The opinion of the court was delivered by: Amy J. St. Eve, District Court Judge:
MEMORANDUM OPINION AND ORDER
Plaintiff Jo Belle Baldonado was diagnosed with breast cancer while
she was taking Prempro, a prescription hormone therapy medication that
Defendant Wyeth designed, manufactured, and marketed.*fn1
Alleging that Prempro caused her breast cancer, Plaintiff
filed the present civil action against Defendant and others. In
advance of trial, Defendant moves to exclude the expert testimony of
Dr. Elizabeth Z. Naftalis, M.D., Plaintiff's designated specific
causation expert. The Court held a Daubert hearing on May 10, 2012,
during which Dr. Naftalis offered extensive testimony. Based on Dr.
Naftalis' testimony, considered together with the parties' briefs and
the record, the Court denies Defendant's motion to exclude Dr.
Naftalis' expert testimony in its entirety.
On May 27, 2003, Plaintiff commenced this action against Defendant and others in the Circuit Court of Cook County, Illinois, alleging that Defendant's hormone therapy products caused Plaintiff to develop breast cancer. In her Amended Complaint, Plaintiff asserts claims including negligence, strict products liability, failure to warn, breach of express warranty, negligent misrepresentation, fraud, and gross negligence. (R. 1 at 15-57, Am. Compl.*fn2
Defendant removed the action to federal court on June 28, 2004 on the basis of diversity of citizenship. See 28 U.S.C. §§ 1332, 1441, 1446. (R. 1at 1-7, Not. of Removal.) Thereafter, on July 27, 2004, Defendant filed an Answer to the Amended Complaint, denying that Defendant's products caused Plaintiff's breast cancer and contending that the products were appropriately tested, labeled, and marketed. (R. 9, Answer.)
On September 8, 2004, the Judicial Panel for Multidistrict Litigation (the "MDL Panel") conditionally transferred this action to the United States District Court for the Eastern District of Arkansas (the "MDL Court"), pursuant to 28 U.S.C. § 1407, for coordinated and consolidated pretrial proceedings with over two hundred similar hormone therapy actions. (R. 13, Conditional Transfer Order at 1 (citing In re Prempro Prods. Liab. Litig., 254 F. Supp. 2d 1366 (J.P.M.L. 2003) (designating transferee court for individual, class action, and other federal cases arising out of the sale or use of prescription hormone therapy medications)).) Following more than seven years of litigation in the MDL Court, the MDL Panel remanded the action to this District on January 26, 2011, pursuant to 28 U.S.C. § 1407. The case was reassigned to this Court on January 25, 2012. A jury trial is scheduled for October 9, 2012.
Hormones are "chemicals formed in one part of the body that circulate  and attach to particular receptors on or within certain other parts of the body." (R. 146, Ex. 30, Decl. & Expert Report of Dr. Elizabeth Z. Naftalis, M.D. ("Expert Report") at 9.) By attaching to receptors, hormones deliver "message[s]" and can "alter the structure and or function of the organ." (Id.) The primary female hormones are Estrogen ("E") and Progesterone ("P"). (Id.) The levels of these hormones fluctuate throughout a woman's life. (Id.)
From puberty through her child-bearing years, a woman is considered to be premenopausal. (Id.) During this time, a woman's hormones "fluctuate monthly in a regular cycle to prepare the woman's body for the possibility of conception." (Id.) This cyclical fluctuation begins to change when a woman approaches menopause, usually between the age of 45 and 55. (Id. at 9-10.) "Menopause is defined typically in the medical literature as a year cessation of periods, when a woman reaches an appropriate age or perhaps has a surgical menopause where the ovaries are removed." (Transcript of Daubert Hearing on Dr. Naftalis ("Hr'g Tr.") at 82.)
The period immediately preceding menopause is called perimenopause. (Id.) During perimenopause, a woman's ovaries "begin to shut down" (Expert Report at 10), and she may experience any number of symptoms, including irregular cycling, irregular bleeding, surges of hormones, hot flashes, night sweats, urinary incontinence, vaginal dryness, vagina atrophy, mood swings, sleeplessness, and restlessness. (Id. at 10-12; Hr'g Tr. at 83, 88, 90.) These symptoms often result from declining hormonal levels, and will range from minor to severe depending on the individual. (Expert Report at10-12.) Many of the symptoms "will come and go" because the women's ovaries are "sputtering out" and will "have periods where they will be able to produce enough hormones to have a regular menstrual cycle[, and periods where the] woman may not have a cycle for two to three months because her ovaries can't produce the hormones." (Hr'g Tr. at 81-85.) A woman's hormonal levels therefore will fluctuate during perimenopause. (Id.)
Although women will experience a decrease in hormonal levels during perimenopause, "the degree of this reduction is highly variable" across the female population. (Expert Report at 10.) Some women become "hormone deficient," a term that refers to "a subset of menopausal women who have such low levels of estrogen and progesterone that they experience symptoms." (Id.) Most women, however, will maintain sufficient levels of estrogen "such that they do not experience significant menopausal symptoms." (Id. at 12.)
The medical term "cancer" describes "a class of diseases that occurs when cells in a part of the body begin to grow out of control." (Id. at 15; see also Hr'g Tr. at 9 ("an uncontrolled growth that can spread outside of the tissue of origin to other parts of the body").) Although "normal cells divide and grow in an orderly fashion, . . . cancer cells do not." (Expert Report at 15.) Instead, "[t]hey continue to grow and crowd out normal cells." (Id.)
The medical term "breast cancer" refers to a subset of cancers "in which a malignant tumor starts from cells in the breast tissue." (Id.) According to Dr. Naftalis:
A woman's breast is made up of glands that make breast milk called lobules. There are ducts, which are the small tubes that carry milk from the lobules to the nipple. There are also fatty and connective tissue, blood vessels, and lymph vessels. Most breast cancers begin in the cells that line the ducts, some begin in the lobules, and a small number start in other tissues. (Hr'g Tr. at 15.)
Breast cancer is "a multi-step process that begins when the normal and orderly process of cell division and controlled cell death goes wrong." (Expert Report at 16.) Most breast cancers progress through a "series of mutations or changes at the cellular level as the tumor changes from benign to malignant." (Id.)
The first step, called "initiation," is the development of the first abnormality in the breast. (Id. at 28 ("[I]nitiation refers to the process whereby the carcinogens damage the cell DNA directly, leading to a series of mutations which may eventually result in the development of cancer decades later."); Hr'g Tr. at 20, 23-24, 206.) At this stage, "the cell can appear to look normal, but it can have an abnormality in its DNA." (Hr'g Tr. at 21.) In the majority of cases, doctors do not know "what causes that first abnormality or first [DNA change] in the initial cell" (id.), although science has identified numerous risk factors. (Expert Report at 15.)
The second stage, called "promotion," is the addition of "a second stimulus to this abnormal cell[, which causes] the abnormal cell to grow and divide." (Hr'g Tr. at 21-22, 206.) As Dr. Naftalis explained in her expert report:
Promotion refers to a process by which the carcinogen causes an increase in cell division and proliferation so that abnormal and even premalignant cells in the breast grow and divide more rapidly. This rapid cell division leads to an increased opportunity for additional mutations or mistakes in those cells, thereby pushing those abnormalities down the path towards cancer. Once the cells become cancerous, this same proliferative effect will stimulate the cancer to grow larger and continue to evolve and mutate, potentially towards metastatic disease.
(Expert Report at 28-29.)
Doctors typically classify breast cancers across two dimensions: histological type and receptor status. (Id. at 16.) Histological type refers to the type of cellular tissue that became cancerous. (Hr'g Tr. at 9-12.) There are three histological types of breast cancer: lobular, ductal, and special, including papillary. (Id.)
Receptor status refers to whether the cancer is hormone receptor positive ("hormone-dependent") or hormone receptor negative ("hormone-independent"). (Expert Report at 16.) "If a tumor is hormone receptor positive, that means it needs or needed hormones to grow." (Hr'g Tr. at 12.) Hormone dependent cancers may have estrogen receptors ("ER") and/or progesterone receptors ("PR"). (Id. at 201-02; Expert Report at 39.) In a hormone-dependent cancer, the hormones will "bind to the [hormone] receptor and cause changes within the cell." (Hr'g Tr. at 17; see also Expert Report at 18 ("The progesterone receptor is created when estrogen binds to the estrogen receptor").) This will occur with ER cancers regardless of whether the estrogen is endogenous (natural) or exogenous (external). (Hr'g Tr. at 19 ("The receptor can't differentiate between endogenous or exogenous hormones.").) Ascertaining the receptor status of a cancer is important for both prognosis and treatment. (Id. at 55.) Doctors typically treat hormone-receptor positive cancers with anti-hormonal therapies. (Id.)
For many woman, menopause will act "like a natural barrier to their risk of getting breast cancer" because they will lack sufficient hormones to promote the development of pre-existing abnormalities that are "hormonally sensitive." (Expert Report at 20.) As Dr. Naftalis writes, "[i]n women who become hormone deficient as they enter menopause and who do not take combination hormone therapy, any hormone sensitive lesions in the breasts would be expected to stop growing and even regress as the available hormone source was removed." (Id. at 21.)
C. Defendant's Menopausal Hormone Therapy Products*fn3 For more than fifty years, Defendant has promoted menopausal hormone therapy ("HT") products to treat the symptoms associated with menopause. (See Am. Compl. ¶¶ 12-13; see also Answer ¶¶ 12-13.) Defendant's earliest HT product was Premarin, "a conjugated equine estrogen [("CEE")] made from the urine of pregnant mares." (See Am. Compl. ¶ 12; see also Answer ¶ 12.) According to Plaintiff, after Defendant received approval for Premarin in 1942, Defendant marketed the drug as a "replace[ment for] the natural female hormone estrogen." (Am. Compl. ¶ 12.) By the mid-1970s, "more than 30 million prescriptions for Premarin were being written every year," eventually making it the "fifth most frequently prescribed drug in the United States." (Id. ¶ 20; see also Answer ¶ 20 ("many women took estrogen in the 1970s").) Sales of Premarin, however, soon "plummeted" after two articles in the New England Journal of Medicine "linked estrogen therapy to a significantly increased risk of women developing endometrial cancer." (Am. Compl. ¶ 21.)
In 1979, an article in the Journal of the American Geriatrics Society reported that "'estrogen related uterine cancer can be avoided if progesterone is added to the regimen.'" (Id. ¶ 22.) Defendant and others "immediately started promoting" hormone therapy that combined estrogen ("E") and progesterone ("P"). (Id. ¶ 23.) In that regard, Defendant "developed a synthetic hormone product called Medroxyprogesterone Acetate [("MPA"]) that was marketed under the brand name Provera." (Id.) Provera "does not have the same chemical or pharmacological effect as the natural hormone progesterone." (Id.) From the mid-1980s until 1995, "a common combination prescription was the use of Premarin with Provera." (Id.) Premarin "became the most frequently dispensed prescription drug in the United States." (Id. ¶ 28.)
In 1994, Defendant received approval for "combination hormone therapy in a single pill" that it marketed under the brand name Prempro. (Id. ¶ 31; see also Answer ¶ 31.) Prempro is an oral medication that "combines the estrogenic compound CEE with the progestin MPA in a single pill taken one time per day." (Am. Compl. ¶ 31; see also Answer ¶ 31.) Because Prempro combines estrogen ("E") with progestin ("P"), many refer to the medication as "E." (See, e.g., Expert Report at 7.) Defendant continues to sell Prempro today. (R. 118 at 9 & Ex. 26.)
D. Plaintiff's Medical History and Use of Hormone Therapy
Plaintiff Jo Belle Baldonado, a woman born in 1947, had her first menstrual period at the age of 11. (R. 115, Ex. 2 at 5, 18.) In 1989, Plaintiff had a baseline mammogram that revealed moderately dense breasts, but was otherwise "normal." (Expert Report at 4.) Between 1991 and 1994, Plaintiff began to experience menopausal symptoms including irregular periods and night sweats. (Hr'g Tr. at 82-85.) She also experienced amenorrhea from August of 1993 to January of 1994, a heavy period in January of 1994, and regular periods from January until June of 1994. (Id. at 88-89.) Her mammograms during this time remained unchanged. (Expert Report at 4.)
On September 14, 1994, Dr. Mani Akkineni saw Plaintiff as a new patient, and noted that Plaintiff experienced periodic menopausal symptoms, including hot flashes, night sweats, and irregular periods. (Id.; Hr'g Tr. at 90-91.) Dr. Akkineni characterized Plaintiff as a "perimenopausal patient" who might consider estrogen replacement therapy. (Hr'g Tr. at 89.)
At this time, a blood test showed that Plaintiff had an Estradiol level at 141. (Id. at 177; Expert Report at 5.)
By January 17, 1995, Plaintiff was prescribed and taking Provera to "help her cycles become regular, since she was having irregular cycles and she also had a thickened uterine lining." (Hr'g Tr. at 93; see also id. at 77.) While on Provera, Plaintiff continued to experience menopausal symptoms and on September 25, 1996, reported to Dr. Teresita Avila that she was "very uncomfortable with hot flashes." (Id. at 92; Expert Report at 5.) On April 29, 1996, a medical record states that Plaintiff's primary care physician believed that she "needs HRT." (Expert Report at 5; see also Hr'g Tr. at 92.) At that point, Plaintiff had not had a period for the past four months, and she reported that her hot flashes were becoming "terrible." (Hr'g Tr. at 92.) Plaintiff continued to take Provera until May of 1996, when Plaintiff switched to Prempro to help alleviate her menopausal symptoms. (Id. at 78, 92-93.)
On September 12, 1996, Dr. Akkineni prescribed Prempro to Plaintiff, observing that Plaintiff "has been doing a lot better since she has been on ERT." (Id. at 94.) On November 17, 1997, Plaintiff saw Dr. Avila for an annual exam, and Dr. Avila noted that Plaintiff is "still taking her Prempro and is doing fine on it." (R. 186, Ex. 43 at 14.) Dr. Avila ...