Obesity is a major risk factor for cardiovascular disease (CVD), with weight loss offering improvement in CVD risk factors.
To examine whether weight loss in laparoscopic adjustable gastric band (LAGB)-treated obese patients is associated with meaningful reductions in estimated 10- and 30- year Framingham CVD risk 12–15 months post-LAGB.
Obese adult patients [body mass index (BMI) ≥30 kg/m2] treated with LAGB were identified in a large US healthcare database. Patients without CVD at baseline and with measures of BMI, systolic blood pressure, diabetes, and smoking status at baseline and follow-up were eligible. Non-LAGB patients were propensity score matched to LAGB patients on baseline BMI, age, and gender. Estimated 10- and 30-year risk of developing CVD using office-based data, including BMI, was calculated at baseline and 12–15 months follow-up.
Mean BMI in LAGB patients (n = 647, average age 45.66 years, 81.1% female) decreased from 42.7 to 33.4 kg/m2 (P < 0.0001), with 35.4% no longer obese; 10- and 30-year estimated CVD risk decreased from 10.8 to 7.6% (P < 0.0001) and 44.34 to 32.30% (P < 0.0001), respectively, 12–15 months post-LAGB. Improvements were significantly greater than in non-LAGB patients (N = 4,295) (P < 0.0001). In the subset with lipid data (n = 74), improvements in total (−20.6 mg/dL; P < 0.05) and high-density lipoprotein (+10.6 mg/dL, P < 0.0001) cholesterol 1 year post-LAGB were also observed.
Data from a US healthcare database show that individuals undergoing LAGB have significant weight loss and reductions in estimated 10- to 30-year CVD risk within 1 year post-LAGB.
Cardiology; Cardiovascular disease; Framingham risk score; Laparoscopic adjustable gastric banding; Obesity; Weight loss
Although underweight and obesity have been associated with increased risk of mortality, it remains unclear whether the associations differ by hormone therapy (HT) use and smoking. The authors examined the relationship between body mass index (BMI) and mortality within the California Teachers Study (CTS), specifically considering the impact of hormone therapy (HT) and smoking. The authors examined the associations of underweight and obesity with risks of all-cause and cause-specific mortality, among 115,433 women participating in the CTS, and specifically examined whether HT use or smoking modifies the effects of obesity. Multivariable Cox proportional hazards regression provided estimates of relative risks (RRs) and 95% confidence intervals (CIs). During follow up, 10,574 deaths occurred. All-cause mortality was increased for underweight (BMI < 18.5; adjusted relative risk [RR] = 1.33, 95% confidence interval [CI] =1.20–1.47) and obese participants (BMI ≥ 30: RR = 1.27, 95% CI = 1.19–1.37) relative to BMI of 18.5 – 24.9). Respiratory disease mortality was increased for underweight and obese participants. Death from any cancer, and breast cancer specifically, and cardiovascular disease was observed only for obese participants. The obesity and mortality association remained after stratification on HT and smoking. Obese participants remained at greater risk for mortality after stratification on menopausal hormone therapy and smoking. Obesity was associated with increased all-cause mortality, as well as death from any cancer (including breast), and cardiovascular and respiratory diseases. These findings help to identify groups at risk for BMI-related poor health outcomes.
To investigate whether obesity and hormone therapy (HT) are associated with ovarian cancer risk among women in the California Teachers Study cohort.
Of 56,091 women age ≥45 years, 277 developed epithelial ovarian cancer between 1995 and 2007. Multivariate Cox regression was performed.
Among women who never used HT, greater adult weight gain, waist circumference and waist-to-height ratio, but not adult BMI, increased risk of ovarian cancer. Compared to women who never used HT and had a stable adult weight, risk of ovarian cancer was increased in women who gained ≥40 lb (relative risk (RR) 1.8, 95% confidence interval (CI): 1.0–3.0) or used HT for >5 years (RR 2.3 95% CI: 1.3–4.1). Having both exposures (RR 1.9, 95% CI: 0.99–3.5), however, did not increase risk more than having either alone. Results were similar for waist circumference and weight-to-height ratio; however, differences across HT groups were not statistically significant.
This study suggests that abdominal adiposity and weight gain, but not overall obesity, increase ovarian cancer risk and that there may be a threshold level beyond which additional hormones, whether exogenous or endogenous, do not result in additional elevation in risk. However, large pooled analyses are needed to confirm these findings.
Ovarian cancer; Obesity; Abdominal adiposity; Hormone therapy
To investigate whether hormone therapy (HT) and obesity are associated with endometrial cancer risk among postmenopausal women in the California Teachers Study cohort.
Of 28,418 postmenopausal women, 395 developed type 1 endometrial cancer between 1995 and 2006. Multivariate Cox regression was performed to estimate relative risks (RR), stratified by HT use (never used, ever estrogen-alone (ET), or exclusively estrogen-plus-progestin (EPT)).
Among women who never used HT, overall and abdominal adiposity were associated with increased risk; when evaluated simultaneously, abdominal adiposity was more strongly associated (RR 2.2, 95% confidence interval (CI): 1.1–4.5 for waist ≥35 vs. <35 inches). Among women who ever used ET, risk was increased in women with BMI ≥25 kg/m2 (RR 1.6, 95% CI: 1.1–2.3 vs. <25 kg/m2). Neither overall nor abdominal obesity was associated with risk in women who exclusively used EPT (P-interaction<0.001 for BMI by HT use).
Among women who never used HT, risk was strongly positively related to obesity and may have been influenced more by abdominal than overall adiposity; however, due to small numbers, this latter finding requires replication. Among women who ever used ET, being overweight at baseline predicted higher risk, whereas use of EPT mitigated any effect of obesity.
endometrial cancer; obesity; abdominal adiposity; hormone therapy
A low meat diet and regular non-steroidal anti-inflammatory drugs (NSAIDs) have been associated with decreased mortality among colorectal cancer (CRC) patients. Here we investigated the association between pre-diagnosis usual meat consumption and CRC-specific mortality, and whether meat consumption modifies the previously noted association between NSAID use and CRC-specific mortality among women in the California Teachers Study (CTS) cohort. Women joining CTS in 1995–1996 without prior CRC diagnosis, diagnosed with incident CRC during follow-up through December 2007, were eligible for inclusion. Meat intake (frequency and serving size) and NSAID use (aspirin or ibuprofen use) were ascertained via self-administered questionnaires before diagnosis. Vital status and cause of death were determined by linkage with mortality files. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HR) for death and 95% confidence intervals (CI). Pre-diagnosis meat consumption was not associated with CRC-specific mortality among 704 CRC patients (and 201 CRC-specific deaths), comparing patients in the lowest consumption tertile (0–5.4 medium-size servings/week) to those with higher consumption. Regular NSAID use (1–3 times/week, 4–6 times/week, daily) vs. none was associated with decreased CRC-specific mortality among patients in the lowest meat consumption tertile (HR=0.22, 95% CI 0.06–0.82), but not among patients in the higher meat intake tertiles. The previously observed mortality risk reduction among female CRC patients associated with regular NSAID use was restricted to patients who reported low meat intake before diagnosis. These findings have implications for CRC survivorship and tertiary CRC prevention.
Reproductive factors, such as early age at menarche, late age at menopause, and nulliparity are known risk factors for breast cancer. Previously, we reported these factors to be associated with risk of developing contralateral breast cancer (CBC). In this study, we evaluated the association between these factors and CBC risk among BRCA1 and BRCA2 (BRCA1/2) mutation carriers and non-carriers.
The WECARE Study is a population-based multi-center case–control study of 705 women with CBC (cases) and 1,397 women with unilateral breast cancer (controls). All participants were screened for BRCA1/2 mutations and 181 carriers were identified. Conditional logistic regression models were used to evaluate associations between reproductive factors and CBC for mutation carriers and non-carriers.
None of the associations between reproductive factors and CBC risk differed between mutation carriers and non-carriers. The increase in risk with younger age at menarche and decrease in risk in women with more than two full-term pregnancies seen in non-carriers were not significantly different in carriers (adjusted RRs = 1.31, 95% CI 0.65–2.65 and 0.53, 95% CI 0.19–1.51, respectively). No significant associations between the other reproductive factors and CBC risk were observed in mutation carriers or non-carriers.
For two reproductive factors previously shown to be associated with CBC risk, we observed similar associations for BRCA1/2 carriers. This suggests that reproductive variables that affect CBC risk may have similar effects in mutation carriers and non-carriers.
Contralateral breast cancer; BRCA1; BRCA2; Reproductive factors
The potential effects of oral contraceptive (OC) and post-menopausal hormone (PMH) use are not well understood among BRCA1 or BRCA2 deleterious mutation carriers with a history of breast cancer. In this study, we investigated the association between OC and PMH use and risk of contralateral breast cancer (CBC) in the WECARE (Women’s Environment, Cancer and Radiation Epidemiology) Study. The WECARE Study is a population-based case-control study of 705 women with asynchronous CBC and 1,398 women with unilateral breast cancer, including 181 BRCA1/2 mutation carriers. Risk factor information was assessed by telephone interview. Mutation status was measured using denaturing high-performance liquid chromatography followed by direct sequencing in all participants. Outcomes, treatment and tumor characteristics were abstracted from medical records. Ever use of OCs was not associated with risk among non-carriers (RR=0.87; 95% CI=0.66–1.15) or BRCA2 carriers (RR=0.82; 95% CI=0.21–3.13). BRCA1 carriers who used OCs had a non-significant greater risk than non-users (RR=2.38; 95% CI=0.72–7.83). Total duration of OC use and at least five years of use before age 30 were associated with a non-significant increased risk among mutation carriers, but not among non-carriers. Few women had ever used PMH and we found no significant associations between lifetime use and CBC risk among carriers and non-carriers. In conclusion, the association between OC/PMH use and risk of CBC does not differ significantly between carriers and non-carriers; however, because carriers have a higher baseline risk of second primaries even a potential small increase in risk as a result of OC use may be clinically relevant.
breast cancer; asynchronous bilateral; contralateral; oral contraceptives; postmenopausal hormones; BRCA1; BRCA2
Non-steroidal anti-inflammatory drug (NSAID) use has been associated with decreased colorectal cancer (CRC) risk. However, NSAID effects on clinical outcomes after CRC diagnosis are not well-defined. We investigated the association of pre-diagnosis NSAID use and mortality after CRC diagnosis among women in the California Teachers Study (CTS) cohort.
Women under 85 years participating in the CTS, without prior CRC diagnosis at baseline (1995-1996), and diagnosed with CRC during follow-up through December 2005, were eligible for analysis of the association of pre-diagnosis NSAID use and mortality. NSAID use (including aspirin, and ibuprofen) was collected through a self-administered questionnaire. Cancer occurrence was identified through California Cancer Registry linkage. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HR) for death and 95% confidence intervals (CI).
Among 621 CRC cases identified, 64% reported no pre-diagnosis regular NSAID use, 17% reported use 1-6 days/week, and 20% reported daily use; duration of NSAID use < 5 years was reported by 17% and ≥5 years reported by 18%. Regular pre-diagnosis NSAID use (1-3 days/week, 4-6 days/week, daily) vs. none was associated with improved overall survival (OS) (HR=0.71, 95% CI 0.53-0.95) and CRC-specific survival (CRC-SS) (HR=0.58, 95% CI 0.40-0.84) after adjustment for clinically relevant factors. Pre-diagnosis NSAID use ≥5 years (versus none) was associated with improved OS (HR=0.55, 95% CI 0.37-0.84) and CRC-SS (HR=0.40, 95% CI 0.23-0.71) in adjusted analyses.
When used regularly or over a prolonged duration prior to CRC diagnosis, NSAIDs are associated with decreased mortality among female CRC cases.
Colon cancer; colorectal cancer; non-steroidal anti-inflammatory drugs; NSAIDs; rectal cancer; survival
Although recent reviews have suggested active smoking to be a risk factor for breast cancer, the association with passive smoke exposure remains controversial. This risk association was explored in a large prospective study of women, the California Teachers Study.
Detailed lifetime information on passive smoke exposure by setting (home, work, or social) and by age of exposure were collected in 1997 from 57,523 women who were lifetime nonsmokers and had no history of breast cancer. In the ensuing decade, a total of 1,754 women were diagnosed with invasive breast cancer. Cox proportional hazards models were fit to estimate hazard ratios (HRs) and 95% confidence intervals (95% CI) associated with several lifetime passive smoke exposure metrics.
For all breast cancer, measures of higher lifetime passive smoking intensity and duration were associated with non-statistically significant HRs of 1.11 to 1.14. For postmenopausal women, HRs for lifetime low, medium and high cumulative exposure were 1.17 (95%CI 0.91, 1.49), 1.19 (95%CI 0.93, 1.53), and 1.26 (95% CI 0.99, 1.60). For women exposed in adulthood (age ≥20) risk was elevated at the highest level of cumulative exposure (HR=1.18, 95% CI 1.00, 1.40), primarily among postmenopausal women (HR=1.25, 95% CI 1.01, 1.56). A statistically significant dose response was detected when analysis was restricted to women with moderate to high levels of passive smoke exposure.
These results suggest that cumulative exposures to high levels of side stream smoke may increase breast cancer risk among postmenopausal women who themselves have never smoked tobacco products.
passive smoking; tobacco; breast cancer; cohort study; women
To describe reproductive and lifestyle correlates of surgically confirmed fibroids.
Prospective Cohort Study
The California Teachers Study (CTS), an ongoing prospective study of over 133,000 female teachers and school administrators identified through the California State Teachers Retirement System.
CTS cohort members reporting no prior history of fibroids were ascertained prospectively for surgical diagnosis of fibroids using hospital patient discharge records.
Main Outcome Measure(s)
Multivariable Cox proportional hazards regression methods were used to assess the association of self-reported menstrual, reproductive, and lifestyle characteristics with fibroids, using ages at the start and end of follow-up (in months) to define time on study. Hazard rate ratios, presented as relative risks (RR) with 95% confidence intervals (CI), were estimated.
The strongest risk factor we identified was African-American race/ethnicity, as compared to non-Latina white women. We observed a reduced risk of fibroids for postmenopausal women in comparison to premenopausal women, but use of hormone replacement therapies (regardless of formulation) were associated with an increased risk. Other risk factors included race, a family history of fibroids, being overweight and drinking alcohol, Smoking and diabetes were associated with a decreased risk of fibroids.
These observations provide a more detailed epidemiologic profile of women with surgically managed fibroids
Shorter survival has been associated with low socioeconomic status (SES) among elderly non-Hodgkin's lymphoma (NHL) patients; however it remains unknown whether the same relationship holds for younger patients. We explored the California Cancer Registry (CCR), to investigate this relationship in adolescent and young adult (AYA) NHL patients diagnosed from 1996 to 2005. A case-only survival analysis was conducted to examine demographic and clinical variables hypothesized to be related to survival. Included in the final analysis were 3,489 incident NHL cases. In the multivariate analyses, all-cause mortality (ACM) was higher in individuals who had later stage at diagnosis (P < .05) or did not receive first-course chemotherapy (P < .05). There was also a significant gradient decrease in survival, with higher ACM at each decreasing quintile of SES (P < .001). Overall results were similar for lymphoma-specific mortality. In the race/ethnicity stratified analyses, only non-Hispanic Whites (NHWs) had a significant SES-ACM trend (P < .001). Reduced overall and lymphoma-specific survival was associated with lower SES in AYAs with NHL, although a significant trend was only observed for NHWs.
Although pregnancy-related factors such as nulliparity and late age at first full-term pregnancy are well-established risk factors for invasive breast cancer, the roles of these factors in the natural history of breast cancer development remain unclear.
Among 52,464 postmenopausal women participating in the California Teachers Study (CTS), 624 were diagnosed with breast carcinoma in situ (CIS) and 2,828 with invasive breast cancer between 1995 and 2007. Multivariable Cox proportional hazards regression methods were used to estimate relative risks associated with parity, age at first full-term pregnancy, breastfeeding, nausea or vomiting during pregnancy, and preeclampsia.
Compared with never-pregnant women, an increasing number of full-term pregnancies was associated with greater risk reduction for both breast CIS and invasive breast cancer (both P trend < 0.01). Women having four or more full-term pregnancies had a 31% lower breast CIS risk (RR = 0.69, 95% CI = 0.51 to 0.93) and 18% lower invasive breast cancer risk (RR = 0.82, 95% CI = 0.72 to 0.94). Parous women whose first full-term pregnancy occurred at age 35 years or later had a 118% greater risk for breast CIS (RR = 2.18, 95% CI = 1.36 to 3.49) and 27% greater risk for invasive breast cancer (RR = 1.27, 95% CI = 0.99 to 1.65) than those whose first full-term pregnancy occurred before age 21 years. Furthermore, parity was negatively associated with the risk of estrogen receptor-positive (ER+) or ER+/progesterone receptor-positive (PR+) while age at first full-term pregnancy was positively associated with the risk of ER+ or ER+/PR+ invasive breast cancer. Neither of these factors was statistically significantly associated with the risk of ER-negative (ER-) or ER-/PR- invasive breast cancer, tests for heterogeneity between subtypes did not reach statistical significance. No clear associations were detected for other pregnancy-related factors.
These results provide some epidemiologic evidence that parity and age at first full-term pregnancy are involved in the development of breast cancer among postmenopausal women. The role of these factors in risk of in situ versus invasive, and hormone receptor-positive versus -negative breast cancer merits further exploration.
We investigated the association between hypertension, antihypertensive (AH) medication use, and breast cancer in a large prospective study, the California Teachers Study (CTS).
Information on history of hypertension and lifetime regular use of AH medications was collected from 114,549 women in 1995–1996. Among them, 4,151 invasive breast cancers were diagnosed between 1995 and 2006. Additional information on AH use was collected from 73,742 women in 2000–2001, and 1,714 of these women were subsequently diagnosed with breast cancer. Cox proportional hazards regression was used to estimate relative risks (RR) and 95% confidence intervals (CI) for breast cancer.
Use of AH medication for ≥5 years, when compared with no use, was associated with a modest increased risk of invasive breast cancer (RR = 1.18, 95%CI 1.02–1.36). This increased risk appeared to be confined to estrogen receptor (ER)-positive tumors (RR = 1.21, 95%CI 1.03–1.43) and pre-/peri-menopausal women (RR = 1.58, 95%CI 1.11–2.25).
Increased risk of invasive breast cancer was observed for long-term (≥5 years) AH use, and this appeared to be confined to ER + breast cancer and younger women.
Hypertension; Breast cancer; Antihypertensive medication
Women with primary breast cancer are at increased risk of developing second primary breast cancer. Few studies have evaluated risk factors for the development of asynchronous contralateral breast cancer in women with breast cancer. In the Women's Environmental Cancer and Radiation Epidemiology Study (1985–2001), the roles of alcohol and smoking were examined in 708 women with asynchronous contralateral breast cancer (cases) compared with 1,399 women with unilateral breast cancer (controls). Cases and controls aged less than 55 years at first breast cancer diagnosis were identified from 5 population-based cancer registries in the United States and Denmark. Controls were matched to cases on birth year, diagnosis year, registry region, and race and countermatched on radiation treatment. Risk factor information was collected by telephone interview. Rate ratios and 95% confidence intervals were estimated by using conditional logistic regression. Ever regular drinking was associated with an increased risk of asynchronous contralateral breast cancer (rate ratio = 1.3, 95% confidence interval: 1.0, 1.6), and the risk increased with increasing duration (P = 0.03). Smoking was not related to asynchronous contralateral breast cancer. In this, the largest study of asynchronous contralateral breast cancer to date, alcohol is a risk factor for the disease, as it is for a first primary breast cancer.
alcohol drinking; breast neoplasms; neoplasms, second primary; smoking
Advances have been made in treatment and outcomes for pediatric cancer. However adolescents and young adults (AYAs) with cancer have not experienced similar relative improvements. We undertook a study to develop the methodology necessary for epidemiologic cancer research in these age groups. Our goal was to create the Kids, Adolescents, and Young Adults Cancer (KAYAC) project to create a resource to address research questions relevant to this population. We used a combination of clinic and population-based ascertainment to enroll 111 cases aged 0–39 for this methodology development study. The largest groups of cancer types enrolled include: breast cancer, leukemia, lymphoma, and melanoma. The overall participation rate is 69.8% and varies by age and tumor type. The study included patients, mothers, and fathers. The methods used to establish this resource are described, and the values of the resource in studies of childhood and young adult cancer are outlined.
Recent, international declines in breast cancer incidence are unprecedented, and the causes remain controversial. Few data sources can address breast cancer incidence trends according to pertinent characteristics like hormone therapy use history.
We used the prospective California Teachers Study to evaluate changes in self-reported use of menopausal hormone therapy (HT) between 1995 to 1996 and 2005 to 2006 and age-adjusted breast cancer incidence among 74,647 participants aged 50 years or older. Breast cancer occurrence was determined by linkage with the California Cancer Registry.
During 517,286 woman years of follow up, 565 in situ and 2,668 invasive breast cancers were diagnosed. In situ breast cancer incidence rates in this population did not change significantly from 2000 to 2002 to 2003 to 2005, whereas rates of invasive breast cancer declined significantly by 26.0% from 528.0 (95% confidence intervals (CI) = 491.1, 564.9) per 100,000 women in 2000 to 2002 to 390.6 (95% CI = 355.6, 425.7) in 2003 to 2005. The decline in invasive breast cancer incidence rates was restricted to estrogen receptor-positive tumors. In 1996 to 1999 and 2000 to 2002 invasive breast cancer incidence was higher for women who reported current HT use especially estrogen-progestin (EP) use at baseline than for never or past users; but by 2003 to 2005 rates were comparable between these groups. For women who were taking EP in 2001 to 2002,75% of whom had stopped use by 2005 to 2006, incidence had declined 30.6% by 2003 to 2005 (P = 0.001); whereas incidence did not change significantly for those who never took HT (P = 0.33).
Few data resources can examine prospectively individual HT use and breast cancer diagnosis. Stable in situ breast cancer rates imply consistent levels of screening and suggest recent declines in invasive breast cancer to be explained predominantly by changes in HT use.
In California, leukemia represents ~35, 5, and 2% of all cancers in children (aged 0–14), adolescents (15–29), and young adults (30–39), respectively. Poorer survival has been previously noted in individuals residing in lower socioeconomic status (SES) neighborhoods. We explored the relationship between SES and survival as modified by age and race/ethnicity using data from the California Cancer Registry.
A total of 7,688 incident cases of first primary leukemia diagnosed during 1996–2005 in individuals aged 0–39 at diagnosis were included in this study. Univariate analyses of overall survival were conducted using the Kaplan–Meier method and multivariate survival analyses were performed using Cox proportional hazard regression to estimate hazard ratios.
Multivariate analyses showed that overall survival and lymphoid cancer–specific survival was reduced in those individuals aged 15–39 compared to children aged 0–14. Although shorter survival was observed in non-whites, an association between lower-SES neighborhood and shorter survival was significant only for non-Hispanic whites (NHWs) (p value for trend <0.05). Lack of insurance was significantly associated with shorter survival for all race/ethnicities examined except Asian/Pacific Islanders (p value < 0.05).
Lower survival in individuals diagnosed with leukemia was observed in adolescents and young adults compared to children and in non-whites compared to NHWs. Further, the independent effects on survival of both low SES and lack of insurance at diagnosis persisted after adjustment for demographic variables and varied across race/ethnicities.
Leukemia; Survival analysis; Adolescent and young adult; Socioeconomic
Women younger than 35 years who are diagnosed with breast cancer tend to have more advanced stage tumors and poorer prognoses than do older women. Pregnancy is associated with elevated exposure to estrogen, which may influence the progression of breast cancer in young women. The objective of the present study was to examine the relationship between reproductive events and tumor stage, grade, estrogen receptor and progesterone receptor status, and survival in women diagnosed with early-onset breast cancer.
In a population-based, case–case study of 254 women diagnosed with invasive breast cancer at age under 35 years, odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression with tumor characteristics as dependent variables and adjusting for age and education. Survival analyses also examined the relationship between reproductive events and overall survival.
Compared with nulliparous women, women with three or more childbirths were more likely to be diagnosed with nonlocalized tumors (OR = 3.1, 95% CI = 1.3–7.7), and early age (<20 years) at first full-term pregnancy was also associated with a diagnosis of breast cancer that was nonlocalized (OR = 3.0, 95% CI = 1.2–7.4) and of higher grade (OR = 3.2, 95% CI 1.0–9.9). The hazard ratio for death among women with two or more full-term pregnancies, as compared with those with one full-term pregnancy or none, was 2.1 (95% CI = 1.0–4.5), adjusting for stage. Among parous women, those who lactated were at decreased risk for both estrogen receptor and progesterone receptor negative tumors (OR = 0.2, 95% CI = 0.1–0.5, and OR = 0.4, 95% CI = 0.2–0.8, respectively).
The results of the present study suggest that pregnancy and lactation may influence tumor presentation and survival in women with early-onset breast cancer.