Certainly yes but is difficult to guess how to do it even it is somehow documented in https://www.mapserver.org/mapfile/expressions.html
The function to use is "tostring"
tostring ( n1, “Format1” )
uses “Format1” to format the number n1 (C style formatting - sprintf).
Example with field SQKM that contains areas in square kilometers with decimals. Notice also how you can add the unit into the label.
COLOR 58 132 59
OUTLINECOLOR 30 30 30
END # STYLE
TEXT (tostring(([SQKM]),"%.0f")+" km2")
COLOR 150 200 200
END # CLASS
The result looks like this
It is possible to combine with math and show thousands of square kilometers with