Tamoxifen Citrate (Page 3 of 12)

Ductal Carcinoma in Situ:

NSABP B-24, a double-blind, randomized trial included women with ductal carcinoma in situ (DCIS). This trial compared the addition of tamoxifen or placebo to treatment with lumpectomy and radiation therapy for women with DCIS. The primary objective was to determine whether 5 years of tamoxifen therapy (20 mg/day) would reduce the incidence of invasive breast cancer in the ipsilateral (the same) or contralateral (the opposite) breast.

In this trial 1804 women were randomized to receive either tamoxifen or placebo for 5 years: 902 women were randomized to tamoxifen 10 mg tablets twice a day and 902 women were randomized to placebo. As of December 31, 1998, follow-up data were available for 1798 women and the median duration of follow-up was 74 months.

The tamoxifen and placebo groups were well balanced for baseline demographic and prognostic factors. Over 80% of the tumors were less than or equal to 1 cm in their maximum dimension, were not palpable, and were detected by mammography alone. Over 60% of the study population was postmenopausal. In 16% of patients, the margin of the resected specimen was reported as being positive after surgery. Approximately half of the tumors were reported to contain comedo necrosis.

For the primary endpoint, the incidence of invasive breast cancer was reduced by 43% among women assigned to tamoxifen (44 cases-tamoxifen, 74 cases-placebo; p=0.004; relative risk (RR)=0.57, 95% CI: 0.39 to 0.84). No data are available regarding the ER status of the invasive cancers. The stage distribution of the invasive cancers at diagnosis was similar to that reported annually in the SEER data base.

Results are shown in Table 1. For each endpoint the following results are presented: the number of events and rate per 1000 women per year for the placebo and tamoxifen groups; and the relative risk (RR) and its associated 95% confidence interval (CI) between tamoxifen and placebo. Relative risks less than 1.0 indicate a benefit of tamoxifen citrate therapy. The limits of the confidence intervals can be used to assess the statistical significance of the benefits of tamoxifen therapy. If the upper limit of the CI is less than 1.0, then a statistically significant benefit exists.

Table 1: Major Outcomes of the NSABP B-24 Trial

Type of Event

Lumpectomy, radiotherapy, and placebo

Lumpectomy, radiotherapy, and tamoxifen

RR

95% CI Limits

No. of events

Rate per 1000 women per year

No. of events

Rate per 1000 women per year

Invasive Breast Cancer (Primary Endpoint)

74

16.73

44

9.60

0.57

0.39 to 0.84

Ipsilateral

47

10.61

27

5.90

0.56

0.33 to 0.91

Contralateral

25

5.64

17

3.71

0.66

0.33 to 1.27

Side undertermined

2

0

Secondary Endpoints

DCIS

56

12.66

41

8.95

0.71

0.46 to 1.08

Ipsilateral

46

10.40

38

8.29

0.88

0.51 to 1.25

Contralateral

10

2.26

3

0.65

0.29

0.05 to 1.13

All Breast Cancer Events

129

29.16

84

18.34

0.63

0.47 to 0.83

All ipsilateral events

96

21.70

65

14.19

0.65

0.47 to 0.91

All contralateral events

37

8.36

20

4.37

0.52

0.29 to 0.92

Deaths

32

28

Uterine Malignancies1

4

9

Endometrial Adenocarcinoma1

4

0.57

8

1.15

Uterine Sarcoma1

0

0.0

1

0.14

Second primary malignancies (other than endometrial and breast)

30

29

Stroke

2

7

Thromboembolic events (DVT, PE)

5

15

1 Updated follow-up data (median 8.1 years)

Survival was similar in the placebo and tamoxifen groups. At 5 years from study entry, survival was 97% for both groups.

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