Whether the constellation of various symptoms reported in various case-study reports on some patients who have had augmentation mammoplasty with silicone implants reflects a distinct, novel “silicone syndrome”or disease is important to settingproper endpoints for the epidemiological study of this patient population. To date, epidemiology studies on breast implant patients have focused on end-points which are typical of connective tissue disease, rheumatoid disease, and/ or autoimmune disorders. The consensus at this time, as was recently stated in a paper authored by Food and Drug Administration (FDA) personnel, is that the weight of the evidence from existing epidemiology studies is that silicone breast implants do not appreciably, if at all, increase the risk of these types of diseases. Critics of the epidemiology database have countered that had the analysis of association in these studies been done for a “silicone syndrome,” as opposed to the disease types which were analyzed, an association between silicone breast implantation and increased risk of “silicone syndrome” would have been observed. In the present analysis, this question is approached from two directions: First, the available single or multi-patient case reports available in the open literature were evaluated. The objective was to define those symptoms/ complaints that were reported in all studies or in at least 50% of the patients reported and to assign frequency distributions to individual symptoms or complaints reported in breast implant patients presenting for various complaints. By definition, if a “silicone syndrome” exists, then it can only be characterized by those symptoms or complaints which appear with regular frequency in patients so afflicted. Second, the symptoms or complaints which were used as criteria in the existing epidemiology studies were correlated with their frequency of occurrence among single or multi-patient case-reported breast implant patients. The working hypothesis in this present study is that if the number of “silicone syndrome” symptoms or complaints that also are symptoms of the existing epidemiology endpoints is large, then a distinct “silicone syndrome” is not likely to exist, and it can be concluded that existing epidemiology studies have adequately addressed the relevant issues. Also, to the extent that the frequency of symptom occurrence in “silicone syndrome” is similar to the distribution seen for known connective tissue, rheumatoid, and/ or autoimmune diseases, this will then add to the weight of evidence that no distinct “silicone syndrome” needs be postulated. Conversely, if a different set of symptoms or complaints occurs in silicone breast-implanted patients than is seen in patients with connective tissue diseases, this will argue that a distinct syndrome may exist. In the present study, the more recent suggestion that silicone may be broken down to silica in the body, and evidence for and against this suggestion are also discussed. The present analysis does not support the contention that a distinct “silicone syndrome” exists, but does support the contention that the disease endpoints used in existing epidemiology studies are adequate for examining the patient population. Also, consideration of the chemistry of silicone and its potential hydrolysis or oxidative cleavage indicates that if such reactions occur in the body at any significant rate, the product will be silicic acid, a normal and necessary constituent of the body, and not silica (i.e., silicon dioxide).
Making causal inferences in allergy epidemiology studies
