From the Guidelines
Lobular breast cancer is not considered more aggressive than invasive ductal carcinoma, as evidenced by the largest phase III cohort of lobulars analyzed, which showed no difference in aggressiveness between the two types 1.
Key Characteristics of Lobular Breast Cancer
- Typically grows more slowly and has a better short-term prognosis than invasive ductal carcinoma
- Can be more difficult to detect on mammograms and physical exams due to its growth pattern
- Tends to be hormone receptor-positive (estrogen and progesterone) and HER2-negative, which generally responds well to hormone therapy
Treatment Approach
- Similar to invasive ductal carcinoma, including surgery, radiation, and systemic therapies based on the specific characteristics of the tumor
- The aggressiveness of any breast cancer is more accurately determined by factors like grade, stage, hormone receptor status, and molecular subtype rather than whether it's lobular or ductal
Important Considerations
- Late recurrence is a unique pattern of lobular breast cancer, sometimes appearing 10-15 years after initial treatment
- The Endopredict study, referenced in the St. Gallen International Consensus Guidelines for treatment of early breast cancer 2021, supports the notion that lobular breast cancer is not more aggressive than invasive ductal carcinoma 1
From the Research
Comparison of Lobular and Ductal Carcinoma
- Lobular breast cancer is believed to be more often multicentric and bilateral compared with invasive ductal cancer (IDC) 2.
- However, studies have shown that local control and survival are similar to IDC, suggesting that ILC can be treated similarly to IDC with good results 2.
- The incidence of invasive lobular carcinoma has increased in recent times due to hormone replacement therapy and improvement in diagnostic modalities 3.
Biological Characteristics
- Invasive lobular carcinomas (ILCs) are a distinct entity with different regulating genetic pathways, characteristic histologies, and different biology compared to IDC 3.
- ILCs often exhibit estrogen receptor positivity and Her2 neu negativity, making endocrine therapy a common treatment approach 3.
- A higher frequency of mutations has been observed in ILC, with more cases of multiple mutations 4.
Treatment Outcomes
- Combined chemo-endocrine therapy (CET) has been shown to confer better overall survival (OS) over endocrine therapy (ET) in patients with HR+/HER2+ ILC 5.
- Chemotherapy followed by endocrine therapy and Anti-Her2 therapy has been shown to be the most effective treatment modality in HR+/HER2+ ILC 5.
- ILC has been found to respond well to adjuvant hormonal therapy, with improvement in survival in patients who received HT compared with matched patients with IDC 6.
Recurrence Patterns
- HER2-positive ILC has been found to have a different pattern of first recurrence compared to HER2-positive IDC, with a higher frequency of bone and visceral recurrences 4.
- No difference in the recurrence rate between the two histologies has been observed in patients treated with adjuvant trastuzumab 4.