Treatment Outcomes of Re-irradiation Using Stereotactic Ablative Radiotherapy to Lung: A Propensity Score Matching Analysis

立體定向肺消融放療再照射的治療效果:傾向評分匹配分析

Introduction
介紹

The purpose of this study was to compare the treatment efficacy and safety of re-irradiation using stereotactic ablative radiotherapy (SABR) and initial SABR for lung cancer and metastasis.

本研究的目的是比較再照射立體定向消融術(SABR)和初次SABR治療肺癌及轉移的療效和安全性。

Methods
研究方法

A retrospective review of the medical records of 337 patients who underwent lung SABR was performed. Re-irradiation was defined as overlapping of the 70% isodose line of second-course SABR with that of the initial radiotherapy, and 21 patients were classified as re-irradiation group. A median dose of re-irradiation SABR was 54 Gy (range, 48 to 60 Gy), and a median fraction number was 4 (range, 4 to 6). Median time to re-irradiation was 13.7 months (range, 0.36 to 51.6 months). One-to-three propensity score matching was used to compare treatment outcomes and toxicity rate, and 63 patients were included in initial SABR group of matched cohort.

回顧性回顧了337例肺SABR患者的醫療記錄。再照射定義為二期SABR 70%等劑量線與初次放療重疊，21例患者歸為再照射組。再照射SABR的中位劑量為54 Gy(範圍為48 ~ 60 Gy)，中位分數數為4(範圍為4 ~ 6)。中位再照射時間為13.7個月(範圍為0.36 ~ 51.6個月)。使用1 - 3傾向評分匹配來比較治療結果和毒性率，並將63例患者納入配對隊列的初始SABR組。

Results
結果

The median follow-up period of the matched cohort after SABR was 28.0 months (range, 3.48 to 95.8 months). The 1 and 2-year local control rates were 75.2% and 65.2% for re-irradiation group, respectively, and 93.2% and 88.3% for initial SABR group of matched cohort, respectively. The difference was statically significant (p = 0.019). The 1 and 2-year distant control rates were 75.9% and 51.4% for re-irradiation group, respectively, and 72.5% and 60.8% for initial SABR group, respectively. There was no significant difference between two groups (p = 0.93). The crude grade ≥2 toxicity rates were 42.9% for re-irradiation group, and 23.8% for initial SABR group (p=0.163). The 1 and 2-year freedom from grade ≥2 toxicity rates were 57.1% and 57.1% for re-irradiation group, respectively, and 81.6% and 77.8% in initial SABR group, respectively. Marginally significant difference between two groups (p=0.086) was found. In re-irradiation group, one grade 3 toxicity (pulmonary) was reported, and there was no grade 4-5 toxicity.

SABR後匹配隊列的中位隨訪時間為28.0個月(範圍為3.48至95.8個月)。再照射組1年和2年局部控製率分別為75.2%和65.2%，配對隊列初始SABR組1年和2年局部控製率分別為93.2%和88.3%。差異有統計學意義(p = 0.019)。再照射組1年和2年遠處控製率分別為75.9%和51.4%，首次SABR組分別為72.5%和60.8%。兩組間差異無統計學意義(p = 0.93)。粗級≥2級的毒性再照射組為42.9%，初始SABR組為23.8% (p=0.163)。再照射組1年和2年≥2級毒副反應發生率分別為57.1%和57.1%，初始SABR組分別為81.6%和77.8%。兩組間有極顯著差異(p=0.086)。再照射組1例3級毒性(肺)，無4-5級毒性。

Conclusion
結論

The local control rate of in-field re-irradiation SABR was lower than initial SABR. Biological background of the worse outcome needs to be discussed by further research. Toxicities of re-irradiation SABR was manageable.

在再照射SABR的局部控製率低於初始SABR。其生物學背景有待進一步研究探討。再照射SABR的毒性是可控的。