The risk of cancer among persons with a history of injecting drug use in Sweden – a cohort study based on participants in a needle exchange program

Figures & data

Figure 1. Flow diagram of the potential participants in the study, reasons for exclusion and outcomes for the included participants.

Figure 2. Box plots showing the age distribution among study participants, divided into male and female.

Table I. Baseline characteristics of needle-exchange program participants.

	Included	Excluded
Number in each group	3255	884
Mean birth year	1964	1963
Percentage men	75%	81%
Percentage born in Sweden	85%	82%
Mean year of NEP registration	1996	1996
Median number of visits to NEP	70	1
Mean year of starting amphetamine injection use	1985	1984
Mean year of starting heroin injection use	1991	1990
Amphetamine injection use	88%	85%
Heroin injection use	66%	56%

Table II. Observed and expected number of cancer cases, standardized incidence ratios, and 95% confidence intervals among 3255 injecting drug users in a needle exchange program in Malmö, Sweden (follow-up until 12 December 2007).

		Male (number)				Female (number)
Cancer site	ICD-9*	Observed	Expected*	SIR*	95% CI*	Observed	Expected*	SIR*	95% CI*
Oropharyngeal*	144,146	3	0.41	7.3	1.5–21.2	1	0.04	22.7	0.6–126.6
Digestive tract
Esophagus	150	1	0.42	2.4	0.1–13.4	0	–	–	–
Stomach	151	1	1.00	1.0	0.0–5.6	1	0.17	5.9	0.2–32.6
Colon	153	2	2.18	0.9	0.1–3.3	1	0.55	1.8	0.1–10.1
Rectum	1541	1	1.50	0.7	0.0–3.7	1	0.28	3.6	0.1–20.1
Anus	1542	1	0.09	10.6	0.3–59.3	0	–	–	–
Liver, primary	1550	5	0.39	12.8	4.2–30.0	1	0.05	18.5	0.5–12.5
Respiratory
Larynx	161	3	0.33	9.2	1.9–26.8	0	–	–	–
Trachea, bronchus, lung	162	9	2.81	3.2	1.5–6.1	2	0.58	3.5	0.4–12.5
Skin
Melanoma	172	3	3.40	0.9	0.2–2.6	0	–	–	–
Non-melanoma	173	5	1.42	3.5	1.1–8.2	0	–	–	–
Breast	174	0	–	–	–	2	6.43	0.3	0.0–1.1
Female genital organs
Cervix uteri	180	0	–	–	–	4	1.16	3.5	0.9–8.8
Corpus uteri	182	0	–	–	–	1	0.48	2.1	0.1–11.7
Male genital organs
Prostate	185	4	5.12	0.8	0.2–2.0	0	–	–	–
Testis	186	2	2.52	0.8	0.1–2.9	0	–	–	–
Urinary organs
Bladder	188	4	2.13	1.9	0.5–4.8	1	0.18	5.7	0.2–31.8
Kidney	189	3	1.36	2.2	0.5–6.5	1	0.19	5.3	0.1–29.6
Other and unspecified
Brain	191	1	2.82	0.4	0.0–2.0	0	–	–	–
Endocrine organs*	193.194	0	–	–	–	5†	0.94	5.3	1.7–12.4
Unknown site	199	2	1.13	1.8	0.2–6.4	0	–	–	–
Blood and lymphatic
Non-Hodgkin lymphoma	200	3	1.93	1.6	0.3–4.6	1	0.36	2.8	0.1–15.5
Hodgkin’s disease	201	1	0.60	1.7	0.0–9.4	0	–	–	–
Multiple myeolma	203	1	0.51	2.0	0.1–10.9	0	–	–	–
Myeloid leukemia	205	1	0.64	1.6	0.0–8.7	0	–	–	–
All sites		56	49.79	1.1	0.9–1.5	22	18.72	1.2	0.7–1.8
All sites, entire cohort (male and female)		78	68.50	1.1	0.9–1.4

CI, confidence interval; endocrine organs, the thyroid and other endocrine glands and related structures; expected, number of cancer cases expected using age group, sex and calendar year-specific incidence rates from the Swedish Cancer Registry; ICD-9, International Classification of Diseases, Ninth Revision; SIR, standardized incidence ratio; Oropharyngeal, floor of mouth and oropharynx.

†2 thyroid cancers, 1 parathyroid cancer, 1 cancer of the pituitary gland and 1 cancer of the aortic body

Table III. Prevalence of serological markers for HIV, HBV and HCV.

	All			Male			Female
	Positive	Negative	Missing	Positive	Negative	Missing	Positive	Negative	Missing
Hepatitis C virus	87%	7%	6%	87%	7%	6%	87%	7%	6%
Hepatitis B virus	47%	25%	28%	49%	25%	26%	42%	26%	32%
Human immunodeficiency virus	1%	96%	3%	1%	96%	3%	1%	96%	3%

For HBV: anti-HBV core antibodies; for HCV: anti-HCV antibodies; for HIV: anti-HIV antibodies.

Positive denotes subjects who ever tested positive for the respective marker; negative denotes subjects with no known positive test result for the respective marker; Missing, no data available.