Abstract 320P
Background
It is increasingly appreciated that oligometastatic breast cancer (OMBC) differs from muli-metastatic disease but to our knowledge, basic data such as incidence and clinical presentation at diagnosis are missing or outdated. Purpose of this study was to quantify the incidence of OMBC and to characterize their clinical/biological features at the time of diagnosis.
Methods
A retrospective review was performed on our institutional database of Stage IV BC patients treated from January 2014 to December 2017 (n=767). Patients were classified as OMBC if ≤ 5 distant metastases (met) including primary tumour were detected at diagnosis, regardless whether focal treatment was feasible. Exclusive local relapse without distant met were not included. Number of met and number of sites (brain, lung, liver, skin, bone and lymph nodes) were analysed. Surrogate intrinsic breast cancer subtypes (according to 2013 St Gallen International Expert Consensus) were defined: Luminal A-like, Luminal B-like, Her2-enriched and triple negative.
Results
Of 767 de novo or recurrent stage IV breast cancer patients reviewed, 131 (17 %) had five or less met with a mean of 1.8 met per patient. 86 (66 %) had an oligorecurrence after the primary treatment, and 45 (34 %) were de novo OMBC. Full immunohistochemistry data were available on primitive tumours for 114 patients, allowing cancer classification as Luminal A (19, 17 %), Luminal B (64, 56 %), triple negative (20, 17 %) and Her2 enriched (11, 10 %). One hundred and two (78 %) had less than 2 distant met. 67 patients (51 %) had an 18-FDG PET-Scan for staging, other had at least CT scan. 121 patients had only one affected organ (92 %) and all the others had two. A large majority had bone met (70/131, 53 %). 65 (93 %) OMBC with bone met were luminal A/B and only six of them had non bone met. One patient with brain met (16/131, 12%) had extra encephalic met. No patient with liver met (17/131, 13 %) had extra hepatic met. Among patients with pulmonary met (13/131, 10 %), 2 had mediastinal met, and one had also bone met. 14 patients (11/131 %) had only lymph node met.
Conclusions
OMBC incidence is significant. OMBC is a clinically and biologically heterogeneous entity. Each subgroup may require specific management.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.