oxygenation status of squamous cell carcinoma of the head and neck: comparison of primary tumors, their neck node metastases and normal tissue]

[Metabolic markers of the head and neck cancers--clinical applications and the biochemical background]

The problem of diagnosis in the field of head and neck region is still valid. Specific diagnosis and precise estimation of the tumor's size with the use of CT and MRI imaging is generally unsatisfactory. The Positron Emission Tomography (PET) supports this process with additional information about the tumor's metabolism. Numerous publications show that PET-CT has a great influence on the evaluation of the size of the tumor, presence of lymph node metastases, choice of treatment and the prognosis of the recurrence. Cancer cells represent a specific metabolic state. These cells intake large quantities of glucose and utilize it in the process of glycolysis. The oxidative phosphorylation is not efficient in the transformed cells and defects in mitochondrial functions are at the heart of malignant cell transformation. Disruption of the oxidative phosphorylation chain has been described in the neoplasms. As a consequence, in cancer the glycolysis is active even in the normoxic environment. This metabolic shift in cell transformation has been described in early XX century and so called Warburg's hypothesis profoundly influenced the present perception of cancer metabolism, positioning what is termed aerobic glycolysis in the mainstream of clinical oncology. Today we know that neoplastic cells differ at the proteomic level. A subset of different proteins such as hexokinase II or HIF are upregulated. These abnormalities might be used as the neoplastic markers.

Detection and characterization of tumor hypoxia using pO2 histography

Data from 125 studies describing the pretreatment oxygenation status as measured in the clinical setting using the computerized Eppendorf pO2 histography system have been compiled in this article. Tumor oxygenation is heterogeneous and severely compromised as compared to normal tissue. Hypoxia results from inadequate perfusion and diffusion within tumors and from a reduced O2 transport capacity in anemic patients. The development of tumor hypoxia is independent of a series of relevant tumor characteristics (e.g., clinical size, stage, histology, and grade) and various patient demographics. Overall median pO2 in cancers of the uterine cervix, head and neck, and breast is 10 mm Hg with the overall hypoxic fraction (pO2 <or= 2.5 mm Hg) being approx. 25%. Metastatic lesions do not substantially deviate from the oxygenation status of (their) primary tumors. Whereas normal tissue oxygenation is independent of the hemoglobin level over the range of 8-15 g/dL, hypoxia is more pronounced in anemic patients and above this range in some cancers. Identification of tumor hypoxia may allow an assessment of a tumor's potential to develop an aggressive phenotype or acquired treatment resistance, both of which lead to poor prognosis. Detection of hypoxia in the clinical setting may therefore be helpful in selecting high-risk patients for individual and/or more intensive treatment schedules.

Impact of anemia in patients with head and neck cancer treated with radiation therapy

Locoregional recurrence remains a major obstacle to achieving a cure of locally advanced head and neck cancers, despite multimodality therapy. Multiple studies report that a low hemoglobin (Hgb) before or during radiation therapy is an important risk factor for poor locoregional disease control and survival. Anemia is common in the head and neck cancer population and is suspected to contribute to intratumoral hypoxia with resultant radioresistance. Although having a low Hgb level has been shown to be detrimental, it is unclear as to exactly what the threshold should be for low Hgb (studies in this area have used thresholds ranging from 9-14.5 g/dL). Quality-of-life studies suggest that correction of moderately severe anemia may result in significant gains. Optimal Hgb levels for improving outcomes may vary across and within tumor types, and this is an area that requires further evaluation. However, the correction of anemia may be a worthwhile strategy for radiation oncologists to improve local control and survival. This article reviews the impact of anemia on outcomes after radiotherapy of head and neck cancers.

Blood flow and oxygenation status of human tumors. Clinical investigations

PURPOSE

There is a large body of evidence suggesting that blood flow and oxygenation of human tumors are important research topics which may explain, in particular, resistance to radiation and to many antineoplastic drugs, which can limit the curability of solid tumors by radiotherapy and chemotherapy.

MATERIALS AND METHODS

This manuscript reviews the clinical investigations which have been performed regarding blood flow and oxygenation status of human tumors in radiation oncology.

RESULTS

The possible uses and limitations of the prognostic significance and the changes under therapy measuring blood flow and oxygenation in human tumors were discussed. In addition, several approaches were summarized, which can improve the microvascular O2 availability and perfusion-limited O2 delivery.

CONCLUSION

The clinical data concerning the prognostic significance of blood flow, vascular function and oxygenation of human tumors are relevant for patient selection in clinical oncology. Strategies to improve traditional cancer therapy by modulation of the oxygenation status remain quite promising but more critical research and sophisticated clinical studies are necessary before its true potential is known.