Increased incidence of neoplasia in patients with pituitary adenomas. The Pituitary Study Group

The goal of our study was to determine the rate of neoplasms in patients with other pituitary adenomas (non-functioning and prolactinomas) in comparison with acromegaly which is known to favour the development of neoplasia.

We reviewed clinical records for 220 patients with acromegaly, 151 patients with non-functioning pituitary adenoma (NF) and 98 patients with prolactinomas. Incidence rates of cancer for patients with pituitary tumours were calculated per person-years of follow-up study. These rates were then compared with sex and age adjusted incidence rates reported by National Tumour Registry. An internal control group of 163 subjects with a non-neoplastic condition, i.e. Graves' disease followed chronically in the same clinic was also studied. The ratios observed to expected were expressed as standardized incidence rates (SIR). The only significant difference between the acromegalic and other pituitary tumours patients was in hypopituitarism, present in 18.2% (acromegaly) 47% (NF) and 18.6% (prolactinomas).

Twenty-three malignant tumours were registered in 19 acromegalics (1 Hodgkin disease, 1 myelogenous leukaemia, 1 lymphocytic leukaemia, 3 papillary thyroid carcinomas, 1 ovarian carcinoma, 2 colorectal carcinoma, 1 renal cell carcinoma, 4 cervical carcinoma, 2 skin cancers, 2 pancreatic carcinoma, 4 breast carcinoma, 1 bladder carcinoma). Three acromegalics harboured two malignancies. Patients with acromegaly had a 3.39-fold increased rate of malignant tumours compared with the general population and a 3.21-fold increased rate compared with our internal control group. Eleven malignant tumours were found in patients with NF-pituitary adenomas and 2 in prolactinoma patients (1 lymphoma, 1 multiple myeloma, 1 colonic cancer, 1 renal cell cancer, 1 stomach cancer, 2 lung cancers, 1 cervix carcinoma, 1 breast cancer, 1 testicular carcinoma and 3 melanoma). Patients with NF pituitary adenomas had a 3.91-fold increased rate of malignant tumours compared with the general population and 4.07-fold increase compared with the internal control group. Patients harbouring prolactinomas did not have an increased incidence rate of malignancy compared with the general population or our internal controls. Female patients with acromegaly and male patients with NF-pituitary adenoma had higher incidences of neoplasia.

We have demonstrated that the overall incidence of malignant tumours in patients with non-functioning pituitary adenomas and acromegaly is significantly higher than expected for general population and for our internal control group.