Brain mets Flashcards
Common primary sites associated with brain mets
Lung
Melanoma
Breast
Renal cell carcinoma
Colorectal cancer (and other GI tract adenocarcinoma)
These 5 account for 80% of brain mets
Pathophysiology of brain mets
Metastatic cancer passes through the bloodstream and enters the central nervous system through a breakdown of the blood-brain barrier. Clonal cells then proliferate, causing local invasion, displacement, inflammation, and edema. Distribution throughout the central nervous system is more common in areas of high blood flow
Pathophysiology of leptomeningeal disease
Metastatic malignant cells may invade the meninges by:
(1) direct invasion via surrounding structures, such as the dura mater, bone, or nerves;
(2) hematogenous spread often by way of venous vasculature;
(3) entry of the fenestrated pores of the choroid plexus typically permitting solute transport
What are the management options of intact brain metastases?
Surgery
SRS
WBRT
HA-WBRT
Targeted systemic therapy or immunotherapy if relevant tumour type
Best supportive care
In what situations may supportive care alone be the most appropriate for a patient with brain mets?
The QUARTZ trial showed that omitting WBRT in poor prognosis patients did not significantly affect quality of life or overall survival when these patients also had access to supportive care.
The Quality of Life after Treatment for Brain Metastases (QUARTZ) noninferiority trial studied patients with poor prognosis and NSCLC with brain metastases not suitable for resection or SRS. Patients were randomized to WBRT with supportive care versus supportive care alone (oral dexamethasone).
There was no evidence of a difference in overall survival, QoL, or dexamethasone usage between the 2 groups.
What are strategies to reduce RT related toxicity in brain mets?
HA-WBRT
Memantine
SRS over WBRT
Where do brain mets most commonly occur?
grey-white matter junction in cerebral hemispheres due to decrease in diameter of blood vessels, or in arterial watershed areas
What % of brain mets are found in different locations in the brain?
80% supratentorial
15% cerebellum
5% brainstem
Which types of histologies are most assoc with haemorrhagic brain mets?
Melanoma
Choriocarcinoma
Testicular
Thyroid
Renal cell carcinoma
CT appearances of brain mets
Variable
On pre-contrast imaging:
isodense, hypodense or hyperdense (classically melanoma) compared to normal brain parenchyma with variable amounts of surrounding vasogenic oedema.
Post contrast: enhancement is also variable and can be intense, punctate, nodular or ring-enhancing
Brain met appearance on T1 MRI
typically iso- to hypointense
Brain met appearance on T2 MRI
typically hyperintense
Brain met appearance on MRI T1 + contrast
enhancement pattern can be uniform, punctate, or ring-enhancing, but it is usually intense
delayed sequences may show additional lesions, therefore contrast-enhanced MR is the current standard for small metastases detection
Brain met appearance on MRI FLAIR
typically hyperintense
hyperintense peri-tumoural oedema of variable amounts
What prognostic systems exist for brain mets? Why are they useful?
Original Graded prognostic assessment (GPA)
Diagnosis specific GPA
RTOG RPA classes
Useful because they allow estimation of Median survival which can help inform which treatment is most appropriate
What features are part of the original GPA
CNS metastases
Age
KPS
Extracranial mets
What are the 3 RPA classes?
Class I: KPS>70
Age <65
primary controlled and no extra cranial mets
Class II:
KPS >70
Either age >65 or primary uncontrolled
Class III:
KPS <70
What features make up the diagnosis specific GPA?
For each histological type: NSCLC, Breast, renal, Melanoma, GI
Domains for Age, KPS, number of brain mets, extra cranial mets plus specific feature for diff types
Lung- EGFR or ALK
Breast- subtype
Renal- Hb
Melanoma- BRAF
What is the ASTRO recommendation for ECOG 0-2 and up to 4 intact brain mets
SRS
What is the ASTRO recommendation for ECOG 0-2 and 5-10 intact brain mets?
SRS conditionally recommended
ASTRO recommends which dose for intact brain mets <2cm in diameter
Single fraction SRS using 20-24Gy
Multifraction 27GY/3# or 30Gy/5#
What should the estimated life expectancy be for patients undergoing SRS
Atleast 6mo
Dose for brain mets 2-3cm diameter (ASTRO)
Single fraction 18Gy
Multifraction 27GY/3# or 30Gy/5#
Dose for brain mets 3-4cm in size (ASTRO)
Multifraction 27GY/3# or 30GY/5#
If single fraction choses, 15Gy/1#
Above which size is SRS discouraged
> 6cm
Management of brain met >4cm (ASTRO)
Surgery is preferred option
If surgery cannot be performed then multifraction SRS
What is a requirement (logistical) of offering a patient SRS rather than WBRT
Must be able to offer them MRI follow up regular as there is an increased risk of local recurrence for SRS than with WBRT