Koutcher J A, Okunieff P, Neuringer L, Suit H, Brady T
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Int J Radiat Oncol Biol Phys. 1987 Dec;13(12):1851-5. doi: 10.1016/0360-3016(87)90351-8.
In Vivo 31P NMR spectroscopy was used to study changes in phosphate metabolism that occur after irradiation of the C3H fibrosarcoma, FSaII. Previously, we have shown that small FSaII tumors (less than 250 mm3) have a greater phosphocreatinine/inorganic phosphate (PCr/Pi) ratio and a lower hypoxic cell fraction (HCF) than large FSaII tumors (greater than 250 mm3). Six small tumors (113 +/- 26 mm3) were treated with radiation doses chosen to induce local control in greater than 50% of animals, (70-100 Gy, single fraction). Minimal changes in the tumor 31P NMR spectrum were seen over eight days of monitoring. During this interval, tumor regression began a minimum of 36 hours after radiation. This contrasted with large tumors (650-1000 mm3) wherein a significant increase in the Pcr/Pi ratio was seen 44 hr after irradiation. In tumors of this size range, a tumor growth delay of 4 to 7 days is obtained after a single 70 Gy fraction of radiation. Since small FSaII tumors have a minimal HCF (approximately equal to 4%), radiation induced reoxygenation would not be expected to have a large effect on their average cellular metabolism. Large tumors of this histology have a high HCF (greater than or equal to 40%), and may therefore be expected to have a significant average change in tumor cell metabolism with reoxygenation. The 31P NMR observations of small and large tumors after irradiation are compatible with radiation induced reoxygenation in the larger tumors.
采用体内31P核磁共振波谱法研究了C3H纤维肉瘤FSaII受照射后磷酸盐代谢的变化。此前，我们已经表明，小型FSaII肿瘤（小于250立方毫米）比大型FSaII肿瘤（大于250立方毫米）具有更高的磷酸肌酸/无机磷酸盐（PCr/Pi）比值和更低的乏氧细胞分数（HCF）。对6个小型肿瘤（113±26立方毫米）给予选定的辐射剂量进行治疗，以在超过50%的动物中实现局部控制（70 - 100 Gy，单次分割）。在8天的监测期间，肿瘤的31P核磁共振波谱变化极小。在此期间，肿瘤消退至少在放疗后36小时开始。这与大型肿瘤（650 - 1000立方毫米）形成对比，在大型肿瘤中，照射后44小时可见Pcr/Pi比值显著增加。在这个大小范围内的肿瘤，单次70 Gy分割放疗后可获得4至7天的肿瘤生长延迟。由于小型FSaII肿瘤的乏氧细胞分数极低（约等于4%），预计辐射诱导的再氧合对其平均细胞代谢不会有太大影响。这种组织学类型的大型肿瘤具有较高的乏氧细胞分数（大于或等于40%），因此预计再氧合会使肿瘤细胞代谢发生显著的平均变化。照射后小型和大型肿瘤的31P核磁共振观察结果与大型肿瘤中辐射诱导的再氧合相符。
