从鼻咽癌放疗后颅神经放射损伤探讨当前放疗技术上的问题

RADIATION INDUCED CRANIAL NEUROPATHY(RICN)AFTER RADIOTHERAPY FOR NASOPHARYNGEAL CARCINOMA(NPC):Cause related to radiation technique

１９６９年～１９８２年鼻咽癌放疗存活５年以上的１０２６例病人中，有１４１例（１３．７％）引起鼻咽癌放疗后颅神经放射损伤（ＲＩＣＮ）。ＲＩＣＮ侵犯后组颅神经者远多于前组颅神经，且１９６９年～１９７２年放疗者的ＲＩＣＮ发病率６．５％（９／１３８），远低于１９７３年～１９８２年放疗者的１４石％（１３２／８８８），（Ｐ＜０．０１）；提示在１９７３年开始采用的上颈前切野，与耳前野在下颌角处的重叠增高了颈动脉鞘区的剂量，从而导致后组颅神经经过的颈动脉鞘区域的放射性纤维变化和ＲＩＣＮ。等剂量曲线图显示不仅在颈动脉鞘区有过高的总剂量，而且因每次轮流只用一侧耳前野照射中线剂量２００ｃＧｙ，而使当天受照侧的颈动脉鞘区的分割剂量（３１２ｃＧｙ）远高于当天未受照侧（１５４ｃＧｙ）。此外，因射线束的发散效应和上述两相邻野的照射体位不相同，以致在野重叠处挡铅也不能完全消除颈动脉鞘区的高剂量。建议停用上颈前切野以降低ＲＩＣＮ发病率。

AbstractIn order to assess the cause of RIC H in NPcpatients after radiotherapy, 141 patients withRICH in 1026 NPC patients (13.7%)survived over 5 years after radiotherapy by telecobaIt treated1969-1982 were analyzed. The last four cranial nerves were commonly affected.Due to thedifference between the radiation techniques used 1969-1982,the incidence of RICH was different: 6.5%(9/138)for patients treated 1969-1972 and 14.9%(132/888),1973.1982 (P<0.05).Since 1973,anterior upper neck tangential portals plus preauricular portals were used which suggested thatoverlap of the two field combination in the submandibular angle might have caused the overdosagein the carotid sheath space. The isodose curves also revealed that not only was there totaloverdosage in the carotid space, but also much higher fractional dose on each side alternatively.