Steen R G
Department of Radiology, University of Washington School of Medicine, Seattle 98195.
AJR Am J Roentgenol. 1991 Aug;157(2):243-8. doi: 10.2214/ajr.157.2.1853799.
Tumor hypoxia is of considerable importance to the oncologist in selecting and optimizing cancer therapy, because hypoxia can determine the effectiveness of various therapies. The relationship between tumor hypoxia and tumor bioenergetics, assessed by 31P MR spectroscopy, is examined to determine whether 31P MR spectroscopy can be clinically useful to measure or characterize tumor hypoxia. Work with experimental tumors has suggested that several different types of hypoxia may exist and that 31P MR spectroscopy cannot be used to characterize all types. Metabolic hypoxia is the level of hypoxia that results in mitochondrial impairment in cells, and it is associated with declining cellular bioenergetic status, which can be measured by enzymatic assay of adenosine triphosphate (ATP). Because 31P MR spectroscopy is sensitive to levels of ATP, it is potentially sensitive to metabolic hypoxia in vivo and may provide a rapid and noninvasive technique for characterizing metabolic hypoxia in tumors. Radiobiologic hypoxia is the level of hypoxia that results in attenuated cell death due to radiation, because radiotoxicity is directly related to tissue levels of oxygen. Radiobiologic hypoxia of tumors thus has more impact on choice of therapy, yet the relationship between metabolic hypoxia and radiobiologic hypoxia remains to be elucidated. An analysis of published data suggests that 31P MR spectroscopy is directly sensitive to metabolic hypoxia in tumors, but it is only indirectly sensitive to radiobiologic hypoxia in tumors. Therefore, 31P MR spectroscopy may be unable to quantify the cell fraction of a tumor that has radiobiologic hypoxia. However, preliminary data suggest that MR spectroscopy may prove useful for determining the effectiveness of therapeutic interventions designed to manipulate radiobiologic hypoxia in tumors or for monitoring the kinetics of tumor reoxygenation after treatment.
肿瘤缺氧对于肿瘤学家在选择和优化癌症治疗方面具有相当重要的意义，因为缺氧可决定各种治疗的效果。通过磷-31磁共振波谱（31P MR光谱）评估肿瘤缺氧与肿瘤生物能量学之间的关系，以确定31P MR光谱在临床上是否可用于测量或表征肿瘤缺氧。对实验性肿瘤的研究表明，可能存在几种不同类型的缺氧，且31P MR光谱不能用于表征所有类型的缺氧。代谢性缺氧是导致细胞线粒体功能受损的缺氧水平，它与细胞生物能量状态下降有关，可通过三磷酸腺苷（ATP）的酶促测定来测量。由于31P MR光谱对ATP水平敏感，它在体内可能对代谢性缺氧敏感，并可能提供一种快速且无创的技术来表征肿瘤中的代谢性缺氧。放射生物学缺氧是导致因辐射引起的细胞死亡减弱的缺氧水平，因为放射毒性与组织中的氧水平直接相关。因此，肿瘤的放射生物学缺氧对治疗选择的影响更大，然而代谢性缺氧与放射生物学缺氧之间的关系仍有待阐明。对已发表数据的分析表明，31P MR光谱对肿瘤中的代谢性缺氧直接敏感，但对肿瘤中的放射生物学缺氧仅间接敏感。因此，31P MR光谱可能无法量化具有放射生物学缺氧的肿瘤细胞比例。然而，初步数据表明，磁共振波谱可能被证明有助于确定旨在控制肿瘤放射生物学缺氧的治疗干预措施的有效性，或用于监测治疗后肿瘤再氧合的动力学。
