Surgery Might Promote Growth of Metastases

Clinical lore says that resection of a primary tumor can cause previously inapparent metastatic deposits to flare. In a mouse model of breast cancer, researchers tested whether and how this phenomenon might occur.

In a series of experiments in 273 mice that had not developed breast cancer naturally, aggressive mouse breast cancer cells were implanted in various locations (i.e., “pseudo-metastases”). Initially, the tumor cells grew, but then they entered a period of dormancy. This dormancy occurred only in mice with intact immunity, not in immunodeficient mice, which suggests that the immune system contains (but doesn't eliminate) pseudo-metastases. Surgery of any type (not just resection of a primary tumor) led to the aggressive growth of ps…