Background/Purpose

Few studies have explored risk of cancer in psoriatic arthritis (PsA). There are concerns that the risk may be raised, not only by the primary disease, but also by the treatments given including conventional disease modifying treatments (especially ciclosporin), tumour necrosis factor inhibitors (TNFi) and phototherapy. Skin psoriasis itself is associated with an increased risk of non-melanoma skin cancer (NMSC). Our objective was to compare the incidence of cancer among a cohort of patients with severe PsA patients receiving tumour TNFi to that in the general population.

Methods

All patients with PsA starting a TNFi in the British Society for Rheumatology Biologics Register (BSRBR, recruited 2002-2006) were included. Cancers were identified by flagging patients with the national cancer register which reported using the International Classification of Diseases version 10 (ICD 10). All patients were followed from registration (start of TNFi) until death or 2011/12/31, whichever came first.  Standardised incidence ratios (SIR) with 95% confidence intervals (CI) were calculated using age and gender specific cancer rates for the general English population for (1) overall cancer risk (ICD 10: C1-C9) and (2) NMSC (C44) for the whole cohort and separately for men and women. 

Results

709 patients contributed 5286 patient years of follow-up; mean (SD) age was 45.7 (11.2), median disease duration (IQR) was 11 (6-17) years. Mean (SD) DAS28 was 6.0 (1.2).  11 (1.6%) patients had a cancer registered prior to baseline, none of which had a further cancer.  Nearly all (98%) had previous or current exposure to methotrexate at baseline and 45.6% had previous or current exposure to ciclosporin. Information on baseline PUVA exposure was only available for 163 (23%) patients and 11 (6.7%) had been exposed. 27 cancers in 26 patients were observed, including 14 skin cancers (12 NMSC and 2 melanomas). Overall, there was no increased risk of malignancy observed in this cohort (SIR 0.87, 95% CI 0.58-1.27) compared to the general population. There was a significantly increased incidence for NMSC although the precision of the estimate was low (SIR 1.97, 95% CI 1.02-3.45) likely reflecting low number of events.

Table: Overall and non-melanoma skin cancer standardised incidence ratios 

	Overall n=709		Male n=331		Female n=378
Total follow-up (person-years)	5286		2437		2849
	O/E	SIR (95% CI)	0/E	SIR (95% CI)	0/E	SIR (95% CI)
All malignancies	27/30.9	0.87 (0.58-1.27)	13/12.8	1.02 (0.54-1.74)	14/18.1	0.77 (0.42-1.29)
NMSC	12/6.1	1.97 (1.02-3.45)	4/2.9	1.40 (0.38-3.58)	8/3.2	2.49 (1.07-4.91)

O = Observed, E = Expected

Conclusion

In this population of severely active PsA patients recruited early in the TNFi-era, the overall incidence of malignancy was reassuringly similar to that of the general population. Incidence of NMSC was increased, which may be related to PsA itself, skin psoriasis, phototherapy and/or immune-modulatory treatment.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-of-cancer-in-patients-with-severe-psoriatic-arthritis-requiring-tumour-necrosis-factor-alpha-inhibition/