Dubray B, Giraud P, Helfre S, Dendale R, Cosset J M
Département d'oncologie-radiothérapie, institut Curie, Paris, France.
Cancer Radiother. 1999 Mar-Apr;3(2):154-61. doi: 10.1016/S1278-3218(99)80046-8.
A comprehensive understanding of the radiobiological bases of total body irradiation (TBI) is made difficult by the large number of normal and malignant tissues that must be taken into account. In addition, tissue responses to irradiation are also sensitive to associated treatments, type of graft and a number of patient characteristics. Experimental studies have yielded a large body of data, the clinical relevance of which still requires definite validation through randomized trials. Fractionated TBI schemes are able to reduce late normal tissue toxicity, but the ultimate consequences of the fractional dose reduction do not appear to be equivocal. Thus, leukemia and lymphoma cells are probably more radiobiologically heterogeneous than previously thought, with several cell lines displaying relatively high radioresistance and repair capability patterns. The most primitive host-type hematopoietic stem cells are likely to be at least partly protected by TBI fractionation and may hamper late engraftment. Similarly, but with possibly conflicting consequences on the probability of engraftment, the persistence of a functional marrow stroma may also be fractionation-sensitive, while higher rejection rates have been reported after T-depletion grafts and fractionated TBI. In clinical practice (as for the performance of relevant clinical trials), the influence of these results are rather limited by the heavy logistic constraints created by a sophisticated and time-consuming procedure. Lastly, clinicians are now facing an increasing incidence of second cancers, at least partly induced by irradiation, which jeopardize the long-term prospects of otherwise cured patients.
由于需要考虑大量正常组织和恶性组织，全面理解全身照射（TBI）的放射生物学基础变得困难。此外，组织对辐射的反应也对相关治疗、移植物类型和许多患者特征敏感。实验研究已产生大量数据，但其临床相关性仍需通过随机试验进行明确验证。分次TBI方案能够降低晚期正常组织毒性，但分次剂量降低的最终后果似乎并不明确。因此，白血病和淋巴瘤细胞的放射生物学异质性可能比以前认为的更大，有几种细胞系表现出相对较高的放射抗性和修复能力模式。最原始的宿主型造血干细胞可能至少部分受到TBI分次照射的保护，并可能妨碍晚期植入。同样，但对植入概率可能产生相互矛盾的影响，功能性骨髓基质的持续存在也可能对分次照射敏感，而在T细胞清除移植物和分次TBI后，报告的排斥率更高。在临床实践中（如同进行相关临床试验一样），这些结果的影响在很大程度上受到复杂且耗时程序所带来的沉重后勤限制。最后，临床医生现在面临着二次癌症发病率不断上升的问题，至少部分是由辐射引起的，这危及了原本治愈患者的长期前景。
