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Background: Prior studies examining the cancer risk in polymyalgia rheumatica (PMR) have reported conflicting results, with some indicating an increased risk within 6-12 months after diagnosis [1].
Objectives: This study assessed malignancy risk over the lifetime and across different follow-up periods in a population-based inception cohort of PMR patients.
Methods: All incident PMR cases (n=296) diagnosed between 1987 and 1997 in Aust-Agder County, Norway, were enrolled in a prospective, population-based study [2]. Diagnosis was ascertained clinically by rheumatologists, with all cases fulfilling Bird`s criteria. In the present study, each PMR case was matched by age, sex, and residency to 15 randomly selected population comparators (n=4,440) from the Norwegian Population Registry. Cancer incidence data were obtained from the Norwegian Cancer Registry, a nationwide registry with mandatory reporting of all cancer cases since 1952. Participants were followed until first cancer diagnosis, death or December 31, 2024. Incidence rates of malignancies were calculated as the number of first primary cancers occurring after index date divided by the total person-time at risk in each group, expressed per 1,000 person-years. Malignancy risk was estimated using Cox regression stratified on matched groups. All analyses were adjusted for sex and age by design.
Results: The mean age at PMR diagnosis was 72 years, 67.6% were female, and 95.6% were deceased by December 31, 2024. The overall prevalence of malignancies prior to the index date did not differ between the PMR patients and comparators (Odds ratio 0.68; 95% CI 0.42, 1.09). The median follow-up was 14.1 years (3,748 person-years) in PMR patients and 13.9 years (55,622 person-years) among comparators. Following the index date, 70 PMR patients (23.6%) and 1,104 comparators (24.9%) developed malignancy. PMR was not associated with increased malignancy risk (Hazard ratio [HR] 0.94, 95% CI 0.73, 1.21), nor with significant excess risk for any specific cancer type (Table 1). A non-significantly increased risk of malignancy during the first 6 months after PMR diagnosis was observed (HR 1.84, 95% 0.65, 5.20), with lower risk estimates between 6 and 12 months and comparable rates thereafter (Table 2). In a secondary analysis combining the first 12 months, the HR was 1.18 (95% CI 0.51, 2.72).
Conclusions: PMR was not associated with an increased lifetime risk of malignancy, further reinforcing the evidence against a true association between PMR and malignancy. Our findings support adhering to standard national cancer screening guidelines based on age and sex for patients with PMR.
Incidence and risk of overall and organ-specific malignancies in patients with PMR and matched comparators following the index date.
| Malignancy group (ICD-10) | PMR patients
| Matched comparators
| HR† | 95% CI | ||
|---|---|---|---|---|---|---|
| N | Incidence rate* | N | Incidence rate* | |||
| Any malignancy | 70 | 18.7 | 1,104 | 19.8 | 0.94 | 0.73, 1.21 |
| Lip, oral cavity and pharynx (C00–C14) | 0 | 0 | 8 | 0.14 | NE | - |
| Digestive organs (C15–C26) | 10 | 2.67 | 282 | 5.07 | 0.55 | 0.29, 1.03 |
| Respiratory organs (C30–C39) | 7 | 1.87 | 121 | 2.18 | 0.80 | 0.37, 1.74 |
| Malignant & other melanomas (C43) | 6 | 1.60 | 41 | 0.74 | 2.19 | 0.89, 5.39 |
| Other skin neoplasms (C44) | 12 | 3.20 | 150 | 2.70 | 1.09 | 0.55, 2.13 |
| Bone and soft tissue (C40–41, C45–49) | 0 | 0 | 10 | 0.18 | NE | - |
| Breast (C50) ‡ | 5 | 1.96 | 88 | 2.19 | 1.05 | 0.42, 2.64 |
| Female genital organs (C51–C58) ‡ | 2 | 0.78 | 86 | 2.14 | 0.37 | - |
| Male genital organs (C60–C63) ‡ | 11 | 9.22 | 134 | 8.69 | 1.10 | 0.58, 2.08 |
| Urinary tract (C64–C68) | 5 | 1.33 | 60 | 1.08 | 1.26 | 0.43, 3.70 |
| Eye and CNS (C69–C72) | 1 | 0.27 | 9 | 0.16 | 2.00 | - |
| Endocrine glands (C73–C75) | 1 | 0.27 | 3 | 0.05 | 6.08 | - |
| Lymphoid and hematopoietic (C81–C96) | 7 | 1.87 | 65 | 1.17 | 1.84 | 0.81, 4.15 |
| Other/ unspecified | 3 | 0.80 | 47 | 0.85 | 0.91 | - |
Abbreviations: ICD-10; International Classification of Diseases, 10th Revision; N, number of malignancies; HR, hazard ratio; CI, confidence intervals; NE = Not estimable due to absence of events in the PMR group.
* Incidence rate calculated as first primary cancers after index date divided by the total person-time at risk, per 1,000 person-years.
† Estimated by Cox regression stratified on matched groups.
‡ Opposite sex excluded respective analysis
Risk of malignancy across different follow-up periods after PMR diagnosis: incidence rates and hazard estimates.
| PMR
| Matched comparators
| HR† | 95%CI | |||
|---|---|---|---|---|---|---|
| N | Incidence rate* | N | Incidence rate* | |||
| overall | 70 | 18.7 | 1104 | 19.8 | 0.94 | 0.73, 1.21 |
| 0-6 months | 4 | 27.2 | 32 | 14.6 | 1.84 | 0.65, 5.20 |
| 6-12 months | 2 | 13.9 | 44 | 20.7 | 0.69 | 0.17, 2.85 |
| 1-2 years | 5 | 18.1 | 69 | 17.0 | 0.99 | 0.40, 2.45 |
| 2-5 years | 12 | 15.8 | 196 | 18.0 | 0.92 | 0.51, 1.66 |
| 5-10 years | 16 | 15.9 | 265 | 18.5 | 0.80 | 0.48, 1.34 |
| 10-20 years | 24 | 22.2 | 342 | 21.4 | 1.03 | 0.66, 1.61 |
| >20 years | 7 | 20.9 | 156 | 25.6 | 0.88 | 0.34, 2.26 |
Abbreviations: N, number of malignancies; HR, hazard ratio; CI, confidence intervals.
* Incidence rate calculated as first primary cancers after index date divided by the total person-time at risk, per 1,000 person-years.
† Estimated by Cox regression stratified on matched groups.
REFERENCES: [1] Muller S et al. Is cancer associated with polymyalgia rheumatica? A cohort study in the General Practice Research Database. Ann Rheum Dis. 2014;73(10):1769–73.
[2] Gran JT, Myklebust G, Wilsgaard T, Jacobsen BK. Survival in polymyalgia rheumatica and temporal arteritis: a study of 398 cases and matched population controls. Rheumatology (Oxford). 2001;40(11):1238–42.
Acknowledgments: NIL.
Disclosure of Interests: None declared.