Metastatic dormancy imposed by the primary tumor: does it exist in humans?

Area of Science:

• Oncology
• Cancer Biology
• Tumor Microenvironment

Background:

• Occult micrometastases can emerge post-primary tumor removal.
• Primary tumors may secrete factors inhibiting angiogenesis at distant sites.
• Metastatic dormancy is linked to apoptosis and angiogenesis regulation.

Purpose of the Study:

• To investigate if primary tumors inhibit angiogenesis in human cancers.
• To explore the clinical relevance of primary-tumor-induced angiogenesis inhibition.
• To assess therapeutic consequences for cancer treatment.

Main Methods:

• Analysis of metastasis tissue samples before and after primary lesion removal.
• Measurement of vascular density in metastases.
• Assessment of metabolic activity using (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET).

Main Results:

• Absence of the primary tumor increased vascular density and metabolic activity in metastases.
• Mitotic activity showed a mild increase.
• Apoptosis levels significantly decreased post-primary tumor removal.

Conclusions:

• A mechanism of primary-tumor-induced angiogenesis inhibition maintains metastatic dormancy.
• This natural inhibition could be leveraged to avoid neoadjuvant angiogenesis inhibitors like bevacizumab.
• Chemotherapy alone may suffice when the primary tumor is present, due to its inherent angiogenesis inhibition.