Understanding the Biology and Treatment Options for Breast Cancer

by Anthony M Magliocco MD

Breast cancer is a common disease with up to 1 in 8 women receiving this diagnosis in her lifetime. It is more common in older women but it certainly can strike the young and even can occur in men at about 1/100 the rate seen in women.

We have learned a lot about the biology of breast cancer over the years and the condition is becoming easier to detect at an earlier stage and fortunately more effective therapies are now being developed.

We now know that breast cancer is complex and has multiple molecular and biological subtypes. The main types are called Luminal A, Luminal B, HER2 positive, and Triple Negative.

Luminal Cancers – Endocrine responsive tumors

The Luminal types of breast cancer are defined by expressing estrogen receptor. They tend to have better differentiation and generally a more indolent course. The standard treatment is surgery, potentially radiation, and endocrine treatment (an anti estrogen agent) for 5 to 10 years. If the tumor appears more aggressive- ie involves lymph nodes, or has higher grade, chemotherapy may be added to the treatment in an adjuvant way. One of the problems with luminal type breast cancer is it can recur many years after the original cancer has been treated. Its thought the cancer cells can spread and remain dormant in distant organs or bone for many years with some mysterious events causing them to become reactivated.

 

The HER2 positive breast cancers

A subset of breast cancers, about 15% seem driven by the oncogene ERBB2 (which produces the protein HER2).  For some reason this gene can become “amplified” – ie many copies are made in a single cell leading to vast over production of the HER2 protein. This over production seems to drive the cancer cell to proliferate and metastasize.

Fortunately, therapies have been designed for HER2 cancer, these include Trastuzumab and Pertuzumab – antibodies that react and block the function of the HER2 gene. These treatments appear to be able to halt the grow of the cancer and prevent metastases from occurring.

The Triple Negative Breast Cancers (TNBC)

The third main type of breast cancer are the Triple Negative Cancers or TNBC. This group is actually a mixed group of tumors defined by lack of expression of estrogen receptor or HER2.  They frequently occur in younger women, they may be familial, are over represented in African American women and often progress more quickly. Some of them seem to have a high immune infiltrate, some carry the BRCA gene mutation, and some show strange growth characteristics such as bone formation or “metaplasia”.

 

 

The problem with TNBC is they are a generally a diagnosis by exclusion. However there are certain tests a pathologist can order to help prove that a cancer is TNBC such as Nestin.

Because the TNBC is diagnosed by exclusion there is a significant possibility of error. For example some tumors are heterogenous, and only a small portion might be sampled. If the portion is ER negative or HER2 negative the tumor might be erroneously classified as TNBC.

In other cases, TNBC cancers with very low false expression of HER2 or ER may end up being misclassified as HER2 positive or ER positive which could lead to erroneous use of potentially toxic and ineffective anti -HER2 therapy

Use of Second opinion Expert Review Pathology 

A second opinion pathology review by an expert pathologist can help a patient and her oncology be confident that a tumor is indeed a TNBC. The pathologist may order a repeat immunohistochemical stain on additional case material which frequently changes a diagnosis of TNBC to ER positive or HER2 positive. Occasionally a ER positive or HER2 positive will be reclassified as TNBC also.

TNBC is a unique form of breast cancer with subtypes. further classification of TNBC into tumors with BRCA mutation will help with selection of Parp inhibitor or chemotherapy with carboplatinum.

Further, some TNBC tumors have been shown to be sensitive to immunotherapy.

Some TNBC also seem to express androgen receptor, which could be a therapeutic target.

 

Use of Liquid Biopsy

In some patients a liquid biopsy could also be helpful. If a patient has metastatic disease the cancer cells can be isolated and analyzed from a blood sample.  ER and HER2 status can be measured in these circulating tumor cells. In addition fragments of DNA from disintegrating cancer cells can also be measured and classified providing further evidence as to the amount of cancer and whether the cancer is changing or responding to therapy.

Of interest, it seems that breast cancers may undergo biomarker change as they progress or metastasize. for example an ER positive tumor might change and become ER negative or switch to HER2 overexpression.

Patients should seek second opinion pathology review if they have concern regarding the accuracy of their diagnosis or want to ensure that all treatment opportunities are properly considered.

 

 

As treatment options continue to expand, and testing methods improve, it is important that patients with breast cancer have access to the highest quality pathology services and they should also not hesitate to seek second opinion if there is concern regarding the accuracy of diagnosis.

New Window into Brain Metastasis Using Modified CTC and cfDNA Technologies

Anthony M Magliocco MD

Many cancers metastasize to the central nervous system including the brain and its coverings, the leptomeninges. These cancers are difficult to treat and monitor. The so called “liquid biopsy” is making excellent progress in monitoring disease progression and response using blood samples in patients with disseminated solid tumors. In this technique, either circulating tumor cells (CTCs), or cell free DNA (cfDNA) can be harvested and captured for analysis.

These new “real time” monitoring methods create a new opportunity to monitor cancer progression and evolution while patients are actually under therapy- for example are the number of circulating tumor cells increasing, or is their phenotype evolving into something different.

For example, metastatic breast cancer cells may change their receptor status to go from estrogen receptor positive to negative, or they may acquire a new targetable change, for example acquiring HER2 over expression.

Images of circulating tumor cells captured in the Cell Search System

Intact tumor cells might also allow for examination of activation of signalling cascades and perhaps a pharmacodynamic read out.  One of the challenges of CTCs is their extreme fragility- with current method they generally need to be captured and examined within 48-72 hours. These cells also tend to be exquisitely rare, especially in early stage disease raising questions as to how representative they may be of the systemic disease.

 

Cell Free DNA cfDNA

A complementary assay method,  the measurement of cell free DNA (or cfDNA), provides a new application for monitoring cfDNA in patients. It has found widespread use monitoring lung cancer patients for the development of tyrosine kinase resistance while under therapy.  A common mechanism of resistance is the the switch or evolution to EGFR T790M mutation that portends the looming end of response to first generation TKI drugs and an opportunity to intervene with a switch to the 3rd generation Osimertinib therapy.

Liquid Biopsy is a powerful method to enable real time monitoring of solid tumor evolution and response to therapy using a blood sample to cature CTCs and cfDNA. Unfortunately, this does not typically work for CNS tumors due to the blood brain barrier

Unfortunately tumors occurring or metastasizing to the CNS are not easily followed by blood tests due to the presence of the blood brain barrier. However, these tumors are in contact with the cerebrospinal fluid, a specialized liquid that circulates around the brain cushioning it.

This fluid can be extracted in small amounts for analysis using a spinal tap, or in some cases of patients with malignancy an in-dwelling catheter is placed to enable CSF to be drained off to reduce the central nervous system pressure. This CSF fluid is traditionally sent to pathology for cytopathology analysis. Unfortunately standardized cytopathology methods do not lend themselves to evaluation of rare cells and molecular events in CSF.

 

Because CSF is very similar to blood, we reasoned that liquid biopsy methods used for blood samples might be potentially adapted for use on CSF samples. Recently, the Moffitt teams of the Neuro Oncology group, led by Dr Peter Forsyth and the Morsani Molecular Laboratory teamed up to attempt to modify the liquid biopsy procedures currently used for blood to adapt for CSF.

The current CTC platform in use at the Morsani Molecular Laboratory at Moffitt is the CellSearch system which is designed for magnetic capture of EPCAM expressing carcinoma cells in blood followed by evaluation of keratin expression in an automated scanning step with exclusion of non- specific cells using stains for nuclei and lymphocytes.

The adaptation of this system for analysis of melanoma in CSF was not trivial, as the volume of CSF is significantly less requiring adjustments on the liquid handling approaches. Further, the Neuroncology team was particularly interested in metastatic and primary melanomas of the central nervous system. This required changing capture antibodies to CD146 which targets melanoma and visualization with MelPE.

The Moffitt Morsani Molecular Laboratory has Developed New Methods to Monitor Melanoma in the CSF using both CTCs and cfDNA approaches

We also determined that DNA could be extracted and sequenced from CSF using both the NGS sequencing methods and MassArray systems. Further, we determined that melanoma cells captured from CSF can be grown ex-vivo and cultured for further analysis.

These advances create new opportunities to apply advances from personalized oncology to patients with metastatic melanoma in the CSF and central nervous system enabling potential real time adaptation of treatment strategies based on directly monitoring tumor molecular responsiveness to therapy in real time \\.

REFERENCES

Fedorenko IV, Evernden B, Kenchappa RS, et al. A rare case of leptomeningeal carcinomatosis in a patient with uveal melanoma: case report and review of literature. Melanoma research. 2016;26(5):481-486. doi:10.1097/CMR.0000000000000274.

Neuro-Oncology, Volume 19, Issue suppl_6, 6 November 2017, Pages vi46,https://doi.org/10.1093/neuonc/nox168.183 Published: 06 November 2017

 

A Tale of 2 Biomarkers: CTCs and cfDNA are Key to Managing the Plethora of New Trial Options

By Anthony M Magliocco MD

 

We are currently living in revolutionary times when it comes to cancer therapy and treatment options. There are literally hundreds of clinical trials under way evaluating dozens of new therapeutic compounds and combinations of therapy. In fact there are so many trials that its difficult to always find enough patients for them and also to design them to produce the level of evidence expected in traditional multi-armed phase III trials.

There are hundreds of open clinical trials testing dozens of compounds and combinations of therapy

 

Indeed, we seem to be arriving at the point where cancer therapy really is being tailored and delivered to the individual. This shift from evidence based conventional cancer therapy clinical trials, to newer, matched and “N of One” trials creates new challenges for the oncologist and diagnostic laboratory industry.

In a traditional trial, selection and enrollment would depend on results of a key biomarker such as HER2 overexpression for Trastuzumab therapy

Traditionally a biomarker would be required to select a patient for a specific therapy. For example, in breast cancer, presence of HER2 over expression or amplification was a marker to help select patients for enrollment in a trial. Because the frequency of the biomarker was relatively common in a common disease, it was possible to build a well powered phase III trial to collect convincing evidence that on a population based setting that this was an effective strategy. This led to FDA approval and the development of companion diagnostics such as the Herceptin Test.

Fast forward twenty years or so. Now we have so called “basket trials” where cancers can be tested with complex genomic tests that will evaluate hundreds of genes, for example the Moffitt STAR assay that covers 170 actionable mutations and alterations resulting in detection of relatively rare, but still actionable mutations in many tumors. However the mutations are variable and the choices for treatment complex meaning that more than one combination of therapy could be considered. Whats an oncologist to do?

Going forward, it appears that if patients cannot be managed or enrolled in large trials, there will need to be an approach to effectively manage the so called “N of One” patient. In fact, it could be considered that almost every patient is a now unique in some way and could be classified as a rare disease

With a movement away from classical evidence based clinical trials toward n of one trials, off label therapy, and basket trials new approaches to companion diagnostics are urgently needed

In this situation, it appears that physicians will need to act on “best available evidence” or actual bioinformatics or other predictive models of possible response based on understanding the underlying molecular circuitry in the cancer in question. In this situation a “best guess” is made for assignment of therapy (either in a basket trial or in an off-label situation).

This approach can be problematic and has numerous complications such as the possibility of providing futile or toxic treatment. Fortunately, there are plenty of new advances in technology that might address this problem. The most help may come from the so-called “liquid biopsy”. Which is essentially usually a simple blood test evaluated with a exotic new technology.

Liquid Biopsy

The main components of a liquid Biopsy include circulating normal cells (WBC, Platelets, RBCs) possibly circulating living cancer cells (CTCs) and bits of dying cancer cells (cell free DNA, miRNA etc).

A Story of Two Biomarkers CTCs and cfDNA

CTCs Circulating Tumor Cells

The CTCs are very fragile, rare and hard to detect but give a window into the living cancer in the patient as treatment progresses. These cells can be further evaluated to determine if they are proliferating or if certain signalling pathways are active. In fact they can also be harvested, sequenced, and in some cases grown and expanded in culture.

Cell Free DNA cfDNA

Cell Free DNA or cfDNA gives a more stable read out of the tumor load, and mutation composition of the DNA, or at least the DNA leaking into the blood. It might be expected that when a new treatment begins, cancer cells in the host may undergo death and leak DNA into the blood. Consequently there could be an initial “Spike” in the amount of circulating DNA – this could be a positve signal. In other instances, cfDNA might indicate if there is residual cancer left in a patient after a surgery was completed that was initially intended to remove all disease giving a type of molecular staging. If a therapy is working well we would expect that CTCs and cfDNA would decrease and perhaps become immeasurable. On development of resistance there would be detection of new clones and expansion of the concentration of CTCs and cfDNA fragments.

Liquid biopsy provides a means to monitor tumor response to therapy in a dynamic and real time manner giving unprecedented opportunities to modulate treatment and truly personalize therapy for cancer patients

I expect that the twin technologies of CTC and cfDNA analysis will become more valued by oncologists, patients and payers as these tools will provide a way to dynamically monitor tumor response to treatment and provide immediate evidence of efficacy of a therapy or also of impending relapse potentially allowing a window of opportunity to adjust treatment.

 

FDA approves osimertinib for first line use in lung cancer with EGFR mutation

By Anthony Magliocco MD

TAGRISSO delivered unprecedented median progression-free survival of 18.9 months versus 10.2 months for EGFR-TKIs (erlotinib or gefitinib) in 1st-line EGFRm NSCLC

 

the US Food and Drug Administration (FDA) has approved TAGRISSO® (osimertinib) for the 1st-line treatment of patients with metastatic non-small cell lung cancer (NSCLC) whose tumors have epidermal growth factor receptor (EGFR) mutations (exon 19 deletions or exon 21 L858R mutations), as detected by an FDA-approved test. The approval is based on results from the Phase III FLAURA trial, which were presented at the European Society of Medical Oncology 2017 Congress and published in the New England Journal of Medicine.

 

The results of the phase III FLAURA trial were impressive with dramatic improvements to progression free survival.

The FLAURA trial compared TAGRISSO to current 1st-line EGFR tyrosine kinase inhibitors (TKIs), erlotinib or gefitinib, in previously untreated patients with locally advanced or metastatic EGFR-mutated (EGFRm) NSCLC. TAGRISSO met the primary endpoint of progression-free survival. PFS results with TAGRISSO were consistent across all pre-specified patient subgroups, including in patients with or without central nervous system (CNS) metastases. Overall survival data were not mature at the time of the final PFS analysis.

 

Osimertinib was previously approved for use as second line therapy in patients who had progressed on a TKI treatment or for those whose tumors developed a T790M mutation confering resistance to the first generation TKI therapies.

Osimerinibs mechanism of action is thought to be irreversible binding to the EGFR receptor.  Perhaps this explains the improvement in PFS compared to other TKIs. These findings are potentially practice changing.

Despite these impressive improvements in PFS almost all patients eventually fail targeted therapies with TKI agents. Consequently more work is needed to understand the biological mechanisms of resistance and progression in lung cancer patients to enable more effective therapies to be developed.

https://www.onclive.com/web-exclusives/fda-approves-frontline-osimertinib-for-nsclc