Polymyalgia rheumatica and cancer risk: the importance of the diagnostic set

In the last few years, the relationship between polymyalgia rheumatica (PMR) and cancer has been considered with very different conclusions. In particular, in 2010, Ji et al examined the overall and specific cancer risks among Swedish subjects following hospitalization for PMR and giant cell arteritis and noted that the risk of cancer was highest in the first year after hospitalization (of 3941 total cancer diagnoses, 783 [19.1%] were in the first year). In 2013, Muller et al, using data from General Practice Research Database, highlighted that elderly patients with a PMR diagnosis were significantly more likely to receive a cancer diagnosis in the year after PMR diagnosis (313/667 cancer cases [69%]). In a series of 200 patients with PMR consecutively observed in our geriatric rheumatologic outpatient clinic from 2004 to 2014, we have observed 51 cancer cases; five of these were observed in the first year after diagnosis of PMR (percentage equal to 9.8%). In our article, we point out the importance of the diagnostic set. PMR is a disease that can be managed in a rheumatologic outpatient clinic without patients' hospitalization. On the other hand, hospitalization of the elderly with PMR is useful when there are grounds for suspicion for a paraneoplastic syndrome, and this represents per se an important inclusion bias. The studies from institutional databases such as those of Ji et al and Muller et al have a very large series but diagnoses of the various diseases are based on coding and not always confirmed by individual medical record review. On the other hand, studies based on cohorts followed by single rheumatologic outpatient clinics can have much smaller data but have a higher diagnostic accuracy, because all patients are visited by rheumatologists and data are usually more accurate. The specificity of geriatric rheumatologic outpatient clinics with respect to elderly patients and to disease with an outpatient management (such as PMR) is often underestimated. In the health care organization of the geographic area that belongs to the hospital "Mariano Lauro", the majority of patients for whom the general practitioner suspects a PMR are visited by a rheumatologist, as a consequence of an active collaboration between the general practitioner and the rheumatologist and thanks to the very short (5-7 days on average) waiting lists. In our cohort, diagnosis of PMR must be confirmed at least by a second rheumatologist. No change in the initial diagnosis was observed in any of our patients with PMR over the years and even after being examined by other colleagues from different centers. The repercussions of cancer risk in the elderly with PMR on health policies are easily understandable, and therefore the detection of all potential bias is mandatory. Data from other rheumatologic outpatient clinics are necessary.