Materials and Methods

This trial was approved by local human investigations committees or institutional review boards in accordance with assurances filed with and approved by the Department of Health and Human Services. Written informed consent was required for participation in this trial.

To be eligible, women had to be postmenopausal, be at least 35 years old, and have a 5-year predicted risk for breast cancer of at least 1.66%. Breast cancer risk was determined with the Gail model, as modified and applied in the Breast Cancer Prevention Trial (P-1). The details of the STAR/P-2 methodology are described in the initial report of the study. The participants were assigned randomly to receive either 20 mg/d of tamoxifen plus placebo (9736 women) or 60 mg/d of raloxifene plus placebo (9754 women) for 5 years. Because the formulations of tamoxifen and raloxifene tablets were dissimilar, it was necessary to use placebo tablets to maintain the double blinding of treatment assignment. The enrollment period began on June 1, 1999, and ended on November 4, 2004. This report is based on a cutoff date of March 31, 2009.

On enrollment in the NSABP STAR/P-2 trial, the study population consisted of 9456 postmenopausal women with an intact uterus. As in the Breast Cancer Prevention Trial trial, women were monitored for symptoms of hot flashes, vaginal discharge, vaginal dryness, and abnormal vaginal bleeding; the occurrence of numerous gynecologic conditions that were diagnosed during the study period were reported and included endometrial adenocarcinomas, endometrial hyperplasia, leiomyomas, polyps, endometritis, endometriosis, and ovarian cysts. Surgical interventions (such as dilation and curettage, hysteroscopy, laparoscopy, oophorectomy, and hysterectomy) similarly were recorded in the study database.

The χ ² test was used to compare the raloxifene and tamoxifen groups with regard to age, parity, history of oral contraceptive use, history of estrogen therapy, number of relatives with breast cancer, history of diabetes mellitus and hypertension, smoking status, and body mass index. The χ ² test also was used to compare treatment groups by distribution of severity of self-reported symptoms. The analyses of the incidence of gynecologic conditions and surgical procedures mentioned earlier were performed to evaluate the differences between treatment groups. These analyses were based on the determination of risk ratios (RRs) of the incidence rates by treatment group (raloxifene compared with tamoxifen) and the 95% confidence intervals (CIs) on the RR. The incidence rates were calculated as the number of events divided by the person-years at risk. The 95% CIs were determined by the exact method, assuming that the events followed a Poisson distribution, on the condition of the total number of events and person-years at risk.

Results were considered to be statistically significant if the probability value was < .05 or when the 95% CI for the RR did not include 1.00. The date file cutoff that was used for this analysis of March 31, 2009, was chosen to be consistent with that used for the update report of the main findings.

Results

A total 4739 women who received tamoxifen and 4717 women who received raloxifene had an intact uterus on entry ( Figure ). The characteristics of the participants who were included in the current analysis are shown in Table 1 . The groups were similar in baseline characteristics, which included age, parity, body mass index, history of oral contraceptive or estrogen use, family history of breast cancer, diabetes mellitus, hypertension, and smoking status. At a median follow-up period of 81 months, significant differences existed in self-reported bothersome hot flashes ( P < .0001), vaginal discharge ( P < .0001), and vaginal bleeding ( P < .0001) in patients who received tamoxifen, compared with raloxifene ( Table 2 ). Vaginal dryness was more common in patients who received raloxifene ( P < .0001).

CONSORT diagram: National Surgical Adjuvant Breast and Bowel Project P-2

The asterisk indicates that 2 women with bilateral mastectomy before entry and 1 woman with a diagnosis of breast cancer before entry were discovered after random assignment.

Runowicz. Gynecologic conditions in STAR/P-2 trial participants. Am J Obstet Gynecol 2011 .

TABLE 1

Baseline characteristics for women with an intact uterus

Characteristic	Tamoxifen (n = 4739)		Raloxifene (n = 4717)		P value
	N	%	n	%
Age, y a
≤49	237	5.0	233	4.9	.99
50-59	2592	54.7	2584	54.8
60-69	1516	32.0	1515	32.1
≥70	394	8.3	385	8.2
Parity, n
≤1	1252	26.4	1211	25.7	.41
≥2	3487	73.6	3506	74.3
History of oral contraceptive use
No	1501	31.7	1540	32.6	.31
Yes	3238	68.3	3177	67.4
History of estrogen therapy
No	1763	37.2	1823	38.6	.15
Yes	2976	62.8	2894	61.4
Relatives with breast cancer, n
0	1489	31.4	1446	30.7	.22
1	2399	50.6	2404	51.0
2	710	15.0	752	15.9
≥3	141	3.0	115	2.4
History of diabetes mellitus
Yes	241	5.1	227	4.8	.54
No	4498	94.9	4490	95.2
History of hypertension
Yes	1417	29.9	1383	29.3	.54
No	3322	70.1	3334	70.7
Smoking status
Never	2414	50.9	2448	51.9	.29
Former	1860	39.2	1780	37.7
Current	443	9.3	458	9.7
Unknown	22	0.5	31	0.7
Body mass index, kg/m 2 b
<25.0	1619	34.2	1576	33.4	.74
25.0-29.9	1638	34.6	1646	34.9
≥30	1481	31.3	1494	31.7

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