Læknablaðið - 15.05.1992, Page 55

LÆKNABLAÐIÐ
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with positive patch tests, but not in 3,675
females. When individual sites were analyzed,
cancers of the lung, larynx, uterine cervix
and prostate were significantly increased.
The implications of this are uncertain, but
might indicate a common failure of the
immune system which might predispose for
both conditions, or be a marker of certain
occupational exposure.
Risk of squamous cell carcinoma of the skin
was increased in 4,799 patients treated with
PUVA. Male patients who had received more
than 200 treatments had over 30 times the
incidence of squamous cell cancer found in
the general population. Significant increases
were also found in the incidences of some
intemal malignancies. This study confirms
previous reports of dose-dependent increase
in the incidence of squamous cell cancer in
patients treated with PUVA.
The risk of malignancy was clearly increased
in 392 patients with dermatomyositis (2.4; 1.6
to 3.6), but in 396 patients with polymyositis
the associated risk was lower (1.8; 1.1 to
2.7). The increase in risk was mirrored in
cancer mortality in dermatomyositis patients
but not in polymyositis patients. The results
suggest that in dermatomyositis patients
there is truly an increased risk of malignancy
but the increase in incidence of malignancy
in polymyositis patients might be due to
diagnostic suspicion bias.