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Radiation Therapy in Practice > Pituitary Adenomas > Flashcards

Pituitary Adenomas Flashcards

1
Q

Pituitary adenoma nomenclature

A
  • pituitary adenomas are benign and account for 10-15% of primary brain tumours
  • 75% are ‘functional’ tumours while 25% are ‘non functional’ tumours
  • ‘functional’ means that these tumours hypersecrete hormones
  • ‘non-functional’ tumours are defined as tumours who do not secrete excess hormones
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2
Q

size classification

A
  • microadenomas (<10mm)
  • macroadenomas (>= 10mm)
  • giant adenomas (>=40mm)
    -> pituitary carcinomas are rare (0.1% to 0.2% of cases)
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3
Q

Classification changes in WHO 2016

A
  • pituitary adenomas have previously been classified by histopathology and pituitary hormone content of the tumour cells
  • update now classifies adenomas according to their pituitary cell lineage, rather than the hormone they produce
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4
Q

Functional tumours
**

A

functional tumours include:
- lactotroph adenomas (prolactinoma) (30%)
- somatotroph adenomas (Growth Hormone-secreting) (25%)
- corticotroph adenomas (Adrenocorticotrophic ACTH) (15%)

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5
Q

Workup

A
  • tumours impinging on optic chiasm on MRI requires visual field testing
  • all patients with macroadenomas and patients with ‘larger’ microadenomas (6-9mm) should be evaluated for hypopituitarism
  • approximately two-thirds of pituitary adenomas may secrete excess hormones
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6
Q

General overview of Treatment

A
  • transsphenoidal surgical resection is the initial treatment for all tumours except lactotroph adenomas
  • remission rates of 80-90%: microadenomas
  • remission rates of 40-70%: macroadenomas
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7
Q

Radiotherapy

A

RT is reserved for patients who:
- do not achieve adequate reduction in tumour size
- do not achieve adequate reduction in hormone levels
- do not achieve adequate reduction in tumour size AND hormone levels
when using surgery, medical therapy or both

Stereotactic treatment is now favoured over conventional fractionated therapy except:
- in the case of large, invasive tumours
- tumours close to the optic chiasm
?stereotactic results in faster overall reduction in hormone secretion than conventionally fractionated regimens
Risk of hypopituitarism remains high - 20% at 5 years and 80% by 10-15 year

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8
Q

Radiation Techniques

A

fractionated radiation
- 3D conformal, IMRT (>3cm in size and <2mm from the optic chiasm)
- 45-50.4Gy/28# over 5.5 weeks
- can go up to 54Gy in 1.8Gy dose per # for aggressive adenomas (Nelson’s syndrome - where adrenal glands have been removed due to Cushing’s syndrome)

stereotactic radiosurgery
- small lesions <3cm in size and between 3-5mm from the optic chiasm
- dose 12-16Gy non-functional 18-34Gy functional (literature-based doses)

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9
Q

? Advantages of increased conformity

A

not proven
- theoretically less brain tissue irradiated should result in less morbidity and less cognitive impairment
- ?? fewer secondary malignancies

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10
Q

pituitary adenoma SRS

A
  • best if tumour 3-5mm from optic chiasm
    -> dose = 15-25Gy SRS and 45-50Gy for SRT (SLRON doses)
  • SRT is increasingly being employed with repeat localiser frames. lower complication rate but slower response (9 months vs. 18 months)
  • acromegaly responds better to SRS than SRT
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11
Q

Risk of cerebrovascular accident

A

There is a long-standing controversy regarding a possible increased risk of death from cerebrovascular disease after radiation therapy to the pituitary gland
- risk factors for cerebrovascular deaths in patients operated on and irradiated for pituitary tumours

Erfurth EM, et al., 2002

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12
Q

Lactrotroph adenomas (Prolactinomas)

A
  • lactotroph adenomas make up about 50% of all pituitary adenomas
  • occur most frequently in females aged 20-50 years
  • more than 90% of lactotroph adenomas are microadenomas
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13
Q

lactotroph adenoma presentation

A

high levels of prolactin suppress the hypothalamic-pituitary gonadal axis leading to:
- loss of libido
- infertility
- osteoporosis
- oligomenorrhea / amenorrhea / galactorrhea in females
- erectile dysfunction in males

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14
Q

lactotroph adenoma: goals of treatment

A

1) to restore normal gonadal function and fertility
2) to reduce tumour size for those patients who present with macroadenomas

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15
Q

lactotroph adenoma treatment

A

most patients are treated with dopamine agonists
- these activate dopamine receptors on tumours
- cabergoline is preferable to bromocriptine as it is more effective in reducing prolactin levels and reducing tumour size

transsphenoidal resection is an option
- achieves a normalisation of prolactin in
-> 65-85% microadenoma patients
-> 40-40% macroadenoma patients
recurrence rate of 20% over 10 years

RT is reserved for those patients where medical/surgical management has failed (rare)

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16
Q

Somatotroph adenomas
Growth hormone (GH) secreting tumours

A
  • GH disturbance can result in acromegaly (thickening of facial features)
  • Increased production of GH stimulates the release of insulin-like growth factor (IGF-1) from primarily the liver
  • presents with systemic complications
    -> Diabetes Mellitus, hypertension, arthritis, carpal tunnel, sleep apnoea, enlargement of feet and hands
    -> Tongue, lip and nose enlargement and prominent forehead
17
Q

GH-secreting tumours

A

Initial test is measuring IGF-1 level
- Elevated, age-adjusted IGF-1 level is 90% specific for a GH-secreting adenoma of the pituitary
- About two-thirds of GH-secreting tumours are macroadenomas
- Patients have an increased risk of colon neoplasia so colonoscopy is required at time of diagnosis
- Also risk of thyroid dysplasia, so a thyroid ultrasound is advised

18
Q

GH-secreting tumours treatment

A
  • primary aim is to achieve biochemical control (reduction in GH levels to < 1 ug/L and IGF-levels to normal age-adjusted level)
  • secondary aim is to reduce or remove tumour mass
  • transsphenoidal surgery is recommended as primary treatment
    -> achieves therapeutic goals in 80-90% microadenomas and 40-60% macroadenomas
    -> 5 year recurrence rate is 2-8%
  • repeat IGF-1 and GH levels and MRI should be repeated 12 weeks post surgery
  • if therapeutic goals are not met, then repeat surgery can achieve biochemical control in 50% of patients
  • dopamine agonist (Cabergoline), somatostatin analogs (Octreotide, Lanreotide, Pasireotide) and GH receptor blockers (Pegvisomant) can be utilised to medically reach biochemical control
  • no role for radiotherapy
19
Q

Corticotroph adenomas
Adrenocortitropic hormone (ACTH)-screting tumour

A
  • ACTH-secreting pituitary adenoma is the cause of Cushing syndrome in 65-70% of cases
  • Presentation is one or more of the symptoms of hypercortisolism: weight gain, increase in centripetal obesity, facial rounding, skin striae, diabetes mellitus, hypertension, mood disorders (depression), osteoporosis
20
Q

ACTH feedback loop

A

ACTH is secreted from the anterior pituitary in response to corticotropin-releasing hormone from the hypothalamus. Corticotropin-releasing hormone is secreted in response to many types of stress, which makes sense in view of the “stress management” functions of glucocorticoids. Corticotropin-releasing hormone itself is inhibited by glucocorticoids, making it part of a classical negative feedback

21
Q

ACTH-secreting tumour

A
  • initial test is to confirm presence of hypercortisolism with the late-night salivary cortisol level (diurnal pattern is lost)
  • > 80% are microadenomas and may have normal MRI in up to 50% of cases
22
Q

ACTH-secreting tumour treatment

A
  • preferred treatment is transsphenoidal resection
  • cure rates are 80-90% with recurrence rates at 10-20%
  • if not cured at initial surgery, then options are repeat surgery (50% success rate), medical therapy, RT or bilateral adrenalectomy
  • RT can take 2-5 years to be effective, so medical therapy required during that period to control hypercortisol over-secretion
23
Q

Non-functioning adenomas

A
  • defined as no secretion of excess hormones
  • make up about a third of all adenomas
  • can range from symptomless to causing significant hypothalamic or pituitary dysfunction, if a large size
  • if symptoms are present, they are:
    headaches, visual field defects (bitemporal hemianopia, central scotoma, homonymous hemianopia), hypopituitarism (signs of mass effect)
24
Q

non-functioning adenomas treatment

A
  • transsphenoidal resection for large or symptomatic tumours
  • RT as primary treatment is rare-reserved for patients who are medically unfit for surgery
  • RT is more commonly delivered adjuvantly if residual tumour is present on MRI
    -> Kamer et al (2009) tumour control of 88-97% of 904 patients in 28 series using stereotactic techniques, but only over a 4-year period

Radiation Therapy in Practice (19 decks)

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