PURPOSE Stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR) has been shown to increase survival rates in oligometastatic disease (OMD), but local control of colorectal metastases remains poor. We aimed to explore the natural course of oligometastatic colorectal cancer and to investigate how SBRT of lung metastases can delay the progression to polymetastatic disease (PMD). METHODS 107 lung oligometastases in 38 patients were treated with SBRT at a single institution. The median number of treated lesions was 2 (range 1-5). Time to PMD (ttPMD) was defined as the time from SBRT to the occurrence of >5 new metastases. Genetic biomarkers such as EGFR, KRAS, NRAS, BRAF, and microsatellite instability were investigated as predictive factors for response rates. RESULTS Median follow-up was 28 months. At median follow-up, 7 patients were free from disease and 31 had progression: 18 patients had sequential oligometastatic disease (SOMD) and 13 polymetastatic progression. All SOMD cases received a second SBRT course. Median progression-free survival (PFS) was 7 months (range 4-9 months); median ttPMD was 25.8 months (range 12-39 months) with 1‑ and 2‑year PFS rates of 62.5% and 53.4%, respectively. 1‑ and 2‑year local PFS (LPFS) rates were 91.5% and 80%, respectively. At univariate analysis, BRAF wildtype correlated with better LPFS (p = 0.003), SOMD after primary SBRT was associated with longer cancer-specific survival (p = 0.031). Median overall survival (OS) was 39.5 months (range 26-64 months) and 2‑year OS was 71.1%. CONCLUSION The present results support local ablative treatment of lung metastases using SBRT in oligometastatic colorectal cancer patients, as it can delay the transition to PMD. Patients who progressed as SOMD maintained a survival advantage compared to those who developed PMD.

中文翻译：

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立体定向放疗治疗肺部少转移性大肠癌的病程。

目的已证明立体定向放射疗法（SBRT）或立体定向消融放射疗法（SABR）可以提高少转移性疾病（OMD）的存活率，但是对结直肠转移的局部控制仍然很差。我们旨在探讨少转移性结直肠癌的自然病程，并研究肺转移的SBRT如何延缓向多转移性疾病（PMD）的发展。方法38例患者中107例肺部低聚转移在单一机构接受SBRT治疗。治疗病变的中位数为2（范围1-5）。达到PMD的时间（ttPMD）被定义为从SBRT到发生> 5个新转移的时间。研究了诸如EGFR，KRAS，NRAS，BRAF和微卫星不稳定性之类的遗传生物标记物作为反应率的预测因素。结果中位随访时间为28个月。在中位随访时，7例患者无疾病且31例进展，其中：18例继发性低转移性疾病（SOMD）和13例多转移性进展。所有SOMD案例都接受了第二次SBRT课程。中位无进展生存期（PFS）为7个月（4-9个月）；ttPMD中位数为25.8个月（范围为12-39个月），其中1年和2年PFS率分别为62.5％和53.4％。1年和2年本地PFS（LPFS）的比率分别为91.5％和80％。在单变量分析中，BRAF野生型与较好的LPFS相关（p = 0.003），初次SBRT后的SOMD与更长的癌症特异性生存率相关（p = 0.031）。中位总体生存期（OS）为39.5个月（范围26-64个月），两年生存期为71.1％。结论本研究结果支持在少转移性结直肠癌患者中使用SBRT局部消融治疗肺转移，因为它会延迟过渡到PMD。与发生PMD的患者相比，进展为SOMD的患者保持了生存优势。