Contralateral prophylactic mastectomy (CPM) use and utility in New Zealand
(NZ) breast cancer patients
Jebb, Abbey1,2; Campbell, Ian3; Shirley, Rachel3; Barrios, Mark4; Porter, David1
1Auckland
City Hospital, Auckland, New Zealand
of Auckland, Auckland, New Zealand
3Waikato Breast Cancer Trust, Waikato, New Zealand
4The Auckland Breast Cancer Study Group, Auckland, New Zealand
2University
Background:
CPM use is increasing internationally, despite uncertain evidence of survival benefit in sporadic
cancers, and with falling contralateral breast cancer (CBC) rates. CPM use in NZ is currently
undescribed.
Methods:
Information for all patients with invasive unilateral breast cancer (UBC) diagnosed between June 2000
and December 2012 was provided by NZ cancer registers. Patients having a mastectomy of the
healthy contralateral breast concurrently or within a year of definitive surgery for UBC were classed as
having had a CPM. Patient and cancer characteristics were compared using Fisher’s exact test, and
survival outcomes determined by log rank test.
Results:
244 of 10,374 patients with UBC underwent CPM. CPM use increased over time, from 2 patients
(0.6%) in 2000 to 46 patients (4.9%) in 2010.
Compared with women not having surgical prophylaxis, CPM patients were significantly younger at
diagnosis (mean 51.2 years, cf. 57.8 years), and more often European (80.7%, cf. 68.7%) or Maori
(10.7%, cf. 8.8%). 44.4% had family history of breast or ovarian cancer affecting a first degree relative
(cf. 19.1%), and 58.1% had a relative of any degree affected (cf. 29.4%). 4.5% having CPM were
BRCA mutation positive (cf. 0.4%).
CPM was more commonly performed in patients with multifocal cancer (68.9%, cf. 18%), lobular
carcinoma (18.6%, cf. 11%), and tumours of higher pathological T stage (T3 or T4 cancer in 9.8%, cf.
6.8% in T1 or T2). Groups were similar regarding nodal status (node positive 37.7%, cf. 36.8%),
tumour grade (grade 3 33.3%, cf. 28.7%) and receptor status (ER positive 78.2%, cf. 80.2%; and
HER2 expression positive 18.1%, cf. 16.1%). The use of endocrine therapy did not significantly differ
between groups (55.6% cf. 60.6%).
With median follow-up of 4.6 years, CPM use did not significantly change survival outcomes (overall
survival HR 0.94, p= 0.74; breast cancer specific survival HR 1.25, p= 0.32) or incidence of
metastases (12.4% cf. 12.0%, p= 0.85). 48 patients without CPM (0.5%) developed CBC, whereas
1234 developed metastases (ratio 26:1).
Conclusion:
CPM use is increasing in NZ despite a very low incidence of CBC. CPM has not improved patient
survival or reduced the risk of developing metastatic disease.