Abstract P3-04-04: Detection of ESR1 mutations in matched primary and metastatic samples from endocrine-resistant lobular breast cancer patients

Background:

Invasive lobular breast cancer (ILBC) represents the second most common histology of breast cancer (BC) and accounts for 10-15% of all invasive cases. Since >90% of ILBCs express the estrogen receptor (ER, coded by the ESR1 gene), the vast majority of these patients receive endocrine therapy. ESR1 mutations have mainly been identified in metastases from ER-positive BC at a frequency ranging from 11 to 50% and were shown to be associated with resistance to endocrine therapy. Nevertheless, ESR1 mutations have never been assessed in metastatic ILBC, hence the present study.

Patients and methods:

We aimed at interrogating the five most commonly reported ESR1 mutations (Y537S/C/N, D538G, E380Q) by droplet digital PCR (BioRad) in matched primary, axillary and metastatic ILBC samples (N=212) from 69 endocrine-resistant patients collected retrospectively from five hospitals.

Results:

We present here the results for the two most frequent ESR1 mutations (Y537S and D538G); data from the remaining mutations will be available at the time of the conference. We observed Y537S and D538G mutations in metastases from three and four patients, respectively. For one patient, the sampled metastasis harbored both the Y537S and the D538G mutations, confirming that ESR1 polyclonality can be present in the same metastasis. For another patient, two metastases were sampled and the D538G mutation was only present in one metastasis. Intriguingly, for two patients we observed D538G mutations only in the primary tumor but not in the corresponding metastasis, and for another only in an axillary lymph node. We could hypothesize that the clone carrying the mutation in the early setting has been removed either by the primary surgery or subsequent adjuvant chemotherapy. The ESR1 Y537S and D538G mutational frequencies observed in our metastatic ILC cohort (3/69, 4.35% and 4/69, 5.80%, respectively) are not statistically different from the frequencies reported in breast cancer metastases in the literature across the different studies (6.62% and 6.20%, respectively). All patients with ESR1-mutated metastases received at least 4 years of endocrine therapy and all but one were treated with an aromatase inhibitor (AI). However, half of these patients received exclusively endocrine therapy in the adjuvant setting.

Conclusion:

This is to the best of our knowledge, the first metastatic ILBC series in which the most frequently reported ESR1 mutations are being investigated, and the largest series in which ESR1 mutations are being investigated in matched metastatic, primary tumor and axillary lymph node samples. The frequencies that we found for the Y537S and D538G mutations are in line with those reported in the literature in metastatic biopsies for the general BC population. We further demonstrated using multiple samples from the primary tumor and an ultra-sensitive technology that there was no patient presenting an ESR1 mutation both in the early and metastatic disease. Data on the remaining mutations (Y537S/N, E380Q) will complete these results.

Citation Format: Desmedt C, Pingitore J, Rothé F, Rouas G, Bertucci F, Galant C, Rotmensz N, van den Eynden G, Salgado R, Larsimont D, Pruneri G, Sotiriou C. Detection of ESR1 mutations in matched primary and metastatic samples from endocrine-resistant lobular breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-04.

Abstract P1-05-17: Interrogating the impact of pregnancy on breast cancer biology using DNA copy number profiling

Background

Epidemiological evidence indicates a clear relationship between pregnancy and breast cancer (BC) risk. However, little is known regarding the impact of pregnancy on BC biology. DNA copy number aberrations (CNAs) play an important role in breast carcinogenesis. BC during pregnancy is a rare disease but yet could serve as a good model to study the impact of pregnancy on BC biology.

Methods

We retrospectively included 54 pregnant and 113 non-pregnant BC patients matched for age and stage with complete clinico-pathological, gene expression and 5-year follow-up data. CNAs were assessed using Affymetrix OncoScan FFPE arrays. We identified the CNAs associated with pregnancy using a multivariate logistic regression adjusted for classical clinico-pathological features. We further evaluated their impact on gene expression.

Results

After quality control, CNA profiles were obtained for 38 pregnant and 87 non-pregnant BC patients. We identified 13 regions with copy number gains, 11 of which were more frequently gained in pregnant compared to non-pregnant controls and 5 regions with copy number loss, 3 of which were more frequently lost in pregnant patients (p≤0.05). Of interest, we identified 4 genes previously identified as driver event associated with CNAs in breast cancer (S. Nik-Zainal et al, Nature 2016). AKT1 and CDKN2A/B were more frequently gained in the pregnant compared to the non-pregnant (23.7% vs. 8.0%, p=0.068 and 18.4% vs. 4.6% p=0.036) and ARID1B was less frequently gained in the pregnant cohort (2.6% vs. 13.8%, p=0.02). Interestingly, PAPPA which had been previously identified as a pregnancy-dependent oncogene (Takabatake Y. et al, EMBO Mol Med. 2016) was also more frequently gained in the pregnant compared to the non-pregnant patients (21.1% vs 5.8%, p=0.03). We next evaluated the effect of these CNAs on their own gene expression levels and found that AKT1 and CDKN2A/B CNAs were affected by gene-dosage effect.

Conclusions

In this study, we were able to identify several genomic alterations associated with pregnancy that could further elucidate the impact of pregnancy on BC risk. Moreover, by combining CNAs with gene expression, we were able to identify genes whose expression were associated with CNAs and therefore could be considered potential drivers of this rare disease.

Citation Format: Nguyen B, Brown DN, Rothé F, Desmedt C, Majjaj S, Pruneri G, Peccatori F, Azim Jr HA, Sotiriou C. Interrogating the impact of pregnancy on breast cancer biology using DNA copy number profiling [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-05-17.

Abstract S1-02: Lymphocytic infiltration in invasive lobular breast cancer

Background: The presence and prognostic value of tumor infiltrating lymphocytes (TILs) in invasive breast carcinoma has been demonstrated in several studies, especially in the triple-negative and HER2-positive subtypes. So far, TILs have not been investigated with sufficient detail in invasive lobular breast cancer (ILBC). Here we therefore aimed at: first, assessing the distribution of stromal TILs in ILBC; second, correlating the presence of TILs with standard clinical and pathological markers; third, exploring associations of TILs with recurrent genomic alterations; and, fourth, comparing the lymphocytic composition of ER-positive/HER2-negative lobular to ER-positive/HER2-negative ductal tumors.

Material and methods: The percentage of stromal TILs was independently assessed according to Salgado et al. (Ann Oncol 2015) by three pathologists on full-face hematoxylin and eosin slides in a well-annotated retrospective series of 614 primary ILBCs previously characterized at the genomic level. The median value of TILs was used for the analyses. For the association analyses, we focused on the more homogeneous group of ER-positive/HER2-negative ILBC (555/614). Breast cancer-free interval was used as survival endpoint and the analyses were censored at 12 years of follow-up. The comparison of the lymphocytic composition (relative percentage of CD45+ TILs which are CD4+, CD8+ or CD19+) was assessed by FACS in a separate prospective cohort of 51 ER-positive/HER2-negative lobular and 112 ER-positive/HER2-negative ductal tumors.

Results: The intraclass correlation coefficient between the three pathologists was 0.71 (95%CI:0.65-0.76). The median percentage of stromal TILs was 5% and the interquartile range 5-10%, with only 9% of the samples having ≥ 20%. Greater numbers of TILs were significantly associated with younger age at diagnosis, axillary lymph node involvement, high proliferative tumors as assessed by Ki67, and with the mixed non-classic ILBC subtypes. Greater numbers of TILs were associated with worse prognosis (HR=1.22; 95%CI:1.07-1.38, p=0.003) only in the unadjusted analysis, as it lost significance after adjustment for standard clinical and pathological variables. Greater numbers of TILs were observed in tumors harboring ARID1A, BRCA2, KMT2C and TP53 mutations, as well as chr3p21.31 and chr8q24.23 (PTK2) loss; whereas lower numbers were observed in tumors with ERBB3 mutations as well as chr7p and chr11q14.1 (PAK1) gains. There were no significant differences in the relative proportion of CD4+, CD8+ or CD19+ lymphocytes between ER-positive/HER2-negative lobular and ductal tumors.

Conclusion: In this work, which reports to our knowledge on the largest series of ILBC ever assessed for TILs, we showed that most ILBCs were characterized by low lymphocytic infiltration. Besides the association of TILs with clinical and pathological features of ILBC patients, we found that higher TIL levels were observed in the presence of specific mutations and copy number alterations. Higher numbers of TILs were associated with worse prognosis at the univariate analysis. Finally, based on the assessed markers, we have no evidence of differential lymphocytic composition between ER-positive/HER2-negative lobular and ductal tumors.

Citation Format: Desmedt C, Salgado R, Buisseret L, Zoppoli G, Fornili M, Van den Eynden G, Garaud S, Gundem G, Rothé F, Brown D, Kheddoumi N, Rouas G, Galant C, Bertucci F, Piccart M, Campbell P, Viale G, Larsimont D, Willard-Gallo K, Biganzoli E, Pruneri G, Sotiriou C. Lymphocytic infiltration in invasive lobular 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 S1-02.

Abstract P1-05-01: The epithelial to mesenchymal transition: Identifying a signature of recurrence in ductal carcinoma in situ

Background: The epithelial to mesenchymal transition (EMT) plays a critical role in the progression from non-invasive to invasive breast carcinomas (IBC). It is characterized by alterations in gene expression, changes in cellular polarity, the disruption of tight junctions; production of metalloproteinases, transforming growth factor-β (TGFβ) induction, expression of cancer stem cell markers, hypoxia, decrease in e-cadherin expression, along with other molecular biological events. Several transcription factors including ZEB1/2, TWIST1, SNAIL1/2, FOX family, GATA4/6 are involved in the process. There is a need to identify the molecular events driving the progression of ductal carcinoma in situ (DCIS); and to derive a signature that differentiates DCIS lesions that have the potential to recur as a subsequent DCIS, an IBC, or to not recur. To catalog the changes associated with EMT that may reveal a clinically relevant signature of progression from DCIS to DCIS or IBC recurrences using a panel of 200 genes related to EMT.

Methodology: RNA was extracted from formalin-fixed paraffin embedded (FFPE) sections of pure primary DCIS lesions representing three categories of outcome: those that did not recur; those that recurred with a subsequent DCIS; and those that recurred with invasive cancer. RNA abundance profiling was performed using Nanostring platform and data processing using an R statistical environment. Levels of mRNA abundance were modelled as a function of recurrence status. Coefficients were fit to terms representing the effect and the standard errors of the coefficient were adjusted with an empirical Bayes moderation. Model-based t-tests were then used to test if the coefficients were significantly different from zero.

Results: Using a technical control sample, pairwise comparisons across three replicates showed high correlation (ρ=0.99, Pρ<2.2x10-16 for all 3 comparisons), suggesting the robustness of the assay. In our preliminary survey of 45 patients across the three groups, we have identified a number of genes that showed differential mRNA abundance levels between patients who recurred (either DCIS or invasive recurrence) vs. those who did not recur. Using Random Forest analysis in a leave-one-out cross-validation approach, we were able to obtain a classifier with a sensitivity of 82% and specificity of 58%. Based on these initial findings, an additional 200 samples have been processed to support these initial findings.

Conclusion: The current literature provided increasing evidence that transcriptomic patterns reflecting the EMT may reveal novel biomarkers and elucidate molecular mechanisms leading to improved prognosis. Among breast carcinomas, differential expression of the EMT genes has been associated with a worse outcome, among estrogen receptor-negative and basal-like carcinomas. However, the understanding of the role of EMT genes in DCIS is limited; therefore, to elucidate whether the EMT plays a role in the progression of DCIS, we have designed an EMT gene panel that also includes genes that are significant prognosticators for IBC, including ER, PgR, Ki67 and HER2. In an exploratory analysis of cases trained based on clinical outcome, the sensitivity for predicting recurrence (whether DCIS or invasive) was 82%.

Citation Format: Felipe Lima J, Yao CQ, Yan F, Dion D, Quintayo MA, Lungu I, Nofech-Mozes S, Pruneri G, Viale G, Boutros PC, Bartlett JMS, Bayani J. The epithelial to mesenchymal transition: Identifying a signature of recurrence in ductal carcinoma in situ. [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 P1-05-01.

Operation and commissioning of IFMIF (International Fusion Materials Irradiation Facility) LIPAc injector

The objective of linear IFMIF prototype accelerator is to demonstrate 125 mA/CW deuterium ion beam acceleration up to 9 MeV. The injector has been developed in CEA Saclay and already demonstrated 140 mA/100 keV deuterium beam [R. Gobin et al., Rev. Sci. Instrum. 85, 02A918 (2014)]. The injector was disassembled and delivered to the International Fusion Energy Research Center in Rokkasho, Japan. After reassembling the injector, commissioning has started in 2014. Up to now, 100 keV/120 mA/CW hydrogen and 100 keV/90 mA/CW deuterium ion beams have been produced stably from a 10 mm diameter extraction aperture with a low beam emittance of 0.21 π mm mrad (rms, normalized). Neutron production by D-D reaction up to 2.4 × 10(9) n/s has been observed in the deuterium operation.

Clinical validity of tumor-infiltrating lymphocytes analysis in patients with triple-negative breast cancer

BACKGROUND

Although tumor-infiltrating lymphocytes (TILs) have been associated with a favorable prognosis in triple-negative breast cancer (TNBC) patients, this marker is not currently considered robust enough for entering the clinical practice. In the present study, we assessed the clinical validity of the guidelines recently issued by the International TIL Working Group in a large retrospective series of well-annotated TNBC patients.

PATIENTS AND METHODS

TILs were evaluated in all the full-face H&E sections from 897 consecutive TNBC (i.e. tumors with <1% of ER and PgR immunoreactivity and absence of HER2 overexpression or amplification) patients diagnosed and treated at the European Institute of Oncology between 1995 and 2010 (median follow-up 8.2 years, range 6 months to 18 years). All mononuclear cells were evaluated in the stromal area within the borders of the invasive tumor, reported as a percentage value and treated as a continuous variable in survival analysis.

RESULTS

The median percentage of TILs was 20%, and 21.9% of the cases had ≥50% (lymphocyte predominant breast cancer, LPBC) TILs. At univariable survival analysis, TILs were a significant predictor of better disease-free survival (DFS), distant disease-free survival (DDFS) and overall survival (OS) (P < 0.0001). Multivariable analysis confirmed that each 10% increase in TILs strongly predicted better survival, independent of patients' age, lymph node status, tumor size, histological grade, peritumoral vascular invasion and Ki-67 labeling index. Patients with LPBC had a 10-year survival rate of 71%, 84% and 96% for DFS, DDFS and OS, respectively. Stratified analysis revealed a positive correlation between TILs and OS across all the subgroups analyzed.

CONCLUSION

Our data support the analytical validity of the recently issued TILs evaluation guidelines in the clinical practice.

Guidelines for time-to-event end point definitions in breast cancer trials: results of the DATECAN initiative (Definition for the Assessment of Time-to-event Endpoints in CANcer trials)†

BACKGROUND

Using surrogate end points for overall survival, such as disease-free survival, is increasingly common in randomized controlled trials. However, the definitions of several of these time-to-event (TTE) end points are imprecisely which limits interpretation and cross-trial comparisons. The estimation of treatment effects may be directly affected by the definitions of end points. The DATECAN initiative (Definition for the Assessment of Time-to-event Endpoints in CANcer trials) aims to provide recommendations for definitions of TTE end points. We report guidelines for randomized cancer clinical trials (RCTs) in breast cancer.

PATIENTS AND METHODS

A literature review was carried out to identify TTE end points (primary or secondary) reported in publications of randomized trials or guidelines. An international multidisciplinary panel of experts proposed recommendations for the definitions of these end points based on a validated consensus method that formalize the degree of agreement among experts.

RESULTS

Recommended guidelines for the definitions of TTE end points commonly used in RCTs for breast cancer are provided for non-metastatic and metastatic settings.

CONCLUSION

The use of standardized definitions should facilitate comparisons of trial results and improve the quality of trial design and reporting. These guidelines could be of particular interest to those involved in the design, conducting, reporting, or assessment of RCT.

The evaluation of tumor-infiltrating lymphocytes (TILs) in breast cancer: recommendations by an International TILs Working Group 2014

BACKGROUND

The morphological evaluation of tumor-infiltrating lymphocytes (TILs) in breast cancer (BC) is gaining momentum as evidence strengthens for the clinical relevance of this immunological biomarker. Accumulating evidence suggests that the extent of lymphocytic infiltration in tumor tissue can be assessed as a major parameter by evaluation of hematoxylin and eosin (H&E)-stained tumor sections. TILs have been shown to provide prognostic and potentially predictive value, particularly in triple-negative and human epidermal growth factor receptor 2-overexpressing BC.

DESIGN

A standardized methodology for evaluating TILs is now needed as a prerequisite for integrating this parameter in standard histopathological practice, in a research setting as well as in clinical trials. This article reviews current data on the clinical validity and utility of TILs in BC in an effort to foster better knowledge and insight in this rapidly evolving field, and to develop a standardized methodology for visual assessment on H&E sections, acknowledging the future potential of molecular/multiplexed approaches.

CONCLUSIONS

The methodology provided is sufficiently detailed to offer a uniformly applied, pragmatic starting point and improve consistency and reproducibility in the measurement of TILs for future studies.

The evaluation of tumor-infiltrating lymphocytes (TILs) in breast cancer: recommendations by an International TILs Working Group 2014

BACKGROUND

The morphological evaluation of tumor-infiltrating lymphocytes (TILs) in breast cancer (BC) is gaining momentum as evidence strengthens for the clinical relevance of this immunological biomarker. Accumulating evidence suggests that the extent of lymphocytic infiltration in tumor tissue can be assessed as a major parameter by evaluation of hematoxylin and eosin (H&E)-stained tumor sections. TILs have been shown to provide prognostic and potentially predictive value, particularly in triple-negative and human epidermal growth factor receptor 2-overexpressing BC.

DESIGN

A standardized methodology for evaluating TILs is now needed as a prerequisite for integrating this parameter in standard histopathological practice, in a research setting as well as in clinical trials. This article reviews current data on the clinical validity and utility of TILs in BC in an effort to foster better knowledge and insight in this rapidly evolving field, and to develop a standardized methodology for visual assessment on H&E sections, acknowledging the future potential of molecular/multiplexed approaches.

CONCLUSIONS

The methodology provided is sufficiently detailed to offer a uniformly applied, pragmatic starting point and improve consistency and reproducibility in the measurement of TILs for future studies.

Association of molecular subtypes with Ki-67 changes in untreated breast cancer patients undergoing pre-surgical trials

BACKGROUND

Ki-67 is increasingly being used as a response biomarker in window of opportunity, pre-surgical trials for breast cancer patients. Since Ki-67 is often higher at surgery than at baseline core biopsy in subjects allocated to placebo, we investigated which factors affected this change.

PATIENTS AND METHODS

We retrieved data from 274 patients who received no active treatment in three consecutive pre-surgical trials from a single institution. We assessed the association between changes in Ki-67 from diagnostic biopsy to surgical specimen and the following factors: age, body mass index, tumor prognostic and predictive factors, including immunohistochemical molecular subtype, number and size of biopsy specimens, time from biopsy to surgery, circulating insulin-like growth factor-I, sex hormone-binding globulin and hsCRP.

RESULTS

A total of 269 patients with paired measures of Ki-67 at biopsy and surgery were analyzed. Overall, the mean (±SD) change was 2.2 ± 9.2% after a median interval of 41 days (inter-quartile range 33-48). Molecular subtype was the only factor associated with a significant change of Ki-67 (P = 0.004), with a mean absolute increase of 5.3% [95% confidence interval (CI): 2.3-8.3, P = 0.0005] in estrogen receptor-negative HER2-positive tumors (n = 36) and 5.4% (95% CI: 2.9-7.9, P < 0.0001) in triple-negative tumors (n = 78). No significant change in luminal-A (n = 46), luminal-B (n = 85) and luminal-B HER2-positive (n = 24) tumors was observed.

CONCLUSIONS

A significant increase in Ki-67 from baseline biopsy to end point surgery in untreated subjects was ascertained in HER2-positive and triple-negative tumors. This biological association suggests a real increase in cancer proliferation, possibly as a result of a biopsy-driven wound healing effect, and should be considered in the design and interpretation of pre-surgical studies.

REGISTERED CLINICAL TRIAL NUMBERS

ISRCTN86894592; ISRCTN16493703.

Gene expression profiling reveals GC and CEACAM1 as new tools in the diagnosis of lung carcinoids

Background:

Classification of lung carcinoids into typical and atypical is a diagnostic challenge since no immunohistochemical tools are available to support pathologists in distinguishing between the two subtypes. A differential diagnosis is essential for clinicians to correctly discuss therapy, prognosis and follow-up with patients. Indeed, the distinction between the two typical and atypical subtypes on biopsies/cytological specimens is still unfeasible and sometimes limited also after radical surgeries. By comparing the gene expression profile of typical (TC) and atypical carcinoids (AC), we intended to find genes specifically expressed in one of the two subtypes that could be used as diagnostic markers.

Methods:

Expression profiling, with Affymetrix arrays, was performed on six typical and seven atypical samples. Data were validated on an independent cohort of 29 tumours, by means of quantitative PCR and immunohistochemistry (IHC).

Results:

High-throughput gene expression profiling was successfully used to identify a gene signature specific for atypical lung carcinoids. Among the 273 upregulated genes in the atypical vs typical subtype, GC (vitamin D-binding protein) and CEACAM1 (carcinoembryonic antigen family member) emerged as potent diagnostic markers. Quantitative PCR and IHC on a validation set of 17 ACs and 12 TCs confirmed their reproducibility and feasibility.

Conclusions:

GC and CEACAM1 can distinguish between TC and AC, defining an IHC assay potentially useful for routine cytological and histochemical diagnostic procedures. The high sensitivity and reproducibility of this new diagnostic algorithm strongly support a further validation on a wider sample size.

Effect of low-dose tamoxifen after surgical excision of ductal intraepithelial neoplasia: results of a large retrospective monoinstitutional cohort study

BACKGROUND

Postsurgical treatment of ductal intraepithelial neoplasia (DIN) with standard doses of tamoxifen has not reached a consensus yet. Given positive results of low-dose tamoxifen on breast cancer biomarkers modulation, we analyzed a large cohort of DIN patients treated with low-dose tamoxifen or no treatment as per institutional guidelines.

PATIENTS AND METHODS

All consecutive women operated on at the European Institute of Oncology for estrogen receptor (ER)-positive DIN (474 treated with low-dose tamoxifen and 509 untreated patients) were followed up for a median of 7 years.

RESULTS

Compared with untreated patients, a significant 30% reduction in breast cancer risk was observed on low-dose tamoxifen with an adjusted hazard ratio (HR) = 0.70 [95% confidence interval (CI) 0.51-0.94], with a greater benefit in postmenopausal (HR = 0.57; 95% CI 0.34-0.94) than in premenopausal women (HR = 0.79; 95% CI 0.54-1.17). Treated patients with ER and progesterone receptor (PgR) >50% DIN had a lower incidence of breast events than untreated ones (HR = 0.61; 95% CI 0.40-0.94), whereas no protective effect has been observed in patients with ER or PgR <50% DIN. Drug discontinuation resulted in a doubled risk of recurrence in premenopausal women only (HR = 1.95; 95% CI 0.98-3.89). No excess of endometrial cancer occurred.

CONCLUSIONS

Low-dose tamoxifen is a promising and safe strategy for highly endocrine responsive DIN. Treatment adherence is crucial in premenopausal women. A definitive trial is ongoing.

Tailoring treatment for ductal intraepithelial neoplasia of the breast according to Ki-67 and molecular phenotype

Background:

The post-surgical management of ductal intraepithelial neoplasia (DIN) of the breast is still a dilemma. Ki-67 labelling index (LI) has been proposed as an independent predictive and prognostic factor in early breast cancer.

Methods:

The prognostic and predictive roles of Ki-67 LI were evaluated with a multivariable Cox regression model in a cohort of 1171 consecutive patients operated for DIN in a single institution from 1997 to 2007.

Results:

Radiotherapy (RT) was protective in subjects with DIN with Ki-67 LI ≥14%, whereas no evidence of benefit was seen for Ki-67 LI <14%, irrespective of nuclear grade and presence of necrosis. Notably, the higher the Ki-67 LI, the stronger the effect of RT (P-interaction <0.01). Hormonal therapy (HT) was effective in both Luminal A (adjusted hazard ratio (HR)=0.56 (95% CI, 0.33–0.97)) and Luminal B/Her2neg DIN (HR 0.51 (95% CI, 0.27–0.95)).

Conclusion:

Our data suggest that Ki-67 LI may be a useful prognostic and predictive adjunct in DIN patients. The Ki-67 LI of 14% could be a potential cutoff for better categorising this population of women at increased risk for breast cancer and in which adjuvant treatment (RT, HT) should be differently addressed, independent of histological grade and presence of necrosis.

Abstract PD06-06: RELATIONSHIP BETWEEN MOLECULAR SUBTYPE AND CHANGE IN KI-67 IN THE PLACEBO ARMS OF WINDOW OF OPPORTUNITY TRIALS

Background: Window-of-opportunity (WOP), presurgical models often use Ki-67 labeling index (LI) as the main surrogate biomarker for screening therapeutic activity of candidate agents and characterize their mechanism of action. Ki-67 LI in the placebo arm has been frequently reported to be higher at surgery than at baseline biopsy in WOP studies, a finding that has been ascribed to the higher proliferative activity in the tumor edge of surgical specimens that cannot be detected in the baseline core biopsy. Since this observation has important implications in sample size calculation and effect interpretation, we investigated which factors affected the changes of Ki-67 LI in a series of patients allocated to the placebo arms of a number of WOP trials carried out at IEO.

Methods: Data from 181 patients with pT1-2 invasive breast cancer from the placebo arms of three WOP randomized trials were pooled with those of 98 untreated patients, who had a diagnostic core biopsy preceding surgery but declined participation to the study or were ineligible for histological characteristics. Ki-67 LI was measured by evaluating the prevalence of neoplastic cells showing any definite nuclear immunostaining with the Mib-1 monoclonal antibody, in the whole invasive component of baseline core biopsies and in at least 2000 invasive neoplastic cells of surgical samples, in accordance to the recently licensed international recommendations.

Results: We collected data of 273 breast cancer patients with information on the changes in Ki-67 LI: 46 (17%) were Luminal A, 85 (31%) Luminal B/HER2−, 24 (9%) Luminal B/HER2+, 38 (14%) HER2+ and 81 (30%) Triple Negative (TN). Median (IQR) Ki-67LI at baseline in each molecular subtype was 10% (7–11), 20% (16–29), 28% (22–35), 30% (25–45) and 50% (32–75) in the Luminal A, Luminal B/HER2−, Luminal B/HER2+, HER2+ and TN, respectively. Median (IQR) age was 50 years (44–60), median BMI was 24 (22–27), 50% were post-menopausal. The median (range) time elapsed from biopsy to surgery was 41 days (33–48). Overall, the median change in Ki-67 LI between baseline biopsies and surgical samples was 0 (IQR, −2, 5). Results from multivariate analysis showed that none of the factors investigated, including patient and tumor characteristics, time elapsed from biopsy to surgery and circulating biomarkers (IGF-I, SHBG and ultrasensitive CRP) were associated with the Ki-67 LI change except for the immunohistochemically defined molecular subtype, which explained most of the variability of the changes (p = 0.004). As a matter of fact, we observed a 5%, significant increase of Ki-67 LI both in HER2+ and TN tumors, after adjustment for baseline values.

Abstract P3-05-03: Characterization of PIK3CA mutations in lobular breast cancer

Background: Invasive lobular carcinoma (ILC) is the second most common breast cancer (BC) histotype, after invasive ductal carcinoma (IDC), representing ∼10-15% of the global BC population. The vast majority of ILC are estrogen receptor (ER)-positive. PIK3CA has been reported to be the most frequently mutated gene in ER-positive BC. However, until now PIK3CA mutations have mainly been described in IDC. In this study, we sought to characterize the type, prevalence, intra-patient (pt) mutational heterogeneity, and the association with transcriptomic phenotype and clinical outcome of PIK3CA mutations in ILC.

Methods: Gene expression data (HG-U133 Plus2.0) was generated from frozen samples of 116 ILC (primary tumors). For the same series, PIK3CA mutation profiling (Sequenom) was performed on at least 2 formalin-fixed paraffin embedded (FFPE) tissue blocks of the primary tumor for 102 cases, and on the only available block for the remaining 14 cases. Matched local recurrence (LR) and multiple metastatic (M) samples were also characterized for 3 and 8 pts respectively. For the transcriptomic and survival analyses, we evaluated the association between PIK3CA mutation status and gene signatures recapitulating important biological processes, and invasive disease-free & overall survival, respectively.

Results: PIK3CA mutations were detected in the primary tumor of 40/116 (35%) ILC pts: 14 (35%) mutations in the helical domain and 25 (62.5%) in the kinase domain. PIK3CA analysis in different blocks from the same primary tumors revealed a mutational heterogeneity in 7/102 (7%) cases. There was a discordance between primary and LR samples in 1/3 patients with LR, with a mutation reported in the primary but in not the LR. In 3/8 pts for which M samples were available, we observed intra-pt heterogeneity. In the first pt, a mutation in the kinase domain was reported only in 1/2 investigated blocks from the primary tumor, and in only 1/2 liver Ms. In the second pt, a mutation in the helical domain was found in the primary tumor and in the LR but not in the pleura M. In the third pt, although no mutation was observed in the primary tumor, a mutation in the helical domain was found in the M of the epiploon, but not in the Ms from the diaphragm or the ovary. Transcriptomic analyses revealed that primary tumors with a PIK3CA mutation in the helical domain were associated with increased levels of 2 stroma signatures (Bonferroni p-val: PLAU sign -Desmedt 2008–0.042 and DCN sign- Farmer 2009 – 0.048) compared to tumors without mutation. The survival analyses did not reveal any significant difference in survival between pts with and without a PIK3CA mutation.

Conclusions: This study represents the largest series described so far which investigated PIK3CA mutations in ILC. The incidence of PIK3CA mutations reported here is similar to the one reported for IDC. The investigation of multiple tumor samples per pt revealed intra-tumor as well as primary/recurrence heterogeneity. To get a definitive answer on the prognostic role of PIK3CA mutation in ILC, we are currently performing a PIK3CA mutation profiling study (Sequenom) on a series of ∼1000 consecutive ILC with long-term follow up (Iorfida et al. 2012); results will be available by SABCS2012.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-05-03.

Abstract PD04-07: The Ki-67 labeling index predicts the risk of recurrence of DIN patients treated with radiotherapy following breast conserving surgery

Purpose: To investigate the prognostic relevance of Ki-67 labeling index (LI) in patients with Ductal Intraepithelial Neoplasia (DIN) of the breast.

Patients and Methods: From January 1997 to December 2007, histological samples and clinical data of 1,171 consecutive patients operated for DIN in a single institution were collected. The study was performed in accordance with the REMARK criteria. The independent prognostic role of Ki-67 LI was evaluated with a multivariable Cox regression model. A restricted cubic splines model was used to evaluate the prognostic role of Ki-67 LI as a continuous variable.

Results: Overall, median age was 52 years (range 23–88), median Ki-67 LI 15% (range 1–80) and median follow-up 86 months (range 1–192). Overall, 549 (46.9%) women were premenopausal at the time of diagnosis. A total of 872 (74.5%) patients underwent breast conservative surgery (BCS). Whole breast radiotherapy (RT) was administered to 356 patients, and 506 patients received low dose tamoxifen (HT) (20mg/week or 5 mg/day). Histologically, most of the cases had a prevalent solid or cribriform pattern (75%), were DIN1c and DIN2 (80%), ER+ (80%), and showed a high (≥14%) Ki-67 LI (54%). The prevalence of the immunohistochemically defined subtypes was 39.5% for Luminal (Lum) A, 22.8% for LumB/Her-2−, 18.2% for LumB/Her2+, 15.8% for Her-2+, and 3.7% for Triple Negative. Overall, the rate of invasive and in situ recurrences (5-year cumulative incidence) was 10.7%. Firstly, we analyzed the role of RT according to Ki-67 LI as a continuous variable in DIN2/DIN3 patients after BCS. The curve and interaction model was adjusted for menopause, BMI, Her-2 and ER status, histological grade, presence of necrosis and microcalcifications, and HT. RT was protective in subjects with DIN with Ki-67 LI ≥14%, while no evidence of effect was seen for Ki-67 LI &lt;14%. Notably, the higher the Ki-67 LI, the stronger the effect of RT (P-value for the interaction between RT and Ki-67 LI &lt;0.01). Accordingly, RT was effective in all DIN subtypes with the exception of LumA. The adjusted HRRT vs No RT for LumB/Her2−, LumB/Her2+, and Her2 subtypes was 0.20 (95 % CI, 0.08–0.48), 0.44 (95 % CI, 0.16–1.20), and 0.15 (95 % CI, 0.04–0.50), respectively. The HRRT vs No RT for Triple Negative subtype was 0.40 (95 % CI, 0.07–2.41) and was not adjusted because of the sparse number of events. Finally, we focused the analysis on DIN2 patients stratified by Ki-67 LI. Again, after adjustment for menopause, surgical margins, presence of necrosis, microcalcifications, and HT, RT was not effective in DIN2 patients with Ki-67 LI &lt;14% [HRRT vs No RT: 1.15 (95 % CI 0.47–2.80)]. On the contrary, DIN2 patients with a Ki-67 LI ≥14% mostly benefit of RT in terms of ipsilateral recurrence[HRRT vs No RT: 0.18 (95% CI 0.07–0.46)]. Low dose tamoxifen was effective in either LumA [adjusted HRHT vs No HT: 0.56 (95 % CI 0.33–0.97)] and LumB/HER2− DIN [HRHT vs No HT: 0.51 (95 % CI 0.27–0.95)], but not in LumB/Her2+ [HRHT vs No HT: 1.06 (95 % CI 0.56–2.05).

Conclusion: Our data suggest that Ki-67 LI may be a useful prognostic and predictive adjunct in DIN patients.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD04-07.