title: "Resurrection of clinical efficacy" after resistance to endocrine therapy in metastatic breast cancer.
abstract: BACKGROUND
  In a significant proportion of metastatic breast cancer (MBC) patients whose tumour has progressed within 6 months of endocrine therapy (de novo resistance), it is generally believed that the chance of achieving clinical benefit (CB) with further endocrine therapy is minimal.
  
  
  METHODS
  Data was retrieved from a prospectively updated database of metastatic breast cancer. Relevant data was exported to SPSS software for statistical analysis.
  
  
  RESULTS
  In oestrogen receptor (ER) positive MBC patients with assessable disease, CB was achieved in 159 (71.3%) (1st line) patients. When these patients were put on further endocrine therapy, the CB rates were 63.2% (on 2nd line), 46.1% (on 3rd line) and 20% (on 4th line) with a median duration of response (DOR) in those with CB of 22, 12, 11 and 15 months respectively. The remaining 64 (28.7%) patients had de novo resistance on 1st line endocrine therapy. Seventeen of these patients were treated with further endocrine therapy. The CB rates were 29.4% (on 2nd line) and 22.2% (on 3rd line) with a median DOR in those with CB of 22.7 months and 14 months respectively.
  
  
  CONCLUSIONS
  The chance of further endocrine response continues to decrease with each line of therapy, yet CB is still seen with reasonable duration even with a 4th line agent. In addition, further endocrine response, with long duration, can be seen in a significant proportion of patients who have developed de novo resistance to 1st line endocrine therapy. The use of further endocrine therapy should not be excluded under these circumstances.
authors.affiliation: Professorial Unit of Surgery, City Hospital, University of Nottingham, Nottingham, NG5 1PB, UK. amit.agrawal@nottingham.ac.uk
authors.forename: Amit
authors.initials: A
authors.lastname: Agrawal
authors.forename: John F R
authors.initials: JF
authors.lastname: Robertson
authors.forename: K L
authors.initials: KL
authors.lastname: Cheung