Investigation of the growth patterns of non-functioning pituitary macroadenomas using volumetric assessments on serial MRI investigations

Jaco Pieterse,Susanna F Otto,Coert S De Vries

doi:10.4102/sajr.v20i1.962

Abstract

Background: Benign non-functioning pituitary macroadenomas (NFMA) often cause mass effect on the optic chiasm necessitating transsphenoidal surgery to prevent blindness.However, surgery is complicated and there is a high tumour recurrence rate. Currently, very little is known about the natural (and residual post-surgical) growth patterns of these NFMA. Conflicting data describe decreased growth to exponential growth over various time periods.Due to lack of information on growth dynamics of these NFMA, suitable follow-up imaging protocols have not been described to date.Objective: To determine if NFMA grow or stay quiescent over a time period using serial MRI investigations and a stereo logical method to determine tumour volume. In addition, to evaluate if NFMA adhere to a certain growth pattern or grow at random.Method: Thirteen patients with NFMA had serial MRI investigations over a 73-month period at the Universitas Academic Hospital. Six of the selected patients had undergone previous surgery, while seven patients had received no medical or surgical intervention. By using astereological method, tumour volumes were calculated and plotted over time to demonstrate growth curves. The data were then fitted to tumour growth models already described in literature in order to obtain the best fit by calculating the r2 value.Results: Positive tumour growth was demonstrated in all cases. Tumour growth patterns of nine patients best fitted the exponential growth curve while the growth patterns of three patients best fitted the logistic growth curve. The remaining patient demonstrated a linear growth pattern.Conclusion: A specific growth model best described tumour growth observed in non-surgical and surgical cases. If follow-up imaging confirms positive growth, future growth can be predicted by extrapolation. This information can then be used to determine the relevant follow-up-imaging interval in each individual patient.

Highlights

Non-functioning pituitary macroadenomas (NFMA) are the most prevalent pituitary neoplasm and their growth is haphazard with lobulation.[7]
If the entire volume of a solid tumour grows at a constant rate, exponential tumour growth would be expected resulting in a constant tumour volume doubling time.[11]
All the patients in this study showed an increase in tumour volume over time

Summary

Introduction

Pituitary adenomas are almost always benign (>99.9%), arise from the anterior pituitary and account for approximately 15% of all intra-cranial tumours.[1,2] The majority of these adenomas show no local invasion of bone, cavernous sinus or vascular encasement and malignant transformation and metastases are extremely rare (0.2% of all adenoma cases).[2,3]Pituitary adenomas can be divided into microadenomas (< 1 cm) or macroadenomas (> 1 cm) according to their widest diameter.[1,4] The prevalence of pituitary adenomas in the general population has been reported to be 10%–27%, with macroadenomas considerably lower at 0.2%.5 Macroadenomas are predominantly non-functioning (> 80%),[5,6] that is, there is no clinical and biochemical evidence of pituitary hormonal overproduction and serum prolactin levels of ≤ 100 ng/mL are required for classification as such.[1,5]Non-functioning pituitary macroadenomas (NFMA) are the most prevalent pituitary neoplasm and their growth is haphazard with lobulation.[7]. Pituitary adenomas can be divided into microadenomas (< 1 cm) or macroadenomas (> 1 cm) according to their widest diameter.[1,4] The prevalence of pituitary adenomas in the general population has been reported to be 10%–27%, with macroadenomas considerably lower at 0.2%.5. Macroadenomas are predominantly non-functioning (> 80%),[5,6] that is, there is no clinical and biochemical evidence of pituitary hormonal overproduction and serum prolactin levels of ≤ 100 ng/mL are required for classification as such.[1,5]. Non-functioning pituitary macroadenomas (NFMA) are the most prevalent pituitary neoplasm and their growth is haphazard with lobulation.[7] Growth normally occurs through the diaphragma sellae into the suprasellar cistern with a characteristic ‘snowman’ appearance.[1]. Benign non-functioning pituitary macroadenomas (NFMA) often cause mass effect on the optic chiasm necessitating transsphenoidal surgery to prevent blindness. Due to lack of information on growth dynamics of these NFMA, suitable follow-up imaging protocols have not been described to date

Results

Discussion

Conclusion