Levitating human sperm--an Adman's dream.

REFERENCES 1. Staffa JA, Newschaffer CJ, Jones JK, Miller V. Progestins and breast cancer: an epidemiological review. Fertil Steril 2. Grimes DA. Progestins, breast cancer, and the limitations of epidemiology. Fertil Steril 1992;57:492-4. 3. Sturtevant FM. Breast cancer and oral contraceptives: cri- tique of the proposition that high potency progestagen prod- ucts confer excess risk. Biomed PharmacoI1984;38:371-9. 4. Swyer GIM. Potency ofprogestogens in oral contraceptives- further delay of menses data. Contraception 1982;26:23-7. 5. Edgren RA, Sturtevant FM. Potencies of oral contraceptives. Am J Obstet Gynecol 1976;125:1029-38. Reply of the Authors: We thank Professor Sismondi and associates for their most interesting letter. We appreciate the ad- ditional information based on their current research on potential mechanisms whereby certain progestins may cause breast cancer, in conjunction with or in- dependent of estrogens. Such basic research is cru- cial not only for deciphering the sometimes confus- ing results of previous epidemiologic studies but for aiding in the optimal design of future studies. For example, if an intermediate growth factor or hor- mone were implicated in a causal pathway (such as sex hormone-binding globulin, serum insulin-like growth factor I, or serum growth hormone as dis- cussed by Sismondi and associates), then measure- ment ofthis factor directly, in addition to exogenous hormone dose, would be necessary to explore this relationship in large populations. We would also like to thank Dr. Edgren for his response to our review, as it addresses what we be- lieve to be one of the key methodological issues in studying the relationship between progestins, as a therapeutic 'class, and breast cancer. However, we would like to take this opportunity to clarify two comments made by him. First, Dr. Edgren asserts that we have con- tinue[d] the now discredited concept that ethynodiol diacetate, the progestagen in Demulen, is a high po- tency progestagen. Although we did describe two epidemiologic studies that both classified ethynodiol diacetate as a high potency progestin and found an association between products containing this drug and breast cancer (1, 2), we did not intentionally infer support of this concept; rather, we presented the classification of progestins as a major weakness ofthe Pike study. Indeed, in our introductory section on Progestins, we discussed the different types of potency testing and the fact that potencies of pro- gestins vary by type of potency studied, the test used Letters-to-the-editor to determine potency, the species of animal tested, and the presence or absence of estrogens (3). In this discussion, we tried to convey the view that the methods used to determine potency are not without variation or controversy; a point also made very clearly by Dr. Edgren. Second, Dr. Edgren states that we advocate the use of single numbers for potency of combination oral contraceptives. Again, because our purpose was to review previous studies, we described studies where such classification was used and briefly dis- cussed the controversy surrounding the determi- nation of relative potencies of progestins, with and without progestins. An in-depth discussion, we felt, was beyond the scope of our paper, but an excellent review of this topic is available, as was indicated by Dr. Edgren (4). We agree with Dr. Edgren's view- point that each progestin and progestin-estrogen combination should ideally be considered as a dis- tinct exposure in epidemiologic studies and further point out the need for baseline information regarding endogenous hormone levels before drug administra- tion to further understand varying impact of that exposure between individuals. Judy A. Staffa, M.S., R.Ph. Judith K. Jones, M.D., Ph.D. The Degge Group, Ltd. Drug Safety, Research and Information Arlington, Virginia August 12, 1992 REFERENCES 1. Pike MC, Henderson BE, Krailo MD, Duke A, Roy S. Breast cancer in young women and use of oral contraceptives: pos- sible modifying effect of formulation and age at use. Lancet 2. Stadel BV, Lai S, Schlesselman JJ, Murray P. Oral contra- ceptives and premenopausal breast cancer in nulliparous women. Contraception 1988;38:287-99. 3. Staffa JA, Newschaffer CJ, Jones JK, Miller V. Progestins and breast cancer: an epidemiologic review. Fertil Steril 4. Edgren RA, Sturtevant FM. Potencies of oral contraceptives. Am J Obstet Gynecol 1976;125:1029-38. Levitating Human Sperm-An Adman's Dream To the Editor (Letter 1 of 2): We would like to refer to the article by Blanchet et al. (1). As the group who pioneered laser micro- manipulation of gametes, we are pleased to see more studies that might elucidate the complexity of light Fertility and Sterility