Abstract P2-07-05: A clinical calculator to predict disease outcomes in women with hormone receptor-positive advanced stage breast cancer treated with first-line endocrine therapy

Purpose: Endocrine based therapy is an effective strategy to manage hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC). However, nearly all patients exhibit/develop either de novo or acquired resistance. While prognostic biomarkers of endocrine responsiveness are well established for the adjuvant treatment in ER+ breast cancer, less is known regarding prognostic and predictive biomarkers of response in the first line ABC setting. We sought to develop a clinical calculator based on clinical criteria for predicting progression-free survival (PFS) and overall survival (OS) of women with HR+/HER2- ABC who will be receiving endocrine monotherapy as first-line treatment for ABC.

Methods: The development of the clinical calculator will be based on data from modern clinical trials in women with HR+/HER2- ABC. The studies to be included in the final analyses are given in Table 1. The control arm data from trials1-6 will form the training dataset (N = 1,223) and be used to construct the clinical prediction models. Variables considered include age, race, ECOG status, disease measurability, body mass index, disease-free interval, number of metastatic sites, locations of metastatic sites, prior endocrine therapy, and prior chemotherapy. Missing values will be imputed using single imputation with all variables included in the imputation model. For continuous variables, restricted cubic splines will be used to determine if non-linear effects may be more appropriate. The Lasso regression will be used as a variable selection technique to reduce the dimensionality of covariates; initially all pairwise interactions will be included in the model. Following Lasso regression, the multivariable Cox proportional hazards models will be constructed for PFS and OS including only variables retained in Lasso. The final model will be internally validated for discrimination and calibration using 10-fold cross-validation. External validation will be performed using control arm data from EGF 30008 (N = 536).

Results: To date, control arm data from four trials (trials 1-4) have been received. The preliminary results presented here are based on pooled data from C40503 and LEA, for which data elements have been harmonized. Models for predicting PFS and OS have good calibration and are associated with bias-corrected C-indices of 0.61 and 0.65, respectively. These models will be updated using pooled data from trials 1-6.

Conclusions: Our preliminary data demonstrate that clinical calculators based on baseline clinical factors can provide accurate prediction of PFS and OS in patients with HR+/HER2- ABC treated with first-line ET. If validated, these tools may be used for risk stratification in future clinical trials and to identify patients who may require more or less aggressive therapy.

Table 1:Studies to be includedTrial NumberTrial NameTrial PISample Size in Control Arm1C40503Maura Dickler152 (letrozole)2LEAMiguel Martin179 (letrozole)3FACTJonas Bergh188 (anastrozole)4FALCONJohn Robertson194 (anastrozole)5S0226Rita Mehta345 (anastrozole)6MONARCH 3Matthew Goetz165 (nonsteroidal AI)7EGF 30008Stephen Johnston536 (letrozole)

Citation Format: Polley M-YC, Dickler MN, Johnston S, Goetz MP, de la Haba J, Loibl S, Mehta RS, Bergh J, Roberston J, Barlow W, Liu H, Tenner K, Martin M. A clinical calculator to predict disease outcomes in women with hormone receptor-positive advanced stage breast cancer treated with first-line endocrine therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-07-05.

EGFR expression is associated with decreased benefit from trastuzumab in the NCCTG N9831 (Alliance) trial

BACKGROUND

Epidermal growth factor receptor (EGFR) has been hypothesised to modulate the effectiveness of anti-HER2 therapy. We used a standardised, quantitative immunofluorescence assay and a novel EGFR antibody to evaluate the correlation between EGFR expression and clinical outcome in the North Central Cancer Treatment Group (NCCTG) N9831 trial.

METHODS

Tissue microarrays were constructed that allowed analysis of 1365 patients randomly assigned to receive chemotherapy alone (Arm A), sequential trastuzumab after chemotherapy (Arm B) and chemotherapy with concurrent trastuzumab (Arm C). Measurement of EGFR was performed using the EGFR antibody, D38B1, on the fluorescence-based AQUA platform. The result was validated using an independent retrospective metastatic breast cancer cohort (n=130).

RESULTS

Epidermal growth factor receptor assessed as a continuous (logarithmic transformed) variable shows an association with disease-free survival in Arm C (P=0.009) but not in Arm A or B. High EGFR expression was associated with worse outcome (Hazard ratio (HR)=2.15; 95% CI 1.28-3.60, P=0.004). Validation in a Greek metastatic breast cancer cohort showed an HR associated with high EGFR expression of 1.92 (P=0.0073).

CONCLUSIONS

High expression of EGFR appears to be associated with decreased benefit from adjuvant concurrent trastuzumab. Since other treatment options exist for HER2-driven tumours, further validation of these data may select patients for alternative or additive therapy.

Do the ASCO/CAP 2007 HER2 Testing Guidelines Improve Prediction of Benefit to Adjuvant Trastuzumab?: Data from North Central Cancer Treatment Group N9831 Adjuvant Trial

Background: In 2007, the American Society of Clinical Oncology and College of American Pathologists (ASCO/CAP) recommended new guidelines to define HER2 positivity by immunohistochemistry (3+ IHC: uniform intense membrane staining of >30% of invasive tumor cells) or fluorescent in situ hybridization (FISH+: HER2/CEP17 ratio >2.2). The original criteria used for enrollment in the pivotal N9831 trial conducted from 2000-2005 were IHC>10% (3+) or FISH ≥2.0.Purpose: To investigate the impact of the ASCO/CAP guidelines on patient (pt) eligibility and disease free survival (DFS) compared to the originally used FDA-approved definitions.Patients/Methods: This analysis included 2268 patients from the HER2+ N9831 adjuvant trastuzumab phase III trial. IHC was centrally performed at the Mayo Clinic using the DAKO HercepTest™ and was re-analyzed to determine the percent of tumor cells with 0, 1+, 2+, and 3+ staining intensities. DFS was compared between pts randomized to standard chemotherapy +/- concurrent trastuzumab (Arms A and C of the trial) within IHC/FISH subgroups using Cox proportional hazards regression stratified by hormone receptor and nodal status.Results: Based on 2268 pts, 83 pts (3.7%) were 3+ by FDA-approved guidelines but not 3+ by the ASCO/CAP guidelines. Among these pts, 77% (64/83) were FISH amplified centrally by ASCO/CAP guidelines. Only 1.5% (34/2268) of pts eligible under FDA-approved definitions from N9831 in this sample set would not meet the ASCO/CAP guidelines. In 1441 patients randomized to standard chemotherapy +/- concurrent trastuzumab, the exploratory DFS hazard ratio (HR) associated with trastuzumab in IHC/FISH subgroups were as follows: ASCO/CAP HER2+ HR=0.59 (95% CI: 0.47-0.75; p<0.001); FDA-approved HER2+ HR=0.60 (95% CI: 0.47-0.75; p<0.001); ASCO/CAP HER2 normal(not positive) HR=0.74 (95% CI: 0.35-1.57; p=0.43); and FDA-approved HER2 normal HR=0.53 (95% CI: 0.22-1.26; p=0.15).Conclusions: A small percentage (1.5%) of N9831 patients did not meet ASCO/CAP 2007 guidelines when applied retrospectively. Trastuzumab effect appeared similar for HER2+ patients regardless of ASCO/CAP or FDA-approved guidelines. Additional DFS analyses by IHC/FISH subgroups will be presented. We gratefully acknowledge support from the Breast Cancer Research Foundation, Genentech, and NIH CA25224 for this study.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 701.

Paclitaxel-Related Peripheral Neuropathy Associated with Improved Outcome of Patients with Early Stage HER2+ Breast Cancer Who Did Not Receive Trastuzumab in the N9831 Clinical Trial

Background: Microtubules are crucial for spindle formation during mitosis and for cellular proliferation. The antineoplastic effect of paclitaxel is mainly related to its ability to bind the beta subunit of tubulin, thus preventing tubulin chain depolarization and inducing apoptosis. Tubulins are expressed in human peripheral nerves and the binding of paclitaxel to tubulin may lead to neuropathy. Peripheral neuropathy is a common dose limiting toxicity of paclitaxel. We hypothesized that the occurrence of peripheral neuropathy may correlate with outcome (disease-free survival; DFS).Methods: This analysis sought to describe incidence of peripheral neuropathy following paclitaxel and its association to outcome (DFS) in patients who received paclitaxel (weekly x 12) in the adjuvant HER2+ intergroup trial N9831. Only eligible pts who initiated paclitaxel and did not have peripheral neuropathy at initiation of paclitaxel that were randomized to arms A (955 pts; chemotherapy alone) and C (889 pts; chemotherapy plus concurrent trastuzumab) of N9831 were included. Cox regression analysis stratified by ER/PR status and nodal status was used to compare DFS within arm between patients with and without peripheral neuropathy.Results: Out of 1844 eligible pts, 379 developed neuropathy (20.5%). For pts in arm A, those who developed neuropathy had better DFS than pts who did not (3 yr DFS: 86.2% vs 81.8%; HR 0.65; p=0.01), despite lower doses of paclitaxel in the pts with neuropathy. Grade of neuropathy did not appear to impact DFS. No statistical difference was noted for pts treated in the trastuzumab-containing arm (3 yr DFS: 92.8% vs 91.1% for pts with neuropathy vs not; HR 0.79; p=0.34). There were no differences in paclitaxel dose intensity between arms A and C.Conclusion: Patients with early stage HER2+ breast cancer who received adjuvant paclitaxel-containing chemotherapy in arm A and developed peripheral neuropathy had a better DFS than pts who did not develop neuropathy. This effect was possibly abrogated by the use of trastuzumab in Arm C. This side effect may represent effective bindings of paclitaxel to the target tubulin, lack of point mutations in tubulin at the paclitaxel binding site and/or lack of selective overexpression of β-III tubulin. This is a hypothesis generating study and additional analysis needs to be conducted from other large taxane-based trials.Partial support from Genentech and the Breast Cancer Research Foundation

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2100.

Impact of poor prognostic features on the surgical treatment of breast cancer in an intergroup adjuvant chemotherapic trial

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Background: The adoption of new breast surgical techniques has been rapid for early stage breast cancer. The utilization of these techniques in patients with high risk operable breast cancer has not been thoroughly investigated. Methods: Retrospective surgical data was summarized for patients entered into N9831 “Phase III Trial of Doxorubicin and Cyclophosphamide Followed by Weekly Paclitaxel With or Without Trastuzumab as Adjuvant Treatment for Women With HER-2 Over-expressing or Amplified Node Positive or High-Risk Node Negative Breast Cancer.” Results: 3,505 patients were entered into N9831 from 2000–2005 following primary surgery for breast cancer. The median age was 50 and 43% were premenopausal. 93% of patients underwent a diagnostic biopsy prior to their definitive surgical procedure. Whether HER2-neu status was available at time of definitive surgery is unknown. 61% underwent a mastectomy whereas 39% underwent breast conserving surgery (BCS). The rate of BCS was relative stable over the course of the trial. Patients with T1 tumors had a higher rate of BCS (49%) compared to T2 tumors (37%) and T3 tumors (6%). Sentinel lymph node (SLN) biopsy was performed in 54% of the cases. The rate of SLN biopsy increased from 40% in 2000 to 66% in 2005. Patients who underwent mastectomy had a lower rate of SLN biopsy than patients who underwent BCS (44% versus 71%, respectively). Tumor size was also associated with the rate of SLN biopsy: T1 (60%), T2 (53%), and T3 (36%). Data on local and regional recurrences are still maturing. Conclusions: Surprisingly, low numbers of patients on this trial underwent BCS whereas the adoption of the SLN biopsy procedure among the same group of surgeons was relatively high. The relatively low rate of BCS in this study population needs further investigation to determine what surgeon and patient factors impacted the surgical decision.

No significant financial relationships to disclose.

Influence of human tryptophan hydroxylase 2 N- and C-terminus on enzymatic activity and oligomerization

Tryptophan hydroxylase (TPH) catalyses the first and rate limiting step in the biosynthesis of the neurotransmitter serotonin. There are two TPH isoenzymes in humans, encoded by two different genes: TPH1 and the recently described TPH2. We have expressed both human enzymes and various deletion mutants of TPH2 (DeltaN44, DeltaC17, DeltaC19, DeltaC51) in COS7 cells. TPH1 and 2 displayed different kinetic properties with a lower K(m) value of TPH1. Removal of 44 amino acids from the N-terminus of TPH2 resulted in a 3-4-fold increased V(max), which indicates a strong inhibitory function of this part on the enzymes activity. TPH1 and 2 were able to form homooligomers and also heterooligomers with each other. The different deletion mutants (DeltaC17, DeltaC19 and DeltaC51), which lack the putative C-terminal leucine zipper tetramerization domain, existed as monomeric enzymes. While short deletions (DeltaC17 and DeltaC19) hardly changed V(max) values, the DeltaC51 mutant lost 99% of TPH activity. These data identify a region between the C-terminal oligomerization domain and the catalytic domain, which is indispensable for TPH2 activity.

[Histopathological alterations in rhesus monkeys after experimental infections with African lung flukes (Paragonimus africanus and P. uterobilateralis) (author's transl)]

Histopathological observations in monkeys experimentally infected with African lung flukes are reported. The observations were made on 3 Rhesus monkeys, infected with Paragonimus africanus from West-Cameroon, and on 5 Rhesus monkeys, infected with P. uterobilateralis from Eastern Nigeria. For comparison, the lung of a naturally infected Drill (Mandrillus leucophaeus) was included in the study. The following lesions were found: formation of parasite cavernae, intense infiltration of the cavern wall with plasma cells; formation of egg granulomata in the lung tissue with intense plasma cell infiltration; peribronchial and perivascular cellular infiltration, concomitant and consistent pleuritis; reactive cellular hyperplasia of hilar lymph nodes and of spleen. Evidently, in the stages of infection examined so far, the immune response of the host is mainly of the humoral type. Experimental Paragonimus infections in monkeys may serve as a model in studies on human paragonimiasis in Eastern Nigeria and West-Cameroon. Likewise, they may serve in studies on granulomatous inflammation.