Pituitary Adenoma Recurrence: Modeling Using a New Modification of the SIPAP Classification

Introduction: Pituitary adenomas are a common skull base tumor that varies in size, often classified based on function and size, either micro- or macroadenoma. Patient clinical presentation depends on multiple factors, including excessive hormone secretion, the mass effect of large tumors, and tumor invasion to surrounding structures. With the advancement of diagnostic modalities, MRI is considered being the modality of choice to evaluate pituitary tumor features including parasellar extension. Endoscopic endonasal transsphenoidal (EETS) resection is the surgical standard of care for pituitary adenoma resection due to its superior visualization of the sella and surrounding anatomy. However, recurrence of the pituitary tumor following surgery has been reported widely. Yet, intuitively, adenoma size and involvement of parasellar structures should impact gross tumor resection (GTR) and recurrence. We evaluated a modified score using the SIPAP classification system, combining the suprasellar and paraseller extension scores of the pituitary tumor to determine its impact on adenoma recurrence.

Study Design: Retrospective cohort, single institutional study.

Methods: Institutional REB approval was attained for a retrospective review of all EETS cases for pituitary tumor resection between November 2009 and October 2018. Queries of the hospital database were completed by medical records personnel to identify cases of pituitary tumor treated using the EETS approach. Patient characteristics, tumor type, endocrine data, and operation characteristics were then extracted from medical records pertaining to patient baseline characteristics. Preoperative MRI images were reviewed and the SIPAP classification applied to the pituitary tumors. Postoperative results were extracted for the duration of the follow-up period available for each patient. Within the SIPAP score, the suprasellar (S) and parasellar (P) scores are the most variable and believed to be the main drivers of surgical GTR. The suprasellar score and the highest parasellar score from both sides were numerically summed a bilateral suprasellar and parasellar (SaP) score and combined to make four grades.

Results: A total of 276 patients were identified, 56.5% of the cohort was male. The mean age of the cohort was 54 years old. During the study period, five different neurosurgeons performed EETS for patients with pituitary tumors. The mean of the length of follow-up was 32 months. Patient perioperative tumor grade according to SaP classification and recurrence rate in each grade were as follows: grade 1: 11%; grade 2: 10%; grade 3: 15%; and grade 4: 22%. The results followed a pattern of logarithmic curve.

Conclusion: The SaP classification was demonstrated to be useful for determining the expected recurrence of pituitary tumor following EETS, with the most advanced tumors demonstrating the highest rates of recurrence. Use of the SaP score will allow for more accurate preoperative counseling of patients with pituitary adenoma when considering recurrence requiring further surgery.