Yes, another large study of 755 women was done by Chilvers1, but it confined itself to studying women under the age of 36. It found that women who took OCPs for 4 or more years prior to their FFTP had at least a 44% increased risk of breast cancer.
Table 9A: | |||
---|---|---|---|
The Chilvers Study of Women under the Age of 36 | |||
AUTHOR | FINDINGS | SIZE OF STUDY | YEAR STUDIED |
Chilvers [1]
United Kingdom Study |
44% increase in women
> 4 years use prior to their FFTP |
755 less than age 36 | 1/82 - 12/85 |
Yes, Pike et al showed that women age 32 or less had a 2.25-fold breast cancer risk if they took OCPs for 4 or more years prior to their FFTP2.
When two factors affect the risk of obtaining breast cancer, and a woman has both of these risk factors, she can calculate her estimated risk by multiplying the independent risk of both of these factors. Several examples demonstrate that oral contraceptives increase the risk of breast cancer when combined with another risk factor. Brinton et al noted: "Among women with an affected relative, use of oral contraceptives for 5 or more years was associated with a RR of 3.1 (0.7-13.6) compared to a RR of 1.9 (1.2-3.1) among those without such a family history" [3, p.832]. Ravnihar4 noted that women who have a family history of breast cancer and used OCPs had a 5.2-fold risk over women who had a positive family history and had no use of OCPs. Last, Pike et al [2] noted that women without benign breast disease who used OCPs for at least 49 months prior to their FFTP had a 1.69-fold increased risk of breast cancer, but women who took OCPs and did have a history of benign breast disease had an infinitely increased risk as compared to the "control" population.
Chapter 8 addressed the data and results of the four largest retrospective studies known to date. Table 9B shows the results of all of the "case/control" retrospective studies, the bulk of whose data come primarily after 1980. Eighteen out of 20 studies show an increased trend or significant risk in the development of breast cancer from oral contraceptive use before a woman's FFTP. In fact, most of the studies show an increased risk of greater than 40%. This means that the breast cancer risk of OCP use prior to a FFTP is almost certainly higher than the conservative estimate of 40% given in Chapter 8.
Table 9B: | ||||
---|---|---|---|---|
Breast Cancer Risk From Starting OCPS Before A FFTP In Women under The Age Of 45 | ||||
Author Change | Percent Change | Year |
Study Size
(RR) or Odds Ratio (OR) |
Findings |
Brinton et al [3] | 42% increase* | 1990-1992 | 1648< 45 years old | 1.42 OR (calculated) |
Chie et al [5] | 10% increase* | 1993-1994 | 97 premenopausal | OR=1.1 (0.2-5.5) |
Chilvers [1] | 2-51% increase | 1982-1985 | 755 less than 36 |
1.02 RR for 0-4 yrs;
1.51 for 4-8 yrs; 1.44> 8 yrs pFFTP |
Clavel [6] | 50% increase** | 1983-1987 | 358 premenopausal | OR=1.5 (1.0-2.2) |
Ewertz [7] | 50% increase** | 1983-1984 | 203 less than 40 | 1.50 (0.87-2.58) |
Lee [8] | 90% increase** | ?1988-1990 | about 100 premenopausal | 1.9 (0.4-7.7) |
McCredie et al [9] | 20% decrease** | 1992-1995 | 467 under 40 | 0.8 (0.6-1.0) |
McPherson et al [10] | 2-97% increase** | 1980-1984 | 351<45 |
1.02 (0.5-1.9) 1-12
months pFFTP; 1.97 (1.0-3.8) for 1-4 yrs pFFTP; 2.59 (1.3-4.5) > 4 yrs pFFTP |
Meirik et al [11] | 0-100% increase | 1984-1985 | 422 less than age 45 |
1.2 (0.8-1.7 0-3 yrs;
1.0 (0.6-1.7) 4-7 yrs; 2.0 (1.8-4.2) > 8 yrs pFFTP |
Miller et al [12] | 100% increase | 1983-1986 | 407 less than 45 | 2.0 (1.2-3.6) |
Olsson [13] | 80-110% increase | 1979-1985 | 174 premenopausal |
1.8 (1.0-3.2) for 0-
3 yrs and 2.1 (1.1- 3.8) for 4-7 yrs prior to FFTP |
Palmer [14] | 60-220% increase | 1977-1992 |
219 less than age 45
(black women) |
3.2 (1.1-9.2) 0-3
yrs; 1.7 (0.5-5.5) 3-4 yrs; 1.6 (0.4- 6.1) > 5 yrs pFFTP |
Paul et al [15] | 20% decrease** | 1983-1987 |
155 less than 45
(severe stack effect) |
0.80 (0.59-1.1 |
Rohan et al [16] | 93% increase** | 1982-1984 | 113 premenopausal |
1.93 (0.44-4.42)
for > 19 months use prior to FFTP |
Rookus et al [17] | 250% increase*** | 1986-1989 | 132 less than 36 |
3.5 (p< 0.01)
starting at or before age 19 |
Rosenberg et al [18] | 88% increase* | 1977-1992 | 1427 less than 45 |
OR = 1.88
(calculated) |
Ursin et al [19] |
36% decrease
to 74% increase |
1983-1988 | 742 less than age 40 |
OR= 0.64 (0.32-
1.27) 1-12 months; 1.74 (0.75-4.03) > 13 months use pFFTP |
Weinstein et al [20] | 59% increase | 1984-1986 |
about 326 less
than or equal to 49 |
OR= 1.59 (1.02-2.47) |
White et al [21] | 50% increase*** | 1983-1990 |
747 < than 45
(suffers from stack effect) |
OR= 1.5 (1.1-2.2)
for > 1 yr use within 5 yrs of menarche (in parous women |
Wingo et al [22] | 40% increase | 12/80-82 |
2089 less
than age 45 |
1.40 (0.9-2.4)
ages 20-34; 1.40 (1.1-1.8) ages 35-44 |
* Calculated from raw data.
|
The only two studies that showed an overall negative relationship were that of Paul et al [15] and McCredie [9]. The former study suffered from a huge stack effect having more than 6 times as many "controls" compared to "cases" in the 20 to 29 year-old age group (0.1035% vs. 0.0168%). The latter study found that women who had one child were at higher risk for breast cancer than nulliparous women, which raises concerns about the entire study. In addition, McCredie et al used the unconventional tactic of employing a p level greater than 0.05 to compute the data for risk of OCP use prior to a FFTP.
We have already noted that Romieu23 found a 72% increased risk [RR=1.72 (1.36-2.19)] in her meta-analysis from 1990 in women who took OCPs for 4 or more years before their FFTP. In addition, the Brinton study [3] is significant in that she allowed a longer latent period to pass and found a 210% increased risk of deueloping breast cancer for young women (ie, under the age of 35) who took OCPs for more than 10 years and began before the age of 18.
We note in Table 9C that most studies whose data comes predominantly after 1980 still show some risk of developing breast cancer from OCP use after a FFTP but in general this does not appear to be as great as the risk of OCP use before a FFTP.
Table 9C: | ||||
---|---|---|---|---|
Breast Cancer Risk From Using OCPS After A First Full-Term Pregnancy (FFTP) | ||||
Author | Percent Change | Year | Study Size |
Findings (RR) or
Odds Ratio (OR) |
Brinton et al [3] | 15% increase** | 1990-1992 | 1648< 45 years old | OR = 1.15 |
Chie et al [5] | 80% increase* | 1993-1994 | about 80 less than 45 | OR=1.8 (0.7-5.5) |
Chilvers [1] | 23-97% increase | 1984-1988 | 755 less than 36 |
1.23 for 0-4 years;
1.97 for > 8 yrs |
Ewertz [7] | no change | 1983-1984 | 203 less than 40 | 1.00 (0.58-1.72 |
Mcpherson et al [10] | 29% decrease** | 1980-1984 | 351 less than 45 | OR = 0.71 |
Miller et al [12] | 160% increase | 1983-1986 | 407 less than 45 | 2.6 (1.5-4.5) |
Palmer [14] | 20-150% increase | 1977-1992 |
524 less than 45
(black women) |
1.2 (0.6-2.1) < 3 yrs;
2.5 (1.2-5.3) 3-4 yrs; 1.7 (1.0-2.9) > 5 yrs |
Rosenberg et al [18] | 6% increase** | 1977-1992 | 1427 less than 45 | OR = 1.06 |
Ursin et al [19] |
30% decrease
to 23% increase |
1983-1988 | 742 less than age 40 |
OR= 0.70 (0.47-1.03)
1-48 months; 0.89 (0.54-1.47) 4-8 yrs; 1.23 (0.63-2.40) > 8 yrs |
Weinstein et al [20] | 29% increase* | 1984-1986 |
about 326 less
than or equal to 49 |
1.29 (0.89-1.88) |
White et al [21] | 0-17% increase* | 1983-1990 | 747 less than 45 |
OR = 1.00 (0.73-1.37) to
1.17 (0.85-1.61) |
Wingo et al [22] CASH Study |
0-40% increase* | 12/80-82 | 2089 less than 45 |
1.40 (0.8-2.4) in
age 20-34; 1.0 (0.8-1.3) in age 35-44 |
* This result reflects a trend toward an increased or decreased risk but does not attain statistical significance.
|
Table 9D compares the risks of OCP use before a FFTP to after a FFTP. One will note that in general, taking OCPs prior to a FFTP carries a higher risk than taking them after a FFTP.
Table 9D: | ||||
---|---|---|---|---|
Comparison of Risks of developing Breast Cancer in Women Who Took OCPS Before or After Their FFTP | ||||
AUTHOR | YEAR |
FINDINGS FOR RISK
BEFORE FFTP |
FINDINGS FOR RISK
AFTER FFTP |
|
Brinton et al [3] | 1990-1992 | 42% increase | 15% increase | |
Chie et al [5] | 1993-1994 | 10% increase* | 80% increase* | |
Chilvers [1] | 1982-1985 | 2-51% increase | 23-97% increase | |
Ewertz [7] | 1983-1984 | 50% increase* | no change | |
Mcpherson et al [10] | 1980-1984 | 2-97% increase* | 29% decrease* | |
Miller et al [12] | 1983-1986 | 100% increase | 160% increase | |
Palmer [14] | 1977-1992 | 60-220% increase* | 20-150% increase* | |
Rosenberg et al [18] | 1977-1992 | 88% increase | 6% increase | |
Ursin et al [19] | 1983-1988 |
36% decrease to
74% increase* |
30% decrease to
23% increase* |
|
Weinstein et al [20] | 1984-1986 | 59% increase | 29% increase* | |
White et al [21] | 1983-1990 | 50% increase | 0-17% increase* | |
Wingo [22]
CASH Study |
12/80-82 | 40% increase | 0-40% increase | |
* This result reflects a trend toward an increased or decreased risk but does not attain statistical significance. |
We can see that the CASH study [22] found a 40% increased risk in women aged 20 to 34. Palmer [14], who studied young black women, found a 120% increased risk. Overall, Table 9E demonstrates clearly that the bulk of the studies since 1980, especially some of the larger ones, point to an increased risk for "ever" versus "never use."
Table 9E: | ||||
---|---|---|---|---|
Breast Cancer Risk From Of Ever vs Never Use Of OCPS In Women under The Age Of 45 | ||||
Author | Percent Change | Year |
Study Size
(RR) or Odds Ratio (OR) |
Findings
(RR) or Odds Ratio (OR) |
Brinton et al [3] | 27% increase* | 1990-1992 | 1648< 45 years old | 1.27 (1.1-1.5) |
Chie et al [5] | 60% increase* | 1993-1994 | about 80 less than 45 | 1.6 (0.7-3.8) |
Chilvers [1] |
6% decrease to
57% increase |
1984-1988 | 755 less than 36 |
0.94 for 0-4 yrs;
1.42 for 4-8 yrs; 1.57 for > 8 yrs |
Clavel [6] | 50% increase | 1983-1987 | 278 premenopausal | 1.5 (1.1-2.1) |
Ewertz [7] | 18% increase* | 1983-1984 | 203 less than 40 | 1.18 (0.73-1.91) |
Gomes [24] | 81% increase | 1978-1987 | 71 < 43 | 1.81 (1.15-2.1) |
La Vecchia [25] | 30-90% increase | 1991-1993 | 454 less than 45 | OR = 1.3-1.9 |
Lee [8] | 10% increase | ?1988-1990 | about 100 premenopausal | 0.9 (0.5-1.6) |
Lee et al [26] | 13% increase | 1982-1984 | 64 less than age 44 |
OR = 1.13
Costa Rican women |
Lund et al [27] | 29% increase | 1984-1985 | 422 less than 45 |
OR = 1.29
(calculated) |
Mayberry [28] | 40-100% increase | 1980-1982 |
177 less than 40
(all black) |
1.4 (1.0-1.9) < 5 years; 2.0 (1.1-3.6) > 5 years |
McCredie et al [9] | 4% increase | 1992-1995 | 467 under 40 | OR = 1.04 |
Miller et al [12] | 100% increase | 1983-1986 | 407 less than 45 | 2.0 (1.4-2.9) |
Newcomb [29] | 0-40% increase* | 1988-1991 | 1050 < 45 |
1.4 (0.8-2.3) in
women < 35; 1.0 (0.8-1.3) 35-44 |
Noonan et al [30] | 26% increase | 1979-1984 | 301 less than 35 |
1.26 (0.95-
1.66) severe stack effect |
Palmer [14] | 120% increase | 1977-1992 |
184 less than 45
(black women) |
2.2 (1.5-3.3) |
Paul et al [15] | no change | 1983-1987 | 489 premenopausal |
1.0 (0.77-1.3)
severe stack effect |
Primic-Zakelj et al [31] | 4% increase* | 1988-1990 | 501 premenopausal | 1.04 (0.80-1.37) |
Rosenberg [32] | 76% increase | 1982-1986 |
79 less than 40
(Canadian women) |
OR = 1.76 |
Rosenberg et al [18] |
10% decrease to
70% increase |
1977-1992 | 1427 less than 45 |
1.7 (1.3-2.3)
ages 25-34; 0.9 (0.7-1.0) ages 35-44 |
Ursin et al [19] | 17% decrease | 1983-1988 | 742 less than age 40 |
OR = 0.83
(0.62-1.12) |
Weinstein et al [20] | 68% increase | 1984-1986 |
about 326 less
than or equal to 49 |
OR= 1.68
(1.16-2.42) |
White et al [21] | 2% increase* | 1983-1990 | 747 < than 45 |
OR = 1.02
(0.71-1.48) |
Wingo [22]
CASH Study |
10-40% increase* | 12/80-82 |
2089 less
than age 45 |
1.4 (1.1-2.1)
in age 20-34; 1.1 (0.9-1.3) in ages 35-44 |
* This result reflects a trend toward an increased or decreased risk but does not attain statistical significance. |
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Q-9I: Why does Table 9E exhibit that ....
1,
2,
3