
Leiomyosarcoma, once removed, has an alarming tendency to return.  Surveillance is necessary so as to identify recurrences when they are small and surgically resectable.  Scans therefore become a very important part of living with LMS.  

What is surveillance?  It means watching.  It means regular scans, usually every three months for the first two years, then every six months for the next three years, then yearly, so that any returning LMS is picked up early and small.  Dealing with recurrences when they are small is easier, and they are more often surgically removed.  

If each recurrence can be dealt with appropriately, remissions [when there is No Evidence of Disease, NED,] will be achieved, prolonging survival time.

With high grade LMS, a majority of LMS recurrences happen by two years.  And it would make sense also, that the tumors that recur earlier are the more aggressive, higher mitotic index tumors that are reproducing faster.  

So close surveillance for the first two years is important.  And it is every three months because the tumors that recur earlier also grow faster, and might easily get inoperable if you wait six months between scans.

After two years, there is still a recurrence rate, although much lower.  And these tumors might grow more slowly as well.  So the scan interval is lengthened to six months.   

After five years there is still a recurrence rate, but low.  And again, the probability is that the tumor would be slower growing.  So yearly scans are done.  It is not known how long one must do these; there are reports of LMS lung metastases discovered at 10 to 20 years after initial diagnosis.