Grant 2014 (High-Dose SRS Pituitary Adenoma)

Background

Single-institution retrospective (Yale). N=31 secretory (functioning) pituitary adenomas treated with high-dose Gamma Knife SRS at marginal dose 35 Gy (vs historical 20–24 Gy). ACTH-secreting n=15, GH-secreting n=13, prolactinoma n=2, TSH-secreting n=1; all had prior transsphenoidal surgery with residual/recurrent hypersecretion.

Interventions and follow up

Treatment: High-dose Gamma Knife SRS, marginal dose 35 Gy at 50% isodose line, for functioning adenomas with persistent hypersecretion after transsphenoidal surgery
Primary endpoint: Hormone normalization; time to remission; relapse rate; complications
mFollow up: Mean 40.2 mo (range 12–96)

Results

Initial hormone normalization: 70% (22/31)
Median time to remission: 17.7 mo
Endocrine relapse after normalization: 32% (7/22), mean 21 mo to relapse
New hypopituitarism: 32% (10/31)
New optic neuropathy: 3% (1 patient)

Adverse events

New hypopituitarism (any axis): 32% (10/31; GH, ACTH, TSH, gonadal)
New unilateral optic nerve pallor: 3% (1 patient, at 3 yr)
Transient frontal headaches: 10%
Grade 4–5: None; serious-AE rate comparable to 20–24 Gy literature

Conclusions

High-dose SRS at 35 Gy for secretory pituitary adenomas achieved 70% initial hormone normalization with faster time to remission than historical 20–24 Gy series. Complication rates (hypopituitarism 32%, optic neuropathy 3%) were not significantly elevated, suggesting 35 Gy may be safe and potentially more effective in cavernous-sinus-contained adenomas.

Key Limitations

Very small (N=31), retrospective, single-institution; heterogeneous adenoma subtypes; short mean follow-up for late toxicity; historical (not concurrent) dose comparator.

Clinical Context

Hypothesis-generating for dose escalation in functioning adenomas; standard marginal doses remain ~20–30 Gy with optic-apparatus constraint <8–10 Gy.

References