Breast cancer associated with primary hyperparathyroidism: a nested case control study

BACKGROUND Primary hyperparathyroidism (pHPT) is associated with an increased risk of developing breast cancer, but little is known about the underlying factors. The aim of this study was to compare women with a history of pHPT and a reference population in terms of standard factors predictive of prognosis and response to therapy for breast cancer. METHODS We analyzed data collected from the National Swedish Cancer Register and from two regional oncologic center registries. Seventy-one women with breast cancer and a history of parathyroid adenomectomy were compared with 338 matched controls with breast cancer only. Tumor size, stage, hormone receptor status, lymph node status, cause of death, and cumulative survival were analyzed. RESULTS The mean age was 69 ± 11 years (95% confidence interval [CI]: 68-70) in both groups and the mean time interval between the parathyroid surgery and breast cancer diagnosis was 91 ± 68 months (95% CI: 72-111). There were no differences between the two groups regarding size, stage, lymph node metastases, or survival, but none of the cases with a history of pHPT were found in Stage III or IV. CONCLUSION In conclusion, factors predictive of prognosis and response to therapy in women with a history of pHPT and breast cancer are similar to those in breast cancer patients without pHPT.