Background/Purpose:

To investigate the cancer risk in patients with biopsy-proven giant cell arteritis (GCA).

Methods:

The study population consisted of 830 patients (74 % women) with biopsy-proven GCA diagnosed between 1997 and 2010. The mean age at diagnosis of GCA was 76.3 years, 77.2 years for men and 75.8 for women. The cohort was cross-linked with data from the Swedish Cancer Registry. The patients were followed from GCA diagnosis until death or December 31, 2013. All malignancies that occurred throughout the observation time were identified. Malignancies were divided into two groups; those preceding the date of the GCA diagnosis and those subsequently diagnosed. As a measure of relative risk, the age- and sex standardized incidence ratios (SIR) were calculated compared to the background population, i.e. the ratio of the incidence of observed cancer cases after the diagnosis of GCA to that of the expected number, based on cancer rates in the background population. SIRs were calculated for all types of cancer combined and for site-specific cancers.

Results:

107 patients (13%) were diagnosed with a total of 133 malignancies after the onset of GCA. Malignancies in the same organ/system were excluded, and thus 118 malignancies were included in SIR calculation. The overall risk for cancer after the GCA diagnosis was not increased with a SIR 0.98 (95% CI 0.81 – 1.17). However, there was an increased risk for myeloid leukemia SIR 2.31 (95% CI 1.06 – 4.39) and a reduced risk for breast cancer SIR 0.33 (95% CI 0.12 – 0.72) and upper gastrointestinal (GI) tract cancer SIR 0.16 (95% 0.004- 0.91). Rates of other site-specific cancers, e.g. cancer of the skin, lower GI tract, prostate or respiratory system, were not different from the expected (Table 1).

Conclusion:

The overall risk for cancer in GCA patients was not increased compared to the background population. However, we found an increased risk for leukemia and a decreased risk for breast and upper gastrointestinal tract cancer. Possible explanations for these findings include effects of inflammation on tumor genesis and differences in other exposures that contribute to cancer risk. For example, some traditional risk factors for breast cancer, such as obesity, diabetes and late menopause, have been reported to be reduced in patients with GCA.

Table 1. Site-specific and total standardized incidence ratio of cancer in 830 patients with biopsy-proven GCA

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/malignancies-in-giant-cell-arteritis-a-population-based-cohort-study/