Amazing news ... Baltimore Orioles star Trey Mancini just finished 6 months of chemotherapy treatments -- and his GF couldn't have been happier, saying, "This is the best day ever!!!!"
Mancini has been battling stage-3 colon cancer ever since docs discovered a tumor last spring ... and the road for the MLB slugger to get better has been tough as hell.
Mancini described getting chemo treatments amid the coronavirus pandemic as "crazy" ... and added he's been forced to receive his drugs through a mediport in his chest.
But Mancini's GF, Sara Perlman, said Monday the 28-year-old was finally done with his chemo treatments ... and she was THRILLED for Baltimore's outfielder!!
"TREY DID IT!!!!" Perlman said. "He completed chemotherapy!!! What a six months it has been. I’ve never been more proud & joyful."
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She added, "Thank you for all the love and support. We are SOOOO grateful!!!!"
The Orioles, meanwhile, gave Mancini a sweet present for completing the treatments -- a signed team photo with personal messages from the guys.
Mancini was moved by the gift ... saying of the framed pic, "I'm speechless right now. This is one of the coolest things I've ever gotten."
Trey -- who's sat out this season to fight the disease -- has said repeatedly it's his goal to join back up with his teammates for spring training next March.