TTP, HUS and aHUS: Different diseases – Different treatments

SUMMARY: Thrombotic Thrombocytopenic Purpura (TTP), Hemolytic Uremic Syndrome (HUS) and Atypical Hemolytic Uremic Syndrome (aHUS) are Thrombotic Microangiopathies (TMA’s) associated with MicroAngiopathic Hemolytic Anemia and thrombocytopenia. Even though their clinical presentation has some similarities, they are distinct entities with different pathophysiology and hence managed differently. With the identification of von Willebrand Factor (vWF) cleaving protease ADAMTS13 (A disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13) in 1996, we are now able to better understand and appropriately manage these TMA’s. Patients with TTP are deficient in ADAMTS13 and therefore develop platelet microthrombin in small blood vessels due to uninhibited propagation of platelet aggregates bound to ultra high molecular weight VWF multimers. Approximately 10% or less of Shiga-Toxin producing Escherichia Coli (STEC) infections may be associated with HUS. aHUS is caused by a genetic deficiency of one or more complement regulatory proteins which results in uncontrolled activity of the alternate complement pathway. Plasma Exchange in TTP restores the protease activity of ADAMTS13 whereas aHUS is treated with SOLIRIS® (Eculizumab) to inhibit complement mediated TMA. Once a diagnosis of STEC-HUS is confirmed, hospitalization and intensive care with transfusions and kidney dialysis may become necessary. George JN. Blood 2010:116; 4060-4069

HER2 Testing in Breast Cancer American Society of Clinical Oncology/College of American Pathologists Clinical Practice Guideline Focused Update

HER2 Testing in Breast Cancer: American Society of Clinical Oncology/College of American Pathologists Clinical Practice Guideline Focused Update
SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. Approximately 266,120 new cases of invasive breast cancer will be diagnosed in 2018 and about 40,920 women will die of the disease. The HER or erbB family of receptors consist of HER1, HER2, HER3 and HER4. Approximately 15-20% of invasive breast cancers overexpress HER2/neu oncogene, which is a negative predictor of outcomes without systemic therapy. HERCEPTIN® (Trastuzumab) is a humanized monoclonal antibody targeting HER2, and adjuvant and neoadjuvant chemotherapy given along with HERCEPTIN® reduces the risk of disease recurrence and death, among patients with HER2-positive, early stage as well as advanced metastatic breast cancer. Since the approval of HERCEPTIN®, several other HER2-targeted therapies have become available. Accurate determination of HER2 status of the tumor is therefore essential for patients with invasive breast cancer, to ensure that those most likely to benefit are offered a HER2-targeted therapy and those who are unlikely to benefit can avoid toxicities as well as financial burden associated with those drugs.
Laboratory testing for HER2 status in patients with breast cancer in the US is performed according to guidelines developed by an Expert panel of members of the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP). The ASCO/CAP guidelines were first published in 2007 and were updated in 2013. The Expert panel in 2018 developed and issued a focused update of the clinical practice guideline on HER2 testing in breast cancer. This new information made available since the previous update in 2013 addresses uncommon clinical scenarios and improves clarity, particularly for infrequent HER2 test results that are of uncertain biologic or clinical significance. There are currently two approved methods for determining HER2 status in breast cancer: ImmunoHistoChemistry (IHC) and In Situ Hybridization (ISH). This new guideline enables the Health Care Provider, how to best evaluate some of the less common patterns in HER2 results emerging from ISH. 
Guideline Questions
1) What is the most appropriate definition for ImmunoHistoChemistry (IHC) 2+ (IHC equivocal)?
2) Must Human Epidermal growth factor Receptor 2 (HER2) testing be repeated on a surgical specimen if the initially tested core biopsy is negative?
3) What is the optimal algorithm for less common patterns observed when performing dual-probe In Situ Hybridization (ISH) HER2 testing in breast cancer?
Updated Recommendations
1) Immunohistochemistry (IHC) 2+ is defined as invasive breast cancer with weak to moderate complete membrane staining observed in more than 10% of tumor cells.
2) If the initial HER2 test result in a core needle biopsy specimen of a primary breast cancer is negative, a new HER2 test may (not “must”) be ordered on the excision specimen based on some criteria (such as tumor grade 3).
3)The HER2 testing algorithm now includes more rigorous interpretation criteria of the less common patterns that can be seen in about 5% of all cases when HER2 status in breast cancer is evaluated using a dual-probe ISH assay. These scenarios are described as ISH group 2 (HER2/Chromosome Enumeration Probe 17 [CEP17] ratio of 2.0 or more; average HER2 copy number less than 4.0 signals per cell), ISH group 3 (HER2/CEP17 ratio less than 2.0; average HER2 copy number 6.0 or more signals per cell), and ISH group 4 (HER2/CEP17 ratio less than 2.0; average HER2 copy number 4.0 or more and less than 6.0 signals per cell). These cases, described as ISH groups 2-4, should now be assessed using a diagnostic approach that includes a concomitant review of the IHC (ImmunoHistoChemistry) test, which will help the pathologist make a final determination of the tumor specimen as HER2 positive or negative.
4)The Expert Panel also preferentially recommends the use of dual-probe instead of single-probe ISH assays, but it recognizes that several single-probe ISH assays have regulatory approval in many parts of the world. 
Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: American Society of Clinical Oncology/College of American Pathologists Clinical Practice Guideline Focused Update. Wolff AC, Hammond EH, Allison KH, et al. J Clin Oncol 2018; 36:2105-2122.

Dual Inhibition Improves Outcomes for Patients with BRAF-Mutated Colorectal Tumors

Dual Inhibition Improves Outcomes for Patients with BRAF-Mutated Colorectal Tumors
SUMMARY: ColoRectal Cancer (CRC) is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that approximately 135,430 new cases of ColoRectal Cancer will be diagnosed in the United States in 2017 and over 50,260 patients are expected to die of the disease. The DNA MisMatchRepair (MMR) system is responsible for molecular surveillance and works as an editing tool that identifies errors within the microsatellite regions of DNA and removes them. Defective MMR system leads to MSI (Micro Satellite Instability) and hypermutation, triggering an enhanced antitumor immune response. MSI (Micro Satellite Instability) is therefore a hallmark of defective/deficient DNA MisMatchRepair (MMR) system and occurs in 15% of all colorectal cancers. Defective MisMatchRepair can be a sporadic or heritable event. Approximately 65% of the MSI tumors are sporadic and MSI-High tumors tend to have better outcomes. Patients with stage IV colorectal cancer are now routinely analyzed for extended RAS and BRAF mutations. KRAS mutations are predictive of resistance to Epidermal Growth Factor Receptor (EGFR) targeted therapy. Approximately 5-10% of all metastatic CRC tumors present with BRAF V600 mutations and BRAF V600 is recognized as a marker of poor prognosis in this patient group. These patients tend to have aggressive disease with a higher rate of peritoneal metastasis and do not respond well to standard treatment intervention. Approximately 25% of the BRAF-mutated population in the metastatic setting has MSI-High tumors, but MSI-High status does not confer protection to this patient group.BRAF-and-EGFR-Inhibition-in-MAPK-Pathway
The Mitogen-Activated Protein Kinase pathway (MAPK pathway) is an important signaling pathway which enables the cell to respond to external stimuli. This pathway plays a dual role, regulating cytokine production and participating in cytokine dependent signaling cascade. The MAPK pathway of interest is the RAS-RAF-MEK-ERK pathway. The RAF family of kinases includes ARAF, BRAF and CRAF signaling molecules.BRAF is a very important intermediary of the RAS-RAF-MEK-ERK pathway. The BRAF V600 mutations results in constitutive activation of the MAP kinase pathway. Inhibiting BRAF can transiently reduce MAP kinase signaling. However, this can result in feedback upregulation of EGFR signaling pathway, which can then reactivate the MAP kinase pathway. This aberrant signaling can be blocked by dual inhibition of both BRAF and EGFR.
ZELBORAF® (Vemurafenib), is a selective oral inhibitor of mutated BRAF whereas ERBITUX® (Cetuximab) is a monoclonal antibody targeting Epidermal Growth Factor Receptor (EGFR). Preclinical studies have shown that adding CAMPTOSAR® (Irinotecan) to ZELBORAF® and ERBITUX®, in patients with refractory BRAF V600E metastatic CRC, led to a durable responses and this combination was safe and tolerable. However, both single agent ZELBORAF® and ERBITUX® were shown to have limited activity in this patient group.
Based on this scientific rationale, a phase II trial was conducted (SWOG 1406), in which 106 metastatic ColoRectal Cancer patients, with mutations in BRAF V600 and extended RAS wild-type, were enrolled. Patients were randomized to receive CAMPTOSAR® 180 mg/m2 IV every 14 days and ERBITUX® 500 mg/m2 IV every 14 days, with or without ZELBORAF® 960 mg orally twice daily. The median age was 62 years and about 50% of patients had received 1 prior regimen for metastatic or locally advanced unresectable metastatic CRC, and 39% had received prior treatment with CAMPTOSAR® . Prior therapy with anti-EGFR agent or RAF or MEK inhibitors was not allowed. Crossover from the control arm to the experimental group was allowed, after documented disease progression. The primary endpoint was Progression Free Survival.
The median Progression Free Survival was 4.4 months with the triplet, versus 2.0 months with CAMPTOSAR® plus ERBITUX® (HR=0.42; P =0.0002). The response rate was 16% versus 4%, and the Disease Control Rate was 67% versus 22% (P =0.001), with a higher Duration of Response with the addition of ZELBORAF® to CAMPTOSAR® and ERBITUX® (Triplet). Approximately 50% of the patients in the control group crossed over to the experimental group at the time of disease progression. Overall Survival data and efficacy at cross-over, data, remain immature. Patients in the experimental group (Triplet group) experienced more grade 3/4 toxicities such as neutropenia, anemia and nausea, and this increase was attributed to increased duration of exposure to therapy.
The authors concluded that the addition of ZELBORAF® to the combination of CAMPTOSAR® and ERBITUX® resulted in a 58% reduction in the risk of disease progression and a higher Disease Control Rate, suggesting that simultaneous EGFR and BRAF inhibition (Dual Inhibition) is effective in BRAF V600 mutated ColoRectal Cancer. Subgroup analysis will examine the role of CAMPTOSAR® pre-treatment and the outcomes of patients based on tumor MicroSatellite Instability. Randomized trial of irinotecan and cetuximab with or without vemurafenib in BRAF-mutant metastatic colorectal cancer (SWOG 1406). Kopetz S, McDonough SL, Morris VK, et al. J Clin Oncol 35, 2017 (suppl 4S; abstract 520)

FDA Approves ENDARI®, A New Treatment for Sickle Cell Disease

SUMMARY: The FDA on July 7, 2017 approved ENDARI® (L-Glutamine oral powder) for patients age five years and older with Sickle Cell disease to reduce severe complications associated with the blood disorder. Sickle cell disease or Sickle Cell anemia is an Autosomal Recessive disorder and affects approximately 100,000 Americans. It is estimated that it affects 1 out of every 365 African-American births and 1 out of every 16,300 Hispanic-American births. The average life expectancy for patients with Sickle Cell disease in the United States is approximately 40 to 60 years.

HbSS disease or Sickle Cell anemia is the most common Sickle Cell disease genotype and is associated with the most severe manifestations. HbSS disease is caused by a mutation substituting thymine for adenine in the sixth codon of the beta-globin chain gene. This in turn affects the hemoglobin’s ability to carry oxygen and causes it to polymerize. This results in decreased solubility thereby distorting the shape of the red blood cells, increasing their rigidity and resulting in red blood cells that are sickle shaped rather than biconcave. These sickle shaped red blood cells limit oxygen delivery to the tissues by restricting the flow in blood vessels, leading to severe pain and organ damage (vaso-occlusive crises). Oxidative stress is an important contributing factor to hemoglobin polymerization with polymer formation occurring only in the deoxy state. HbS/b-0 thalassemia (double heterozygote for HbS and b-0 thalassemia) is clinically indistinguishable from HbSS disease.

L-glutamine is a precursor for the synthesis of essential metabolic Oxidation-Reduction cofactors including Nicotinamide Adenine Dinucleotide (NAD). It has been shown in previous studies that there is higher L-glutamine utilization in Sickle Cell Anemia resulting in its depletion and thereby contributing to oxidative stress. Based on a phase II study showing favorable outcomes with ENDARI® compared with placebo, a phase III, randomized trial was conducted, in which the safety and efficacy of ENDARI® was studied in 230 Sickle Cell disease or beta-0 thalassemia patients, who had at least two episodes of painful crises during the 12 months before screening. Patients were randomized in a 2:1 ratio to receive ENDARI® (N=152) or placebo (N=78). Enrolled patients were 5-58 yrs old and ENDARI® was administered orally at 0.3 mg/kg/day for 48 weeks followed by a 3 week tapering period. Two thirds of the patients were on Hydroxyurea. The effect of treatment was evaluated over 48 weeks.

Patients who were treated with ENDARI® experienced fewer hospital visits for Sickle Cell crises pain management with parenteral narcotics or Ketorolac compared to those who received a placebo, fewer hospitalizations for Sickle Cell pain , and fewer days in the hospital (median 6.5 days versus median 11 days) compared to those on placebo. Further, patients who received ENDARI® also had fewer occurrences of acute chest syndrome (a life-threatening complication of sickle cell disease), compared with patients who received a placebo (8.6% versus 23.1%). The common side effects of ENDARI® included, nausea, constipation, headache, abdominal pain, cough, pain in the extremities, back pain and chest pain.

It was concluded that the benefit with ENDARI® for patients with Sickle Cell disease, was seen in all age groups and there was a consistent advantage with ENDARI® regardless of whether the patient was on Hydroxyurea or not. ENDARI® is the first treatment approved for patients with Sickle Cell disease in almost 20 years. Phase 3 Study of L-Glutamine Therapy in Sickle Cell Anemia and Sickle ß0-Thalassemia Subgroup Analyses Show Consistent Clinical Improvement. Niihara Y, Viswanathan K, Miller ST, et al. Abstarct#1318. Presented at ASH 58th Annual Meeting & Exposition, San Diego, CA. December 3-6, 2016

Reduced Lung-Cancer Mortality with Low-Dose Computed Tomographic Screening

SUMMARY: The rationale for Lung Cancer screening is based on the National Lung Cancer Screening Trial (NLST) in which the use of low dose CT scan in high risk, healthy patients, resulted in a 20% reduction in lung cancer mortality, compared to screening with a chest x-ray. It is important that eligible people who are smokers participate in a smoking cessation program and quit smoking. Further, those eligible for screening should understand the limitations associated with any screening methodology and potential risks associated with procedures that may follow a false positive result.

Lung cancer screening is performed using a non-contrast low dose CT scan. Criteria for lung cancer screening include-

1) People 55-74 years of age with no signs or symptoms of lung cancer

2) Current or former smoker with a 30 pack year smoking history (Number of years smoked multiplied by the number of packs of cigarettes per day)

3) Current smokers are strongly urged to enter a smoking cessation program

4) Former smokers must have quit smoking within the past 15 years

People with serious comorbid conditions, those on home oxygen and individuals with metallic devices or implants in the chest or back (which can interfere with the scan) should be excluded from lung cancer screening. Lung cancer screening with low dose CT scan is presently not covered by most insurance plans. The National Lung Screening Trial Research Team. N Engl J Med 2011; 365:395-409

Use of Molecular Biomarkers to Inform Adjuvant Therapy for Colon Cancer

SUMMARY: The role of adjuvant chemotherapy in patients with stage III ColoRectalCancer (CRC) has been well established, with improvement in Disease Free Survival (DFS) and Overall Survival (OS). The same however, cannot be stated for patients with Stage II CRC. Several Prognostic (outcome regardless of specific treatment) and Predictive (benefit from a specific therapy) molecular biomarkers have been developed to help make treatment decisions which include MSI (MicroSatellite Instability), LOH 18q (Loss of heterozygosity on the long arm of chromosome 18), P53, TS (Thymidylate Synthase), KRAS, BRAF, ERCC1 (Excision Repair Cross-Complementation group 1), Oncotype DX and Coloprint. Even though LOH 18q, P53, TS, KRAS, BRAF and ERCC1 are of prognostic value, they presently do not provide clinical utility in the management of early stage CRC. The biomarkers of interest are MSI, Oncotype DX Colon Cancer Assay and ColoPrint. MMR and MSI: MSI is the hallmark of defective/deficient DNA MisMatchRepair (MMR) system and develops following a germline mutation in one of the MMR genes. The MMR gene system consists of several proteins which are responsible for surveillance and correction of DNA errors. These genes include MLH1, MSH2, MSH6, PMS2 and EPCAM. MSI-high (MSI-H, MMR deficient) is actually a good prognostic marker in early stage CRC, with less likelihood of lymph node involvement, systemic metastases and with improved survival. These patients do not benefit from DNA inhibiting anti-metabolites such as 5-FluoroUracil (5-FU). In fact, treatment with 5-FU could be detrimental, whereas they may be more responsive to Irinotecan. This is in contrast to early stage CRC patients with tumors that are MicroSatelliteStable (MSS) or MSI-low (MSI-L) and MMR proficient, who benefit from 5-FU based adjuvant chemotherapy with significantly improved DFS. It should be noted that the prognosis for patients with early stage CRC, whose tumors harbor V600E BRAF mutation and are MSI-H, is similar to CRC patients with MSS tumors. MSI is a genetic marker of Lynch Syndrome (Hereditary Nonpolyposis Colorectal Carcinoma – HNPCC) and approximately 15% of sporadic CRC share the genetics of Lynch Syndrome and are MSI-H and MMR-deficient. By evaluating the MMR/MSI status of a CRC patient, a clinician may be able to assess a patient’s prognosis, predict response to therapy and detect Lynch’s Syndrome, which constitutes about 3-5% of CRC cases. MSI is a functional assay and can be detected by PCR whereas ImmunoHistoChemistry (IHC) can confirm the presence or absence of MMR proteins.

ONCOTYPE DX COLON CANCER ASSAY: Oncotype DX Colon Cancer assay is a multigene expression assay and evaluates genes in the patient’s tumor, using paraffin slides. It consists of 7 potential recurrence genes and 5 internal reference genes and has been clinically validated from three prospective trials, to assess risk of recurrence, in patients with Stage II and III CRC. The Oncotype DX colon cancer assay is able to prognosticate the risk of recurrence of a particular CRC tumor but unlike the Oncotype DX assay for Breast Cancer, is unable to predict clinical benefit from adjuvant chemotherapy.

COLOPRINT: This assay uses an18 gene expression profile and requires fresh tissue. This assay is also able to assess the risk of recurrence in Stage II CRC but is unable to predict the benefit from adjuvant chemotherapy.

In summary, testing for MSI should be performed in all patients with Stage II CRC. Genetic signatures derived from Oncotype Dx Colon Cancer assay and ColoPrint may have limited clinical value for patients with early stage CRC. NCCN guidelines recommend adjuvant chemotherapy for high risk Stage II CRC. High risk for recurrence is defined as tumors that are poorly differentiated (except those tumors that are MSI-H), lymphovascular invasion, perineural invasion, bowel obstruction, localized perforation, close, indeterminate or positive margins and examination of less than 12 lymph nodes. Mettu NB, Hurwitz H and Hsu DS. Oncology 2013;27:746-754

TTP, HUS and aHUS Different diseases – Different treatments

SUMMARY: Thrombotic Thrombocytopenic Purpura (TTP), Hemolytic Uremic Syndrome (HUS) and Atypical Hemolytic Uremic Syndrome (aHUS) are Thrombotic Microangiopathies (TMA’s) associated with MicroAngiopathic Hemolytic Anemia and thrombocytopenia. Even though their clinical presentation has some similarities, they are distinct entities with different pathophysiology and hence managed differently. With the identification of von Willebrand Factor (vWF) cleaving protease ADAMTS13 (A disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13) in 1996, we are now able to better understand and appropriately manage these TMA’s. Patients with TTP are deficient in ADAMTS13 and therefore develop platelet microthrombin in small blood vessels due to uninhibited propagation of platelet aggregates bound to ultra high molecular weight VWF multimers. Approximately 10% or less of Shiga-Toxin producing Escherichia Coli (STEC) infections may be associated with HUS. aHUS is caused by a genetic deficiency of one or more complement regulatory proteins which results in uncontrolled activity of the alternate complement pathway. Plasma Exchange in TTP restores the protease activity of ADAMTS13 whereas aHUS is treated with SOLIRIS® (Eculizumab) to inhibit complement mediated TMA. Once a diagnosis of STEC-HUS is confirmed, hospitalization and intensive care with transfusions and kidney dialysis may become necessary. George JN. Blood 2010:116; 4060-4069