Introduction

Question 1

What does the prognosis of bone cancer depend on?

Answer 1

• Overall Stage
• Presence of Metastasis
• Skip ( discontinuous) lesion within the same bone
• Histologic grade
• tumour size

Question 2

Name a staging system?

Answer 2

• Enneking
• the musculoskeletal tumour society system
• Most popular for orthopaedic surgeons
• Two systems- one for benign & one for malignant
• Malignant lesion used Roman numerials I,II III
• Benign lesions use Arabic numbers 1,2,3

Question 3

Dsecribe the enneking staging system for malignant tumours?

Answer 3

Stage IA

• Low grade
• T1 intracompartmental
• Mo no mets

Stage IB

• Low grade
• T2- Extracompartmental
• Mo - no mets

Stage IIA

• High grade
• T1- Intracompartmental
• Mo- no mets

Stage IIB

• High grade
• T2- Extracompartmental
• Mo- no mets

Stage IIIA

• Metastatic
• T1- _intracompartmental _
• M1- regional or distant mets

Stage III B

• Metastatic
• T2- extracompartmental
• M1- mets distant or regional

Question 4

What are difference between tumour compartments?

Answer 4

• Intracompartmental
  
  • bone tumours confined within cortex of the bone
• Extracompartmental
  
  • Bone tumours extend beyond the bone cortex

Question 5

What are the differences between high and low grade tumours?

Answer 5

• Histologically , tumours graded based on percentagee of cellular atypia
• Low grade tumours
  
  • ​Low metastatic potential
• High grade tumours
  
  • _Greater metastatic potential _

Question 6

Can you describe the numbering for benign tumours?

Answer 6

1. Latent lesion - non osssifying fibroma
2. Active lesion- ABC, chondroblastoma
3. Agressive lesion- GCT of bone

Question 7

What is the criteria to predict the risk of pathological fx?

Answer 7

• the presence of significant functional pain
• >50% destruction of cortical bone
• Formal staging systems
  • Mirel criteria
  • Harington criteria

Question 8

Why is prophylatic fixation of fx preferred to fixation of pathological fx?

Answer 8

• Shorter operation time
• Decreased Morbidity
• Quicker recovery

Question 9

Describe the Harington criteria?

Answer 9

• >50% destruction of diaphyseal cortices
• >50-75% destruction of metaphysis (>2.5cm)
• Permeative destruction of subtrochanteric femoral region
• Persistent pain following irradiation

Question 10

Describe the Mirel criteria?

Answer 10

• Score >8 = prophylatix pinning
• score divided into
  
  • Site
    
    • Upper limb (1), Lower lImb (2), Peritrochanteric (3)
  • Pain
    
    • Mild (1), Moderate (2), severe (3)
  • Lesion
    
    • Blastic (1), Mixed (2) , Lytic (3)
  • Size
    
    • <1/3 (1), 1/3-2/3 (2), >2/3 (3)

Question 11

What is the tx logarthim for a Path fx ?

Answer 11

• Obtain tissue diagnosis
  
  • Unless pt has known primary neoplasm w bone biopsy proven skeletal mets, the treating surgeon should biopsy lesion in question
  • biopsy may require separate incision used for im nailing of bone
  • if biopsy suggests primary neoplasm ( like sarcoma) may benefit from neoadjuvant chemo/radiotx then close wound & refer to local sarcoma centre prior to stabilisation- as surgical tx will contaminate entire bone w sarcoma and affect ability to preform limb salvage
• Surgical Fixation
  
  • ​don’t proceed unless primary neoplasm ruled out.
  • goals of fixation
    
    • ​maximise ability to immediate mobilistion & WB.
    • Protect entire bone in setting of systemic /met disease
    • Optimise implant choice in content of pt;s overall prognosis
    • Type of fixation depends on site of lesion
      
      • ​hemi for femoral neck/im nail for peritrochanteric
• ​​​Post op radiation
  
  • **​refer to oncologist for post op radiotx to **
    
    • ​decrease pain
    • slow progression
    • tx remaining burden not removed in surgery

Question 12

What cancers have the worse life expectancy?

Answer 12

• Lung cancer
• **Melanoma **
• < 6months and <5% 5 yr survival when bone mets are present

Question 13

Where is the common site for all boney mets?

Answer 13

• The spine

Question 14

Where is the common site for pathological fracture secondary to metastasis in bone?

Answer 14

• Proximal femur
• femur is most common long bone assoc with mets disease
• the stress risers around the proximal femur make it vunerable to fx

Question 15

What is the mechanism of chemotherapy?

Answer 15

• It induces Apoptosis
  
  • ​= programmed cell death
• may target specific proteins over expressed in cancer cells
  
  • e.g. tyrosine kinase inhibitors block tyrosine kinase receptos overexpressed in neoplastic cancer cells - herceptin in breast cancer
• elimates micrometastasis in lungs
• >98% necrosis with chemotherapy is good prognostic sign

Question 16

Describe the important of resistance to chemotherapy

Answer 16

• Expression of multi- drug resistant (MDR) gene portends very poor prognosis
  
  • ​cells can pump out chemotherapy out of cell
  • present in 25% of Primary lesion and 50% metastatic lesion

Question 17

What are the indications to use chemotherapy?

Answer 17

• Integral component of tx along with surgical resection in
  
  • Osteosarcoma ( Intramedullary /periosteal)
  • **Ewing’s sarcoma **
  • Primary neuroectodermal tumour
  • Malignant fibrous histocytoma
  • Dedefferentiated chondrosarcoma
  • Chemotherapy for soft tissue sarcoma is contraversial

Question 18

What is the administration of chemotherapy ?

Answer 18

• Preoperative- neoadjuvant- given for 8-12 weeks
• Post operative given for 6-12 months

Question 19

Can you name a chemotherapy agent and its side effects?

Answer 19

• Doxorubicin
  
  • is an anthracylcine antibiotic commonly used in oncological protocols- tx osteosarcoma
  • Inhibits DNA/RNA synthesis and blocks topoisomerase II=> apoptosis
  • functions as a cytostatic agent
• Side effct
  
  • cardiac toxicity-> cardiomyopathy
  • dexrazone- drug protective against cardiac effects of doxorubicin
• ​Cyclophospphamide- SE = myelosuppression/ urotoxicity

***chemo targets rapidly dividing cells - so also lining the gut, bone marrow, hair and skin

Question 20

What is radiotherapy’s mode of action?

Answer 20

• Production of free radicals
• direct genetic chnage

Question 21

What are the indications for radiotherapy?

Answer 21

• Definitive control of primary malignant bone tumours
  
  • Ewing’s sarcoma
  • Primary neuroectodermal toumour
  • Hemangioendoelioma
  • solitary plasmacytoma of bone
• Adjuvant to surgical excision
  
  • soft tissue sarcoma
  • given pre/post surgical excision
• Palliative care & impending fracture fixation
  
  • mets bone disease
  • require to reduce overall tumour burden
  • prostate cancer are very radiosensitive
  • breast cancer is 70% sensitive, 30% Resistant
  • Gi and renal are not radiosensitive

Question 22

What is the typical dose of radiotherapy?

Answer 22

• I rad= IcentiGray
• Typical dose = 180-200 cGy/day
• radiation is given in fractions as radiotherapy is accumulative
• the total dose is summuation of all the separate fractions given during tx
• <45 gray => uncomplicated tissue healing
• 45-55= usually heals with no problems
• >60 Gray= tissue not likely to heal

Question 23

What are the complications of radiotherapy?

Answer 23

• Early effects
  
  • delayed wound healing
  • infection
  • desquamation
• Late effects
  
  • fibrosis
  • joint stiffness
  • secondary sarcoma
  • fractures

Question 24

Describe the epidemiology of post radiation sarcoma?

Answer 24

• defined by the development of sarcoma in a region previosuly radiated for malignancy
• inicidence 13%
• more frequent in pts prior to chemotherapy
• overall pt prognosis is poor

Question 25

Describe the epidemiology of post radiation fx?

Answer 25

• Approx 25% incidence following soft tissue sarcoma resection and external beam irradiation
• risk factors
  
  • female
  • anterior femoral compartment resection
  • age >50 yrs
  • periosteal stripping
  • radiation dose >60 Gy
  • osteoporosis