04 August 2009

Mechanism of Bone Metastases



Mechanism of Bone Metastases
by: Dr.Priya Gopalan

Outline
* Background
* Predictors of metastasis to bone
* Tumor cell homing to bone
* Tumor cell interaction with bone
* Therapeutic interventions

Bone Metastases
Types of bone metastases
Diagnosis
* Bone scan - best for osteoblastic lesions
* MRI
* CT scan with bone windows
* PET-CT
* Plain films
* Markers of bone turnover

Prognosis
Relative risk ratios during zoledronic acid therapy
(skeletal-related events)
NSCLC and solid tumors
High vs. low NTX levels
Reasons for preferential metastasis to bone
* Highly vascular organ (sluggish blood flow)
* Paget’s “seed-and-soil” hypothesis
o Bone marrow niche provides:
+ Chemotactic signal to home (e.g. SDF-1)
+ Adhesion receptors to extravasate
+ Growth factors to proliferate (e.g. TGF-b, IGF-1)
Predictors of metastasis to bone (Breast Cancer)
Tumor cell homing
* Organs that are primary sites of breast cancer metastasis produce high levels of SDF-1
* Blocking CXCR4 in vitro inhibited prostate cancer migration through bone marrow endothelial cells
* Blocking CXCR4 in vivo reduces bone metastases in breast and prostate cancers
* CXCR4/ SDF-1 axis also important in
o NSCLC:
o RCC:
* Integrins may also direct organ-specific mets
o When avb3 is overexpressed on breast cancer cells, bone metastases are enhanced
o CXCR4 binding to SDF-1 activates avb3 and mediates its binding to endothelial cells
o avb3 antagonist inhibits bone colonization by avb3-expressing tumor cells
o a2b1 on prostate cancer cells supports bone colonization
* Other chemokines produced by OBs
o Osteopontin
o Bone sialoprotein

Normal bone remodeling
Osteoprotegerin
Osteoblasts/osteoclasts interaction with tumor cells
Osteomimicry by tumor cells
Therapeutic targets
* Osteoblastic lesions
o Endothelin-1 (anti-receptor antibody)
* Osteolytic lesions
o Bisphosphonates
o RANKL (anti-RANKL antibody)
o PTHrP
o Osteoprotegerin (Fc-OPG)
* Endothelin A receptor inhibitor, Atrasentan
o M00-211 trial - Double-blinded, randomized, multi-institutional placebo-controlled Phase III trial with 809 patients with hormone-resistant metastatic prostate cancer

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Cutaneous Toxicities of Cancer Therapy



Cutaneous Toxicities of Cancer Therapy
By:Dr.Saiama Waqar

Outline
* Alopecia
* Hyperpigmentation
* Hand-foot syndrome
* Radiation sensitivity and recall
* Hypersensitivity
* Nail dystrophies
* Extravasation injuries
* Skin toxicity from targeted therapies
* Conclusion

Alopecia
* Drugs that target rapidly dividing cells often affect the proliferating cells in the hair follicle
* Terminal hair follicles with rapid matrix formation more affected (scalp more than body hair, eyebrows, eyelashes)
o completely lost in a short time: transplant
o gradually lost over several weeks: cyclic chemotherapy
* Methotrexate: affects the follicle melanocytes, resulting in depigmented band of hair, “flag sign”
* Visible regrowth within 3-6 months
* Often regrows with a change in color or texture (switching from straight to curly), mechanism of change unclear
* Psychologically, one of the most stressful side effects

Grading of alopecia
Grade
Minimal loss, grade 1
< 25%; obvious to the patient but not necessarily to others

Moderate loss, grade 2
25 to 50 %; obvious thinning of scalp hair but not enough to lead to the use of a wig or alternate head covering

Severe loss, grade 3

> 50% of hair lost; generally indicates the need for a wig or alternate head covering in those for whom alopecia is a major concern

Chemotherapy drugs causing alopecia

* Often
o Bleomycin
o Etoposide
o Methotrexate
o Mitoxantrone
o Paclitaxel
* Common
o Cyclophosphamide
o Daunorubicin
o Doxorubicin
o Docetaxel
o Idarubicin
o Ifosphamide
o Paclitaxel
* Infrequent
o 5-FU
o Hydroxyurea
o Thiotepa
o Vinblastine
o Vincristine
o Vinorelbine
* Rare
o procarbazine

Prevention of alopecia
* scalp tourniquets:
o pneumatic device placed around the hairline during chemo infusion
o inflated to a pressure >SBP
o Several studies: effective for preventing hair loss
+ utilized different techniques, variation in chemotherapy regimens, tourniquet pressure, sample size, and criteria to assess alopecia (data difficult to interpret)
o Side effects: headache, varying degrees of nerve compression

Prevention of alopecia
* Hypothermia with scalp icing devices:
o Vasoconstriction of scalp blood vessels, less absorption of chemo as hair follicles less metabolically active at 24C
o ice turban, gel packs, cool caps, thermocirculator, room air conditioner
o 50-80% response, though variable chemotherapy regimens and definitions of alopecia, small sample size
* Not effective in liver disease
o Delayed drug metabolism, persistent levels beyond protective period
* Scalp metastases:
o mycosis fungoides, limited to scalp. CR after chemo without scalp cooling
o 61 pts with met breast cancer and liver dysfunction, 1 pt scalp met

Preventive devices
* 1990- FDA stopped sale of these devices citing absence of safety or efficacy data
* Cranial prostheses (wigs) and scarves use encouraged

Pharmacologic interventions for alopecia
* Topical minoxidil (shorten time to maximum regrowth, did not prevent alopecia)
* AS101(NSCLC pts: garlic-like halitosis and post-infusion fevers)
* Alpha tocopherol (cardioprotection for doxorubicin, noted less alopecia)
* Topical calcitriol (cell lines- protects cancer cells)
* IL-1(rats, cytarabine, cell cycle specific, protected)
* Inhibitors of p53 (mice deficient p53, no alopecia)

Hyperpigmentation
* usually resolves with drug discontinuation
o gingival margin pigmentation seen with cyclophosphamide is usually permanent
* Patterns of pigmentation:
o Diffuse
o Local at site of infusion
* Sites of pressure /trauma
o Hydrea and cisplatin
* Busulfan
o “busulfan tan” can mimic Addison's disease.
o Although busulfan can also cause adrenal insufficiency, the skin change is 2/2 toxic effect on melanocytes
o Distinguish busulfan toxicity from true Addison's disease by normal levels of MSH & ACTH
* Liposomal doxorubicin
o macular hyperpigmentation over the trunk and extremities, including the palms and soles
o not been described with unencapsulated doxorubicin

Drugs causing hyperpigmentation

HAND-FOOT SYNDROME
* also known as palmar–plantar erythrodysesthesia (PPE)
* originally described in patients receiving high-dose cytarabine
* skin lesions begin as erythema and edema of the palms or soles and is associated with sensitivity to touch or paresthesia
* can progress to desquamation of the affected areas and significant pain

Hand foot syndrome
Acral erythema from docetaxel

Pathogenesis
* Unclear: small capillaries in the palms and soles rupture with increased pressure from walking or use, creating an inflammatory reaction
* formulation of drugs and duration of exposure can impact the incidence
o liposome-encapsulated doxorubicin more than standard formulation
o 5-FU bolus lower than CIVI and capecitabine (converted into 5-FU in vivo)

Hand foot syndrome Grading
Grade
Signs and symptoms

1 Minimal skin changes or dermatitis (eg, erythema) without pain
2 Skin changes (eg, peeling, blisters, bleeding, edema) or pain, not interfering with function
3 Skin changes with pain, interfering with function

Treatment
* No proven preventive therapy
o Pyridoxine (vitamin B6) may help reduce the incidence and severity
o Celecoxib reported to reduce incidence
* Management largely symptomatic with reduction of drug doses where appropriate
* emollients and protective gloves can be helpful

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Acute Intermittent Porphyria



Acute Intermittent Porphyria
Heme/Onc Grand Rounds
By:Jane Chawla, M.D.

History of Present Illness
Physical Exam & Laboratory Data

* VS: T 36.2 P 142 R 20 BP 178/112
* Gen: Sleepy but arousable, AxO x3
* HEENT: PERRL, EOMI, OP Clear
* Neck: Supple, no LAD
* CV: tachy, regular rhythm, no m/g/r
* Lungs: CTAB
* GI: soft, ND, mild periumbilical discomfort to palpation
* Extr: no c/c/e
* Skin: No rashes or skin lesion
* Neuro: CN II-XII intact, strength 4/5 throughout, paresthesia in bilat lower extremities, 2+ reflexes, upgoing toes



Labs:
Random Problem List?
* Hyponatremia
* Tachycardia
* Hypertension
* Elevated Creatinine
* Abdominal Pain
* Transaminitis
* Weakness
* Cortisol – wnl
Cosyntropin Stim Test – wnl
Urine lytes → SIADH
* EKG – sinus tachycardia
CT Angio (-)
Urine VMA/metanephrine (-)
* Renal Ultrasound – wnl
responded to fluids
* LFTs – Mild transaminitis
CT Abdomen/Pelvis (-)
Hepatitis panel (-)

PORPHYRIA
Heme central to understanding Porphria
* Heme is part of hemoglobin, myoglobin, catalases, peroxidases, and cytochromes
* Heme is made in every human cell (85% in erythroid cells & much of the rest in the liver)
* First enzyme in heme synthesis pathway is ALA synthetase (ALAS)
* Increase demand induces ALAS
* Heme downregulates ALAS by feedback inhibition
* Partial block in this pathway induces ALAS and causes accumulation of heme precursors upstream from block

Porphyria is a disruption in the heme pathway
* Group of metabolic diseases resulting from a partial deficiency of an enzyme in the heme biosynthetic pathway
* Seven enzymes in the pathway
* Four of the porphyrias cause acute attacks
* Increased demand for heme can precipitate attacks secondary to overproduction of toxic heme precursors (porphyrins, ALA)
* The porphyrins have no useful function and act as highly reactive oxidants damaging tissues

Overview of the Seven Porphyrias
Overview of the Four Acute Porphyrias
* Four acute porphyrias cause acute, self-limiting attacks that lead to chronic and progressive deficits
* Symptoms of acute attacks mimic other diseases and increase the potential for misdiagnosis.
* Acute porphyrias are clinically indistinguishable during acute attacks, except the neurocutaneous porphyrias (variegate porphyria and hereditary coproporphyria) can cause dermatologic changes
* Acute attacks lead to an increase in porphobilinogen (PBG) and 5-aminolevulinic acid (ALA) which can be detected in the urine
* Things that make diagnosis difficult: variable clinic course, lack of understanding about diagnostic process, and lack of a universal standard for test result interpretation

Patient Focus: Acute Intermittent Porphyria
* Most common porphyria
* Deficiency of hepatic PBG deaminase
* Autosomal dominant pattern with incomplete penetrance
* Affected individuals have a 50% reduction in erythrocyte PBG deaminase activity
* Latent prior to puberty
* Symptoms more common in females than males
* Increased urinary ALA & PBG

Prevalence in the General Population
Key Clinical Features
* Gastrointestinal symptoms - Abdominal pain (most common presenting complaint), nausea/vomiting, constipation, and diarrhea.
* Dehydration
* Hyponatremia
* Cardiovascular symptoms - tachycardia, hypertension, arrhythmias
* Neurologic manifestations - motor neuropathy, sensory neuropathy, mental symptoms, seizures.

Pathophysiology of the Acute Attack
Autonomic Nervous System
Peripheral Nervous System
Hypothalamus
Limbic area

Porphyrins excreted from liver
ALA crosses BBB
Causes oxidative damage
Accumulates in brain with neuronal and glial cell damage
Symptoms due to porphyrin
Precursor accumulation
Rather than deficiency of Heme
Porphyrins don’t Cross BBB
ALA induces liver
Damage via oxidative effects
Exacerbating Factors of Acute Attack
* Drugs that increase demand for hepatic heme (especially cytochrome P450 enzymes)
* Crash diets (decrease carbohydrate intake)
* Endogenous hormones (progesterone)
* Cigarette smoking (induces cytochrome P450)
* Metabolic stresses (infections, surgery, psychological stress)

Diagnosis of Acute Porphyria
Algorithm for Acute Porphyria Diagnosis
Treatment of the Acute Attack
* Hospitalization to control/treat acute symptoms:
o Seizures – Seizure precautions, medications?
o Electrolyte abnormalities
o Dehydration / hyponatremia
o Abdominal Pain – narcotic analgesics
o Nausea/vomiting – phenothiazines
o Tachycardia/hypertension – Beta blockers
o Urinary retention / ileus
* Withdraw all unsafe medications
* Monitor respiratory function, muscle strength, neurological status
* Mild attacks (no paresis or hyponatremia) – Intravenous 10% glucose at least 300 g per day
* Severe attacks – Intravenous hemin (3-4 mg/kg qdaily for 4 days) ASAP (can give IV glucose while waiting for IV hemin)
* Cimetidine for treatment of crisis and prevention of attacks

Hematin (Panhematin)

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