Midterm risk of cancer with metal-on-metal hip replacements not increased in a Finnish population

Figures & data

Table 1. Number of patients (n) according to age at operation, and number of person-years (PY) according to the age at follow-up. The non-metal-on-metal cohort consisted of implants with metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic bearing surfaces

	Metal-on-metal cohort				Non-metal-on-metal cohort				Total
	Men		Women		Men		Women		Men		Women
Age	n	PY	n	PY	n	PY	n	PY	n	PY	n	PY
0–9	1	1	–	–	–	–	–	–	1	1	–	–
10–19	5	16	3	16	–	–	–	–	5	16	3	16
20–29	25	136	16	69	4	17	7	29	29	153	23	98
30–39	159	558	67	309	30	119	20	116	189	677	87	425
40–49	741	3,746	471	2,078	143	730	157	578	884	4,476	628	2656
50–59	2,277	11,787	1,643	8,578	850	3,880	922	4,416	3,127	15,667	2,565	12,994
60–69	2,257	19,652	1,581	14,090	2,260	13,980	2,739	16,099	4,517	33,632	4,320	30,189
70–79	763	9,403	594	6,773	3,044	25,854	5,397	39,047	3,807	35,257	5,991	45,820
80–	65	1,276	48	1,036	698	13,610	1,953	33,884	763	14,886	2,001	34,920
Total	6,293	46,573	4,423	32,948	7,029	58,190	11,195	94,168	13,322	104,763	15,618	127,116

PY: person-years

Table 2. Baseline characteristics for the metal-on-metal cohort and for the non-metal-on-metal cohort

Factor	Metal-on- metal cohort	Non-metal-on- metal cohort
Mean age (SD)	59 (10)	71 (9)
Number of women, n (%)	4,426 (41)	11,202 (61)
Primary osteoarthritis, n (%)	9,901 (92)	17,683 (97)
Secondary osteoarthritis, n (%)	827 (8)	552 (3)

Table 3. Observed numbers of cancer cases, the expected numbers of cancer cases approximated from the Finnish population, and standardized incidence ratios with 95% confidence intervals—according to site—are given for the metal-on-metal cohort and for the non-metal-on-metal cohort. The latter cohort consisted of implants with metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic bearing surfaces

	Metal-on-metal cohort					Non-metal-on-metal cohort
Primary site	Obs	Exp	SIR	95% CI	% of cancer	Obs	Exp	SIR	95% CI	% of cancer
All sites	915	973	0.9	0.9–1.0	9	2851	2852	1.0	1.0–1.0	16
Stomach	23	21	1.1	0.7–1.7	0.2	75	74	1.0	0.8–1.3	0.4
Colon	48	55	0.87	0.6–1.2	0.4	187	199	0.9	0.8–1.1	1
Lung	61	95	0.64	0.5–0.8 ^a	0.6	203	260	0.78	0.7–0.9 ^a	1
Corpus uteri	24	22	1.1	0.7–1.6	0.2	78	82	1.0	0.8–1.2	0.4
Prostate	239	216	1.1	1.0–1.2	2	478	461	1.0	1.0–1.1	3
Kidney	31	29	1.1	0.7–1.5	0.3	83	82	1.0	0.8–1.2	0.5
Bladder	32	41	0.8	0.5–1.1	0.3	131	128	1.0	0.9–1.2	0.7
Soft-tissue sarcoma	8	6	1.4	0.6–2.8	0.07	20	17	1.2	0.7–1.8	0.1
Non-Hodgkin lymphoma	37	38	1.0	0.7–1.4	0.3	118	108	1.1	0.9–1.3	0.7
Hodgkin lymphoma	2	2	0.9	0.1–3.1	0.02	3	4	0.7	0.1–2.0	0.02
Multiple myeloma	13	12	1.1	0.6–1.8	0.1	36	41	0.9	0.6–1.2	0.2
Leukemia	17	18	1.0	0.6–1.5	0.2	60	58	1.0	0.8–1.3	0.3
Melanoma	38	36	1.1	0.8–1.5	0.4	105	87	1.2	1.0–1.5	0.6
Basalioma	306	246	1.2	1.1–1.4 ^a	3	913	878	1.0	1.0–1.1	5

Obs: observed number of cancer cases; Exp: expected number of cancer cases based on cancer incidence in the comparable Finnish population; SIR: standardized incidence ratio; CI: confidence interval; % of cancer: the percentage of patients diagnosed with a certain cancer during the follow-up.

^a p < 0.001