To measure the increase in uptake of BCT in NSW and its determinants, we ex
amined Cancer Registry records of 2020 women with breast cancer in 1992 and
2883 in 1995 linked to records of their surgical treatment in the NSW Inpa
tient Statistics' Collection. In parallel, we examined trends and determina
nts in axillary surgery for breast cancer. Breast conservation increased fr
om 39% of breast cancer in 1992 to 45% in 1995, mainly in women with the sm
allest cancers. In 1995, mastectomy was still most common in women with lar
ger cancers (OR for breast cancers 3+ cm relative to <1 cm = 5.6. 95% CI 2.
9-10.7) and cancers that had spread beyond the breast (OR = 2.0. 95% CI 1.4
-2.7 relative to localized to the breast). Urban women had fewer mastectomi
es than rural women. Axillary surgery, common in 1992 (78%) and 1995 (82%),
fell steeply with increasing age and more often accompanied mastectomy (93
% in 1995) than BCT (67% in 1995). In 1995 the odds for axillary surgery we
re some two-fold or more higher for all cancers 1 cm or more in diameter co
mpared with those <1.0 cm and highest for 2.0-2.9 cm cancers (OR = 3.3 95%
CI 1.7-6.7 relative to <1.0 cm). Regional spread of the cancer at diagnosis
was not a strong predictor. In the absence of collection of treatment data
by cancer registries, linkage of cancer registry records with hospital inp
atient data is an effective alternative for monitoring breast cancer treatm
ent trends. (C) 2001 Cancer Research Campaign.