Abstract P1-08-42: High HER2 expression correlates with response to trastuzumab and the combination of trastuzumab and lapatinib in the NeoALTTO phase III trial

Background: Expression of p95HER2, a truncated form of HER2 lacking the extracellular domain, has been associated with resistance to trastuzumab (T)-based therapy in metastatic breast cancer patients. Conversely, high levels of HER2 have been correlated with increased clinical benefit from anti-HER2 therapy in the neoadjuvant setting. In this work we correlated the expression of p95HER2 and HER2 with pathological complete response (pCR) following T, lapatinib (L) or the combination of both agents (T+L) with paclitaxel.

Methods: p95HER2 and HER2 were quantified by VeraTag® and HERmark® (Monogram Biosciences), respectively, in primary tumors of 455 patients enrolled in the phase III neoadjuvant study NeoALTTO (Baselga J. et al. Lancet, 2012). The relationship of pCR status to p95HER2 and HER2 was studied using logistic regression models, which accounted for stratification factors and treatment. Unless specified, p95HER2 and HER2 were included as log terms.

Results: p95HER2 was measurable in 283 cases (62%) and HER2 in 327 cases (72%). A positive correlation between p95HER2 and HER2 levels was found in the 274 cases (60%) where quantification of both markers was available. Increased HER2 was strongly associated with increased pCR rate in patients treated with the combination of T+L (OR 5.09, 95%CI 2.27-11.44; p<0.01), with a trend observed also in the L-only arm (OR 1.88, 95% CI 0.96-3.70; p = 0.067). Overall, patients with tumors that were HER2-positive (>17.8 RF/mm2) by HERmark had a higher pCR rate than those that were HER2-negative by HERmark (39% vs. 11%, respectively; p<0.001). Increasing p95HER2 levels did not predict for pCR in the L or T+L arms and showed weak evidence (p = 0.073) of an increase in pCR in the T arm.

In an unplanned analysis, we examined the odds of achieving response to anti-HER2 therapy in patients with HER2 levels above and below the median (100 RF/mm2, HER2 entered as a binary covariate). HER2 levels above the median predicted a higher response rate to T (OR 3.6, 95% CI 1.2-11; p<0.05) and, more significantly, to T+L (OR 6.01, 95% CI 2.51-14.4; p<0.001). In particular, patients treated with T+L had a higher probability to achieve pCR compared to T alone when HER2 was above the median (T+L = 73% pCR vs. T = 43% pCR, p<0.01; OR 3.74, 95% CI 1.57-8.90), but not when HER2 was below the median (T+L = 29% pCR vs. T = 19% pCR, p>0.2; OR 1.84, 95% CI 0.74-4.55). When tumors were divided in hormone receptor (HR)-positive and HR-negative groups, total levels of HER2 still predicted response to T or T+L.

Conclusions: Increasing HER2 protein expression correlated with increased benefit of adding L to T compared to T alone. In tumors above the median of HER2 expression, the levels of HER2 predicted for response to both T and T+L. Our interpretation is that, in the neoadjuvant setting, the association between p95HER2 expression and response to anti-HER2 therapy is likely a consequence of the correlation between p95HER2 and total HER2 levels. HER2 expression seems to be a stronger predictor of pCR than p95HER2 for response to T, L and especially, T+L. Future studies to understand the impact of p95HER2 and HER2 expression on disease-free and overall survival following anti-HER2 therapy are warranted.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-42.

Abstract P1-08-14: HER2 extracellular domain (ECD): A predictive marker of lapatinib treatment benefit in advanced breast cancer

Pretreatment serum HER2 ECD may be associated with clinical outcome to lapatinib therapy and may also have treatment-independent prognostic value. We performed a meta-analysis to examine the prognostic and predictive role of baseline ECD (bECD) levels for lapatinib therapy. We also compared and contrasted its role with tumor HER2 status.

We analyzed bECD and tumor HER2 data in 1902 of 2264 patients (84%) with advanced breast cancer who were randomly assigned to receive lapatinib-containing therapy or control treatment in three clinical trials: EGF30001 (lapatinib and paclitaxel vs paclitaxel), EGF30008 (lapatinib and letrozole vs letrozole), and EGF100151 (lapatinib and capecitabine vs capecitabine). bECD was centrally measured by enzyme linked immunoassay and tumor HER2 was centrally determined by immunohistochemistry and fluorescence in situ hybridization. bECD and tumor HER2 status were examined for associations with objective tumor response (ORR), progression-free survival (PFS) and overall survival (OS) in the treatment groups.

Of the patients with both bECD and tumor HER2 data, 31% had HER2 bECD≥15 ng/mL and 28% had HER2+ cancer. The effectiveness of lapatinib-containing therapy was significantly associated with bECD level (treatment-bECD interaction P<0.001 [ORR], P<0.001 [PFS]). In patients with bECD≥15 ng/mL, lapatinib-containing therapy, compared to control, significantly improved ORR (odds ratio [OR] for complete and partial response, 1.88; P = 0.001) and PFS (hazards ratio [HR] for progression or death, 0.69; P<0.001). Among patients with bECD<15 ng/mL, there was no significant difference between treatment groups for ORR (OR, 1.17; P = 0.19) or PFS (HR, 0.93; P = 0.30). The effectiveness of lapatinib-containing therapy was also significantly associated with HER2 tumor status for ORR (OR [HER2+] 2.39, P<0.001; OR [HER2-] 1.10, P = 0.43; treatment-HER2 interaction P = 0.001) and PFS (HR [HER2+] 0.63, P<0.001; HR [HER2-] 0.95, P = 0.46; treatment-HER2 interaction P<0.001). When bECD and HER2 tumor status were examined together, the effectiveness of lapatinib-containing therapy was significantly associated with both bECD and HER2 tumor status for PFS (treatment-biomarker interaction P = 0.02[HER2], P = 0.001[bECD]) but only for bECD for ORR (treatment-biomarker interaction P = 0.07 [HER2], P = 0.003 [bECD]). The effectiveness of lapatinib-containing therapy was not significantly associated with OS for both biomarkers (treatment-biomarker interaction P = 0.30 [bECD] and P = 0.80 [HER2]). In the control groups, bECD≥15 ng/mL (HR 1.35, P = 0.003) and HER2+ (HR 1.67, P<0.001) were associated with shorter PFS after adjusting for other baseline characteristics. bECD≥15 ng/mL (HR 1.89, P<0.001) but not HER2+ (HR 0.97, P = 0.81) was associated with shorter OS after adjusting for other baseline characteristics.

Lapatinib therapy was associated with higher ORR and longer PFS in patients with elevated ECD levels. Elevated ECD was also associated with shorter PFS and OS in patients treated with non-lapatinib therapy. ECD provided additional predictive and prognostic information, in addition to tumor HER2 status, that if validated, could aid in treatment decisions. The predictive role of ECD in other anti-HER2 therapies requires further research.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-14.

Abstract PD1-7: Phosphatase and tensin homolog deleted from chromosome 10 (PTEN) evaluation in the NeoALTTO trial (BIG 01-06)

Introduction

Assessment of PTEN might be an important tool in identifying patients unlikely to derive substantial benefit from trastuzumab and lapatinib-based therapies. Current studies failed to demonstrate an unequivocal predictive role of PTEN in human epidermal growth factor receptor-2 (HER2)-positive breast cancer both in neo-adjuvant and adjuvant settings. Lack of standardization of PTEN status determination in formalin fixed paraffin embedded (FFPE) tissue samples together with the small datasets analyzed in previous studies may have contributed to conflicting PTEN results and high variability of PTEN loss rates reported (22%-64%).

Methods

In the present study we have conducted a preliminary analysis investigating the influence of the antibodies, scoring methods and cutoff criteria used, together with the impact of inter-observer variability on PTEN status determination. Core biopsies from 429 FFPE baseline samples from early-stage HER2-positive breast cancer patients prospectively collected in the neoALTTO trial were stained with two widely used anti-PTEN monoclonal antibodies (clone 6H2.1 from DAKO and clone 138G6 from Cell Signaling Technology-CST). Two different pathologists independently scored the slides using the H-score system. Two different cut-off criteria were used to define PTEN loss of expression: H-score < 50 and ≤10% positive staining (any level of intensity).

Results

Out of 429 processed samples, 363 and 369 were evaluable for observer 1 (CST and DAKO, respectively) and 367 were evaluable for observer 2, with an average missing rate of 15%. A strong linear correlation was observed between CST and DAKO antibodies for both observers (R2 > 0.7). After setting a cutoff for PTEN loss, the observed discordance rate was below 10%, with the number of discordant cases ranging from 28 to 33 (depending on the cut-off criteria and observer). Inter-observer correlation was strong with both antibodies (R2 = 0.8). Based on the cutoff criteria and antibodies used, inter-observer discordance rates ranged between 6% and 10%; the lowest rate observed at ≤10% cutoff threshold with CST antibody. PTEN was classified as “loss” in 23%, 19%, 16%, and 13% of cases by observer 1 and in 32%, 29%, 24%, 19% of cases by observer 2 using DAKO H-score<50, CST H-score<50, DAKO≤10%, and CST≤10% criteria, respectively.

Conclusion

Our preliminary analysis showed high inter-antibody and inter-observer concordant rates for PTEN status determination by IHC. However, the lack of a standardized definition of PTEN cutoff thresholds for defining negativity and positivity generated loss call rates ranging from 13% to 32% within the same dataset. Correlative analyses with pCR and PIK3CA status are ongoing to determine the impact of PTEN expression and its variability in predicting response to single-agent or dual HER2 targeting.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD1-7.

Abstract P1-08-09: EGFR expression is associated with decreased response from HER2 targeted therapeutics in the neo-adjuvant setting in the NeoALTTO trial

Background: Epidermal Growth Factor Receptor (EGFR, HER1) is known to heterodimerize with HER2 and may modulate the effectiveness of trastuzumab or lapatinib. Historically, it has been difficult to measure, but recently we reported a new, standardized, quantitative immunofluorescence assay and a novel EGFR antibody which showed that high levels of EGFR were associated with decreased benefit in the concurrent arm of the North Central Cancer Treatment Group (NCCTG/Alliance) N9831 trial (Rimm et al, SABCS 2012). Here we assess its value in the neo-adjuvant setting in the NeoALTTO trial.

Methods: NeoALTTO randomized 455 breast cancer patients to neoadjuvant trastuzumab, lapatinib or both and showed benefit in both single anti-HER2 therapy arms, and the combination therapy showing about twice as much benefit as either single drug arm. We used the previously described AQUA method of quantitative immunofluorescence to measure EGFR levels using the D38B1 antibody on between 4 and 140 fields of view per slide on 353 specimens. The averaged EGFR score was standardized to the absolute concentration using cell lines and western blots and the 13 ng/ug total protein established in the N9831 trial was tested to determine predictive value for pathological complete response (pCR) defined as ypT0/is.

Results: In NeoALTTO, 19% of the patients had EGFR levels above 13 ng/ug, compared to 16% in NCCTG N9831. The pCR rate was 35.3% in the patients with low EGFR, compared with 29.8% for high EGFR but this difference was not statistically significant. However, when adjusted for treatment and hormone receptor (HR) status, high EGFR is statistically significantly associated with lower response rate(p = 0.038). Continuous analysis measures were not significant. The effect on overall response at 6 weeks was also weakly significant when adjusting for treatment and HR status (p = 0.06). Surprisingly, for HR negative patients in the lapatinib only arm, the pCR rate in the low EGFR group was 47.2% compared with 16.0% in the high group. While this difference is statistically significant (p = 0.014), it should be interpreted cautiously because of the small numbers of patients and the multiple tests performed.

Conclusions: High expression of EGFR by the AQUA platform appears to be associated with decreased pCR rate from HER2 targeted therapy in the neoadjuvant setting. This observation is consistent with NCCTG N9831. Although underpowered, high EGFR levels predicted decreased pCR rate from lapatinib, the opposite of that anticipated for this small molecule dual EGFR/HER2 inhibitor. Further studies are required to determine the clinical utility of this assay and the biological mechanisms underlying these observations.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-09.

The management of acute coronary syndrome patients across New Zealand in 2012: results of a third comprehensive nationwide audit and observations of current interventional care

AIMS

To audit all patients admitted to a New Zealand (NZ) Hospital with a suspected or definite acute coronary syndrome (ACS) over a 14-day period, to assess their presentation type and management in hospital and at discharge, with emphasis on time delays for invasive management and revascularisation treatments.

METHODS

We updated the established NZ ACS Audit group of 39 hospitals admitting ACS patients across NZ, and enrolled NZ patients in conjunction with the bi-National Australia and NZ ACS 'SNAPSHOT' audit. Comprehensive data was recorded on all patients admitted between 00.00 hours on 14 May 2012 to 24.00 hours on 27 May 2012. Patient management at intervention centres (7 public, 3 private) was compared with non-intervention centres (29 public).

RESULTS

There were 1007 patient admissions: STEMI (10%), NSTEMI (26%), UAP (17%), other diagnoses including secondary myonecrosis (18%), chest pain thought unlikely to be ischaemic (29%). Cardiac investigations were used in a minority of patients: chest X-ray (91%), echocardiogram (29%), exercise test (23%), computed tomographic (CT) angiogram (4%) and conventional coronary angiogram (33%). Patients admitted to a non-intervention centre (n=439) were less likely to receive an echocardiogram (25 vs 31%, p<0.05). Non-intervention centre patients with NSTEMI/UAP waiting longer for angiography (3.8 vs 2.1 days p<0.0001), and had a longer length of hospital stay (4.0 vs 3.1 days, p=0.043). For patients with a final diagnosis of a definite ACS (n=531), non-intervention centre patients were significantly less likely to be revascularised with PCI (25% vs 37%, p=0.0019) although CABG surgery numbers were not statistically different (4.1% vs 7.3%, p=0.13).

CONCLUSIONS

A collaborative group of clinicians and nurses has performed a third nationwide audit of suspected and definite ACS patients, and shown some gaps in the current service, including limited access to echocardiography and cardiac angiography. In particular we noted significant delays for non-intervention centre patients accessing planned invasive assessment. This study reveals areas of clinical need and emphasises the benefit of ongoing clinical audit, with subsequent feedback and a focus on integrated clinical service delivery, which can improve the care of ACS patients in New Zealand.

Proton magnetic resonance spectroscopy of the striatum in Parkinson's disease patients with motor response fluctuations

We have performed proton magnetic resonance spectroscopy centred on the putamen contralateral to the worst affected side in 10 patients with idiopathic Parkinson's disease (PD) and motor response fluctuations and seven age matched healthy controls. In PD, there was striking reduction in the N-acetylaspartate (NAA) and creatine and NAA/choline ratios compared to controls. This pilot study provides in vivo evidence of striatal neuronal dysfunction in PD and further studies are in progress to establish if the observed changes are due to the disease process itself or due to chronic levodopa therapy.