ROLLA ABU-ARJA, MDPEDIATRIC HEMATOLOGY CONFERENCE

Iron Overload in Hematopoietic cell

Transplantation

Iron

4.5% of earth crustConstitute 0.005% of body weight in humansTotal body iron content Newborn infant 300 mg Adult female 2.5 gm Adult male 3.5 gm

Too much iron is badGenerate free radicalsCauses oxidant injury to cells

Too little iron is badAnemiaNon-hematologic effects of iron depletion

Protective mechanisms Iron absorption highly

regulated and minimized

Iron in cells and plasma is tightly bound to proteins ( transferrin, ferritin, hemoglobin etc.

Preventive mechanisms

Iron absorption efficient and tightly regulated

Iron loss is minimized

Iron

Distribution of Iron

hemoglobinferritin and hemosiderin 22%myoglobin 10% cytochromes trans-ferrin catalase etc 3%

Hemoglobin 65%

Ferritin and Hemosiderin22%

Myoglobin10%

Iron Absorption

Depends on: Iron content in diet bioavailibility of dietary iron receptors on mucosal cells • Heme iron> non-heme iron• Ferrous ( Fe+2) > Ferric (Fe+3)

Systemic and cellular iron balance is very tightly regulated

Around 1-2 mg of iron is absorbed from diet everyday

Iron circulates in plasma bound to transferrin ( no free iron)

60-70% of iron is incorporated into Hb in RBC and the rest is stored in hepatocytes, myoglobin and RES macrophages

1–2 mg of iron is lost daily from the skin and the intestine and, in women, through menstruation

Absorption of Iron by the Enterocyte

Ferrireductase Fe+3

Fe+2 DMT1HemeIron

Mucosal Surface

Basolateral surface

Absorption of Iron by the Enterocyte

Mucosal Surface

Basolateral surface

Ferritin

Ferroportoin

Fe+3Fe+2 Heme IronDMT1

Ferrireductase

Hepcidin

Fe+2Hephaestin (Copper-containing)

Fe+3Fe+3

Transferrin in Plasma

Sloughing of entercyteAnd its remainingiron

Iron metabolism

Transferrin binds iron in blood

-free iron usually not present -saturated in iron overloadFerritin surrounds iron in storage

- elevated in iron overload Normal 20 to 300 g/L Rises to > 1,000 and up for iron overload

Ferritin-iron complex aggregates and degraded into insoluble hemosiderins (hemosiderosis)

Iron can not be excreted

Humans do not have any physiological mechanisms to excrete excess iron

In conditions of iron excess, hepcidin levels increase and inhibit intestinal absorption and release of storage iron

Iron toxicity

Iron mediate the conversion of hydrogen peroxide highly toxic free

radicals Leads to tissue damage by: Oxidation of proteins Peroxidation of membrane lipids Modification of nucleic acids

Tissue damage is clinically most evident in the heart and the liver.

Cardiac failureLiver cirrhosis/fibrosis/cancerDiabetes mellitusInfertilityArthritis

Possible Complications of Iron Overload

Andrews NC. N Engl J Med. 1999;341:1986-1995.

Iron and infections

Iron is an essential cofactor for the growth of a number of opportunistic bacteria and fungi

Free iron can also increase susceptibility to infections by inhibition of chemotaxis and phagocytosis and impairment of cellular immunity

Bone Marrow Transplantation (2008) 41, 997–1003; doi:10.1038/bmt.2008.99 N S Majhai H M Lazarus and L J Burns

Iron overload in transfusion-dependent anemias

RBC transfusionsIneffective erythropoiesis and hemolysis (by

stimulating the body's regulatory mechanisms to inadvertently increase intestinal absorption of iron.)

Tissue iron accumulation leads to progressive dysfunction of the heart, liver and endocrine glands.

Tissue iron deposition can begin within 1–2 years, but clinically evident cardiac or hepatic dysfunction may not occur till 10 or more years from initiation of transfusion therapy.

End-organ damage can occur earlier in patients with other risk factors

Transfusion associated anemias guidelines

Estimation of LIC by liver biopsy or imaging is recommended after 1 year of regular transfusions to determine the need for iron-chelation therapy.

Iron chelation is initiated once LIC rises above 3 mg per gm dry weight and is used to maintain levels between 3-7 mg/gm.

Body iron burdensLIC

> 15 mg per gm liver, dry weight, are at an increased risk of cardiac disease and early death

7–15 mg per gm high risk for hepatic fibrosis and endocrine complications

3–7 mg per gm: organ damage typically does not occur (similar to those seen in heterozygotes for hereditary hemochromatosis

The risk of cardiac disease and early death is increased in patients with serum ferritin of more than 2500 ng/ml

Assessment of body iron stores

Liver biopsy with estimation of liver iron concentration LIC is considered to be the reference method for measuring hepatic iron stores.

Superconducting QUantum Interference Device

-High-power magnetic field-Iron interferes with the field-Changes in the field are detectedNoninvasive, sensitive, and accurate Limited availabilitySuperconductor requires high maintenanceOnly 4 machines worldwide

MRI

Clark PR, et al. Magn Reson Med. 2003;49:572-575.

An R2 image of an iron-overloaded human liver superimposed on a T-2 weighted image.Bright areas represent high iron concentration; dark areas represent low iron concentration

Assessment of body iron stores

Test Advantages Disadvantages

Liver Biopsy Reference methodCan assess the degree of fibrosis and can evaluate other causes of hepatic dysfuction

Invasive procedure, not feasible in patients with coagulopathy or thrombocytopenia

Superconducting susceptometry (SQUID)

Good correlation with liver biopsy/non invasive

Very limited availability

MRI of the liver Good correlation with liver biopsy/non invasive ( T2 or R2 MRI)

Variety of MRI techniques have not been validated with liver bx

CT of the liver Non invasive and available

Variable correlation with liver bx

Serum ferritin and transferrin saturation

Non invasive and available

Sensitive but not specific for iron overload and Poor correlation with liver bx

Iron overload in HCT

Due to RBC transfusions, both during the initial treatment of their disease and in the post transplant period

Carrier state for hereditary hemochromatosis, can amplify this risk

Other mechanisms : Inhibition of erythropoiesis Release of iron from the bone marrow and liver

due to cell damage from conditioning regimen toxicity

Iron overload and HCT

Altes et alReviewed liver samples obtained on autopsy in 59

recipients of auto and allo HCT. The median LIC was 7.7 mg /gm DW40 % of patients had an LIC of >5.6 mg / gram

Rose et al cross sectional study ( 9 year follow up)38/65 (58%) patients had above normal ferritin. Increased LIC 6.5 mg/gm DW was seen in 31/32 patients

with elevated ferritin who underwent a T2* MRI of the liverAltes A, Remacha AF, Sarda P, Sancho FJ, Sureda A, Martino R et

al Bone Marrow Transplant 2004; 34: 505–509Rose C, Ernst O, Hecquet B, Maboudou P, Renom P, Noel MP et al). Haematologica 2007; 92: 850–853.

Majhail et alCross sectional study 19/56 allo HCT

survivors (median followup 2.5 years) had ferritin >1000 ng/ml

Of these, 18 (32%) had elevated LIC (median 7 mg/gm, DW on R2 MRI of the liver

LIC>5 mg per gram DW was present in 13 (23%) patients.

The patients with ferritin level more than 1000 ng/ml before HSCT (F>1000) showed lower OS and EFS, and higher TRM rate than those with ferritin level less than 1000 ng/ml with (IC) or without (F<1000) iron-chelating therapy.

Bone Marrow Transplantation (2009) 44, 793–797; doi:10.1038/bmt.2009.88; Effect of iron overload and iron-chelating therapy on allogeneic hematopoietic SCT in children

Iron overload and transplant complications

Early (<1 year) Post transplant

InfectionsAcute GVHD VODNon relapse mortality

Late (>1 year) post transplant

InfectionsChronic GVHD Liver function

abnormalitiesCardiac late effectsNon relapse mortality

No studies that describe the role of iron overload in late-onset cardiomyopathy and hepatic fibrosis and cirrhosis in patients transplanted for diseases other than thalassemia. In children with thalassemia who have undergone an allo HCT, post transplant iron-chelation has been shown to reverse hepatic fibrosis and cardiomyopathy.

Treatment of iron overload after HCT

Take into consideration:The need for ongoing RBC transfusion

therapy Time since transplantation Ability to tolerate iron-chelating therapy Urgency to reduce body iron stores.

Treatment options for iron overload after HCT

Modality Advantages Disadvantages

Phlebotomy Extensive experience and proven efficacyNo side effects

Not feasible in patients with anemia and poor venous access

Deferoxamine Extensive experience with proven efficacy

Inconvenient administration routeSide effects ( ototoxicity, renal etc.)

Deferiprone Oral iron chelator Unproven efficacy Side effects

Deferasirol Oral iron chelator Efficacy similar to deferoxamine

Long term safety profile not establishedSide effects..

Phlebotomy

Phlebotomy program is recommended to patients with a ferritin value > 1000 ng/mL and IO confirmed by SQUID (LIC >7mgFe/g Dw).

With each phlebotomy, approximately 350-500 mL of whole blood is removed

CBC is analyzed before each phlebotomy, and the procedure should not performed in patients with a hemoglobin level < 11 g/dL.

Phlebotomies are repeated every 1-2 weeks until a serum ferritin level < 500 ng/mL.

Iron removed in the single phlebotomy is calculated by multiplying the volume of the phlebotomy by hemoglobin concentration by 3.4.

Biol Blood Marrow Transplant 2010 June: 16(6): 832-7 Epub 2010 Jan 14. A prospective study of iron overload management in allogeneic hematopoietic cell transplantation survivors

SIDE EFFECTS/TOXOCITYDOSINGDRUG

Retinal/optic nerve damageHigh frequency hearing lossLocal reactionsGrowth retardation(all rare at doses<125mg/kg)

20-50 mg/kg s.q. over 8-12 hrs40-180 mg/kg i.v. over 8-12 hrs (high risk)

Deferoaxmine(Desferal)

Renal tubular damage/proteinuriaSkin Rash

10-40 mg/kg/day poDeferasirol

Agranulocytosis (0.6%)Neutropenia (6%)Arthropathy (6-39%)Zinc deficiency (1%)Change in LFTs (44%)Worsened liver fibrosis (?Hep C)

75 mg/kg/day in divided doses po

Deferiprone(L1)

CHELATION THERAPY

What we learned from Thalassemia patients undergoing HCT

No data for the natural evolution of iron overload following HCT, or evidence regarding the benefit of depleting excess iron stores on long-term morbidity and mortality.

A gradual decline in liver iron stores has been reported in a subgroup of children with thalassemia with no hepatomegaly or hepatic fibrosis and adequate pretransplant chelation therapy who were treated with allo HCT and became transfusion independent

Children cured of their thalassemia after allo HCT, but with moderate to severe liver iron deposition pretransplant, tend to have persistently elevated hepatic iron levels till more than 5 years after transplantation

Recommendation

Patients with LIC less than 5–7 mg/ gm liver,DW) and no iron-related organ toxicity can be observed without treatment

Patients with LIC of more than 7 mg /gm and/or with suspected or proven iron-related hepatic or cardiac dysfunction, phlebotomy or iron-chelation therapy SHOULD be considered

long-term follow-up guidelines recommend screening with serum ferritin measurements at 1 year post-HCT

But no clear-cut guidelines for when to screen and initiate therapy for iron overload

Most studies use ferritin >1000

A Prospective Study of Iron Overload Management in Allogeneic Hematopoietic Cell Transplantation Survivors June 2010Majhail NS,

Biology of Blood and Marrow TransplantationVolume 16, Issue 6, June 2010, Pages 832-837

Change in serum ferritin concentration over 6 months of therapy in 3 patients who received deferasirox for treatment of iron overload. LIC measured by liver R2 MRI at baseline and at completion of 6 months

of therapy is also shown.

Phlebotomy

8 patients were considered for phlebotomy. They tolerated it well with predictable decrease in serum ferritin level and did not require interruptions

16 patients with significant IO 4 had end-organ damage due to iron overload. All 4 of these patients underwent phlebotomy. 2 patients (LIC, 9.0 and

22.8 mg/g) had liver function test abnormalities that improved after a reduction of body iron stores. 1 patient had unexplained congestive heart failure (LIC, 15.8 mg/g) and 1 patient, who also had extensive chronic GVHD (cGVHD), exhibited persistent liver function test abnormalities despite adequate control of GVHD manifestations at other sites. The patient's serum ferritin concentration at 13 months post-HCT was 4074 ng/mL, and his LIC on R2 MRI was 43.0 mg/g. Liver biopsy demonstrated cirrhosis. On further evaluation, the patient was found to be homozygous for the C282Y hemochromatosis gene mutation. He is currently undergoing phlebotomy and has improving liver function test results.

Observation

Five patients chose observation 4/5 patients had decreasing serum ferritin

over time.One patient underwent a follow-up R2 MRI

for LIC assessment. This patient exhibited significant decreases in both serum ferritin concentration and LIC, from 1599 ng/mL and 6.4 mg/g at baseline to 1019 ng/mL and 2.6 mg/g at 17-month follow-up.

Conclusions

(1) phlebotomy is well tolerated in HCT survivors and should be considered the treatment of choice because of its relatively low cost and minimal risk of side effects

(2) deferasirox well tolerated and effective alternative for the treatment of significant iron overload in HCT survivors who cannot undergo phlebotomy.

(3)Serum ferritin concentration and LIC can decrease without treatment in a subset of patients

Future directions

Studying the efficacy of deferasirox post HCT in a larger patient population

The safety and feasibility of using deferasirox concurrently with calcineurin inhibitors requires further study.

The natural history of iron overload in HCT survivors, who receive RBC transfusions transiently around the treatment of their hematologic malignancy and HCT and then become transfusion-independent.

References

• Bone Marrow Transplantation (2008) 41, 997–1003; doi:10.1038/bmt.2008.99; published online 28 April 2008

Iron overload in hematopoietic cell transplantation• Biology of Blood and Marrow Transplantation Volume 16, Issue 1, January 2010 pages 115-122 Overload in Patients Receiving Allogeneic Hematopoietic Stem Cell

Transplantation: Quantification of Iron Burden by a Superconducting Quantum Interference Device (SQUID) and Therapeutic Effectiveness of Phlebotomy

• Bone Marrow Transplantation (2009) 44, 793–797; doi:10.1038/bmt.2009.88; published online 27 April 2009

Effect of iron overload and iron-chelating therapy on allogeneic hematopoietic SCT in children

Biol Blood Marrow Transplant 2010 June: 16(6): 832-7 Epub 2010 Jan 14.

A prospective study of iron overload management in allogeneic hematopoietic cell transplantation survivors.

THE BEST WAY TO TREAT IRON OVERLOAD????