There is now an update topic scope that you can use for this.
curl -i -sS -X PUT "http://localhost:4200/t/-/101.json" \
-H "Content-Type: multipart/form-data" \
-H "Api-Key: 54096675ed84dcf0016a3b05199cccde67e5175057e53f8e005e2625940a15e6" \
-H "Api-Username: blake.erickson" \
-F "title=8bd599 cae3dfdbf 7210753"
HTTP/1.1 200 OK