Pituitary neuroendocrine tumors (PitNETs) are typically treated with multimodal approaches, including surgery, medical therapy, and in some cases, stereotactic radiosurgery (SRS). SRS is an exact form of radiation therapy that delivers high-dose radiation to the tumor while sparing surrounding normal tissues. Below is an overview of the role of SRS in the management of PitNETs.
SRS is considered in the following situations:
Residual or Recurrent Tumors – After incomplete surgical resection, especially if the tumor is not controlled with medical therapy.
Non-Surgical Candidates – Patients who are poor candidates for surgery due to medical comorbidities.
Functioning PitNETs Not Controlled by Medications – Particularly for growth hormone (GH)-secreting tumors (acromegaly), adrenocorticotropic hormone (ACTH)-secreting tumors (Cushing’s disease), or prolactinomas resistant to dopamine agonists.
Non-Functioning PitNETs – If residual tumor growth is demonstrated on follow-up imaging.
Cavernous Sinus Invasion – When tumor remnants involve the cavernous sinus, complete surgical removal is difficult.
The most commonly used SRS platforms for PitNETs include:
Gamma Knife Radiosurgery (GKRS) – The most widely used modality for pituitary tumors due to its high precision.
Linear Accelerator-Based (LINAC) Systems – Including CyberKnife and TrueBeam.
Proton Beam Therapy – An emerging option that may have dosimetric advantages.
Tumor Growth Control: SRS achieves tumor control rates of 80-95% at long-term follow-up.
Hormonal Normalization:
Cushing’s Disease (ACTH-secreting tumors) – Hormonal remission in ~50-70% of cases within 2-5 years.
Acromegaly (GH-secreting tumors) – Biochemical control in ~40-60% over 5-10 years.
Prolactinomas – Less commonly treated with SRS due to dopamine agonist sensitivity, but in refractory cases, remission rates are ~30-50%.
Despite its precision, SRS has potential complications:
Hypopituitarism – The most common side effect, occurring in 20-50% of patients over time.
Optic Neuropathy – Risk increases with doses >8-10 Gy to the optic apparatus.
Cranial Neuropathy – Rare but possible with cavernous sinus involvement.
Radiation-Induced Secondary Tumors – Extremely rare but a theoretical long-term risk.
MRI Brain with Pituitary Protocol – Typically at 6 months post-SRS, then annually for 5 years.
Endocrine Monitoring – Every 6-12 months to assess hormone levels and pituitary function.
Visual Field Testing is used if the tumor is near the optic chiasm.
SRS is a valuable tool in managing PitNETs, particularly for residual, recurrent, or medically refractory tumors. While highly effective in controlling tumor growth, hormonal normalization is slower and less predictable. Careful patient selection, dose planning, and long-term follow-up are essential to optimize outcomes and minimize complications.
A study aimed to elucidate the outcomes of salvage endonasal transsphenoidal surgery (sETS) for progressive PA failing SRS.
This retrospective, two-institution-based cohort study analyzed data from patients who underwent sETS for progressive PA failing SRS. Progression-free survival (PFS), disease-specific survival (DSS), and neurological and endocrinological outcomes in the sETS group were analyzed and compared with those in the primary ETS (pETS) group after propensity score matching using the following variables: age at surgery, maximum tumor diameter, highest Knosp-Steiner classification, and tumor type.
Thirteen sETS patients (8 males [62%], median age at surgery of 56 years) with 5 nonfunctioning (39%), 6 corticotropic (46%), and 2 other functioning (15%) PAs who received median (range) follow-up of 125 ( 23-169) months were included. None of the patients experienced new neurological deficits or death after sETS. The median (range) tumor resection rate was 90% (80%-100%). The 5-year PFS and DSS rates were 55% and 77%, respectively. All 4 patients (31%) who experienced recurrence after sETS had corticotropic tumors. In the matched cohort analysis between the sETS group with 12 patients and the pETS group with 12 patients, no significant differences were observed in surgical outcomes. PFS rates were marginally higher in the sETS group than in the pETS group (80% vs 49% at 3 years, p = 0.216, log-rank test), and DSS was similar between the two groups (p = 0.543, log-rank test).
The authors' results indicate that ETS can be safely performed as a salvage treatment after failed SRS with low complication rates and satisfactory tumor control in treatment-resistant PA 1).