'touch on the topic' is correct and usable in written English.
You can use it to refer to introducing a topic or discussing it briefly. For example, "We don't have enough time to fully discuss the issue of climate change, so I'm just going to touch on the topic."
But it did dare to touch on the topic that undoubtedly played a large part in the referendum's result.
"I don't even want to touch on the topic of 'black quarterback' because I think this game is bigger than black, white or even green," the fifth-year Panther said.
A very old Thing joins a crippled Superman, an over-stretched Mr. Fantastic, and a comatose Catwoman in The Nursing Home, the artist's series of darkly humorous pieces that touch on the topic of aging. .
The patient can for example touch on the topic without going directly to a discussion on own impending death.
Previous studies have touched on this topic.
Of the three comics on the early bill, only one, Russ Meneve, touched on the topic, and only glancingly.
The whole notion of a "green pregnancy" may seem oxymoronic to the hard-core tree huggers among us: My most eco-minded friends would quip that the greenest way to have a pregnancy is to not have one at all (I've previously touched on the topic of population control and the environment).
But the American non-fiction list contains as yet only a single title that touches on the topic, Jere Longman's "Among the Heroes", about the passengers on Flight 93 who fought back.
There have been several attempts, including Anne Nelson's "Guys," which took an instant-cake approach to grief, and Neil LaBute's recent "The Mercy Seat," touching on the topic with his usual mix of derision and dark humor.
In a broad-brush speech, which frequently touched on the topic of freedom and Berliners' resilience, he could not fail to mention the concern felt across Europe about more modern-day encroachments on individual liberty, the recent revelations of internet surveillance and US drone warfare – issues which dominated his 25-hour visit to the German capital.
Carr "wrote a number of critical/unflattering articles about HW over the years," the document says, "none of which touched on the topic of women (due to fear of HW's retaliation, according to HW)." Weinstein's relationships with the private investigators were often routed through law firms that represented him.
