Screening mammography intervals among postmenopausal hormone therapy users and nonusers

Screening mammography use among current, former, and never hormone therapy users may not explain recent declines in breast cancer incidence

BACKGROUND

Screening mammography and invasive breast cancer and ductal carcinoma in situ (DCIS) rates recently declined in the United States; screening mammography declines among former hormone therapy (HT) users may be an important contributor. We longitudinally examined women and compared mammography use and cancer rates by HT use [current, former, and never users of estrogen + progestin (EPT) and estrogen only (ET)].

METHODS

We studied 163,490 unique women aged 50-79 years enrolled in Group Health (Washington State) between 1994-2009. Electronic data identified HT dispensing, mammography use and incident breast cancer diagnosis. We calculated age-adjusted screening compliance as a time-varying variable (screened-within-the-past-26 months, yes/no).

RESULTS

Before 2002, screening compliance differed significantly by HT with current EPT users having the highest rates (83%) followed by former EPT (77%), current ET (77%), former ET (72%), and never users (56%). After 2002, screening was high (∼81%) among current and former EPT and ET users and significantly increased among never users (∼62%). Invasive breast cancer rates significantly decreased over the whole study period (P(trend) ≤ 0.05) for all HT users, except EPT current users (P(trend) = 0.68); DCIS rates did not change in any group.

CONCLUSIONS

Differential screening mammography rates by HT use do not explain invasive breast cancer incidence declines. Our data suggest discontinuing HT has an immediate effect on breast cancer rates, lending support to the mechanism that cessation leads to tumor regression.

IMPACT

Studies examining the influence of a changing exposure in relation to outcomes should account for varying exposures, individuals' characteristics, as well as screening methods and frequency.

Serious health events and discontinuation of routine cancer screening

Recently revised US Preventive Services Task Force screening guidelines for colorectal, breast, and prostate cancer contain separate recommendations for persons younger than 75 years and those 75 years or older. Developing an understanding of whether and how patients discontinue screening is important for evaluating the potential benefits and drawbacks of age-delimited screening recommendations as a tool for reducing overdiagnosis rates. Using Surveillance, Epidemiology, and End

RESULTS

-Medicare data from 1998 to 2007, the authors identified a sample of 32,189 female and 27,669 male fee-for-service Medicare beneficiaries who received 2 consecutive breast or prostate screens, 1 year apart. They then estimated the impact of serious health events, such as heart attacks and strokes, on continuation of screening. Rescreening rates among beneficiaries who did not experience a serious health event were 78% for women and 82% for men. Rescreening rates among beneficiaries who experienced a serious health event were 55% for women and 57% for men. The rate ratios associated with a time-varying indicator for the 2-year period following a serious health event were 0.79 (95% confidence interval: 0.76 to 0.81); P < 0.001) for women and 0.87 (95% confidence interval: 0.85 to 0.89; P < 0.001) for men. Approximately one-third of patients and physicians discontinue or temporarily suspend screening for breast and prostate cancer following serious health events. Findings suggest that not all patients persist with screening until they die.

Changes in invasive breast cancer and ductal carcinoma in situ rates in relation to the decline in hormone therapy use

PURPOSE

To assess trends in invasive breast cancer and ductal carcinoma in situ (DCIS) incidence in association with changes in hormone therapy (HT) use in regular mammography screeners.

METHODS

We included 2,071,814 screening mammography examinations performed between January 1997 and December 2006 on 696,385 women age 40 to 79 years; 9,586 breast cancers were diagnosed within 12 months of a screening examination. We calculated adjusted annual rates (mammogram level) for prevalent HT use, incident invasive breast cancer (overall and by tumor histology and estrogen receptor [ER] status), and incident DCIS.

RESULTS

After a precipitous decrease in HT use in 2002, the incidence of invasive breast cancer decreased significantly in 2002 to 2006 among women age 50 to 69 years (P(trend(2002-2006)) = .005) and 70 to 79 years (P(trend(2002-2006)) = .003) but not in women age 40 to 49 years (P(trend(2002-2006)) = .45). DCIS rates significantly decreased in women age 50 to 69 years after 2002 (P(trend(2002-2006)) = .02). Invasive ductal tumors significantly declined in women age 50 to 69 years and 70 to 79 years in 2002 to 2006. In women age 50 to 69 years, invasive lobular and ER-positive cancer rates declined steadily in 2002 to 2005 (P(trend(2002-2005)) = .02 and .03, respectively), but an elevated rate in 2006 rendered the overall trend nonsignificant (P(trend(2002-2006)) = .89 and .91, respectively).

CONCLUSION

In parallel to the sharp decline in HT use in women undergoing regular mammography screening, invasive breast cancer rates decreased in women age 50 to 69 and 70 to 79 years after 2002, and DCIS rates decreased in women age 50 to 69 years, consistent with evidence that HT cessation reduces breast cancer risk. However, the decrease in incidence may have started to level off in 2006; this finding has not been uniformly reported in other populations, warranting further investigation.

Age-related variation in the relationship between menopausal hormone therapy and the risk of dying from breast cancer

Multiple past studies have reported a reduced risk of breast cancer-related mortality (BCM) in relation to pre-diagnostic use of hormone therapy (HT); however, the extent to which this reduction is due to heightened screening or tumor biology is unknown. Using a population-based cohort of 1,911 post-menopausal women diagnosed with invasive breast cancer at ages 45-79 from 1993 to 1999, we investigated the extent to which the reduced risk in BCM observed in relation to HT might be explained by screening patterns or tumor features. Estrogen-progestin therapy (EPT) use was associated with a decreased risk of BCM (after adjustment for age, study, mammography, stage, and treatment), but only among older women (ever use: ≥ 65 years: HR = 0.45 [95% CI 0.26-0.80]; <65 years: HR = 1.03 [95% CI 0.60-1.79]). Estrogen-alone therapy (ET) use was not associated with risk of BCM (ever use: ≥ 65 years: HR = 0.76 [95% CI 0.51-1.12]; <65 years: HR = 1.20 [95% CI 0.71-2.02]). HT users had a much greater frequency of mammography (P value <0.001). EPT use was associated with tumor characteristics related to improved prognosis in older women after adjustment for screening, including an inverse association with poorly differentiated tumors (OR = 0.57 [95% CI 0.38-0.85]) and an association with lobular tumors (OR = 1.68 [95% CI 1.07-2.65]). Beyond the influence of EPT use on screening uptake, these data indicate that the improved survival associated with pre-diagnostic EPT use may be due in part to the development of more favorable tumor characteristics.