Objective: Current markers predicting tumour progression of pituitary adenomas after surgery are insufficient. Our objective was to investigate if minichromosome maintenance protein 7 (MCM7) expression predicts tumour progression in non-functioning pituitary adenomas (NFPAs).
Methods: In a cohort study of surgically treated NFPAs, two groups with distinctly different behaviour of a residual tumour were selected: one group requiring reintervention due to tumour progression (reintervention group, n=57) and one with residual tumours without progression (radiologically stable group, n=40). MCM7, Ki-67, estrogen receptor-⍺ expression, mitotic index and tumour subtype was assessed by immunohistochemistry and their association with tumour progression requiring reintervention was analysed.
Results: Median (IQR) MCM7 expression was 7.4% (2.4–15.2) in the reintervention group compared with 2.0% (0.6–5.3) in the radiologically stable group (P<0.0001). Cox regression analysis showed an association between high (>13%) MCM7 expression and reintervention (HR 3.1; 95%CI:1.7-5.4; P=0.00012). The probability for reintervention within 6 years for patients with high MCM7 was 93%. Ki-67 expression >3% (P=0.00062), age ≤55 years (P=0.00034) and mitotic index ≥1 (P=0.024) were also associated with reintervention. Using a receiver operating characteristics curve, a predictive model for reintervention with all the above predictors yielded an area under the curve of 82%. All eight patients with both high MCM7 and high Ki-67 needed reintervention.
Conclusion: This cohort study shows that expression of MCM7 is a predictor for clinically significant postoperative tumour progression. Together with age, Ki-67 and mitotic index, MCM7 might be of added value as a predictive marker when managing patients with NFPA after surgery.