Worse outcomes in infiltrating lobular vs ductal carcinoma
Patients with infiltrating lobular carcinoma (ILC) suffer from poorer prognoses compared with those with infiltrating ductal carcinoma (IDC), a new study shows. Moreover, patients with oestrogen receptor-positive (ER+) and progesterone receptor-negative (PR-) tumours have the worst outcomes.
The study included 796,335 breast cancer patients, of which 10.7 percent (n=85,048) had ILC and 89.3 percent (n=711,287) had IDC. Those with squamous cell carcinoma and papillary cystadenocarcinoma histological subtypes and those with mixed diseases were excluded.
Patients in the ILC group tended to have larger tumours (p<0.0001), later stage cancers (p<0.0001), higher percentage of metastatic disease (p<0.0001) and more positive lymph nodes (p<0.0001) compared with those in the IDC group.
Over a median follow-up of 5.5 years, overall survival (OS) for ILC patients was better before 60 months (hazard ratio [HR], 1.118; p<0.0001), while OS beyond 5 years was better for IDC patients (HR, 0.775; p<0.0001).
In terms of disease-specific survival, patients in the IDC group had consistently better outcomes in both the short and long term (HR, 0.809; p<0.0001).
OS and DSS were also significantly better in IDC patients than in ILC patients regardless if they were ER+/PR+ (HR for OS, 0.92; p<0.0001; HR for DSS, 0.66; p<0.0001) or ER+/PR- (HR for OS, 0.81; p<0.0001; HR for DSS, 0.71; p<0.0001).
In both groups, the most common site of metastasis was the bone, with 91.52 percent metastases in the ILC group and 76.04 percent in the IDC group. This was followed by the liver (19.64 percent), lung (13.61 percent) and brain (4.23 percent) in the ILC group, and by the lung (37.11 percent), liver (30.53 percent) and brain (8.24 percent) in the IDC group.