MON-330 Cancer Incidence in 1,296 Patients with Acromegaly Is Not Increased: A Nationwide Population-Based Study

Background: Single- and multi-center studies have shown an increased incidence of malignancies in patients with acromegaly. These findings may be affected by selection bias. Our aim was therefore to investigate the incidence of malignancies in a nationwide unselected cohort of patients with acromegaly. Methods: Adult patients diagnosed with acromegaly due to a pituitary tumor between 1987 and 2017 were identified in the Swedish National Patient Registry. All malignancies following the diagnosis of acromegaly were identified in the Swedish Cancer Registry that has a coverage of over 96%. Standardized incidence ratios (SIRs) for malignancies, with 95% confidence intervals (CI), were calculated by using the Swedish general population as a reference. Incidence of malignancies was also analyzed in sub-groups of patients treated with radiotherapy and in those having diabetes mellitus and hypopituitarism. Results: A total of 1,296 patients with acromegaly were included (621 men, 675 women). The mean age (±SD) at diagnosis was 51.6±14.7 years. The mean follow-up was 12.7±8.3 years, with a total of 16,395 person years at risk. Pituitary surgery was performed in 842 (65%) patients and radiation therapy in 152 (12%) patients. The diagnosis of hypopituitarism and diabetes mellitus was recorded in 29% and 16% of patients, respectively. Overall, 186 malignancies were identified in patients with acromegaly as compared to 179 expected malignancies in the general population (SIR 1.04; 95% CI 0.90-1.20). Incidence of malignancies was similar in men and women [SIR 1.08 (95% CI 0.88-1.32) vs 1.00 (95% CI 0.80-1.23)]. Incidence of colorectal cancer (SIR 1.12; 95% CI 0.75-1.62) or malignancies of the respiratory system (SIR 1.22; 95% CI 0.76-1.84) was not increased. Incidence of kidney and ureter cancer (n=17) was, however, increased (SIR 3.81; 95% CI 2.22-6.11). In the entire study cohort, only three cases of thyroid cancer were recorded. SIR for malignancies in patients treated with radiotherapy (1.12; 95% CI 0.56-2.01) and in patients with hypopituitarism (SIR 0.91; 95% CI 0.68-1.18) or diabetes (SIR 1.08; 95% CI 0.78-1.45) did not differ from the general population. Conclusions: This large nationwide population-based study showed that the overall incidence of malignancies in patients with acromegaly was not different from the general population. In particular, incidence of colorectal and thyroid cancer was not increased. Incidence of malignancies of the urinary tract was, however, increased.