第七章、預防性放射線治療

7.1 預防性腦部照射 (Prophylactic Cranial Irradiation, PCI)

SCLC 患者腦轉移風險極高 (2 年內 >50%) 。PCI 的應用在近年來引發了關於神經毒性的擔憂，NCCN 對此採取了更為細緻的建議。

• 侷限期 (LS-SCLC)：

  • 建議：對於初始治療後達到完全或部分緩解的患者，推薦進行 PCI (Category 1) 。統合分析顯示，在第IIB或第III期SCLC病人手術後使用PCI，能顯著降低三年腦轉移發生率 (33.3% vs 58.6%)。且三年存活率也顯著提升 (20.7% vs 15.3%)。 ⁽²³⁾

  • 例外：對於極早期 (Stage I, T1-2a N0) 接受手術或立體定位放療 (SABR) 的患者，因腦轉移風險相對較低，PCI 的獲益不明確，NCCN 建議可考慮以密切的 MRI 監測 取代 PCI。 ⁽¹⁾

  • 時機：若使用 Durvalumab 鞏固治療，PCI 應在免疫治療開始前完成。 ⁽¹⁾

• 廣泛期 (ES-SCLC)：

  • 爭議：Takahashi等人的第三期試驗顯示，在定期 MRI 監測下，PCI 並未改善中位數存活期 (11.6 個月 vs 13.7 個月, P=0.094) ，且對照組僅在腦轉移出現時才進行補救性放療。 ⁽²⁴⁾

  • NCCN 建議：對於 ES-SCLC 且無腦轉移的患者，可選擇 MRI 監測或 PCI。不再強制推薦 PCI，需與患者討論神經認知風險與潛在獲益。

  • 劑量：若進行 PCI，推薦劑量為 25 Gy 分 10 次。不建議更高劑量 (如 36 Gy) ，因會增加神經毒性與死亡率。

• 神經保護策略：

  • Memantine：NMDA 受體拮抗劑。RTOG 0614 試驗顯示每日服用20 mg memantine其可延緩全腦放療後的認知功能下降 (24週認知功能失調率: 53.8% vs 64.9%, p=0.01)。NCCN 建議在 PCI 或 WBRT 期間及之後使用。 ⁽²⁵⁾

  • 海馬迴迴避 (Hippocampal Avoidance, HA)：NRG CC001 試驗證實 HA-WBRT 能顯著保護認知功能且不影響顱內控制率。NCCN 建議在解剖結構允許的情況下考慮 HA-PCI。 ⁽²⁶⁾

7.2 胸部放射治療 (Thoracic RT) 在廣泛期的角色

對於 ES-SCLC 患者，若化療後胸部殘餘病灶存在但胸外轉移已緩解，是否應進行胸部放療？

• 建議：可考慮進行鞏固性胸部放療 (Consolidative Thoracic RT) ，特別是對於胸外部位腫瘤負荷較低且對化療反應良好的患者。

• CREST 試驗顯示，雖然主要終點 (1 年 OS) 未顯著改善 (33% vs 28%, P=0.066) ，但在次要分析中，2 年 OS 有顯著獲益 (13% vs 3%, P=0.004) ，且顯著降低了胸部復發風險。 ⁽²⁷⁾

結論與展望

1. 侷限期不再僅是放化療的戰場，Durvalumab 鞏固治療的引入 (ADRIATIC 試驗) 是數十年來最大的突破，確立了免疫治療在早期階段的標準地位，有望進一步提高治癒率。

2. 廣泛期的治療策略更加細膩，除了第一線標準的Chemoimmunotherapy外，Lurbinectedin進入一線維持治療 (IMforte 試驗) ，為長期控制提供了新工具。

3. 復發治療迎來了 Tarlatamab 這一革命性的雙特異性抗體，突破了後線治療缺乏有效藥物的困境，為多線治療失敗的患者帶來了顯著的生存希望。

4. 未來的挑戰在於如何最佳化這些新療法的順序 (例如 Tarlatamab 與免疫治療的接續) 、二線療法失效後的新療法、以及降低治療帶來的長期毒性。

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