Tumor infiltrating lymphocytes are prognostic in triple negative breast cancer and predictive for trastuzumab benefit in early breast cancer: results from the FinHER trial

BACKGROUND

We have previously shown the prognostic importance of tumor-infiltrating lymphocytes (TILs) in newly diagnosed triple-negative breast cancer (TNBC) using tumor samples from a large clinical trial cohort. In this study, we aimed to validate these findings and also investigate associations with trastuzumab benefit in HER2-overexpressing disease (HER2+).

PATIENTS AND METHODS

A prospective-retrospective study was conducted using samples from the FinHER adjuvant, phase III trial that enrolled 1010 early-stage BC patients, 778 of whom were HER2-nonamplified. Those with HER2+ disease (n = 232) were randomized to 9 weeks of trastuzumab or no trastuzumab in addition to chemotherapy. Two pathologists independently quantified stromal TILs in 935 (92.6%) available slides. The primary end point of distant disease-free survival (DDFS) and interactions with trastuzumab were studied in Cox regression models.

RESULTS

Confirming our previous findings, in TNBC (n = 134) each 10% increase in TILs was significantly associated with decreased distant recurrence in TNBC; for DDFS the hazard ratio adjusted for clinicopathological factors: 0.77; 95% confidence interval (CI) 0.61-0.98, P = 0.02. In HER2+ BC (n = 209), each 10% increase in lymphocytic infiltration was significantly associated with decreased distant recurrence in patients randomized to the trastuzumab arm (DDFS P interaction = 0.025).

CONCLUSIONS

Higher levels of TILs present at diagnosis were significantly associated with decreased distant recurrence rates in primary TNBC. These results confirm our previous data and further support that TILs should be considered as a robust prognostic factor in this BC subtype. We also report for the first time an association between higher levels of TILs and increased trastuzumab benefit in HER2+ disease. Further research into why some TN and HER2+ BCs can or cannot generate a host antitumor immune response and how trastuzumab can favorably alter the immune microenvironment is warranted.

Abstract P1-08-06: Low tumor CD68 mRNA content (intratumoral macrophages) is predictive for benefit from adjuvant trastuzumab in HER2-positive breast cancer: An analysis of the FinHER trial

Background: Tumor immune cell infiltrates influence prognosis of node negative breast cancer (BC), and intratumoral B-cells and T-cells are of importance for achieving response to chemotherapy in triple negative BC. The role of tumor infiltrating macrophages remains unclear, but they might promote tumorigenesis. We investigated the prognostic value of CD68 mRNA levels within the luminal, HER2-positive and triple negative subtypes in the FinHer trial patient population, and evaluated their predictive value on survival outcomes achieved with adjuvant trastuzumab and chemotherapy in early breast cancer.

Methods: RNA was extracted from formalin-fixed paraffin-embedded (FFPE) tumor tissue of 917 (90.8%) patients out of the 1010 patients who participated in the FinHer trial. Intratumoral macrophage infiltration was assessed by measuring breast tumor CD68 mRNA content using RT-qPCR from representative FFPE tissue samples. Breast cancer molecular subtypes (luminal, HER2 positive and triple-negative) were approximated using immunohistochemistry (IHC) and central CISH testing data obtained from the FinHer trial datafile. Prognostic significance of CD68 on distant disease-free survival (DDFS) was assessed using Kaplan-Meyer analysis and log-rank test.

Results: Tumor CD68 mRNA expression was normally distributed with median expression of 33.56 (dCt). CD68 mRNA levels correlated weakly with estrogen receptor (ER) mRNA expression and ER protein levels (r = 0.11 and r = 0.15, respectively; p<0.0001), but not with tumor HER2 mRNA level or IHC/CISH status (r = -0.06, p = 0.12; and r = 0.01, p = 0.92, respectively). The median tumor CD68 mRNA content was not prognostic for DDFS in the subset of luminal cancers (ER+, HER2-; n = 533, 5-year DDFS 88% versus 88%; p = 0.92), but a lower than the median CD68 level tended to be associated with favorable DDFS in triple negative cancer (n = 143; 81% vs. 70%; p = 0.11) and was significantly associated with favorable DDFS in HER2-positive cancer (n = 191; 86% vs. 67%; p = 0.001). In the subset of HER2-positive cancer with tumor CD68 mRNA expression level lower than the median, patients treated with trastuzumab benefitted from addition of trastuzumab to chemotherapy (5-year DDFS 93% with trastuzumab vs. 79% without trastuzumab; p = 0.02), whereas no benefit from trastuzumab was observed when tumor CD68 content was higher than the median (67% vs. 68%; p = 0.92).

Conclusions: The study validates tumor CD68 concentration as a prognostic biomarker in HER2-positive early breast cancer. Patients with HER2-positive cancer and few tumor macrophages (low tumor CD68 mRNA content) benefitted from addition of trastuzumab to chemotherapy, whereas patients with HER2-positive BC with high tumor macrophage content derived no benefit from adjuvant trastuzumab. Trastuzumab may be effective only for macrophage-poor HER2-positive cancers that are prone to antibody-dependent cellular cytotoxicity (ADCC), whereas it may have little efficacy for cancers that progress despite or due to high intratumoral macrophage content that interferes with ADCC. Other agents, such as T-DM1, might work better than trastuzumab in the subset of women who have HER2-positive BC with a high tumor macrophage content.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-06.

P1-07-01: Comparison of Four HER2 Testing Methods in the Detection of HER2−Positive Breast Cancer: Results from the FinHer Study Cohort

Background: Accurate assessment of the HER2 status is essential for identifying patients who may benefit from HER2 targeted therapy. The current methods, immunohistochemistry (IHC) and in situ hybridization (ISH), determine HER2 status semi-quantitatively as positive (+), equivocal (+/−) and negative (−) with predefined cutoff values. Recent studies have suggested that current HER2 cutoffs may not be optimal for all clinical settings of HER2 targeted therapy. In a small subset of adjuvant NCCTG N9831 patients confirmed as HER2−normal by round-robin review of HER2 testing, trastuzumab benefit was observed (Perez et al, SABCS 2010). Quantification of HER2 as continuous variable may enable a more accurate optimization of HER2 cutoffs for various HER2 targeted therapies. In this study, we measured continuous HER2 protein expression by the HERmark™ assay and continuous mRNA expression by quantitative real time polymerase chain reaction (qPCR), and compared these results with central IHC and central chromogenic in situ hybridization (CISH) results of FinHer.

Methods: Total HER2 protein expression (H2T) was quantified using the HERmark assay as previously described (Huang et al. Am J Clin Pathol 2010;134:303). HER2 mRNA expression (H2N) was measured by qPCR as previously published (Noske et al. Br Cancer Res Treat 2011;126:109). The results of H2T and H2N as continuous variables and as predefined categories were compared with central CISH results from FinHer (Joensuu et al, N Engl J Med 2006;354), and central IHC retesting.

Results: H2T in 899 evaluable samples described a continuum of 0.4 to 721.2 (relative HERmark unit); while H2N in 915 evaluable samples showed a continuum of 31.4 to 42.8 (delta-Ct). Significant correlation between H2T and H2N as continuous variable was found (R2= 0.56, P< .0001). Paired method comparison was performed for samples with valid results in any two of the four testing methods. Overall concordance of H2T and H2N with predefined categories (+, +/−, -) was 81%, and concordance of (+) and (−) subsets was 95% when (+/−) cases (H2T 11%; H2N 6%) were excluded. Overall concordance of central IHC and H2T categories (+, +/−, -) was 75%, and concordance of (+) and (−) subsets was 96% when (+/−) cases (IHC 16%; H2T 11%) were excluded. Overall concordance of IHC and H2N categories (+, +/−, -) was 84%, and concordance of (+) and (−) subsets was 99% when (+/−) cases (IHC 16%; H2N 6%) were excluded. Concordance of central CISH (+, -) with H2T and H2N categories (+, -) was 89% and 91%, respectively, when (+/−) cases were excluded from H2T (13%) and H2N (8%), respectively.

Conclusions: All four methods identified HER2−positive breast cancers. The discordance rate between the methods tested was approximately 10 to 20% despite careful delineation of cancerous tissue in the sample and analysis of adjacent tumor sections. No combination of assays could be identified with concordance rate >95% when the equivocal subsets were included in comparisons. Exclusion of the equivocal subsets (about 10% of samples) yielded high concordance rates of approximately 95% or higher. H2T and H2N showed comparable continuous distribution patterns and significant concordance with standard HER2 status by central IHC and CISH.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-07-01.

P2-12-04: RACGAP1 mRNA Assay Outperforms Ki-67 as a Proliferation Marker in the FinHer Study Cohort

Background: Molecular subtyping of breast cancer has become an integral part of standard evaluation of breast cancer patients. Their assessment requires combining data from analyses on ER, PR, HER2 and cell proliferation markers. However, their immunohistochemical (IHC) testing carries an up to 20% risk of erroneous results. Similarly, assessment of cell proliferation by Ki-67 staining is hampered by lack of standardization of laboratory methods and agreement on cut-offs. Here we tested the prognostic value of objective quantitation of ESR1, PgR, HER2 and the proliferation markers RACGAP1 using RT-qPCR and compared the results with local and central IHC assessments.

Methods: RNA was extracted from FFPE tumor tissue of 917 patients who participated in the FinHer trial. ESR1, PgR, HER2 and RACGAP1 mRNA expression were measured using RT-qPCR. The molecular subtypes (luminal, HER2−enriched and triple-negative) were determined. Prognostic significance of proliferation markers was assessed using univariate and multivariate analyses. The RT-qPCR results were compared with local and central IHC results.

Results: HER2 mRNA showed a bimodal distribution with 197 (21.4%) out of the 917 tumors being above the predefined cut-off. HER2 mRNA expression increased in parallel with HER protein expression. Overall concordance of HER2 mRNA testing with central IHC and CISH was good, while local IHC testing suffered higher false positive rates. RACGAP1 mRNA expression was the greater the higher the histological grade. ESR1 and PgR mRNA correlated negatively with the histological grade (r=-0.38 and r=-0.33; p<0.0001), whereas HER2 and RACGAP1 mRNA were correlated positively (r=0.10 and r=0.49; p=0.002 and p<0.0001, respectively). RACGAP1 mRNA was negatively associated with ESR1 and PgR mRNA (r=-0.17 and r=-0.26, respectively; p<0.0001 for each). Molecular subtypes determined by RT-qPCR using predefined cut-off values were highly prognostic for overall survival (OS) (p<0.001). The 5-year OS rate for patients with luminal cancer was 94% and 86% for HER2−enriched cancer and 84% for triple-negative cancer. In the subset of luminal tumors, high expression of RACGAP1 identified a population of patients who were at a high risk of death (5-year OS 82% versus 95%; p<0.0001). In a multivariate analysis RACGAP1 mRNA expression, nodal status and chemotherapy type were independent prognostic factors, whereas IHC of ER, PgR, Ki-67 and histological grade were not significant.

Conclusions: Molecular subtyping of breast cancer by RT-qPCR using RNA isolated from FFPE tissue proved successfully in this large patient cohort. RACGAP1 mRNA expression distinguished high and low risk luminal breast cancers. In a multivariate analysis mRNA-based molecular markers outperformed the immunohistochemical markers ER, PgR and Ki-67. Of note, quantitative assessment of the proliferation marker RACGAP1 was superior to semiquantitative assessment of Ki-67 from routine FFPE tissues using IHC. We conclude that quantitative assessment of ESR1, PgR, HER2 and RACGAP1 mRNA by RT-qPCR is a robust and reproducible method to assess these key tumor biological factors from archival FFPE tumor tissue. RACGAP1 is novel cell proliferation marker in breast cancer that warrants further validation.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-04.

Expression and prognostic value of transcription factor PROX1 in colorectal cancer

Background:

PROX1 is a specific target of the β-catenin/TCF pathway in the intestinal epithelium. It acts as a regulator of progression from a benign to a highly dysplastic phenotype in colorectal tumours. However, the clinical significance of PROX1 expression is not known.

Methods:

We studied the prognostic value of immunohistochemical expression of PROX1 in a series of 517 patients with colorectal cancer (CRC).

Results:

The majority of the tumour samples expressed PROX1 (91%, 471 out of 517). High PROX1 expression was associated with a poor grade of tumour differentiation (P<0.0001). In the subgroup of patients with colon cancer, high PROX1 expression was associated with unfavourable colorectal cancer-specific survival (CCSS) as compared with low PROX1 expression (CCSS 47% vs 62% P=0.045; RR 1.47). The association between high PROX1 and poor outcome was further strengthened in female colon cancer patients (CCSS 38% vs 63% P=0.007; RR 2.02). Nonetheless, in multivariate survival analysis PROX1 expression was not retained as an independent prognostic factor.

Conclusion:

High PROX1 expression is associated with a poor grade of tumour differentiation, and, in colon cancer patients, also with less favourable patient outcome. Our results strengthen the previous preclinical observations that PROX1 has a role in tumour progression in CRC.

Twelve versus 36 months of adjuvant imatinib (IM) as treatment of operable GIST with a high risk of recurrence: Final results of a randomized trial (SSGXVIII/AIO)

LBA1

Background: Adjuvant IM administered for 12 months (mos) after surgery improves recurrence-free survival (RFS) of patients (pts) diagnosed with operable GIST. We compared 12 vs 36 mos of adjuvant IM as treatment of pts with a high risk for GIST recurrence after surgery. Methods: Pts with histologically diagnosed KIT-positive GIST were entered to this prospective, open-label, multicenter, randomized Phase III study (identifier NCT00116935 ). The risk of recurrence was estimated according to the modified Consensus Criteria. The primary objective was RFS. The secondary objectives included survival (OS) and treatment safety. The key exclusion criteria were ECOG PS >2, metastatic or inoperable GIST, and >12 wks from surgery to the study entry. IM was administered orally 400 mg/d. The sample size (n =200 in each group to obtain ≥110 events) was estimated by simulating log-rank tests assuming an overall hazard ratio (HR) of 0.44, a 20% drop-out rate, 2-sided type-I error rate of .05 and power 0.80. Analysis was based on the intention-to-treat population (ITT). Tumor histology was centrally reviewed. Results: 400 pts were entered to the study from Feb 2004 to Sep 2008. Three pts were excluded due to lack of consent from the ITT, which includes 15 pts who did not have GIST at a central review. The median FU time was 54 mos. RFS was longer in the 36-mo group compared to the 12-mo group (HR 0.46, 95% CI 0.32-0.65; p <.0001; 5-y RFS 65.6% vs 47.9%, respectively). Pts assigned to 36-mo of IM had longer OS (HR 0.45, 0.22-0.89; p =.019; 5-y OS 92.0% vs 81.7%). IM was generally well tolerated. The proportion of pts who discontinued IM during the assigned treatment period for reasons other than GIST recurrence was 25.8% in the 36-mo group and 12.6% in the 12-mo group. Exploratory efficacy subgroup analyses including KIT and PDGFRA mutation analysis data from 366 tumors will be presented. Conclusions: IM administered for 36 mos improves RFS and OS compared to 12 mos of administration as adjuvant treatment of GIST pts who have a high estimated risk of recurrence after surgery.

Vatalanib for metastatic gastrointestinal stromal tumour (GIST) resistant to imatinib: final results of a phase II study

BACKGROUND

Vatalanib (PTK787/ZK 222584) inhibits a few tyrosine kinases including KIT, platelet-derived growth factor receptors (PDGFRs) and vascular endothelial growth factor receptors (VEGFRs). We report efficacy and safety results of vatalanib in advanced gastrointestinal stromal tumour (GIST) resistant to imatinib or both imatinib and sunitinib.

PATIENTS AND METHODS

Forty-five patients whose metastatic GIST had progressed on imatinib were enrolled. Nineteen (42.2%) patients had received also prior sunitinib. Vatalanib 1250 mg was administered orally daily.

RESULTS

Eighteen patients (40.0%; 95% confidence interval (CI), 25.7-54.3%) had clinical benefit including 2 (4.4%) confirmed partial remissions (PR; duration, 9.6 and 39.4 months) and 16 (35.6%) stabilised diseases (SDs; median duration, 12.5 months; range, 6.0-35.6+ months). Twelve (46.2%) out of the 26 patients who had received prior imatinib only achieved either PR or SD compared with 6 (31.6%, all SDs) out of the 19 patients who had received prior imatinib and sunitinib (P=0.324). The median time to progression was 5.8 months (95% CI, 2.9-9.5 months) in the subset without prior sunitinib and 3.2 (95% CI, 2.1-6.0) months among those with prior imatinib and sunitinib (P=0.992). Vatalanib was generally well tolerated.

CONCLUSION

Vatalanib is active despite its narrow kinome interaction spectrum in patients diagnosed with imatinib-resistant GIST or with imatinib and sunitinib-resistant GIST.

Hypertension and overall survival in metastatic colorectal cancer patients treated with bevacizumab-containing chemotherapy

BACKGROUND

Hypertension (HTN) is a common toxicity of anti-VEGF (vascular endothelial growth factor) antibody treatment. It may be a marker of VEGF signalling pathway inhibition and therefore represent a cancer biomarker in metastatic colorectal cancer (mCRC) patients treated with chemotherapy and bevacizumab.

METHODS

A total of 101 consecutive patients with mCRC were treated with standard chemotherapy combined with bevacizumab at dose of 2.5 mg kg(-1) per week in a single centre. The median follow-up time of the patients alive was 64 months. Blood pressure was measured before each bevacizumab infusion, and HTN was graded according to common toxicity criteria for adverse events version 3.0.

RESULTS

Overall, 57 patients (56%) developed ≥grade 1 HTN (median blood pressure 168/97 mm Hg), whereas 44 (44%) remained normotensive when treated with bevacizumab-containing chemotherapy regimen. Overall response rate was higher among patients with HTN (30 vs 20%; P=0.025). Hypertension was associated with improved progression-free survival (10.5 vs 5.3 months; P=0.008) and overall survival (25.8 vs 11.7 months; P<0.001), and development of HTN within 3 months had an independent, prognostic influence in a multivariate landmark survival analysis together with other known mCRC prognostic factors (P=0.007). There was no association between HTN and development of thromboembolic complications.

CONCLUSION

Hypertension may predict outcome of bevacizumab-containing chemotherapy in mCRC. These data require confirmation in prospective studies including pharmacodynamic and pharmacokinetic analyses.

Breast Cancer Patients with Very High Tumor HER2 Expression Levels Might Not Benefit from Treatment with Trastzumab Plus Chemotherapy: A Retrospective Exploratory Analysis of the FinHer Trial

Background: FinHer (NEJM 2006) is one of the several prospective randomized clinical trials that show a clinical benefit from trastuzumab added to adjuvant chemotherapy. We have previously reported that patients with metastatic breast cancer who had very high levels of HER2 protein expression as measured by the HERmark assay and who were treated with trastuzumab had similar time-to-progression (TTP) compared to a group of patients who had FISH-negative and HER2 normal cancer suggesting reduced efficacy of trastuzumab when tumor HER2 content is very high (Sperinde, ASCO 2009). Here we investigate the relationship between clinical benefit from trastuzumab and quantitative HER2 protein expression (H2T) as determined by the HERmark assay.Methods: H2T was quantitated by the HERmark assay in 899 formalin-fixed paraffin-embedded specimens from patients enrolled in the FinHer trial; 196 of the samples were HER2-positive by chromogenic in situ hybridization (CISH). Focusing on the HER2-positive patients who were randomized to trastuzumab treatment or control, Cox proportional hazards analyses, sub-population treatment effect pattern plots (STEPP analyses), positional scanning analyses, and Kaplan-Meier analyses were used to identify sub-populations of HER2 over-expressing patients who experienced different clinical outcomes on trastuzumab.Results: Using time to distant recurrence (TDR) and overall survival (OS) as endpoints, Cox proportional hazards analyses treating H2T as a continuous variable failed to show a relationship between HER2 expression levels and clinical benefit from trastuzumab (HR=1, p=ns for both). STEPP analyses were performed to look for non-linear relationships between H2T and clinical outcome. At the highest levels of H2T, the hazard ratio comparing trastuzumab treatment to control approached and exceeded 1. Positional scanning analyses were conducted to identify the optimal cutoff discriminating the very high H2T group. Patients with very high H2T values (&gt;= 125.9) did not benefit from trastuzumab plus chemotherapy treatment relative to controls (HR=1.23, p=0.75 for TDR, HR=1.05, p=0.95 for OS), while those with H2T values &lt;125.9 did (HR=0.52, p=0.05 for TDR, HR=0.48, p=0.1 for OS). The very high H2T group represented 13% of the HER2-positive population compared with 16% in the prior study from Sperinde et al.Discussion: In this exploratory analysis of a prospectively randomized controlled trial of trastuzumab in the adjuvant setting, the 13% of patients with the highest H2T values showed no evidence of clinical benefit from trastuzumab. Potential explanations include insufficient trastuzumab dose, steric hindrance preventing access of trastuzumab to its epitope target under conditions of HER2 over-crowding, or the existence of trastuzumab-resistant forms of HER2 at the highest levels of over-expression (e.g. p95/HER2, HER2:HER3 heterodimers). Although these results are in agreement with prior observations from the metastatic setting, they need to be confirmed in larger randomized trials of trastuzumab in early breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5083.

Docetaxel versus docetaxel alternating with gemcitabine as treatments of advanced breast cancer: final analysis of a randomised trial

Background: Alternating administration of docetaxel and gemcitabine might result in improved time-to-treatment failure (TTF) and fewer adverse events compared with single-agent docetaxel as treatment of advanced breast cancer.

Patients and methods: Women diagnosed with advanced breast cancer were randomly allocated to receive 3-weekly docetaxel (group D) or 3-weekly docetaxel alternating with 3-weekly gemcitabine (group D/G) until treatment failure as first-line chemotherapy. The primary end point was TTF.

Results: Two hundred and thirty-seven subjects were assigned to treatment (group D, 115; group D/G, 122). The median TTF was 5.6 and 6.2 months in groups D and D/G, respectively (hazard ratio 0.85, 95% confidence interval 0.63–1.16; P = 0.31). There was no significant difference in time-to-disease progression, survival, and response rate between the groups. When adverse events were evaluated for the worst toxicity encountered during treatment, there was little difference between the groups, but when they were assessed per cycle, alternating treatment was associated with fewer severe (grade 3 or 4) adverse effects (P = 0.013), and the difference was highly significant for cycles when gemcitabine was administered in group D/G (P < 0.001).

Conclusion: The alternating regimen was associated with a similar TTF as single-agent docetaxel but with fewer adverse effects during gemcitabine cycles.

Correlation of quantitative total HER2 expression and HER2 homodimers with histopathologic characteristics of breast cancers in the FinHer study

11061

Background: We recently reported that the HERmark assay (Monogram Biosciences) accurately measures continua of total HER2 expression (H2T) and HER2 homodimers (H2D) over a wide (∼3 logs) dynamic range, and that a higher concordance was observed between H2T and HER2 status with more stringent central tests as compared with IHC tests performed locally (Joensuu et al, 2008 SABCS,abstract 2071). H2D/H2T ratio was reported as a marker of activated HER2 and a prognosticator of disease progression in HER2+ patients not treated with trastuzumab in the adjuvant setting (Bates et al, 2008 SABCS,abstract 1074). In this follow-up analysis, H2T, H2D, and H2D/H2T ratio were correlated with histopathologic characteristics of breast cancers in the FinHer study. Methods: The HERmark assay was used to measure H2T and H2D in 899 formalin-fixed, paraffin-embedded FinHer specimens. The results were correlated with histopathologic characteristics of breast cancers in the FinHer study (Joensuu et al, N Engl J Med2006;354), including estrogen receptor/progesterone receptor (ER/PR), tumor grade, tumor size, lymph node metastasis, and stage. Results: Higher H2T and H2D levels correlated with ER/PR negativity and high tumor grade (P<0.0001). 42% (102/244) of ER- and 37% (137/374) of PR- cases were HERmark Positive; while 17% (110/655) of ER+ and 14% (75/524) of PR+ cases were HERmark Positive. 10% (13/136) of grade 1, 18% (65/353) of grade 2, and 35% (131/375) of grade 3 tumors were HERmark Positive. No significant association was found between H2T or H2D and tumor size, lymph node metastasis or stage. ER/PR negative and poorly differentiated cancers had higher H2D/H2T ratios (P=0.013), and H2D/H2T ratios >0.6 were associated with smaller primary tumor diameters at the time of cancer detection (P=0.009). Conclusions: The quantitative H2T measurement confirms the known correlations between HER2 expression and histopathologic characteristics of breast cancer. The novel H2D measurement and H2D/H2T ratio may provide further insights into HER2 activation and better diagnostic tests for targeted HER2 therapy.

[Table: see text]