Population attributable risks for breast cancer in Swedish women by morphological type

Survival, Incidence, and Mortality Trends in Female Cancers in the Nordic Countries

Background

Female cancers cover common breast cancers, relatively common endometrial, ovarian, and cervical cancers and rare vulvar cancer. Survival in these cancers is known to be relatively good compared to all cancers but long-term studies for these cancers are rare, and to fill the gap, here, we generate survival data through 50 years.

Materials and Methods

We applied generalized additive models to data from the NORDCAN database and analyzed 1- and 5-year relative survival for these cancers in Denmark (DK), Finland (FI), Norway (NO), and Sweden (SE) over half a century (1971-2020). Conditional 5/1-year survival for patients who survived the 1st year after diagnosis and annual survival changes was also estimated.

Results

In 2016-20, 5-year survival was best for breast cancer reaching 92.3% (in SE), followed by endometrial cancer at 86.1% (SE) and cervical cancer at 75.6% (NO). Improvement in 5-year survival over the 50 years was the largest for ovarian cancer (20% units), finally reaching 52.9% (SE). For vulvar cancer, the final survival was between 70 and 73%. The best 5-year survival rate in 2016-20 was recorded for SE in breast, endometrial, and ovarian cancers; NO showed the highest rate for cervical and DK for vulvar cancers. DK had the lowest survival for breast and ovarian cancers, and FI, for the other cancers.

Conclusions

The overall survival development appeared to consist of continuous improvements, most likely because of novel treatment and imaging techniques as well as overall organization of patient care. The large survival improvement for ovarian cancer was probably achieved by a surgical focus on tumors spread in the peritoneal cavity. For cervical and vulvar cancers, the high early mortality requires attention and could be helped by raising increasing public awareness of early symptoms in these cancers and developing pathways for fast initiation of treatment.

Risk factors for estrogen receptor positive ductal carcinoma in situ of the breast in African American women

Background

Compared to U.S. white women, African American women are more likely to die from ductal carcinoma in situ (DCIS). Elucidation of risk factors for DCIS in African American women may provide opportunities for risk reduction.

Methods

We used data from three epidemiologic studies in the African American Breast Cancer Epidemiology and Risk Consortium to study risk factors for estrogen receptor (ER) positive DCIS (488 cases; 13,830 controls). Results were compared to associations observed for ER+ invasive breast cancer (n = 2,099).

Results

First degree family history of breast cancer was associated with increased risk of ER+ DCIS [odds ratio (OR): 1.69, 95% confidence interval (CI): 1.31, 2.17]. Oral contraceptive use within the past 10 years (vs. never) was also associated with increased risk (OR: 1.43, 95%CI: 1.03, 1.97), as was late age at first birth (≥25 years vs. <20 years) (OR: 1.26, 95%CI: 0.96, 1.67). Risk was reduced in women with older age at menarche (≥15 years vs. <11 years) (OR: 0.62, 95%CI: 0.42, 0.93) and higher body mass index (BMI) in early adulthood (≥25 vs. <20 kg/m² at age 18 or 21) (OR: 0.75, 95%CI: 0.55, 1.01). There was a positive association of recent BMI with risk in postmenopausal women only. In general, associations of risk factors for ER+ DCIS were similar in magnitude and direction to those for invasive ER+ breast cancer.

Conclusions

Our findings suggest that most risk factors for invasive ER+ breast cancer are also associated with increased risk of ER+ DCIS among African American women.

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Few studies of risk factors for ductal carcinoma in situ (DCIS) have evaluated associations for African American women.

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We analyzed data from the African American African American Breast Cancer Epidemiology and Risk (AMBER) Consortium.

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Family history of breast cancer, reproductive factors, and anthropometric factors were associated with risk of ER+ DCIS.

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In general, risk factor associations for ER+ DCIS were similar to those for ER+ invasive breast cancer.

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Our findings support a common etiology and pathogenesis between ER+ DICS and ER+ invasive cancer in African American women.

The mammography screening detection of ductal carcinoma in situ and invasive breast cancer according to women's characteristics: is it the same?

PURPOSE

Detection of ductal carcinoma in situ (DCIS) has increased with the mammography dissemination. Given the potential role of DCIS as a precursor of invasive breast cancer (IBC), we aimed to assess whether women's characteristics have a different effect on the DCIS compared to IBC detection rate.

METHODS

This study included 3,609,569 screening mammograms performed from 2002 to 2015 in our organized breast cancer screening program, which actively invites women 50-69 years of age. The association between women's characteristics and the DCIS detection rate, the IBC detection rate and the odds ratio of DCIS among screen-detected cancers was assessed by logistic regression and generalized estimating equations with independent correlation matrix and sandwich estimator.

RESULTS

A total of 4173 DCIS and 15,136 IBC were screen-detected. Increasing women's age, current hormone replacement therapy use and higher body mass index were less associated with the DCIS than with IBC detection rates (p value for the odds of DCIS among screen-detected cancers of, respectively, < 0.0001, 0.0244 and < 0.0001). In contrast, having a previous breast aspiration or biopsy and increasing breast density were more strongly associated with DCIS than with IBC detection rates (p value of, respectively, 0.0050 and < 0.0001).

CONCLUSION

The results suggest that some women's characteristics could be playing a role in the initiation and other in the progression from in situ to invasive breast cancer. These characteristics can also affect the screening sensitivity, and this effect may differ depending on whether screen-detected cases were DCIS or IBC.

Attribution to Heterogeneous Risk Factors for Breast Cancer Subtypes Based on Hormone Receptor and Human Epidermal Growth Factor 2 Receptor Expression in Korea

We conducted a heterogeneous risk assessment of breast cancer based on the hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) calculating the risks and population-based attributable fractions (PAFs) for modifiable and nonmodifiable factors.Using matched case-control study design from the Seoul Breast Cancer Study and the national prevalence of exposure, the risks and PAFs for modifiable and nonmodifiable factors were estimated for total breast cancers and subtypes.The attribution to modifiable factors was different for each subtype (luminal A, PAF = 61.4% [95% confidence interval, CI = 54.3%-69.8%]; luminal B, 21.4% [95% CI = 18.6-24.9%]; HER2-overexpression, 59.4% [95% CI = 47.8%-74.3%], and triple negative tumors [TNs], 27.1% [95% CI = 22.9%-32.4%)], and the attribution to the modifiable factors for the luminal A and HER2-overexpression subtypes was higher than that of the luminal B and TN subtypes (P heterogeneity  ≤  0.001). The contribution of modifiable reproductive factors to luminal A type in premenopausal women was higher than that of the other subtypes (18.2% for luminal A; 3.1%, 8.1%, and -3.1% for luminal B, HER2-overexpression, and TN subtypes, respectively; P heterogeneity  ≤  0.001). Physical activity had the highest impact preventing 32.6% of luminal A, 14.5% of luminal B, 38.0% of HER2-overexpression, and 26.9% of TN subtypes (P heterogeneity = 0.014). Total reproductive factors were also heterogeneously attributed to each breast cancer subtype (luminal A, 65.4%; luminal B, 24.1%; HER2-overexpression, 57.9%, and TN subtypes, -3.1%; P heterogeneity  ≤  0.001).Each pathological subtype of breast cancer by HRs and HER2 status may be associated with heterogeneous risk factors and their attributable risk, suggesting a different etiology. The luminal B and TN subtypes seemed to be less preventable despite intervention for alleged risk factors, even though physical activity had a high preventable potential against breast cancer.

Population attributable risks of modifiable reproductive factors for breast and ovarian cancers in Korea

Background

Breast and ovarian cancers are predominant female cancers with increasing prevalence. The purpose of this study was to estimate the population attributable risks (PARs) of breast and ovarian cancer occurrence based on the relative risks (RRs) of modifiable reproductive factors and population-specific exposure prevalence.

Methods

The PAR was calculated by using the 1990 standardized prevalence rates, the 2010 national cancer incidence with a 20 year lag period, the meta-analyzed RRs from studies conducted in the Korean population for breast cancer, and the meta-analyzed RRs from a Korean epithelial ovarian cancer study and a prior meta-analysis, and ovarian cancer cohort results up to 2012. For oral contraceptive and hormone replacement therapy use, we did not consider lag period.

Results

The summary PARs for modifiable reproductive factors were 16.7 % (95 % CI 15.8–17.6) for breast cancer (2404 cases) and 81.9 % (95 % CI 55.0–100.0) for ovarian cancer (1579 cases). The modifiable reproductive factors included pregnancy/age at first birth (8.0 %), total period of breastfeeding (3.1 %), oral contraceptive use (5.3 %), and hormone replacement therapy use (0.3 %) for breast cancer and included breastfeeding experience (2.9 %), pregnancy (1.2 %), tubal ligation (24.5 %), and oral contraceptive use (53.3 %) for ovarian cancer.

Conclusions

Despite inherent uncertainties in the risk factors for breast and ovarian cancers, we suggest that appropriate long-term control of modifiable reproductive factors could reduce breast and ovarian cancer incidences and their related burdens by 16.7 % and 81.9 %, respectively.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-2040-0) contains supplementary material, which is available to authorized users.

Lobular breast cancer: incidence and genetic and non-genetic risk factors

While most invasive breast cancers consist of carcinomas of the ductal type, about 10% are invasive lobular carcinomas. Invasive lobular and ductal carcinomas differ with respect to risk factors. Invasive lobular carcinoma is more strongly associated with exposure to female hormones, and therefore its incidence is more subject to variation. This is illustrated by US figures during the 1987 to 2004 period: after 12 years of increases, breast cancer incidence declined steadily from 1999 to 2004, reflecting among other causes the decreasing use of menopausal hormone therapy, and these variations were stronger for invasive lobular than for invasive ductal carcinoma. Similarly, invasive lobular carcinoma is more strongly associated with early menarche, late menopause and late age at first birth. As for genetic risk factors, four high-penetrance genes are tested in clinical practice when genetic susceptibility to breast cancer is suspected, BRCA1, BRCA2, TP53 and CDH1. Germline mutations in BRCA1 and TP53 are predominantly associated with invasive ductal carcinoma, while BRCA2 mutations are associated with both ductal and lobular cancers. CDH1, the gene coding for the E-cadherin adhesion protein, is of special interest as mutations are associated with invasive lobular carcinoma, but never with ductal carcinoma. It was initially known as the main susceptibility gene for gastric cancer of the diffuse type, but the excess of breast cancers of the lobular type in CDH1 families led researchers to identify it also as a susceptibility gene for invasive lobular carcinoma. The risk of invasive lobular carcinoma is high in female mutation carriers, as about 50% are expected to develop the disease. Carriers must therefore undergo intensive breast cancer screening, with, for example, yearly magnetic resonance imaging and mammogram starting at age 30 years.

Excessive milk production during breast-feeding prior to breast cancer diagnosis is associated with increased risk for early events

Breast-feeding is a known protective factor against breast cancer. Breast-feeding duration is influenced by hormone levels, milk production, and lifestyle factors. The aims were to investigate how breast-feeding duration and milk production affected tumor characteristics and risk for early breast cancer events in primary breast cancer patients. Between 2002 and 2008, 634 breast cancer patients in Lund, Sweden, took part in an ongoing prospective cohort study. Data were extracted from questionnaires, pathology reports, and patients’ charts from 592 patients without preoperative treatment. Breast-feeding duration ≤12 months of the first child was associated with higher frequency of ER+/PgR+ tumors (P=0.02). Median follow-up time was 4.9 years. Higher risk for early events was observed for breast-feeding duration of first child >12 months (LogRank P=0.001), total breast-feeding duration >12 months (LogRank P=0.008), as well as ‘excessive milk production’ during breast-feeding of the first child (LogRank P=0.001). Patients with ‘almost no milk production’ had no events. In a multivariable model including both ‘excessive milk production’ and breast-feeding duration of the first child >12 months, both were associated with a two-fold risk for early events, adjusted HRs 2.33 (95% CI: 1.25-4.36) and 2.39 (0.97-5.85), respectively, while total breast-feeding duration was not. ‘Excessive milk production’ was associated with a two-fold risk of early distant metastases, adjusted HR 2.59 (1.13-5.94), but not duration. In conclusion, ‘excessive milk production’ during breast-feeding was associated with higher risk for early events independent of tumor characteristics, stressing the need to consider host factors in the evaluation of prognostic markers.

Do reproductive factors influence T, N, and M classes of ductal and lobular breast cancers? A nation-wide follow-up study

BACKGROUNDS

The clinical tumor-node-metastasis (T, N and M) classes of breast cancers provide important prognostic information. However, the possible association of TNM classes with reproductive factors has remained largely unexplored. Because every woman has a reproductive history, implications to outcome prediction are potentially significant.

METHODS

During the study period from 2002 through 2008, 5,614 pre- and 27,310 postmenopausal patients were identified in the Swedish Family-Cancer Database. Ordinal logistic regression analysis was used to estimate odds ratios (ORs) for TNM classes of breast cancers by histology. The reproductive variables were parity, age at first and last childbirth and time interval between first and last childbirth.

RESULTS

Among postmenopausal patients, the ORs for high-T class (T2-T4) (tumor size ≥2 cm) and metastasis were decreased by parity. A late age at first and last childbirth associated with high-T class and the effects were higher for lobular (OR for late age at first childbirth  = 2.85) than ductal carcinoma. Overall, long time interval between first and last childbirth was related to high-T class and metastasis. However, a short time interval between first and last childbirth in patients with late age at first or last childbirth increased the risk of metastasis. Late age at last childbirth was associated with increased occurrence of lobular carcinoma in situ. Among premenopausal ductal carcinoma patients, nulliparity and early age at first childbirth were associated with high-T class.

CONCLUSIONS

Increasing parity was protective against high-T class and metastasis; late ages at first and last childbirth were risk factors for high-T class in postmenopausal breast cancers. The current decline in parity and delayed age at first childbirth in many countries may negatively influence prognosis of breast cancer.

POPULATION ATTRIBUTABLE FRACTION AS A MEASURE OF HERITABILITY IN DICHOTOMOUS TWIN DATA

In many genetic analyses of dichotomous twin data odds ratios have been used to test hypotheses on heritability and shared common environment effects of a given disease (Lichtenstein et. al., 2000, Ahlbom et. al., 1997, Ramakrishnan, et. al., 1992, 1996). However, estimates of these two effects have not been dealt with in the literature. In epidemiology, the attributable fraction (AF), a function of the odds ratio and the prevalence of the risk factor has been used to describe the contribution of a risk factor to a disease in a given population (Leviton, 1973). In this article, we adapt the AF to quantify the heritability and the shared common environment. Twin data on cancer, gallstone disease and phobia are used to illustrate the applicability of the AF estimate as a measure of heritability.

Comparison of the effects of genetic and environmental risk factors on in situ and invasive ductal breast cancer

Little is known about the etiology of in situ ductal breast cancer (DCIS) or what influences its possible progression to invasive ductal disease. Comparison of risk factors for DCIS and invasive ductal cancer may throw some light on these issues. We estimated relative risks for DCIS and invasive ductal breast cancer according to 12 genetic and eight environmental risk factors among 1.1 million postmenopausal women in a large prospective UK study. There was no strong evidence of a different association with DCIS versus invasive ductal cancer for any of the 12 susceptibility loci examined. We also found similar associations of age at menarche, age at first birth, parity, age at menopause, family history of breast cancer and use of hormone replacement therapy with DCIS and invasive ductal cancer. Only body mass index (BMI) showed a clear difference in association in that it was positively associated with the risk of invasive ductal cancer but not DCIS (RRs per 5 kg/m(2) = 1.20 and 1.01, respectively; p-value for heterogeneity = 0.002). The very similar risk factor profiles observed here for DCIS and invasive ductal cancer suggest that DCIS is a precursor of invasive ductal cancer and most risk factors affect the risk of invasive ductal cancer primarily through their effects on the risk of DCIS. The lack of association between BMI and DCIS suggests a greater influence of BMI on disease progression.

Reproductive and menstrual factors and risk of ductal carcinoma in situ of the breast in a cohort of postmenopausal women

PURPOSE

The contribution of menstrual and reproductive factors to risk of ductal carcinoma (DCIS) of the breast is poorly understood.

METHODS

The association between menstrual and reproductive factors and subsequent DCIS risk was examined in Women's Health Initiative (WHI) clinical trial participants, in which mammography was protocol mandated. The cohort consisted of 64,060 women, among whom 664 cases of DCIS were ascertained over a median follow-up of 12.0 years. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI).

RESULTS

After adjustment for covariates, only older age at menopause (HR ≥ 55 vs. 45-54 : 1.39, 95% CI 1.08-1.79) was significantly associated with risk; however, greater parity (HR ≥ 5 live births vs. 0: 0.70, 95% CI 0.47-1.03), among parous women, and age at first live birth (HR ≥ 30 years relative to <20 years: 1.32, 95% CI 0.92-1.90) were of borderline significance. Age at menarche and months of breast-feeding were not associated with risk. Associations did not differ between high- and low-/moderate-grade DCIS, or by level of body mass index or family history of breast cancer; however, there was a suggestion that the associations of age at menopause, parity, and age at first live birth were limited to women who had ever used hormone therapy.

CONCLUSIONS

Findings from this large cohort of postmenopausal women suggest that age at menopause, and possibly, age at first live birth, and parity are associated with risk of DCIS, whereas age at menarche and duration of breast-feeding are not.

The enduring and evolving relationship between social class and breast cancer burden: a review of the literature

INTRODUCTION

Breast cancer in women has historically been seen as a "cancer of affluence" and there is a well-documented higher incidence among women of higher social class, as well as in societies with higher resources. However, the relationship between social class and breast cancer disease characteristics, especially those associated with poorer prognosis, is less well documented, and the overall relationship between breast cancer mortality and social class has been shown to vary. Furthermore, rapid changes in women's health and health-related behaviors in societies around the world may have an impact on both incidence and mortality patterns for breast cancer in the future.

METHODS

A PUBMED search on breast cancer and social class (incorporating the MeSH-nested concept of SES) yielded 403 possible studies published between 1978 and 2009, of which 90 met criteria for review. Our review discusses conceptualization and measurement of women's social class in each study, as well as findings related to breast cancer incidence, tumor biology or mortality, associated with social class.

FINDINGS

We found mostly consistent evidence that breast cancer incidence continues to be higher in higher social class groups, with some modification of risk with adjustment for known risk factors, including physical activity and reproductive history. However, biologic characteristics associated with poorer prognosis were negatively associated with social class (i.e., greater occurrence among disadvantaged women), and mortality from breast cancer showed inconsistent relationship to social class.

CONCLUSIONS

We discuss these studies in relation to the growing burden of breast cancer among low resource groups and countries, and the need for cancer control strategies reflecting the emerging demographics of breast cancer risk.

Late age at first full term birth is strongly associated with lobular breast cancer

BACKGROUND

Late age at first full-term birth and nulliparity are known to increase breast cancer risk. The frequency of these risk factors has increased in recent decades.

METHODS

The purpose of this population-based case-control study was to examine associations between parity, age at first birth (AFB), and specific histological subtypes of breast cancer. Women with breast cancer were identified from cancer registries in Wisconsin, Massachusetts, and New Hampshire. Control subjects were randomly selected from population lists. Interviews collected information on reproductive histories and other risk factors. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of ductal, lobular, and mixed ductal-lobular breast cancer diagnosis in association with AFB and nulliparity.

RESULTS

AFB ≥30 years was associated with a 2.4-fold increase in risk of lobular breast cancer compared with AFB <20 years (OR, 2.4; 95% CI, 1.9-2.9). The association was less pronounced for ductal breast cancer (OR, 1.3; 95% CI, 1.2-1.4). Nulliparity was associated with increased risk for all breast cancer subtypes, compared with women with AFB <20 years, but the association was stronger for lobular (OR, 1.7; 95% CI, 1.3-2.2) than for ductal (OR, 1.2; 95% CI, 1.1-1.3) subtypes (P = .004). The adverse effects of later AFB was stronger with obesity (P = .03) in lobular, but not ductal, breast cancer.

CONCLUSIONS

Stronger associations observed for late AFB and nulliparity suggest that these factors preferentially stimulate growth of lobular breast carcinomas. Recent temporal changes in reproductive patterns and rates of obesity may impact the histological presentation of breast cancer.

Reproductive factors and specific histological types of breast cancer: prospective study and meta-analysis

Little is known about how reproductive factors affect the risk of breast cancers of different histology. In an analysis of prospective data on 1.2 million middle-aged UK women, we used proportional hazards models to estimate the relative risks of six histological types in relation to menarche, childbearing and menopause. During 8.7 million person-years of follow-up, 17 923 ductal, 3332 lobular, 1062 tubular, 944 mixed ductal lobular, 330 mucinous and 117 medullary cancers were diagnosed. The effect of both age at menarche and age at first birth was greatest for lobular tumours; relative risks per 5-year increase in age at menarche for ductal, lobular, and tubular cancers were 0.93 (0.87-0.99), 0.65 (0.56-0.76), and 0.75 (0.57-0.98), respectively (P-value for heterogeneity=0.0001); and the relative risks per 5-year increase in age at first birth were 1.10 (1.07-1.12), 1.23 (1.17-1.29), and 1.13 (1.03-1.23), respectively (P-value for heterogeneity=0.0006). Increasing parity reduced the risk of each tumour type, except medullary cancers, but the reduction in risk was greater for mucinous cancers than for any other subtype considered (P<0.05 for comparison with each other subtype in turn). The effect of menopause did not vary significantly by tumour histology. Meta-analysis of published results on the effects of age at menarche and age at first birth on ductal and lobular cancers were in keeping with our findings.