Radiotherapy Review Flashcards
What is RT used for?
Curative/radical/adjuvant/palliative/analgesia/emergencies
Primary uses- primary and secondary tumours (30% of all MT)
Secondary uses- AV malformation/keloids/heterotrophic ossification
Types of radiation
High E- Tx via exploiting absorption capacity of cancer
Low E- Dx via images obtained through CT/CR
Direct- alpha/beta particles/protons/electrons- modify biochemical properties and anatomical structures, interact with dehydrated systems IE. DNA & bio molecules
Indirect- neutrons/X and gamma photons- provide energy to charged particles IE. Water to create OH FR which damage and disrupt DNA/bio molecules
Effects of radiation
Reversible irreversible
Early late
Provisional definitive
Sublethal lethal
Deterministic effects of radiation
Non random and has a threshold
Severity increases but probability doesn’t
Sunburn-early increased ep/marrow turnover
Sunburn-late parenchymal changes to vasculature/fibrosis
Stochastic effects of radiation
Random and does not have a threshold (damage at any exposure)
Probability increases but severity does not
Radiation and cell killing
LOF in non proliferating cells dose-100 Gy
LO reproduction in proliferating cells dose-2Gy
Radiation increases lifetime risk of cancer at any age
Latency
Time between exposure to radiation and development of cancer
Leukaemia- 5-7 years
Solid T- 20 years
Dose fractionation
Prescribe a high dose and divide over X period of time
Increases the targeting of RS T cells
4 R’s
REPAIR- sub lethal damage
Occurs hours post radiation
Affected by oxygenation
Healthy cells are well oxygenated/T cells have variable oxygenation
4 R’s
RE-OXYGENATION
T have an oxygen tension gradient
Normal hypoxia anoxia
Hypoxic cells can repair damage
Reduction in oxygen tension can increase RR and affect Tx success
4 R’s
REPOPULATION
Both T and normal cells divide and repopulate
T cell repopulation- risk of Tx failure and recurrence
Normal cell repopulation- desirable and reduce complications
4 R’s
REASSORTMENT of T cells into RS phases
RS ass. To CC phases
RR phases- G1 and S (dose 1)
RS phase- G2 and M (dose 2)
Cell response to radiation- interphase death/division delay/reproductive failure
Radiation delays CC progression and produces reassortment & synchronous progression of cells in their life cycles
Radio-curability
Possibility of eradicating T at the level of the primary lesion and LN drainage sites
Radio-sensitivity
Response of lesion to radiation wrt speed & magnitude of regression
Dependant on mitotic index and degree of differentiation
RR-T
RS-T
Bone/soft tissue/sarcoma/melanoma
Intermediate- Ep T
Leukaemia/lymphoma/testicular seminoma/SCLC
Target volume
T volume + surrounding healthy tissue/LN drainage sites
Types of radiotherapy
External beam
External radiation source & delivered to T via cutaneous tissue
3D conformational- beam conforms to shape of target volume
Stereotactic radiation- 1 high dose for radio-surgery/multiple small doses for RT
Intensity modulated- beam intensity optimised around P/generates 3D dose distribution and conforms closely to TV
Whole body irradiation- in preparation for marrow transplant 9.5Gy
Or 3Gy+cyclophosphamide to prevent graft rejection
Types of RT
Brachytherapy
Sealed radioactive source in T area
Temporary or permanent
Lips/vulva/breast/prostate/tongue
Types of RT
Systemic radioisotope therapy
Radioisotope administered orally or IV
Ie. 131 Iodine in thyroid cancer
RT success
Dependant on T type/location/stage/RS/extension/histology and P general health
RT indications
Single therapy- when RT is only cure or for palliative care
Alternative therapy- when RT has same efficacy as other Tx with less complications
Associative therapy- improve long term survival or local control
Exclusive RT
Head and neck SqCC- tonsils/retro molar space/glottis/tongue/floor of mouth
Nasopharyngeal carcinoma- at all stages/results comparable to surgery/5years SR 50-90%/use cellulose acetate sheet to reposition chin every day
Prostate- radical Tx of intra/extra capsular adenoC with minimal invasion
Hodgkin’s lymphoma- when there is no LN involvement (10years SR 85-95%)
Uterine cervix- early vaginal/intrauterine brachytherapy 5years SR 60-80%
Uterine cervix- late external RT and intra-cavitary brachytherapy 5years SR 30-50%
Skin- Basal and SqCC of nose/eyelids/ear lobes/forehead
RT and surgery
Increase long term SR/reduce complications and loco regional recurrences
Pre op RT
Intra op RT uses mobile accelerators to emit electrons
Post op RT
Pre op RT
Change T into respectable lesion by reducing size
Create cleavage planes and reduce infiltration
Ie. Distal 1/3 rectal T use RT to spare anal sphincter/reduce need for ostomy + radical surgery + abdominal perineal resection
RT and surgery
Post op RT
Breast post radical surgery- when there is a high risk of cutaneous/subcutaneous relapse
Breast post conservative surgery- for foci and local recurrences
Soft tissue sarcoma- post radical surgery to sterilise T bed
Testicular seminoma- post orchiectomy RT of para aortic LN
Lung- post radical surgery RT of MS LN
Head and neck- post radical surgery with evidence of residues at resection margins
Peri neural/peri lymph/LN/soft tissue invasion and infiltration
RT and chemotherapy
Use RT when T is outside of field of chemo and increase local efficacy ie CNS tumour
Use chemo when T is outside of field of RT
RT chemotherapy
Head & neck- SqCC of oral cavity or larynx
Reduce mutilating surgery/preserve function and structure of organ
Anal canal SqCC- when early and follow with surgery
Lymphoma- Tx of HL/NHL with bulky LN
Urinary bladder- Tx of large T/adjuvant to surgery/alternative Tx to demolition surgery
Palliative RT
No cure/symptomatic relief/local disease control
Lung- control cough/dyspnea/pain/hemoptysis
Eos- control dysphagia by releasing extrinsic compression
Brain- receive neurological signs and symptoms
Bone- reduce Fx and spinal cord compression/Reduce bone pain
RT and emergencies
Spinal cord compression- RT controls pain/can reduce the risk of hemiplegia & quadriplegia if administered within 48 hours (no vascular damage)
SVC compression- reduce acute dyspnea and compression and increase QoL
Breast cancer
Tx- chemo/hormone Tx/conservative surgery/radical mastectomy/RT
RT- post CS/RM or in brain/bone metastasis
RT administered to axilla results in lymphedema
Indications for RT on chest wall post RM-
Tumour of >5cm (multi focal and multi centric)
>4 LN involvement
Peri neural/lymph invasion
Skin and chest strap infiltration
Breast cancer
Local recurrence at axilla/CW/internal mammary LN/subclavian around 20 %
RT side effects
Acute- erythema/epitheliolysis/inflammation/actinic pneumonia
Chronic- brown erythema/post actinic pneumonia/fibrosis
Rectal cancer
Tx- RT (adjuvant/pre and post op) and RT-chemo
RT-chemo
Stage A-B1 (T1/2 N0 M0)-surgery & follow up
Stage B2-C (T3/4 N0-3 M0)- surgery & pre and post op RT- chemo
Stage D (Tn Nn M1)- chemotherapy
Rectal cancer
RT side effects
At SI- diarrhoea/malabsorption/irradiated loop stenosis/Hm proctitis/peritoneal perforation risk
At GUT- cystitis/urinary retention/retrograde ejaculation/dilatation of ureter secondary to RPO fibrosis
Endometrial cancer
No diagnostic tool
Any woman >40 years with RF and endometrial hyperplasia should have biopsy/histology/transvaginal US
Abdominal US/CT- evaluate LN involvement/extension to UB/rectum
Colonic CR and barium enema- evaluate presence of diverticula
Liver US/chest CR- to evaluate metastasis
RT- external beam RT/ 50-54Gy fractionated/4 fields opposed in pairs “box technique”
Endometrial cancer
RT side effects
Early- cystitis/diarrhoea/epitheliolysis of inguinal area and inter gluteal cleft
Late- urinary Incontinence/intestinal disorders/pollakiuria (high frequency/small volumes)
