Prediction of recurrence of nonfunctioning pituitary tumours by loss of heterozygosity analysis

BACKGROUND Postsurgical regrowth or recurrence of nonfunctioning pituitary adenomas (NFAs) is not uncommon and often requires further surgery or radiotherapy (DXT). Routine postoperative DXT increases the incidence of hypopituitarism, which is associated with increased morbidity and mortality. Identification of genetic abnormalities in the tumour tissue, which can predict recurrence, may allow targeting DXT to the most appropriate patients. DESIGN AND METHODS We have performed loss of heterozygosity (LOH) analysis on 96 NFAs of which 43 (45%) were recurrent and 53 (55%) were nonrecurrent tumours. Analysis of all tumours was performed on the surgical specimen obtained at the time of first surgery. All tumours underwent allelotyping across nine highly informative microsatellite markers selected on the basis of high LOH frequency in an earlier study involving genome-wide allelotyping. LOH frequency across all microsatellite markers as well as across individual markers was compared between the two cohorts of tumours. RESULTS LOH frequency in tumours that subsequently recurred was significantly higher across all microsatellite markers as compared to tumours that did not recur (P < 0.05). Allelic loss across one or more microsatellite marker was significantly higher in recurrent tumours (30/43) as compared to their nonrecurrent counterparts (17/53) (P < 0.01). On Poisson regression analysis, the higher LOH frequency in recurrent tumours was independent of the invasiveness of tumours determined radiologically. In addition, LOH at the microsatellite markers D1S215 and D1S459 was significantly higher in tumours that recurred as compared to tumours that did not (32%vs. 3% and 27%vs. 2%, respectively; P < 0.01 for both). No significant difference in LOH frequency between the two tumour groups was evident at the other markers. No association could be demonstrated between the frequency and pattern of LOH and the time to manifest recurrence. CONCLUSIONS We have shown that it may be possible to predict recurrence of NFAs by LOH analysis of the initial tumour specimen at predefined microsatellite markers, especially on chromosome 1q. This merits further prospective study.