网络上找到这一篇文章，把这件事讲的满清楚的。
连结在此
http://www.quackwatch.com/01QuackeryRelatedTopics/Cancer/laetrile.html
节录其中一段关于NCI(National Cancer Institute)做的临床研究
In July 1980, the NCI undertook clinical trials of 178
cancer patients who received Laetrile, vitamins and enzymes
at the Mayo Clinic and three other prominent cancer
centers. The study included patients for whom no other
treatment had been effective or for whom no proven
treatment was known. All patients had tumor masses that
could easily be measured, but most of the patients were in
good physical condition. Since Laetrile proponents were
unable to agree on the formula or testing protocol for
Laetrile, NCI decided to use a preparation that
corresponded to the substance distributed by the major
Mexican supplier, American Biologics. The preparation was
supplied by the NCI Pharmaceutical Resources Branch and
verified by a variety of tests. The dosage of Laetrile was
based on the published recommendations of Krebs, Jr., and
the Bradford Foundation.
The results of the trial were clear-cut. Not one patient
was cured or even stabilized. The median survival rate was
4.8 months from the start of therapy, and in those still
alive after seven months, tumor size had increased. This
was the expected result for patients receiving no treatment
at all. In addition, several patients experienced symptoms
of cyanide toxicity or had blood levels of cyanide
approaching the lethal range [8]. An accompanying editorial
concluded:
简单的解释一下这段，1980年8月， NCI找了178名自愿的癌症病患
来做杏素治疗的临床试验，这些病人包括了一些其他疗法都无效的
病患，这些病患的肿瘤都已经发展至足以量测的大小，且身体条件
良好。给予病患服用的剂量则按照Krebs, Jr.的建议。
试验的结果相当清楚，没有任何一个病患是痊愈的，甚至没有人出
现病情稳定的结果。这些病患的存活时间的中位数是4.8个月(从开
始接受疗程算起)，少数人可以活到7个月后，不过肿瘤的大小也成
长了。这样的结果和未受任何疗程下的预期结果差不多。此外，有
数位病患出现氰中毒或是血中氰化物浓度过高的现像。