Selection of primary breast cancer patients for adjuvant endocrine therapy- is oestrogen receptor alone adequate?

Among 834 patients who had primary breast cancer treated by surgery without adjuvant systemic therapy, 363 had relapse treated by endocrine therapy al one. Patients with oestrogen receptor positive tumours (median: 70 vs. 45 m onths, p < 0.0001) or with non-progression at 6 months of therapy (median: 111 vs. 37 months, p < 0.0001) survived longer than those with oestrogen re ceptor negative tumours or with disease progression respectively, presumabl y due to the effect of therapy. On the other hand, the median disease-free interval, uninfluenced by therapy, showed a similar difference: oestrogen r eceptor positive versus negative = 29 versus 21 months, p < 0.005; non-prog ression versus progression = 40 versus 19 months, p < 0.0001. Patients with oestrogen receptor-positive tumours and non-progression at 6 months had th e longest disease-free interval. The present study has established that the re are factors, other than the oestrogen receptor, inherent in the primary tumour as reflected by the disease-free interval, which affect hormone sens itivity. Selection of adjuvant endocrine therapy based on the oestrogen rec eptor alone would deem inadequate. Further studies to elucidate other possi ble factors are warranted to refine the use of endocrine therapy, especiall y in the adjuvant setting when no indication of response is available.