儿童癌症幸存者中风机率较高

　　November 24, 2006 — 第一个检验儿童癌症幸存者晚期发生中风风险的研究显示，成功治愈脑瘤或急性白血病，这两种儿童最常见癌症的儿童，晚期发生中风的机率较高。
　　
　　位于达拉斯的德州大学西南医学中心的研究者表示，罹患脑瘤儿童发生中风的机率为3.4%，但是接受颅内放射线疗法（CRT）与化学疗法的病患，中风机率上升到6.5%；而罹患白血病的儿童，中风机率为0.8%，其兄弟姐妹发生中风机率为0.2%。
　　
　　主要研究者Daniel Bowers医师在一项声明中表示，许多人认为，你已经脱离癌症5年，你已经被治愈了，你可以好好地过接下来的生活，但是这些病患突然发生癌症与其治疗所带来的并发症。
　　
　　这项试验结果发表于11月20日的临床癌症期刊(Journal of Clinical Oncology)。
　　
　　【癌症治疗所带来的影响】
　　根据研究者表示，该试验有三个目的：
　　* 为了估计被诊断白血病与脑部肿瘤5年后存活者发生中风的机率（晚期发生中风）
　　* 比较白血病与脑部肿瘤存活者及其兄弟姐妹得到晚期中风的机率
　　* 为了评估特定治疗方式与晚期中风之间的关系
　　
　　透过儿童癌症存活者研究（CCSS）的数据，研究者针对一群大型且不同族群的癌症幸存者，分析其因为癌症治疗而发生晚期中风的情形，共收纳了4,828位白血病及1,871位脑瘤幸存者；除此之外，同时评估随机采样之3,846位癌症幸存者兄弟姐妹的中风发生率。
　　
　　整体而言，37位白血病与63位脑瘤幸存者发生晚期中风，定义为发生于癌症诊断5年之后；白血病幸存者发生晚期中风机率为每10万人每年57.9次，而脑瘤幸存者为每10万人每年267.6次。
　　
　　相较之下，这些癌症幸存者之兄弟姐妹发生中风的机率为每10万人每年8.0次。
　　
　　当研究者根据癌症病患所接受的治疗分类进行分析，他们发现接受超过30葛雷以上颅内放射线疗法儿童发生晚期中风机率较高。
　　
　　【CRT剂量反应关系】
　　此外，作者表示放射线疗法剂量与中风机率之间有剂量反应关系，接受50葛雷以上放射线疗法的幸存者，相较于接受30至49葛雷病患，其发生中风风险较高；相对的，低剂量的CRT，剂量自10至29葛雷，相较于未接受CRT治疗，并不会增加中风风险。
　　
　　然而，作者指出，未接受CRT的白血病与脑瘤幸存者，相较于其血缘关系兄弟姐妹，发生晚期中风仍然是显著地较高。
　　
　　根据Bowers博士表示，目前有希望减少使用放射线疗法的趋势，为了要降低与放射线疗法有关的学习障碍；Bowers博士指出，这样的倡议对于这群病患发生中风是否会有影响是很有趣的。
　　
　　作者表示，这项试验结果支持降低白血病与脑瘤治疗疗程放射线疗法剂量的努力。

Stroke Risk Increased in Pediatric Cancer Survivors

By Caroline Cassels
Medscape Medical News


November 24, 2006 — The first study to examine late-occurring stroke risk in pediatric cancer survivors has found that children who have been successfully treated for brain tumors or acute lymphoblastic leukemia — the 2 most common childhood cancers — are at significantly increased risk of stroke in later life.

Researchers from University of Texas Southwestern Medical Center at Dallas, Texas, report that among children with brain tumors the stroke rate was 3.4%, but among patients treated with both cranial radiotherapy (CRT) and chemotherapy, the rate was as high as 6.5%. Among children with leukemia, the stroke rate was 0.8%; among their siblings the rate was 0.2%.

"Many people think, 'You're 5 years out from your cancer, you must be cured, and you can get on with the rest of your life.' But these patients suddenly develop a new complication of the cancer and its treatments," said principal investigator Daniel Bowers, MD, in a statement.

The study was published in the November 20 issue of the Journal of Clinical Oncology.

Impact of Cancer Treatment

According to the investigators, the study had 3 aims:

To estimate the incidence rate of stroke among leukemia and brain-tumor survivors 5 years or more after the diagnosis of cancer (late-occurring stroke)

To compare the rate of late-occurring stroke between leukemia and brain-tumor survivors and their siblings

To assess the association of specific treatments of late-occurring stroke.
Using data from the Childhood Cancer Survivor Study (CCSS), investigators analyzed stroke as a late effect of cancer treatment in a large and diverse cohort of cancer survivors, which included 4828 leukemia survivors and 1871 brain-tumor survivors. In addition, the occurrence of stroke was assessed in a random sample of 3846 cancer survivor siblings.

In total, 37 leukemia and 63 brain-tumor survivors had a late-occurring stroke, defined as a stroke that occurred 5 years or more after cancer diagnosis. The rate of late-occurring stroke for leukemia and brain-tumor survivors was 57.9 per 100,000 person-years and 267.6 per 100,000 person-years, respectively.

In comparison, the sibling group had a rate of stroke of 8.0 per 100,00 person-years.

When researchers analyzed the cohort according to the type of cancer treatment individuals received, they found an increased risk of late-occurring stroke, particularly in children treated with cranial radiotherapy at dose greater than 30 Gy.

CRT Dose Response

In addition, the authors report that there was a dose-response relationship between radiation-therapy dose and risk for stroke. "Survivors treated with CRT greater than 50 Gy had a significantly greater risk for stroke in comparison with those treated with 30 to 49 Gy," they write.

In contrast, lower-dose CRT, ranging from 10 to 29 Gy, was not associated with an increased risk, compared with no CRT.

However, the authors note that among both leukemia and brain-tumor survivors who did not receive CRT, "the risk of late-occurring stroke remained significantly increased, albeit modestly, compared with the sibling comparison group."

According to Dr. Bowers, there is an ongoing trend to try to minimize the use of radiation therapy, a move designed to lessen the learning problems associated with radiation therapy.

Dr. Bowers said it would be interesting to determine whether this initiative would also have an impact on the occurrence of stroke in this patient population.

This study, the authors write, "justifies efforts to continue to reduce radiation doses among both leukemia and brain-tumor treatment regimens whenever practical."

J Clin Oncol. 2006;24:5277-5282.