Ever wonder what happened to prospects that just stopped? Well, here is one: Melvin Cumba

Racked up a decent 10 fight, 5 ko undefeated streak from 1998 to 2005- with some missing years he did not fight. Didn't fight at all in 2001, 2002 or 2004: Melvin Cumba - Boxer

Well, he has drug and prison problems:
2009 Heroin arrest: Massachusetts Man Arrested After Shooting Heroin In Supermarket Bathroom — Massachusetts Criminal Defense Attorney Blog

Currently: Booked on petty theft and drug related charges: Melvin Roberto Cumba's Record Orange County, FL - 10/12/2014

Most likely he had a series of years like this.

See one of his fights: