Body mass index, age at breast cancer diagnosis, and breast cancer subtype: a cross-sectional study

PURPOSE

Evidence suggests that premenopausal obesity decreases and postmenopausal obesity increases breast cancer risk. Because it is not well known whether this is subtype dependent, we studied the association between body mass index (BMI) and age at breast cancer diagnosis, or the probability of being diagnosed with a specific breast cancer phenotype, by menopausal status.

METHODS

All patients with non-metastatic operable breast cancer from the University Hospital Leuven diagnosed between January 1, 2000 and December 31, 2013 were included (n = 7020) in this cross-sectional study. Linear models and logistic regression were used for statistical analysis. Allowing correction for age-related BMI-increase, we used the age-adjusted BMI score which equals the difference between a patient's BMI score and the population-average BMI score corresponding to the patient's age category.

RESULTS

The quadratic relationship between the age-adjusted BMI and age at breast cancer diagnosis (p = 0.0207) interacted with menopausal status (p < 0.0001); increased age at breast cancer diagnosis was observed with above-average BMI scores in postmenopausal women, and with below-average BMI scores in premenopausal women. BMI was linearly related to the probabilities of Luminal B and HER2-like breast cancer phenotypes, but only in postmenopausal women. The relative changes in probabilities between both these subtypes mirrored each other.

CONCLUSION

BMI associates differently before and after menopause with age at breast cancer diagnosis and with the probability that breast cancer belongs to a certain phenotype. The opposite effect of increasing BMI on relative frequencies of Luminal B and HER2-like breast cancers suggests a common origin.

Abstract P6-09-12: Breast cancer characteristics and the levonorgestrel intrauterine device. A monocentric retrospective study

OBJECTIVE: The levonorgestrel-intrauterine device (LNG-IUD) is a widely used contraceptive method. It is not clear if LNG-IUD users are more likely to develop breast cancer. Breast cancer growth through the estrogen and/or the human epidermal growth factor receptor 2 (HER2) pathway could be influenced by a continuous low systemic dose of levonorgestrel. In this study, we compare breast cancer characteristics and the receptor expression of estrogen (ER), progesterone (PR) and HER2 in women with and without a LNG- IUD at the time of diagnosis.

METHODS: In this retrospective, observational study, we included 2599 consecutive breast cancer patients who were younger than 55 years at diagnosis and treated between 2000 and 2014 in the University Hospitals Leuven for a primary invasive, non-metastatic tumor. The non LNG-IUD group was matched by age and parity at diagnosis. ER, PR and HER2 status were reported according to ASCO/CAP guidelines. The Chi-square test was used to compare receptor status between groups. All tests were two-sided, and a 5% significance level was assumed. An additional analysis was performed to detect the occurrence of HER 2 expression with or without intake of oral contraception by diagnosis in the control group.

RESULTS: 366 LNG-IUD users and 2233 women without a LNG-IUD were included. Compared to the control group, the LNG-IUD users had a lower Nottingham prognostic index (4.2 vs 4.4; p=0.048), more PR expression (79.2% vs 73.4%; p=0.021) but less HER2 expression (11.6% vs 17.2%; p=0.009). A significant higher rate of ER+PR+HER2- was observed in the LNG-IUD group (63.26 % vs 73.46%; p&lt;0.001). These differences in receptor expression were mainly observed in the age group 45-49 years at diagnosis. Additionally, a trend of more HER2 positivity associated with oral contraceptive use was noticed in the control group.

CONCLUSION: We found in a breast cancer population, matched for age and parity, significant differences in the PR and HER2 expression according to use of LNG-IUD at time of diagnosis. ER positive, PR positive and HER2 negative breast cancers are more frequently seen in LNG-IUD users. There is a trend of less HER 2 positivity in LNG-IUD users and it is more common seen in oral contraception users.

Citation Format: Borowski E, Poppe A, Laenen A, Remmerie C, Van Asten K, Nevelsteen I, Smeets A, Weltens C, Peeters S, Leunen K, Berteloot P, Amant F, Vergote I, Van Limbergen E, Christiaens M-R, Wildiers H, Floris G, Poppe W, Neven P. Breast cancer characteristics and the levonorgestrel intrauterine device. A monocentric retrospective study. [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 P6-09-12.

Abstract P5-08-31: Withdrawal of exogenous hormones affects prognostic multigene signature results in early luminal breast cancer

Background

Early breast cancer (BC) outcomes are mainly estimated based on clinicopathological parameters and rarely include proliferation markers: (Ki-67), and multigene signatures (MGS), which are typically measured in tumors from resection specimens (RS). We believe that tumor proliferation can change within days of anti-estrogen use. However, little is known how proliferation changes after withdrawal of hormone replacement therapy (HRT) or oral anti-conception (OAC) after a core needle biopsy (CNB) shows BC. Hence, this study compares the Ki-67 labeling index and the MGS results in CNB and RS collected from a cohort of patients under OAC/HRT.

Patients and Methods

This retrospective study included consecutive women diagnosed with a grade 1-2, any pTN0-1, primary operable estrogen receptor-positive, human epidermal growth factor receptor 2-negative, and invasive ductal carcinoma between January 2013 and July 2014 at the Multidisciplinary Breast Center of University Hospitals Leuven were selected from a prospectively managed database. Ki-67 staining was performed on RS (Ki-67RS) to compare those who used HRT/OAC for at least 3 months at diagnosis and those not using OAC/HRT at diagnosis. OAC/HRT was always stopped between CNB and RS. Subsequently, we compared Ki-67 of the CNB (Ki-67CNB) with the matched RS in 15 patients with a low Ki-67RS (14%) stopping OAC/HRT after CNB; revised standard pathology confirmed absence of tumor heterogeneity in all samples. In addition, in a subset of patients (≥50 years, Ki-67RS ≤5%) we compared Ki-67 index and MGS results (MammaPrint (MP) and BluePrint, Agendia) from the CNB versus RS.

Results

193 patients with a known Ki-67RS were included; 38 patients (mean age of 55 years) were on OAC/HRT at CNB and 155 patients (mean age of 64 years) were not. The median time between stopping OAC/HRT and resection was 23 days (range 8-48 days). Ki-67RS was &lt;6%, 6-14% and ≥15% in 30.0%, 36.8% and 33.2% in the whole group of patients, respectively. These figures were 44.7%, 44.7% and 10.5% in patients on OAC/HRT at CNB diagnosis and 26.5%, 34.8% and 38.7% in patients not on OAC/HRT. This difference was significant (p&lt;0.05) for patients ≥50 years on HRT at CNB diagnosis. Four of 15 patients, which stopped OAC/HRT after the CNB (26.7%), showed a low Ki-67RS (≤14%) and had a high matched Ki-67CNB (≥15%). In another subset of four out of 15 patients we compared CNB and RS (table1) where we observed changes in both Ki-67 and MGS.

MP and Ki-67 results from matched CNB and RS. CNBRSPatientKi-67 (%)MP indexKi-67 (%)MP index150.371-20.31280.1150.043100.0650.03425-0.702-0.13Low risk is defined as MP index ≥0.0575 and/or Ki-67 ≤14.

Conclusion

Women on OAC/HRT, at diagnosis of an early luminal BC, are more likely to have a lower Ki-67RS as those not using OAC/HRT. Our findings are likely explained by a sudden decrease in sex steroids after BC diagnosis, resulting in lower proliferation markers. As such, a lower hormonal environment by withdrawing HRT/OAC at BC diagnosis might underestimate proliferation markers used for prognostic and predictive purposes. Therefore we are currently testing this hypothesis in larger cohorts.

Citation Format: Jongen L, De Vries P, Van Asten K, Lintermans A, Laenen A, Wildiers H, Floris G, Neven P. Withdrawal of exogenous hormones affects prognostic multigene signature results in early luminal breast cancer. [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 P5-08-31.

Genetic variant in the osteoprotegerin gene is associated with aromatase inhibitor-related musculoskeletal toxicity in breast cancer patients

BACKGROUND

Aromatase inhibitor (AI) therapy is associated with musculoskeletal (MS) toxicity, which adversely affects quality of life and therapy adherence. Our objective was to evaluate whether genetic variants may predict endocrine therapy-related MS pain and hot flashes in a prospective observational cohort study.

PATIENTS & METHODS

254 early breast cancer patients starting AI (n = 159) or tamoxifen therapy (n = 95) were included in this genetic biomarker study. MS and vasomotor symptoms were assessed at baseline and after 3, 6 and 12 months of therapy. AI-induced MS pain was defined as an increase in arthralgia or myalgia relative to baseline. Single nucleotide polymorphisms (SNP) in candidate genes involved in oestrogen signalling or previously associated with AI-related MS pain or oestrogen levels were selected.

RESULTS

Overall, 13 SNPs in CYP19, CYP17, osteoprotegerin (OPG) and oestrogen receptor 1 exhibited an allele frequency >0.05 and were included in the analysis. Patients carrying the G allele of rs2073618 in OPG experienced significantly more AI-induced MS toxicity compared to the wildtype allele, after correction for multiple testing (P = 0.046). Furthermore, this SNP was associated with severity of pain (P = 0.018). No association was found with regard to the other SNPs, both in AI and tamoxifen-treated patients. Neither could an association with vasomotor symptoms be demonstrated.

CONCLUSION

The SNP rs2073618 in OPG is associated with an increased risk of MS symptoms and pain with AI therapy, which has not been reported previously. Validation of this finding in larger cohorts and further functional studies are required.

Abstract P1-13-09: Sensitive liquid chromatography-tandem mass spectrometry method for serum estradiol and estrone assessment without derivatisation, overcoming cross reactivity with exemestane

Objective Measuring serum estrogen levels in postmenopausal women on oral aromatase inhibitors is important but challenging. Direct immunoassays are the most widely used techniques for measuring serum estradiol (E2) in research and clinical laboratories. Unfortunately, commercially available immunoassays for E2 lack precision and accuracy in the low range (&lt;20 ng/l) and are susceptible to interference. In addition, particularly in exemestane users biochemical monitoring of E2 is problematic because exemestane metabolites cross react in most immunoassays for E2. We developed a sensitive, routinely applicable liquid chromatography-tandem mass spectrometry (LC-MSMS) method for E2 and estrone (E1) quantification in human serum without the need for derivatization or an extended extraction protocol.

Materials and methods Serum E2 levels, assessed with LC-MSMS and electrochemiluminescence estradiol assay (ECLIA) on Modular E170 from Roche Diagnostics, of 10 breast cancer patients treated with exemestane were compared. Limit of quantification (LOQ) was 1.3 ng/l for LC-MSMS (coefficient of variation &lt;20% and signal-to-noise ratio &gt; 10, own validation) and 5 pg/ml for ECLIA (Roche, according to manufacturer).

Results Patients treated with exemestane showed much higher E2 levels when measured by ECLIA compared to E2 levels determined by LC-MSMS (Table 1). All patients, but one, had E2 values below LOQ when assessed with LC-MSMS whereas ECLIA measurements showed higher levels with a large variety (mean: 16.5 ng/l; range: 7-33 ng/l).

Results for E2 via ECLIA and LC-MSMS for patients treated with exemestanePatientE2 LC-MSMS ng/lE2 ECLIA ng/l1&lt;1.3212&lt;1.373&lt;1.3124&lt;1.3335&lt;1.3156&lt;1.3227&lt;1.398&lt;1.32692.51010&lt;1.310

Conclusion E2 levels in exemestane users measured with ECLIA from Roche are overestimated, probably due to cross reactivity of its metabolites. Therefore, this assay can not be used in these patients. Here, we demonstrate that this hurdle can be overcome by assessment of estrogen values with LC-MSMS. Our group was able to develop such a sensitive method, without derivatization.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-13-09.

Abstract OT3-2-04: Prospective multicenter study evaluating the effect of impaired tamoxifen metabolization on efficacy in breast cancer patients receiving tamoxifen in the neo-adjuvant or metastatic setting - The CYPTAM-BRUT 2 trial

Background

Tamoxifen is often used for the prevention and treatment of hormone receptor positive breast cancer. It is a prodrug which is metabolized by human liver enzymes to more active metabolites. The principal active metabolite of tamoxifen is considered to be endoxifen, which is formed by cytochrome P450 (CYP) enzymes. These enzymes are highly polymorphic in humans and endoxifen plasma levels are modulated by the patient's genotype. The effect of lowered endoxifen plasma levels on tamoxifen efficacy, however, is not yet clear as results remain contradictory. However, the association between endoxifen plasma concentrations, multiple CYP-genotypes and clinical outcome has not been studied so far in a prospective study in patients with advanced breast cancer receiving first-line tamoxifen treatment.

Trial design

CYPTAM-BRUT 2 is a prospective multicenter open-label single-arm non-randomized observational trial approved by the UZ Leuven Ethics Committee. Eligibility criteria are postmenopausal women with estrogen receptor positive invasive breast cancer receiving tamoxifen as first-line therapy in the metastatic or neo-adjuvant setting. Prior adjuvant endocrine therapy is allowed if there is more than 12 months after completion of the adjuvant therapy.

Primary endpoint is the association between endoxifen steady-state plasma concentrations and objective response rate after 3-6 months of treatment using RECIST criteria. Main secondary endpoint is the relation between endoxifen plasma concentrations and clinical benefit (CR+PR+SD at 6 months) according to the RECIST criteria. Other secondary endpoints include progression-free survival, toxicity and the association between CYP2D6 genotype and clinical outcome. In addition, we will assess how much of the variation in endoxifen levels is explained by the genetic variants and CYP2D6 inhibitors.

The trial is designed to detect a statistical association between endoxifen and objective tumor response rate (ORR), under the assumption that the relationship is linear with an odds ratio (OR) of 1.49 per 10 nmol/l. Using available data on endoxifen concentrations, this OR is chosen to reflect an improvement from 10% ORR in the lowest endoxifen quartile to 30% in the highest endoxifen quartile when the overall ORR is around 18%. To have 90% power at a 5% significance level, 180 patients have to be included into the study. The main secondary study endpoint is clinical benefit at 6 months. The study has to include 243 patients to detect a statistically significant association with endoxifen with 80% power at a 5% significance level, assuming an OR of 1.28 per 10 nmol/l. This OR is chosen to reflect an improvement of clinical benefit at 6 months from 30% in the lowest endoxifen quartile to 50% in the highest endoxifen quartile (overall clinical benefit around 39%).

Patient accrual

Currently 257 patients from 22 participating centers in Belgium and Switzerland are included (May 2013). As the sample size calculation did not account for missing data, inclusions will continue until 243 patients who fulfill the inclusion criteria are included (i.e. target lesions, blood sample and response evaluation).

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-2-04.