Alcano, who upended German ace Ralf Souquet to bag the world 9-ball crown in Manila last year, took three of the first four racks then thwarted Calasang’s fightback with a steady game en route to the victory, putting the 34-year-old soft-spoken Calamba native within two wins from annexing the other world crown.
But Alcano will have his hands full against semifinal round opponent Niels Feijen of the Netherlands.
Feijen defeated compatriot Nick Van Den Berg in an all-Dutch quarterfinal duel, 10-2.
The 34-year-old Alcano and Feijen dispute the first finals berth later in the day.
Calasang, unfancied until he bundled out Taiwanese veteran campaigner Hsia Hui-kai, 10-6, in the second round of the knockout stage, actually closed within one rack after winning the fifth, 2-3.
But Alcano, with his soft-break coming to fore, quickly stopped Calasang on his track and won the next two, yielded the next, but won the next four to pull away, 9-3.
Calasang tried to hang on by taking the next rack but Alcano scored on a clean-up to wrap up the encounter.
Alcano earlier beat former world 9-ball champion Thorsten Hohmann of Germany, 10-3, in the first round of the knockout phase then blasted Naif Al Jeweni of Saudi, 10-3, in the Last 16 to advance to the quarterfinal round.
Calansang, on the other hand, nipped fellow OFW Joybe Vicente, 10-9, in the Last 32 then surprised Hsia to arrange a quarterfinal showdown with Alcano.
Still playing at presstime are Dennis Orcollo and Joven Bustamante with the former taking on Swede ace Marcus Chamat and the latter up against the talented Thomas Engert of Germany, who booted out former world No. 1 Francisco "Django" Bustamante, 10-9, Tuesday.
Chamat trounced IPT world 8-ball champion Efren "Bata" Reyes, 10-4, in the Last 16.
On his way to the quarters, Orcollo prevailed over Austrian Bun Nunan, 10-3, then held off Souquet, 10-8, while Joven Bustamante whipped Iranian Farhad Shaverdi, 10-6, and Goran Mladenovic, 10-7, to advance.
The other Filipino player who fell by the wayside was Lee Van Corteza, who bowed to Van Den Berg, 7-10, in the first round.