The prognostic value of the mitotic activity index in patients with primary breast cancer who were not treated with adjuvant systemic therapy

Deep learning and manual assessment show that the absolute mitotic count does not contain prognostic information in triple negative breast cancer

PURPOSE

The prognostic value of mitotic count for invasive breast cancer is firmly established. As yet, however, limited studies have been aimed at assessing mitotic counts as a prognostic factor for triple negative breast cancers (TNBC). Here, we assessed the prognostic value of absolute mitotic counts for TNBC, using both deep learning and manual procedures.

METHODS

A retrospective TNBC cohort (n = 298) was used. The absolute manual mitotic count was assessed by averaging counts from three independent observers. Deep learning was performed using a convolutional neural network on digitized H&E slides. Multivariable Cox regression models for relapse-free survival and overall survival served as baseline models. These were expanded with dichotomized mitotic counts, attempting every possible cut-off value, and evaluated by means of the c-statistic.

RESULTS

We found that per 2 mm2 averaged manual mitotic counts ranged from 1 to 187 (mean 37.6, SD 23.4), whereas automatic counts ranged from 1 to 269 (mean 57.6; SD 42.2). None of the cut-off values improved the models' baseline c-statistic, for both manual and automatic assessments.

CONCLUSIONS

Based on our results we conclude that the level of proliferation, as reflected by mitotic count, does not serve as a prognostic factor for TNBC. Therefore, TNBC patient management based on mitotic count should be discouraged.

Dane M, Esch A, Feiler HS, Wang NJ, Hardwicke MA, Laquerre S, Jackson J, W. Wood K, Weber B, Spellman PT, Aparicio S, Wooster R, Caldas C, Gray JW. Genome co-amplification upregulates a mitotic gene network activity that predicts outcome and response to mitotic protein inhibitors in breast cancer

BACKGROUND

High mitotic activity is associated with the genesis and progression of many cancers. Small molecule inhibitors of mitotic apparatus proteins are now being developed and evaluated clinically as anticancer agents. With clinical trials of several of these experimental compounds underway, it is important to understand the molecular mechanisms that determine high mitotic activity, identify tumor subtypes that carry molecular aberrations that confer high mitotic activity, and to develop molecular markers that distinguish which tumors will be most responsive to mitotic apparatus inhibitors.

METHODS

We identified a coordinately regulated mitotic apparatus network by analyzing gene expression profiles for 53 malignant and non-malignant human breast cancer cell lines and two separate primary breast tumor datasets. We defined the mitotic network activity index (MNAI) as the sum of the transcriptional levels of the 54 coordinately regulated mitotic apparatus genes. The effect of those genes on cell growth was evaluated by small interfering RNA (siRNA).

RESULTS

High MNAI was enriched in basal-like breast tumors and was associated with reduced survival duration and preferential sensitivity to inhibitors of the mitotic apparatus proteins, polo-like kinase, centromere associated protein E and aurora kinase designated GSK462364, GSK923295 and GSK1070916, respectively. Co-amplification of regions of chromosomes 8q24, 10p15-p12, 12p13, and 17q24-q25 was associated with the transcriptional upregulation of this network of 54 mitotic apparatus genes, and we identify transcription factors that localize to these regions and putatively regulate mitotic activity. Knockdown of the mitotic network by siRNA identified 22 genes that might be considered as additional therapeutic targets for this clinically relevant patient subgroup.

CONCLUSIONS

We define a molecular signature which may guide therapeutic approaches for tumors with high mitotic network activity.

Mechanical phenotyping of breast cancer using MEMS: a method to demarcate benign and cancerous breast tissues

The mechanical properties of tissue change significantly during the progression from healthy to malignant. Quantifying the mechanical properties of breast tissue within the tumor microenvironment can help to delineate benign from cancerous stages. In this work, we study high-grade invasive ductal carcinoma in comparison with their matched tumor adjacent areas, which exhibit benign morphology. Such paired tissue cores obtained from eight patients were indented using a MEMS-based piezoresistive microcantilever, which was positioned within pre-designated epithelial and stromal areas of the specimen. Field emission scanning electron microscopy studies on breast tissue cores were performed to understand the microstructural changes from benign to malignant. The normal epithelial tissues appeared compact and organized. The appearance of cancer regions, in comparison, not only revealed increased cellularity but also showed disorganization and increased fenestration. Using this technique, reliable discrimination between epithelial and stromal regions throughout both benign and cancerous breast tissue cores was obtained. The mechanical profiling generated using this method has the potential to be an objective, reproducible, and quantitative indicator for detecting and characterizing breast cancer.

Proliferation markers and survival in early breast cancer: a systematic review and meta-analysis of 85 studies in 32,825 patients

We have performed a systematic review and meta-analysis of proliferation markers (Ki-67, mitotic index (MI), proliferating cell nuclear antigen (PCNA) and thymidine or bromodeoxyuridine labelling index (LI)) with respect to survival in early breast cancer. Eighty-five studies involving 32,825 patients were analysed. Ki-67 (43 studies, 15,790 patients), MI (20 studies, 7021 patients), and LI (11 studies, 7337 patients) were associated with significantly shorter overall and disease free survival, using results from univariate and multivariate analyses from the individual studies. PCNA (11 studies, 2677 patients) was associated with shorter overall survival by multivariate analysis only, because of lack of data. There was some evidence for publication bias, but all markers remained significant after allowing for this. Ki-67, MI, PCNA and LI are associated with worse survival outcomes in early breast cancer. However, whether these proliferation markers provide additional prognostic information to commonly used prognostic indices remains unclear.

Phosphohistone H3 expression has much stronger prognostic value than classical prognosticators in invasive lymph node-negative breast cancer patients less than 55 years of age

The proliferation factor mitotic activity index is the strongest prognostic factor in early breast cancer, but it may lack reproducibility. We analyzed the prognostic value of phosphohistone H3, a marker of cells in late G(2) and M phase, measuring highly standardized immunohistochemical nuclear phosphohistone H3 expression by subjective counts and digital image analysis. Expression was compared with classical clinico-pathologic prognostic variables and the mitotic activity index in 119 node-negative invasive breast cancers in patients less than 55 years old treated with adjuvant systemic chemotherapy with long-term follow-up (median 168 months). Nineteen patients (16%) developed distant metastases and 16 (13%) died. Strong phosphohistone H3 expression occurred preferentially in the peripheral growing front; counts were highly reproducible between observers (R=0.92) and highly consistent with digital image analysis (R=0.96). Phosphohistone H3 correlated (P<0.05) with tumor diameter, estrogen receptor, carcinoma grade, and mitotic activity index. Phosphohistone H3 values were systematically (80%) higher than the mitotic activity index. Receiver-operating curve analysis objectively showed that phosphohistone H3 <13 (n=53; 45% of all cases) vs phosphohistone H3> or =13 (n=66; 55% of all cases) was the strongest prognostic threshold, with 20-year recurrence-free survival of distant metastases of 96 and 58%, respectively (P=0.0002, HR=9.6). Mitotic activity index was the second strongest prognostic variable (P=0.003, HR=3.9). In multivariate analysis, phosphohistone H3 <13 vs> or =13 exceeded the prognostic value of the mitotic activity index. None of the other classical prognostic factors examined offered prognostic value additional to phosphohistone H3. Phosphohistone H3 is by far the strongest prognostic variable in early invasive node-negative breast cancer patients less than 55 years old with long-term follow-up.

The prognostic value of proliferation in lymph-node-negative breast cancer patients is age dependent

In lymph-node-negative invasive breast cancer patients<55 years, the proliferation marker mitotic activity index (MAI) has previously been shown to be the strongest prognosticator. In studies without age definition, MAI was not strongly prognostic. We investigated the age dependency of the prognostic value of proliferation for distant metastasis-free (MFS) and overall cancer-related survival (OS) in 1004 histologically diagnosed T1-3N0M0 invasive breast cancers (n=516, <55 years; n=322, 55-70 years; n=166, >70 years) without systemic adjuvant therapy and long follow-up (median: 108 months). The MAI decreases with age and the prognostic value of MAI varied by age group. For patients<55 years, hazard ratios (HR) for MAI>or=10 versus<10 for MFS and OS were 3.1 and 4.4, respectively (P<.0001 for both), but only 1.9 and 1.9 (P=.004 and .006) for patients aged 55-70 years, while over 70 years, MAI was not significant (P=.11). The prognostic value of proliferation was age-dependent. Prognostic breast cancer studies must clearly indicate the age group being studied.

Long-term survival of T1 and T2 lymph node-negative breast cancer patients according to Mitotic Activity Index: a population-based study

Node-negative breast cancer patients have a relatively good prognosis, but eventually one-third will die of the disease. Thus, prognostic factors to identify the high-risk group among these patients are needed. We retrospectively determined the Mitotic Activity Index (MAI) for a large series of node-negative breast cancer patients (n = 468) with tumours smaller than 5 cm, who only received locoregional treatment. Patients were followed for up to 29 years; crude and relative survival were calculated, both univariate and multivariate. Relative survival differed significantly according to MAI (p = 0.05), the difference occurred in the first 5 years after diagnosis and remained constant thereafter. After adjustment, MAI still significantly affected relative survival (RER, 1.9; 95% CI, 1.1-3.5). Tumour size also increased the risk, but this was not statistically significant (RER, 1.5; 95% CI, 0.8-2.7). Survival of patients with a T1 tumour and MAI < 10 was similar to that for the general population in the first 5 years after diagnosis. In conclusion, MAI significantly predicted long-term survival for T1/T2N0 breast cancer. Adjuvant systemic therapy appears to have little benefit for node-negative breast cancer patients with a T1 tumour, regardless of the MAI. For those with a T2 tumour and a MAI > or = 10 systemic therapy might have reduced mortality. The need for close surveillance of node-negative breast cancer patients with a T1 tumour and MAI < 10 seems limited.

Tesmilifene may enhance breast cancer chemotherapy by killing a clone of aggressive, multi-drug resistant cells through its action on the p-glycoprotein pump

Tesmilifene is a novel potentiator of chemotherapy which, when added to doxorubicin, achieved an unexpected and very large survival advantage over doxorubicin alone in a randomized trial in advanced breast cancer. This trial was unusual in that the early endpoints (response rate and median progression-free survival) were equivalent in the two arms, despite the ultimate survival difference. These aspects, coupled with the absence of a coherent molecular mechanism of action, and a pending confirmatory trial, have led oncologists to hold judgement on this drug. This paper reacts to this in three ways: firstly, a forensic subgroup analysis is presented with an explanation as to why it strongly supports the veracity of the survival difference; secondly a novel cellular explanation is provided for the decoupling of the early and late (survival) endpoints; finally, a molecular mechanism of action is proposed, for the first time, which reconciles the peculiarities of the trial with the laboratory data and background literature. This hypothesis explains how tesmilifene could meld two of the apparent strengths of the cancer cell (drug resistance pumps, and hypoxia-adapted energetics) into a potent weapon of self-destruction. Tesmilifene is proposed to allow chemotherapy (e.g. anthracycline or taxane) to additionally kill a small but critical population (clone) of aggressive, multi-drug resistant cells, the benefits of which cannot be appreciated until a period of time (about 6-8 months) has elapsed. These cells, present in women with more rapidly relapsing disease, very likely carry an energy-dependent extrusion pump which is paradoxically activated by tesmilifene plus the chemotherapy. The result is that, despite the chemotherapy's remaining extracellular, the cell dies from reactive oxygen species leaking from the electron chain transport in the abnormal mitochondria which characterize cancer. These mitochondria are activated in response to the ATP cost of this pump activation, in these predominantly glycolytic cells.

Prospective Multicenter Validation of the Independent Prognostic Value of the Mitotic Activity Index in Lymph Node–Negative Breast Cancer Patients Younger Than 55 Years

Purpose

To validate the independent strong prognostic value of mitotic activity index (MAI) in lymph node (LN) –negative invasive breast cancer patients younger than 55 years in a nationwide multicenter prospective study.

Patients and Methods

Analysis of routinely assessed MAI and other prognosticators in 516 patients (median follow-up, 118 months; range, 8 to 185 months), without systemic adjuvant therapy or previous malignancies.

Results

Distant metastases occurred in 127 patients (24.6%); 90 (17.4%) died as a result of metastases. MAI (< 10, ≥ 10) showed strong association with recurrence (hazard ratio [HR], 3.12; 95% CI, 2.17 to 4.50; P ≤ .0001) and mortality (HR, 4.42; 95% CI, 2.79 to 7.01; P < .0001). The absolute difference in 10-year Kaplan-Meier estimates of time to distant recurrence as well as survival was 22% between MAI less than 10 versus ≥ 10. This effect was independent of age, estrogen receptor (ER) status, and tumor diameter (which were significant prognosticators). In multivariate analysis with regard to patient age, tumor diameter, grade, ER status, and the St Gallen criterion, MAI proved to be an independent and the strongest prognosticator. Tubular formation (TF) and nuclear atypia (NA), as constituents of (expert revised) grade, had no (for TF) or limited (for NA, P = .048) additional prognostic value to the MAI. In the group with MAI less than 10, MAI less than 3 versus more than 3 had additional value but the classical threshold of 0 to 5 v 6 to 10 did not. With this additional subdivision of MAI as less than 3, 3 to 9, and more than 9, NA lost its additive prognostic value.

Conclusion

The MAI is the strongest, most widely available, easily assessable, inexpensive, well-reproducible prognosticator and is well suited to routinely differentiate between high- and low-risk LN-negative breast cancer patients younger than 55 years.

Prognostic value of mitotic counts in axillary node negative breast cancer patients with predominantly well-differentiated tumours

AIMS

In axillary node negative (ANN) breast cancer patients additional prognostic markers are needed to decide whether adjuvant systemic treatment might be useful.

METHODS

In the present study, the prognostic relevance of mitotic counts and Bloom-Richardson grade (BR-grade) was evaluated in 164 ANN breast cancer patients. No adjuvant systemic treatment was given to any of these patients. Mitotic counts were determined twice, in routine practice and in revision.

RESULTS

A substantial reproducibility of mitotic counts was found, provided that the cut-off value chosen was high enough. After a median follow-up of 10 years, mitotic counts had no prognostic significance for survival at any cut-off value. A trend towards a significant worse survival was found for patients with Bloom-Richardson grade II or III in comparison with grade I.

CONCLUSIONS

Based on data in the literature a positive association between both mitotic counts and BR-grade and survival in ANN breast cancer may exist, but the extent of this putative association and its clinical relevance can be argued, particularly in a group of patients with predominantly well differentiated tumours.

Prognostic value of proliferation in invasive breast cancer: a review

Breast cancer is the leading cause of death among solid tumours in women, and its incidence is increasing in the West. Adjuvant chemotherapy and hormonal treatment improve survival but have potentially serious side effects, and are costly. Because adjuvant treatment should be given to high risk patients only, and traditional prognostic factors (lymph node status, tumour size) are insufficiently accurate, better predictors of high risk and treatment response are needed. Invasive breast cancer metastasises haematogenously very early on, so many breast cancer prognosticators are directly or indirectly related to proliferation. Although studies evaluating the role of individual proliferation regulating genes have greatly increased our knowledge of this complex process, the functional end result-cells dividing-has remained the most important prognostic factor. This article reviews the prognostic value of different proliferation assays in invasive breast cancer, and concludes that increased proliferation correlates strongly with poor prognosis, irrespective of the methodology used. Mitosis counting provides the most reproducible and independent prognostic value, and Ki67/MIB1 labelling and cyclin A index are promising alternatives that need methodological fine tuning.

In lymph node-negative invasive breast carcinomas, specific chromosomal aberrations are strongly associated with high mitotic activity and predict outcome more accurately than grade, tumour diameter, and oestrogen receptor

The objectives of this study were to analyse whether specific chromosomal gains and losses in lymph node-negative breast cancer correlate with other features and to evaluate their prognostic value. Seventy-six lymph node-negative breast carcinomas (median follow-up 46 months; range 9-105 months) were used. Histological grade, tumour type, maximal tumour diameter, oestrogen/progesterone receptor (ER/PR), mitotic activity index (MAI), and mean nuclear area (MNA) were assessed. Whole genome DNA analysis was performed by comparative genomic hybridization (CGH). Chromosomal aberrations were compared with classical and other prognostic features. Kaplan-Meier curves and multivariate survival analysis (Cox model) were used to assess the prognostic value of the CGH and other data. Fifteen (21.4%) out of 70 patients (six cases were lost to follow-up) developed locoregional (n=3) or distant metastases (n=12). The following criteria were prognostic for (any) recurrence (in decreasing significance): 3q gain, simultaneous gain at 1q and 8q, MAI < versus > or =10, MNA < versus > or =63 microm. Loss of 1p occurred significantly more often in the large group of ductal breast carcinomas with a MAI > or =10 (n=38) than in cancers with a MAI<10. Moreover, 8/15 (53%) patients with recurrences had a gain at 3q, as opposed to three (5.5%) of the 55 recurrence-free patients. This association was even stronger in ductal carcinomas (hazard ratio=10.9, p<0.0001). Cox regression revealed that the 3q gain was the strongest prognostic factor; other features did not have additional prognostic value. In conclusion, loss of 1p is associated with a high MAI. A gain of 3q is a stronger predictor of recurrence than grade, MAI, and other features in invasive breast cancers.