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Dixon JM, McDonald C, Elton RA, Miller WR, for the Edinburgh Breast Group. Risk of breast cancer in women with palpable breast cysts: a prospective study. Lancet. 1999 May 22;353:1742-5.
Do women with palpable breast cysts have a greater risk for breast cancer? Is cyst type associated with risk for breast cancer?
Cohort study with median follow-up of 5 years for women who developed breast cancer and 10 years for women who did not.
Edinburgh Breast Unit, Scotland, United Kingdom.
Complete data were available for 1334 of 1374 women with palpable breast cysts (54% type I, 33% type II, and 13% mixture).
Assessment of risk factors
Type of cyst (Na+K+ ratio < 3 for type I cysts and 3 for type II cysts), num ber of cysts, age, and length of time after cyst aspiration.
Main outcome measures
Incidence of breast cancer was assessed by linkage with cancer registry, hospital discharge, and death-registration data.
74 invasive cases of breast cancer developed, and 65 were studied (7 cases developed before first cyst aspiration, and 2 patients had intracystic cancer). The incidence of breast cancer was greater than that for the general population (standardized incidence rate 2.81, 95% CI 2.17 to 3.59). Age was associated with risk for breast cancer (P < 0.05 for trend) (Table). After adjustment for age, the risk for breast cancer was greatest dur ing the first year after aspiration (Table). The increased risk for breast cancer did not differ according to cyst type, number of cysts, or age at aspiration.
An increased risk for breast cancer was seen in women with palpable breast cysts. The risk was greatest during the first year after cyst aspiration and in younger women and did not differ according to cyst type.
Source of funding: No external funding.
For correspondence: Dr. J.M. Dixon, Edin-burgh Breast Unit, Western General Hospital, Edinburgh EH4 2XU, Scotland, UK. FAX 44-131-228-2661.
Risk for breast cancer in women with palpable cysts*
Risk factors Standardized incidence rate (95% CI)
Age £ 44 y 5.94 (2.97 to 10.63)
Age 45 to 49 y 2.90 (1.79 to 4.43)
Age 50 to 54 y 2.90 (1.82 to 4.39)
Age > 54 y 1.73 (0.86 to 3.10)
£ 1 y after aspiration 7.02 (3.73 to 12.00)
2 to 5 y after aspiration 2.14 (1.29 to 3.34)
> 5 y after aspiration 2.68 (1.84 to 3.76)
*Adjusted for current age.
The finding of Dixon and colleagues that womenparticularly younger womenwith palpable breast cysts had an increased risk for developing breast cancer is provocative. In the United States, Dupont and Page's study (1) from 1985 is the most commonly cited study of women who had biopsies on nonproliferative breast lesions. Dupont and Page found a 50% increase in the relative risk for breast cancer in women with gross cysts and a 200% increase in those with gross cysts and a positive family history.
My primary reservation is whether the cohort studied by Dixon and coworkers truly reflected a population-based group. Although each woman had a full clinical assessment and mammography, no details about family history, various mammography findings, risk indicators, or Gail-risk scores are given (2). In addition, it is possible but unlikely that the cancer registry under- estimated the number of new breast cancer cases (the controls). This should be easy for the investigators to subsequently report.
Whether these findings are sufficient to begin regular mammography screening in women with a history of cysts who are < 50 years of age is controversial at best. Even if the relative risk is slightly increased, no evidence exists that mammography screening will be more effective. Mammography interpretation is likely to be more difficult in these women because of their history of cysts. The frequency of false-positive results and subsequent procedures also will be increased.
Given the frequency of the problem and these concerns, more compelling evidence from additional studies is needed before I will change my style of practice.
Bruce E. Hillner, MD
Virginia Commonwealth University
Richmond, Virginia, USA
1. Dupont WD, Page DL. Risk factors for breast cancer in women with proliferative breast disease. N Engl J Med. 1985; 312: 146-51.
2. Fisher B, Costantino JP, Wickerham DL, et al. Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst. 1998;90:1371-88.
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