The association between lifetime smoking exposure and breast cancer mortality--results from a Norwegian cohort

Differences in breast cancer-risk factors between screen-detected and non-screen-detected cases (MCC-Spain study)

Purpose

The variation in breast cancer (BC)-risk factor associations between screen-detected (SD) and non-screen-detected (NSD) tumors has been poorly studied, despite the interest of this aspect in risk assessment and prevention. This study analyzes the differences in breast cancer-risk factor associations according to detection method and tumor phenotype in Spanish women aged between 50 and 69.

Methods

We examined 900 BC cases and 896 controls aged between 50 and 69, recruited in the multicase–control MCC-Spain study. With regard to the cases, 460 were detected by screening mammography, whereas 144 were diagnosed by other means. By tumor phenotype, 591 were HR+, 153 were HER2+, and 58 were TN. Lifestyle, reproductive factors, family history of BC, and tumor characteristics were analyzed. Logistic regression models were used to compare cases vs. controls and SD vs. NSD cases. Multinomial regression models (controls used as a reference) were adjusted for case analysis according to phenotype and detection method.

Results

TN was associated with a lower risk of SD BC (OR 0.30 IC 0.10–0.89), as were intermediate (OR 0.18 IC 0.07–0.44) and advanced stages at diagnosis (OR 0.11 IC 0.03–0.34). Nulliparity in postmenopausal women and age at menopause were related to an increased risk of SD BC (OR 1.60 IC 1.08–2.36; OR 1.48 IC 1.09–2.00, respectively). Nulliparity in postmenopausal women was associated with a higher risk of HR+ (OR 1.66 IC 1.15–2.40). Age at menopause was related to a greater risk of HR+ (OR 1.60 IC 1.22–2.11) and HER2+ (OR 1.59 IC 1.03–2.45) tumors.

Conclusion

Reproductive risk factors are associated with SD BC, as are HR+ tumors. Differences in BC-risk factor associations according to detection method may be related to prevailing phenotypes among categories.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10552-021-01511-4.

Post-diagnosis smoking and risk of cardiovascular, cancer, and all-cause mortality in survivors of 10 adult cancers: a prospective cohort study

Several studies have examined the relationship between smoking and mortality in cancer survivors. However, few have reported the relationships in several cancer sites (i.e., bladder, non-melanoma skin, uterine, melanoma, and lymphoma), and limited data exist on the dose-response relationship between number of cigarettes smoked per day or duration of smoking cessation and mortality. Cancer survivors (N = 35,093, 61% female, mean age = 47 years old) from the National Health Interview Survey with linked data retrieved from the National Death Index served as our study participants. Cox proportional-hazards models were used to assess associations between smoking status, all-cause, and disease-specific mortality. After a median follow-up of 13 years, 11,066 deaths occurred. Survivors who reported smoking at study entry had a 73%, 75%, 85% higher risk for cardiovascular disease, cancer, and all-cause mortality, respectively when compared to nonsmokers. Former smokers had a 31% and 37% higher risk of all-cause and cancer mortality, respectively when compared to nonsmokers. The observed relationships appeared to differ by the number of cigarettes smoked (i.e., ≥ 10 per day), especially for breast, cervix, lung, prostate, uterine and non-melanoma skin cancer survivors. Those who continued smoking post diagnosis were at greatest risk of all-cause and cancer mortality, but the associations varied substantially by cancer site. These data provide sufficient evidence of the health hazards associated with smoking for cancer survivors and provide further support for public health strategies designed to curb smoking in this vulnerable population.

Impact of smoking history on the outcomes of women with early-stage breast cancer: a secondary analysis of a randomized study

To assess the impact of smoking history on the outcomes of early-stage breast cancer patients treated with sequential anthracyclines-taxanes in a randomized study. This is a secondary analysis of patient-level data of 1242 breast cancer patients referred for adjuvant chemotherapy in the BCIRG005 clinical trial. Overall survival was assessed according to smoking history through Kaplan-Meier analysis. Univariate and multivariate Cox regression analyses of factors affecting overall and relapse-free survival were subsequently conducted. Factors that were evaluated included: age, performance status, number of chemotherapy cycles, T stage, lymph node ratio, estrogen receptor status, adjuvant radiotherapy and smoking history. Kaplan-Meier analysis of overall survival according to smoking status (ever smoker vs. never smoker) was conducted. There was a trend toward a better overall survival among never smokers compared to ever smokers; however, it was not statistically significant (P = 0.098). The following factors were associated with better overall survival in multivariate analysis: older age (P = 0.011), complete chemotherapy course (P = 0.002), lower T stage (P < 0.0001), lower lymph node ratio (P < 0.0001) and positive estrogen receptor status (P = 0.006). Otherwise, the following factors were associated with better relapse-free survival in multivariate analysis: older age (P = 0.001), never smoking status (P = 0.021), lower T stage (P = 0.028), lower lymph node ratio (P < 0.0001) and positive estrogen receptor status (P < 0.0001). Early-stage breast cancer patients with a positive smoking history experienced worse relapse-free survival compared to never smokers. Physicians managing breast cancer patients should prioritize discussion about the benefits of smoking cessation when counseling their patients.

Smoking and mortality in women diagnosed with breast cancer-a systematic review with meta-analysis based on 400,944 breast cancer cases

BACKGROUND

It is evident that smoking is causing disease and increased mortality in general. Recently published data are now suggesting that smoking might increase both the overall mortality in women diagnosed with breast cancer but also increase their risk of dying from their breast cancer.

METHODS

A systematic review and meta-analysis on smoking status in women diagnosed with breast cancer, their mortality rate and cause of death. Based on all cohort studies published within the last ten years.

RESULTS

Twelve studies met our inclusion criteria, and 400,944 women diagnosed with primary invasive breast cancer was included. Hazard ratio (HR) for breast cancer associated death in former smokers was 1.02 (0.93, 1.12) and for current smokers 1.28 (1.17, 1.41) when compared to never smokers. For all-cause death, the HR for former smokers was 1.12 (1.04, 1.19), and for current smokers 1.52 (1.32, 1.76) when compared to never smokers.

CONCLUSIONS

This large systematic review and meta-analysis found a 28% increase in breast cancer-associated mortality in those who were current smokers compared to never smokers. The mortality in former smokers was equal to the one found in never smokers. This indicates that breast cancer patients ceasing to smoke can lower their risk of dying from their breast cancer disease dramatically, and possibly regain the risk of a never smoker.

The fraction of breast cancer attributable to smoking: The Norwegian women and cancer study 1991-2012

Background:

Results from several recent cohort studies on smoking and breast cancer incidence and mortality suggest that the burden of smoking on society is underestimated. We estimated the fraction of breast cancer attributable to smoking in the Norwegian Women and Cancer Study, a nationally representative prospective cohort study.

Methods:

We followed 130 053 women, aged 34–70 years, who completed a baseline questionnaire between 1991 and 2007, through linkages to national registries through December 2012. We used Cox proportional hazards models to estimate hazard ratios (HRs) with 95% confidence intervals (CIs), while adjusting for confounders. Never smokers, excluding passive smokers, were used as the reference group in all main analyses. We estimated attributable fractions (AFs) % in smokers and in the population (PAFs) % with 95% CIs.

Results:

Altogether, 4293 women developed invasive breast cancer, confirmed by histology. Compared with never active, never passive smokers, ever (former and current) smokers had an overall risk of breast cancer that was 21% higher (HR=1.21; 95% CI=1.08–1.34). For ever smokers, the AF was 17.3% (95% CI =7.4–25.4) and for the population the PAF of breast cancer was 11.9% (95% CI=5.3–18.1). For passive smokers, the PAF of breast cancer was 3.2% (95% CI=1.0–5.4). When we applied PAF estimates for ever smoking on the 2907 new breast cancer cases among Norwegian women aged 35+ at diagnosis in 2012, this yielded 345 (95% CI=154–526) breast cancer cases that could have been avoided in the absence of active smoking that year.

Conclusions:

In smokers, one in six and in the population, one in nine breast cancer cases could have been avoided in the absence of active smoking. Our findings support the notion that the global cancer burden due to smoking is substantially underestimated.

[Systematizing support in cessation smoking to improve care for cancer patients]

Approximately 20% of cancer patients smoke at diagnosis (all localizations included), and over two thirds continue despite the therapeutic management of their cancer, especially when cancer is not associated with tobacco. The impact of smoking on quality of care for patients is actually not enough considered. A literature review conducted by the French National Cancer Institute emphasizes the importance of tobacco cessation to improve the prognosis (decreased mortality from all causes and specific); to reduce the risk of second primary cancers; to reduce per- and post-surgical risks as long as some toxicities related to treatments and to improve the quality of physical and mental life of patients. It is important that a communication with the patient takes place at the beginning of the treatment to impact the smoking behavior. All oncology health professionals should deliver a clearly and personalized cessation advice in the light of scientific data and ensure that smoking cessation help will be offered to the patient.

Social inequalities and smoking-associated breast cancer - Results from a prospective cohort study

OBJECTIVE

The association between smoking and breast cancer has been found in most recent, large cohort studies. We wanted to investigate how smoking-associated breast cancer varies by level of education, a well-established measure of socioeconomic status.

METHODS

We included 302,865 women with 7490 breast cancer cases. Participants were assigned to low, moderate or high level of education and analyzed by smoking status (ever/never), and stratified by birth cohorts (≤1950>). We used Cox proportional hazard to estimate hazard ratios (HRs) and confidence intervals (CIs), adjusting for age, number of children, age at first childbirth, BMI, age at enrollment and physical activity.

RESULTS

Women born ≤1950 with low and moderate levels of education had a 40% increase in smoking-associated breast cancer risk (HR=1.40, 95% CI 1.25-1.57 and HR=1.14, 95% CI 1.05-1.24, respectively). Women in the same age group with high level of education did not have an increase in risk. No increased breast cancer risk was found among women born after 1950 for any level of education, when analyzed by smoking status. Longer duration of smoking before first childbirth was consistently associated with increasing risk of breast cancer in all three categories of education (all p for trends<0.01).

CONCLUSION

Smoking for several years before first childbirth increases the risk of breast cancer, regardless of educational level.