Cancer incidence rates are slightly elevated in patients with acromegaly, according to a meta-analysis recently published in The Journal of Clinical Endocrinology & Metabolism.
Researchers led by Jens Otto Lunde Jørgensen, MD, DMSc, of the Department of Endocrinology and Internal Medicine at Aarhus University Hospital in Norrebrogade, Denmark point out that acromegaly has been associated with an increased risk of cancer, since growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are implicated in cancer promotion. Acromegaly is associated with thyroid and colorectal cancer in particular, but the researchers note that all studies have found this association, and it’s not known whether mortality from cancer is increased by acromegaly. “A major reason for the inconsistent epidemiological data on cancer risk is differences in study design, and the need for population-based studies persists,” the authors write.
So the team conducted a nationwide population-based cohort study to examine the long-term risk of cancer incidence and mortality in patients with acromegaly, as well as a meta-analysis of the literature on cancer standardized incidence ratios (SIRs) in acromegaly. The study looked at 529 acromegaly cases from 1978 to 2010. They compared incident cancer diagnoses and mortality with national cancer rates estimating SIRs.
The study identified 81 cases of cancer after excluded cases of cancer diagnosed within the first year. “SIRs were 1.4 (95% CI, 0.7 to 2.6) for colorectal cancer, 1.1 (95% CI, 0.5 to 2.1) for breast cancer, and 1.4 (95% CI, 0.6 to 2.6) for prostate cancer. Whereas overall mortality was elevated in acromegaly (SIR 1.3; 95% CI, 1.1 to 1.6), cancer-specific mortality was not,” the authors write.
The meta-analysis showed a SIR of overall cancer of 1.5 (95% CI, 1.2 to 1.8). SIRs were elevated for colorectal cancer, 2.6 (95% CI, 1.7 to 4.0); thyroid cancer, 9.2 (95% CI, 4.2 to 19.9); breast cancer, 1.6 (1.1 to 2.3); gastric cancer, 2.0 (95% CI, 1.4 to 2.9); and urinary tract cancer, 1.5 (95% CI, 1.0 to 2.3). “In general, cancer SIR was higher in single-center studies and in studies with <10 cancer cases,” the authors write.
The authors note that while the meta-analysis supported their finding that cancer risk is increased in patients with acromegaly, the meta-analysis revealed potential sources of bias. Cancer incidence risk was increased in single-center studies and was lower when the researchers excluded studies with fewer than 10 cases, suggesting selection or sample bias. “It is possible that the patient population in single centers represents difficult cases with previous treatment failure and increased comorbidity,” the authors write. “It is also possible that the comparator group in single-center studies derived from screening programs, which poses the risk of healthy user bias.”
The authors go on to write that surveillance bias might have existed in cases of thyroid cancer, since acromegaly enlarges the thyroid, which may lead to overdiagnosis of occult thyroid cancer, “and endocrinologists are generally more likely to focus on endocrine diseases.”
Taking the results of the cohort study and the meta-analysis together, the authors conclude there is “only a slightly elevated overall risk of cancer in patients with acromegaly.” And while these results should not deter patients or health care professionals from following cancer surveillance guidelines, they write, “our findings agree with the previously drawn conclusion that excessive GH in humans is not a serious cancer risk.”