Abstract P6-08-14: Breast cancer risk in chronic users of phthalate-containing medications: A Danish nationwide cohort study

Background. Phthalates are ubiquitous in consumer goods (e.g., food containers, cosmetics, and pharmaceuticals), from which they readily leach into the environment. Phthalates interfere with hormonal signaling and may affect reproductive, developmental, and cancer endpoints. Preclinical evidence implicates some phthalates in breast cancer progression—particularly dibutyl phthalate (DBP), which potentiates the estrogen receptor (ER). Associations between phthalates and breast cancer incidence have not been thoroughly investigated. Users of phthalate-containing medications have up to 70-fold higher urinary phthalate levels than other individuals, and represent a highly exposed population for efficient study of phthalate health effects.

Methods. We used the Danish Drug Information Database to identify all phthalate-containing oral medications marketed during the study period. We recorded the product code and the type and mass of phthalate per pill. We identified a nationwide cohort of women at risk for a first cancer between 2005—2015, and who had no previous exposure to a phthalate-containing drug. Using the National Prescription Registry we characterized time-varying, medication-borne phthalate exposure. Incident cancers were ascertained by linking to the Danish Cancer Registry. We fit Cox regression models to estimate associations between cumulative phthalate exposures and breast cancer incidence. Exposures were updated annually and lagged by 1 year. We adjusted for established risk factors, comorbidity, co-medications (e.g., HRT), and drug substances exposed to.

Results. We identified 481 products from 24 drug classes containing either DBP, diethyl phthalate (DEP), cellulose acetate phthalate (CAP), hypromellose phthalate (HPMCP), or polyvinyl acetate phthalate (PVAP). Drugs with phthalate-containing products also included phthalate-free products. Phthalate masses ranged from 3 µg to 1.3 g per pill. We followed 1.12 million women over 9.99 million person-years, during which 27,111 women were diagnosed with invasive breast cancer. Fourteen percent of the cohort (n=161,751) was prescribed a phthalate-containing drug. We observed no breast cancer associations with exposure to CAP, DEP, HPMCP, and PVAP. However, the highest level of cumulative DBP exposure (>10,000 mg; range: 10,024 to 71,340 mg; median=15,390 mg) was associated with an 80% increase in breast cancer risk compared with no exposure (HRadj=1.8; 95% CI: 1.0, 3.1). The association was strongest for ER+ disease (HRadj=1.9; 95% CI: 1.1, 3.5) and among premenopausal women (HRadj=2.2; 95% CI: 0.91, 5.3). There was no evidence of a linear trend in the log-hazard across categories of cumulative DBP exposure. No published evidence links exposure to the drug substances represented by the DBP-containing products (bisacodyl, budesonide, mesalazine, multienzymes, diclofenac, and lithium) with breast cancer risk.

Conclusions. High DBP exposure was associated with increased breast cancer incidence, particularly ER+ disease and among premenopausal women. This association merits further investigation. In the meantime, it may be prudent for women taking DBP-containing medications to substitute a phthalate-free version of the same drug, other considerations being equal.

Citation Format: Ahern TP, Cronin-Fenton DP, Broe A, Pilgaard Ulrichsen S, Cole BF, Lash TL, Toft Sørensen H, Tamimi RM, Damkier P. Breast cancer risk in chronic users of phthalate-containing medications: A Danish nationwide cohort study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-08-14.

Breast cancer recurrence after reoperation for surgical bleeding

BACKGROUND

Bleeding activates platelets that can bind tumour cells, potentially promoting metastatic growth in patients with cancer. This study investigated whether reoperation for postoperative bleeding is associated with breast cancer recurrence.

METHODS

Using the Danish Breast Cancer Group database and the Danish National Patient Register (DNPR), a cohort of women with incident stage I-III breast cancer, who underwent breast-conserving surgery or mastectomy during 1996-2008 was identified. Information on reoperation for bleeding within 14 days of the primary surgery was retrieved from the DNPR. Follow-up began 14 days after primary surgery and continued until breast cancer recurrence, death, emigration, 10 years of follow-up, or 1 January 2013. Incidence rates of breast cancer recurrence were calculated and Cox regression models were used to quantify the association between reoperation and recurrence, adjusting for potential confounders. Crude and adjusted hazard ratios according to site of recurrence were calculated.

RESULTS

Among 30 711 patients (205 926 person-years of follow-up), 767 patients had at least one reoperation within 14 days of primary surgery, and 4769 patients developed breast cancer recurrence. Median follow-up was 7·0 years. The incidence of recurrence was 24·0 (95 per cent c.i. 20·2 to 28·6) per 1000 person-years for reoperated patients and 23·1 (22·5 to 23·8) per 1000 person-years for non-reoperated patients. The overall adjusted hazard ratio was 1·06 (95 per cent c.i. 0·89 to 1·26). The estimates did not vary by site of breast cancer recurrence.

CONCLUSION

In this large cohort study, there was no evidence of an association between reoperation for bleeding and breast cancer recurrence.

Abstract P3-07-23: CYP2D6 genotype and breast cancer recurrence in tamoxifen treated patients: An evaluation of the importance of loss-of-heterozygosity

Background: Tamoxifen therapy for estrogen receptor positive (ER+) breast cancer reduces recurrence risk by about half. Steady-state concentrations of endoxifen, a potent anti-estrogenic tamoxifen metabolite, are reduced in women whose CYP2D6 genotypes confer poor enzyme function. Many studies have measured associations between genetically impaired CYP2D6 function and tamoxifen resistance. It has been suggested that the subset of studies using DNA extracted from tumor-infiltrated tissue may have been susceptible to genotyping error induced by loss of heterozygosity (LOH); the putative non-differential genotype misclassification may have biased these studies' estimates toward the null. We reviewed the clinical epidemiology studies conducted to date to assess the importance of loss-of-heterozygosity (LOH) at the CYP2D6 locus and its implications for assessing tamoxifen effectiveness.

Methods: We searched for the terms "tamoxifen" and "CYP2D6" in PubMed, including all papers and abstracts through 31 May 2015 on the association of CYP2D6 gene variants and the risk of breast cancer recurrence or mortality. We used a quantitative bias analysis (QBA) to evaluate the importance of genotype misclassification in studies that extracted DNA from tumor-infiltrated tissue. We conducted a random effects meta-analysis to evaluate all studies simultaneously, and within groups according to whether DNA was derived from tumor-infiltrated tissue or non-neoplastic tissue.

Results: Thirty-one studies investigated CYP2D6 genotype and breast cancer recurrence, yielding relative effect estimates ranging from 0.08 to 14. DNA was extracted from blood or non-neoplastic tissue in 21 of these 31 studies (68%), and from tumor-infiltrated tissue in the remaining 10 (32%). Our analysis of the association between variant/variant genotype compared with wildtype/wildtype genotype included 21 of the 31 studies. Sixteen (76%) of these 21 studies extracted DNA from blood or non-neoplastic tissue and five (24%) extracted DNA from tumor-infiltrated tissue. Genotype misclassification parameters for the QBA were estimated from six concordance studies. There was little difference between the effect estimates (EE) and 95% confidence/simulation intervals (95% CI/SI) before and after QBA (EE=1.71, 95%CI=1.24, 2.36, and 1.80 95%SI=1.28, 2.54, respectively). Studies using non-neoplastic DNA had higher variance than those based on tumor-infiltrated tissue DNA, half reported implausibly high EE, and many were susceptible to design and analysis errors that would bias estimates of association away from the null.

Conclusions: We found little relative bias in the summary estimates of association, either overall or when limited to the tumor-infiltrated tissue DNA studies. Three guideline panels, based on robust evidence, recommend against CYP2D6 genotype-guided tamoxifen therapy. Alternatives for optimizing the effectiveness of tamoxifen therapy, such as assuring adherence and persistence, are more likely to achieve clinically important benefits.

Citation Format: Ahern TP, Hertz DL, Damkier P, Ejlertsen B, Hamilton-Dutoit SJ, Rae JM, Regan MM, Thompson AM, Lash TL, Cronin-Fenton DP. CYP2D6 genotype and breast cancer recurrence in tamoxifen treated patients: An evaluation of the importance of loss-of-heterozygosity. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-23.

Glucocorticoid prescriptions and breast cancer recurrence: a Danish nationwide prospective cohort study

BACKGROUND

Treatment with synthetic glucocorticoids (GCs) depresses the immune response and may therefore modify cancer outcomes. We investigated the association between GC use and breast cancer recurrence.

MATERIALS AND METHODS

We conducted a population-based cohort study to examine the risk of breast cancer recurrence associated with GC use among incident stage I-III female breast cancer patients aged >18 years diagnosed 1996-2003 in Denmark. Data on patients, clinical and treatment factors, recurrence, and comorbidities as well as data on GC prescriptions and potential confounders were obtained from Danish population-based medical registries. GCs were categorized according to administrative route: systemic, inhaled, or intestinal. Women were followed for up to 10 years or until 31 December 2008. We used Cox proportional hazards regression models to compute hazard ratios (HRs) and associated 95% confidence intervals (95% CIs) to evaluate the association between GC use and recurrence. Time-varying drug exposures were lagged by 1 year.

RESULTS

We included 18 251 breast cancer patients. Median recurrence follow-up was 6.9 years; 3408 women developed recurrence during follow-up. Four thousand six hundred two women filled at least one GC prescription after diagnosis. In unadjusted models, no association was observed among users of systemic, inhaled, and intestinal GCs (HRsystemic = 1.1, 95% CI 0.9-1.3; HRinhaled = 0.9, 95% CI 0.7-1.0; and HRintestinal = 1.0, 95% CI 0.9-1.2) versus nonusers. In adjusted models, the results were also near null (HRsystemic = 1.1, 95% CI 0.9-1.2; HRinhaled = 0.8, 95% CI 0.7-1.0; and HRintestinal = 1.0, 95% CI 0.8-1.2).

CONCLUSION

We found no evidence of an effect of GC use on breast cancer recurrence.

Mortality and incidence of new primary cancers in men with prostate cancer: a Danish population-based cohort study

BACKGROUND

Prostate cancer (PC) survivors may have an increased risk of new primary cancers (NPCs) due to shared risk factors or PC-directed treatments.

METHODS

Using Danish registries, we conducted a cohort study of men with (n=30,220) and without PC (n=151,100) (comparators), matched 1:5 on age and PC diagnosis/index date. We computed incidence rates of NPCs per 10,000 person years (PY) and associated 95% confidence intervals (CI), and used Cox proportional hazards regression to compute hazard ratios (HRs) and 95%CI, adjusting for comorbidities. In order to obviate any impact of shorter survival among prostate cancer patients, we censored comparator patients when the matched prostate cancer patient died or was censored.

RESULTS

Follow-up spanned 113,487PY and 462,982PY in the PC and comparison cohorts, respectively. 65% of the cohorts were aged >70 years at diagnosis. Among PC patients, 51% had distant/unspecified stage, and 63% had surgery as primary treatment. The PC cohort had lower incidence of NPCs than their comparators. The adjusted HR of NPC among men with PC versus the comparators was 0.84 (95%CI=0.80, 0.88). Lowest HRs were among older men, those with distant stage, and were particularly evident for cancers of the brain, liver, pancreas, respiratory, upper gastrointestinal, and urinary systems.

CONCLUSIONS

We find no evidence of an increased risk of NPCs among men with PC. The deficit of NPCs among men with PC may be a true effect but is more likely due to lower levels of risk factors (e.g., smoking) in PC patients versus comparators, clinical consideration of cancers at new organs as metastases rather than new primaries, or under-recording/under-reporting of NPCs among PC patients.

Antidepressant use and colorectal cancer risk: a Danish population-based case-control study

Background:

Earlier research suggests that use of selective serotonin reuptake inhibitors (SSRIs), but not tricyclic antidepressants (TCAs), reduces the risk of colorectal cancer (CRC).

Methods:

We conducted a population-based case–control study to investigate the association between antidepressant use and CRC risk. Cases were diagnosed with a first primary CRC from 1991 through 2008. We selected 10 population controls matched to cases on sex, birth year, and residence from the Danish Civil Registration System using risk-set sampling. We estimated the odds ratios (ORs) and 95% confidence intervals (CIs) associating antidepressant use with colorectal cancer occurrence, controlling for potential confounders.

Results:

The study included 9979 cases and 99 790 controls. We found no notable reduction in CRC risk in ever users (⩾2 prescriptions) of TCAs (OR=0.94; 95% CI: 0.84, 1.05), SSRIs (OR=0.97; 95% CI: 0.90, 1.05), or other antidepressants (OR=0.95; 95% CI: 0.83, 1.07). Associations for recent and former use of antidepressants were also near null. Intensity of antidepressant use (number of pills divided by total duration of use), regardless of duration, was not associated with CRC risk.

Conclusions:

We found no evidence that antidepressant use substantially reduces the risk of colorectal cancer.

Hospitalisation for venous thromboembolism in cancer patients and the general population: a population-based cohort study in Denmark, 1997-2006

Background:

Venous thromboembolism (VTE) frequently complicates cancer. Data on tumour-specific VTE predictors are limited, but may inform strategies to prevent thrombosis.

Methods:

We computed incidence rates (IRs) with 95% confidence intervals (CIs) for VTE hospitalisation in a cohort of cancer patients (n=57 591) and in a comparison general-population cohort (n=287 476) in Denmark. The subjects entered the study in 1997–2005, and the follow-up continued through 2006. Using Cox proportional-hazards regression, we estimated relative risks (RRs) for VTE predictors, while adjusting for comorbidity.

Results:

Throughout the follow-up, VTE IR was higher among the cancer patients (IR=8.0, 95% CI=7.6–8.5) than the general population (IR=4.7, 95% CI=4.3–5.1), particularly in the first year after cancer diagnosis (IR=15.0, 95% CI=13.8–16.2, vs IR=8.6, 95% CI=7.6–9.9). Incidence rates of VTE were highest in patients with pancreas (IR=40.9, 95% CI=29.5–56.7), brain (IR=17.7, 95% CI=11.3–27.8) or liver (IR=20.4, 95% CI=9.2–45.3) tumours, multiple myeloma (IR=22.6, 95% CI=15.4–33.2) and among patients with advanced-stage cancers (IR=27.7, 95% CI=24.0–32.0) or those who received chemotherapy or no/symptomatic treatment. The adjusted RR (aRR) for VTE was highest among patients with pancreas (aRR=16.3, 95% CI=8.1–32.6) or brain cancer (aRR=19.8 95% CI=7.1–55.2), multiple myeloma (aRR=46.1, 95% CI=13.1–162.0) and among patients receiving chemotherapy, either alone (aRR=18.5, 95% CI=11.9–28.7) or in combination treatments (aRR=16.2, 95% CI=12.0–21.7).

Conclusions:

Risk of VTE is higher among cancer patients than in the general population. Predictors of VTE include recency of cancer diagnosis, cancer site, stage and the type of cancer-directed treatment.

Comorbidity and survival of Danish breast cancer patients from 1995 to 2005

Comorbid diseases can affect breast cancer prognosis. We conducted a population-based study of Danish women diagnosed with a first primary breast cancer from 1995 to 2005 (n=9300), using hospital discharge registry data to quantify comorbidities by Charlson score. We examined the influence of comorbidities on survival, and quantified their impact on relative mortality rates. The prevalence of patients with a Charlson score='0' fell from 86 to 81%, with an increase in those with Charlson score='1-2' from 13 to 16%, and score='3+' from 1 to 2%. One- and five-year survival for patients with Charlson score='0' and '1-2' was better for those diagnosed in 1998-2000 than in 1995-1997. Overall, patients diagnosed in 2001-2004 (mortality ratio (MR)=0.80, 95% CI=0.68-0.95) and 1998-2000 (MR=0.92, 95% CI=0.78-1.09) had lower 1-year age-adjusted mortality compared to those diagnosed in 1995-1997 (reference period). Patients with Charlson scores '1-2' and '3+' had higher age-adjusted 1-year mortality than those with a Charlson score='0' in each time period (2001-2004: MR('1-2')=1.76, 95% CI=1.35-2.30, and MR('3+')=3.78, 95% CI=2.51-5.68; and 1998-2000: MR('1-2')=1.60, 95% CI=1.36-1.88 and MR('3+')=2.34, 95% CI=1.65-3.33). Similar findings were observed for 5-year age-adjusted mortality. Additional analyses, adjusted for stage, indicated that confounding by stage could not explain these findings. Despite continued improvements in breast cancer survival, we found a trend of poorer survival among breast cancer patients with severe comorbidities even after adjusting for age and stage. Such poorer survival is an important public health concern and can be expected to worsen as the population ages.

Patterns of care and effects on mortality for cancers of the oesophagus and gastric cardia: a population-based study

BACKGROUND

We investigated temporal trends in treatment, and factors influencing treatment receipt and survival, for upper gastrointestinal cancers in routine community-based clinical practice.

PATIENTS AND METHODS

Oesophageal and gastric-cardia cancers, diagnosed during the period 1994-2001, were sourced from the National Cancer Registry (Ireland). Analysis was by Joinpoint regression and multivariate logistic and Cox models.

RESULTS

Thirty-five percent of patients received surgery, 35% radiotherapy and 24% chemotherapy. Over time chemo- and radiotherapy receipt increased significantly, whilst surgery decreased. Treatment patterns varied by tumour site, histology and stage. Older and/or unmarried patients were significantly less likely to receive treatment. Among surgically treated patients, those aged 70+ had higher mortality. Among both surgical and non-surgical patients, those receiving chemotherapy or radiotherapy had a modest, short-term, survival benefit.

CONCLUSIONS

The use of adjuvant therapies is increasing in routine practice. After adjusting for clinical factors, patient-related factors predicted treatment and mortality. Improving equity in gastrointestinal cancer treatment may help improve survival.