PRIMARY HYPERPARATHYROIDISM MAY LEAD TO INCREASED CANCER RISK

June 3, 2009 (Houston, Texas) — Patients diagnosed with primary hyperparathyroidism (PHPT) may have a higher risk for cancer and a higher risk for death from any cause, according to an observational study presented here at the American Association of Clinical Endocrinologists 18th Annual Meeting and Clinical Congress. However, questions need to be answered before risk can be accurately determined.

"People have tended to think [PHPT is] a pretty benign, innocuous disease, but that might not be so," lead investigator Sujoy Ghosh, MD, clinical teaching and clinical research fellow at the Ayr Hospital in Scotland, told Medscape Diabetes & Endocrinology.

The study followed 3039 patients diagnosed with PHPT from 1981 through 2007 and looked at the prevalence of new cancers and deaths in these patients. They compared the results with the risk for cancer and mortality in the general Scottish population. Patients with pre-existing cancer or cancer diagnosed within 1 year of the PHPT diagnosis were excluded from the analysis, resulting in a cohort of 2706 patients. Patients were identified from the Scottish Morbidity Records and linked to the Scottish Cancer Registry and Scottish Mortality Records databases. Of these patients, 77% were women, and the mean age was 63.5 years.

Of the 2706 patients with PHPT, during an average follow-up of 15.1 years, 440 patients with PHPT were diagnosed with cancer (standardized incidence rate, 2.026; 95% confidence interval [CI], 1.841 - 2.224; P < .001). A total of 1601 patients died during the study (standardized incidence rate, 3.085; 95% [CI], 2.936 - 3.240; P < .001). For these patients with PHPT, this correlates to a 2-fold increased risk of developing cancer and a 3-fold increased risk for death, compared with the general population.

Dr. Ghosh said the findings have important implications for cancer screening and treatment in patients with PHPT. About 40% to 50% of patients with PHPT undergo surgery now in the most severe cases, but "in the next 4 to 5 years, at the most 10 years down the line, everyone will and should have surgery." He thinks that surgery will reduce the overall cancer rate as well as improve all-cause mortality, compared with patients with PHPT who do not undergo surgery.

Harmeet Singh Narula, MD, FACP, FACE, assistant professor of medicine at Stony Brook University Medical Center in New York and judge of the poster session, told Medscape Diabetes & Endocrinology that "PHPT has a lot of associations — hypertension, cardiac death, and cancer. This is something really important because people don't realize that a lot of associations with PHPT could be cancer. We need a really large number of people to see if treatment of PHPT would reduce the number of cancers."

Dr. Narula cautioned that the current findings are only observational. "That's all it is, and it's an important observation to keep in mind. The question then becomes: Is it the [high] calcium that's . . .a problem, is it the primary hyperthyroidism hormone that's high that's the problem, or is it something completely different? This study has shown that patients with PHPT have cancers more often, and there's a clear risk." But does treating the PHPT get rid of the cancer risk? "We don't know that," he said.

Dr. Ghosh agreed that to confirm the results of this study would require a large number of treatment centers working together for at least 10 years. Most countries would not be able to replicate this study because few countries have national databases similar to those used in this study. "The only countries would be the Scandinavian countries and Scotland," he said.

"It's very difficult to prevent cancers," Dr. Ghosh added. "Some very small studies in the past have indicated an increased rate of cancer [in patients with PHPT], and patients that had surgery had less chance of cancer, but more studies are needed to say with certainty" whether surgical treatment of PHPT would decrease the risk for cancer.

American Association of Clinical Endocrinologists (AACE) 18th Annual Meeting and Clinical Congress: Abstract 511. Presented May 15, 2009.