Does "not significant" growth have significance in a diagnosis?

I’m not asking for medical advice. I’m asking whether no ‘significant’ growth has an absolute measure in the results from a medical test.

A friend of mine was relieved to learn that an MRI taken last week of a benign tumor showed no significant growth from one done six months ago. At this time they will monitor the situation, presumably with another MRI in three months. She’s in very good hands.

I’ve learned to pay attention to quantifying (qualifying?) words and now I’m curious about the significance of ‘significant’.