Breast Cancer in RA: No Effect of AntiRheumatic Therapy Fred Wolfe1, Kaleb Michaud1 1Outcomes Resear

1
Breast Cancer in RA No Effect of Anti-Rheumatic
Therapy  Fred Wolfe1, Kaleb Michaud11Outcomes
Research, National Data Bank for Rheumatic
Diseases, Wichita, United States
Abstract BREAST CANCER IN RA NO EFFECT OF
ANTI-RHEUMATIC THERAPY   Fred. Wolfe, Kaleb
MichaudOutcomes Research, National Data Bank for
Rheumatic Diseases, Wichita, United States
Background Prior to the anti-tumor necrosis
factor (TNF) era epidemiologic studies of
rheumatoid arthritis (RA) and cancer showed that
cancer rates were increased for lymphoma, lung
cancer and non-melanoma skin cancer, and were
decreased for GI malignancies. However one large
Danish study from a linked RA-cancer registry
found the rate of breast cancer to be decreased
in RA (relative risk 0.8 (95 C.I. 0.7 to 0.9).
The introduction of anti-TNF therapy has
increased interest in RA and cancer because of
the possibility that biologic therapy might alter
the cancer risk and we have previously shown
that anti-TNF use was associated with an increase
in non-melanoma cancer rate (Hazard Ratio (HR)
1.19 (95 C.I. 0.01 to 1.41). However, relative
risks may not provide sufficient detail to
evaluate apparent increases in cancer that may be
seen in clinical trials of anti-TNF therapy.
Objectives To describe the overall and
age-specific incidence rate for breast cancer in
RA and non-RA rheumatic disease patients, and to
describe factors associated with breast cancer,
including treatment factors. Methods We used a
longitudinal rheumatic disease data bank of
16,398 female RA patients who did not have known
breast cancer at their first assessment. Patients
were followed for up to 6 years. As a control
group, 4,763 non-RA rheumatic disease patients
were similarly studied. Predictors of breast
cancer were studied in the RA and the combined
group. Breast cancer was documented by medical
and death records. Results The age-specific
incidence rate for breast cancer in RA is
displayed in Table 1. The overall incidence was
343 (95 C.I. 292 to 401) per 100,000 patient
years of exposure, and the age adjusted incidence
rate was 141.9. By comparison, the US SEER cancer
data base indicated that the rate for all race
women was 137.5 and the rate for Caucasian women
was 143.2. However, in comparison with non-RA
rheumatic disease patients, the age, education
and BMI adjusted hazard ratio was 0.76 (95 C.I.
0.52 to 1.10), p0.108. We found no statistically
significant associations between breast cancer
and current, prior or lifetime RA treatments,
including anti-TNF, methotrexate and
corticosteroid treatments. Nor was any clinical
status variable, including HAQ, global severity,
activity indices or utility measures, predictive
of breast cancer development. Except for 10-year
difference in age (HR 1.43 (95 C.I. 1.27 to
1.62)), no demographic variable predicted breast
cancer, including education, smoking and body
mass index. Conclusion There is no evidence to
date that RA therapy alters the risk of breast
cancer. It remains possible that exposure to
anti-TNF therapy, however, is too short for a
firm conclusion regarding this treatment. Breast
cancer rates in RA are not different from
national rates. Although we found no reduction in
rates of breast cancer in RA compared with
control patients with non-RA rheumatic diseases
(Hazard Ratio 0.76 (95 C.I. 0.52 to 1.10),
p0.108), our data are not inconsistent with a
slight reduction in risk, as shown in the Danish
study. References Mellemkjaer L, Linet MS,
Gridley G, Frisch M, Moller H, Olsen JH.
Rheumatoid arthritis and cancer risk. Eur J
Cancer 1996 32A(10)1753-1757.
Table 1. The incidence of breast cancer in 16,398
women with RA.
Table 3b. Differences between breast cancer ()
and breast cancer (-) RA patients, adjusted for
age.
Table 3a. Differences between breast cancer ()
and breast cancer (-) RA patients, adjusted for
age.



Table 2. The risk of breast cancer in 16,398 RA
patients vs. 4,675 non-RA rheumatic disease
patients.

• Conclusions
• There is no evidence to date that RA therapy
  alters the risk of breast cancer.
• It remains possible that exposure to anti-TNF
  therapy, however, is too short for a firm
  conclusion regarding this treatment.
• Breast cancer rates in RA are not different from
  US national rates.
• Although we found no reduction in rates of breast
  cancer in RA compared with control patients with
  non-RA rheumatic diseases (Hazard Ratio 0.76 (95
  C.I. 0.52 to 1.10), p0.108), our data are not
  inconsistent with a slight reduction in risk, as
  shown in the Danish study.

Supported by a grant from Bristol-Myers-Squibb