讨论,1.安全性方面:PORT-C研究显示PORT是安全可行的。接受放疗的150例患者无严重毒副反应发生,仅1例3度放射性肺炎发生,这归功于现代放疗技术。PORT-C研究中的≥2度放射性肺炎(6%)和≤2度放射性食管炎(36.6%)均低于文献报道(文献报道分别为19%和50.7%)。这与研究中绝大多数患者采用IMRT(89.3%)相关。另外一个原因是研究中对危及器官的严格剂量限制。统计发现,研究中放疗患者平均肺剂量和肺V20仅为9.63Gy和16.73%.此外,CTV未包括对侧纵隔和锁骨上区域,同样使得危及器官受量很大程度上减低。放疗剂量选择50Gy也使得放疗毒副反应得到很好控制。
2.局部复发风险:pN2 NSCLC具有高局部区域复发风险(35%-60%),使用3D-CRT/IMRT技术进行PORT,可以保证放疗靶区的剂量充足,对局部控制作用较大。不过,PORT-C研究及Lung ART研究得到一致结论:尽管PORT可以降低LR,但均未显著改善DFS和OS。毕竟放疗还是属于局部治疗,主要解决局部问题,减少局部复发,而非系统性全身治疗;因此,单纯的术后放疗在未来人群的选择和探索,可能还是在于解决局部切除或淋巴结清扫不完全的患者。
3.随访重要性:PORT-C研究中观察组的OS远远高于预期,与PORT组OS相当,这可能与强化随访策略和有效的挽救治疗手段相关。严格的随访策略可以早期识别肿瘤复发从而及时进行挽救治疗,包括挽救性的放疗,这在临床实践上也是非常可行的。
4.本研究局限性:PORT-C研究最大的局限性就是患者随机后的依从性相对较差,尤其PORT组有高达21.7%的患者最终并未行PORT,而观察组有5.6%的患者实际接受了PORT。这无疑使得mITT分析中检测PORT带来DFS获益的难度加大。其次,单中心研究也是PORT-C研究的局限性之一。最后,入组时间长达8年,期间综合治疗有所改善,如对于EGFR敏感突变的患者,在辅助治疗或挽救治疗时,使用EGFR TKIs比化疗更加有效,这可能掩盖PORT的作用,而在PORT-C研究最初设计时并不能顾及到。
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