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研究者在一项临床试验中表示，预防性颅内放射线治疗应该是所有对起始化学治疗有反应之小细胞肺癌（SCLC）病患的标准治疗；该项试验结果显示，预防性颅内放疗显著降低脑部转移发生率、与延长免于疾病与整体存活时间。
这项研究由荷兰阿姆斯特丹VU大学医学中心Ben Slotman医师领导，发表于8月16日新英格兰医学期刊上，此结果如同当时Medscape的报告，在今年初曾于美国临床癌症学会年会上发表，同时有其他肺癌专家给予正向评论。
研究员发现，患有SCLC的病患易发生脑部转移，至少有18%的病人在诊断时已发生脑部转移，且两年内的发生率增加至80%；Slotman博士与同事解释，先前的临床试验明确显示，预防性颅内放射线治疗可降低局限性小细胞肺癌脑转移的问题，但还不确定在广泛性小细胞肺癌上所扮演的角色，因此他们研究特殊族群病患且报告说，其研究展现明显的好处。
研究将286位罹患广泛性小细胞肺癌、且对全身性化学疗法有反应的病患，与只接受预防性颅内放射线治疗的病患相比较，经过一年的时间，放射线组病患的脑转移症状显著较低（14.6%比上控制组的40.4%；整体危险比为0.27）；同时，在一年的整体存活率也有较明显的效果（27.1%比上控制组的13.3%；整体危险比为0.68），且延长整体存活率时间达6周。
作者提到，在其研究中值得注意的发现是，相较于控制组，接受颅内放射线治疗仍发生颅外病程的病患较能被治疗（45.1%比上68.0%）；在先前的研究中，仅有42%的病患在疾病发展时适合接受二线的化疗，其余的病患只能接受支持性疗法，他们表示这是可预期的。
有一个未获解决的问题，是辐射治疗的最佳剂量；在美国临床癌症学会年会上，美国密西根州底特律Karmanos癌症中心的Andrew Turrisis博士讨论了此议题，他注意到，研究者使用的剂量比美国常用的8到12分次、每次24到30 Gy还低的幅射剂量，相对的，Slotman博士及其同事表示，大多数病患（88/143），目前接受5次每次20 Gy的剂量，他们的脑转移风险并未显著降低，他们建议，与其浪费资源去讨论剂量问题，应该优先给予这群颅外病程进展率达90%的病患更多的关心。
Prophylactic Cranial Irradiation Should Be Standard for SCLC Responsive to Chemo
By Zosia Chustecka
Medscape Medical News
Prophylactic cranial irradiation should be part of standard care for all patients with small-cell lung cancer (SCLC) who have a response to initial chemotherapy, say researchers reporting a trial showing that this measure significantly reduced the incidence of brain metastases and prolonged disease-free and overall survival.
The study, headed by Ben Slotman, MD, PhD, from VU University Medical Center, in Amsterdam, the Netherlands, is published in the August 16 issue of the New England Journal of Medicine. Results were presented earlier this year at the American Society of Clinical Oncology annual meeting and were commented on favorably by other lung cancer experts, as reported by Medscape at the time.
Brain metastases are common in patients with SCLC, the researchers comment. At least 18% of patients already have brain metastases at diagnosis, and the incidence increases during the course of the disease, up to 80% at 2 years. Previous clinical trials have shown unequivocally that prophylactic cranial irradiation reduces the risk for brain metastases in patients with limited SCLC, but there has been uncertainty over its role in patients with extensive disease, Dr. Slotman and colleagues explain. Hence they studied this specific patient population and report: "Our study shows a clear advantage."
The study, carried out in 286 patients with extensive SCLC who had responded to systemic chemotherapy, compared prophylactic cranial irradiation with no further therapy. After a 1-year follow-up, patients in the radiation group had a significantly lower risk for symptomatic brain metastases (14.6% vs 40.4% in the control group; hazard ratio [HR], 0.27). There was also a significant effect on overall survival at 1 year (27.1% vs 13.3% in the control group; HR, 0.68), with a prolongation of median survival by 6 weeks.
"A noteworthy finding in our study," the authors note, "was that patients with extracranial progression who had also undergone cranial irradiation were more often treated for the progression than those in the control group (68.0% vs 45.1%)." This was more than would be expected, as previous studies have reported that only 42% of patients were suitable for second-line chemotherapy at the time of disease progression, and the remaining patients were suitable only for supportive care, they comment.
One unresolved question that remains relates to the best dose of radiation to use. At the American Society of Clinical Oncology meeting, discussant for the paper, Andrew Turrisis, MD, from the Karmanos Cancer Center, in Detroit, Michigan, noted that the researchers had used less radiation than is commonly administered in the United States, where 24 to 30 Gy in 8 to 12 fractions is common. In contrast, the majority of patients (88/143) in the current study received only 20 Gy in 5 fractions, and yet "an impressive reduction in the risk for brain metastases was still seen," Dr. Slotman and colleagues write. They also suggest that, rather than waste resources on further addressing this question of dose, priority should be given to the "more pressing concern" of the extracranial progression rate of about 90% seen in these patients.
N Engl J Med. 2007;357:664-672.