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Journal of Clinical Oncology, Vol 24, No 19 (July 1), 2006: pp. 3215-3216 © 2006 American Society of Clinical Oncology. DOI: 10.1200/JCO.2006.06.2695
Important Bias in the Astragalus Meta-AnalysisCenter of Natural Medicine, S. Giuseppe Public Hospital, Empoli, Italy To the Editor: We have some important remarks in response to the recently published meta-analysis about Astragalus-based Chinese herbs by McCulloch et al,1 which concludes that Astragalus may increase effectiveness of platinum-based chemotherapy in advanced non–small-cell lung cancer. We think that just to write Astragalus is too simple, as it is a generic botanical name. There are many species of Astragalus: McCulloch et al could be referring to A. aleppicus, A. echinus, or A. gummiferus. In the articles considered in their meta-analysis, McCulloch et al do not describe which part of the plant was used (entire plant, only the roots, the flowers or leaves) and which type of extract was administered to patients (a total extract, a decoction of any part of the plant, or a standardized and purified extract). In addition, most of the remedies considered were generic Astragalus-based preparations and were administered mixed with many other plants (17 other herbs in total). What was the percentage of Astragalus content? We think these are important issues that cannot be determined by considering only a statistical analysis, and in our opinion the lack of precise and reliable data from which such an analysis starts could be considered an important bias. McCulloch et al1 cite some articles in their introduction that show the immune stimulating activity of Astragalus membranceus Fisch, whose major chemical constituents seem be triterpene saponins (astragalosides I-X and isoastragalosides I-V) and polysaccharides (eg, astragalan, astraglucan),2 which are secondary metabolites biologically active contained in the roots. However, not all the plants in the genus Astragalus are rich in these substances, which have potential pharmacologic properties. Some plants of the genus Astragalus contain flavonoids that can modify the pharmacokinetic and pharmacodynamic of drugs administered to patients, such as ciclophosphamide3 or paracetamol,4 and polysaccharides which can have hypoglicemic effect.5 It is not easy to do a meta-analysis on herbs, but we think that researchers should choose to study the same genus of a plant, and should include only the same species, in this case, Astragalus membranaceus Fisch, the particular part of the plant used (leaves, root or entire plant), and the same type of extract (decoctions, mother tincture, fluid extract, or dry extract titrated in active principles).6 Authors' Disclosures of Potential Conflicts of Interest The authors indicated no potential conflicts of interest. REFERENCES
1. McCulloch M, Cylie S, Xiao-juan S, et al: Astragalus-based Chinese herbs and platinum based chemotherapy for advanced non-small-cell lung cancer: Meta-analysis of randomized trials. J Clin Oncol 24:419-430, 2006 2. WHO: WHO monographs on selected medicinal plants. http://mednet2.who.int/tbs/trm/s2200e.pdf 3. Firenzuoli F, Gori L, Neri E: Clinical phytotherapy: Opportunities and problematics. Ann Ist Super Sanita 41:27-33, 2005[Medline] 4. Wang DQ, Critchley JA, Ding BG, et al: Protection against paracetamol-induced hepatic damage using total flavonoids of Astragalus. Zhongguo Zhong Yao Za Zhi. 26:617-620, 2001[Medline] 5. Wu Y, Ou-Yang JP, Wu K, et al: Hypoglycemic effect of Astragalus polysaccharide and its effect on PTP1B. Acta Pharmacol Sin 26:345-352, 2005[Medline] 6. Firenzuoli F, Gori L, Crupi A, et al: Flavonoids: Risks or therapeutic opportunities? Recenti Prog Med 95:345-351, 2004[Medline]
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Copyright © 2006 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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