GWANGJU, South Korea – After announcing to the world in January that he was diagnosed with testicular cancer, Nathan Adrian was “home” Sunday at the 18^th FINA World Championships.

As he has done so often in the past, Adrian anchored the American men’s 400m free relay to victory on the first night of competition, he and his teammates – Caeleb Dressel, Blake Pieroni and Zach Apple – setting a meet record in 3:09.06.

“It’s not anything anyone’s prepared to deal with – sitting down with a doctor and learning you have cancer,” Adrian said. “Fortunately, mine was treated with just surgery. The good thing is swimming brings me back to home base. Being on the block with three excellent, excellent swimmers that threw down great legs for me, getting me in the spot that I was – that’s home. That brings me away from the cancer stuff. That brings me away from the anxiety that this might come back at any time, so that was huge for me.”

As much as Adrian needed that swim for peace of mind, his teammates needed him for the experience and leadership he brings to the pool.

The U.S. battled with Russia the whole way in that relay, with Dressel jumping out to a slight, two-tenth-of-a-second lead. Pieroni maintained the Americans’ position out front before Apple put about a second between them and the Russians with the fastest split (46.86) in the field. From there, Adrian held off Evgeny Rylov for the win.

“The last leg is just about getting your hand on the wall first,” Adrian said. “You’ve got to kind of adjust your strategy based on what’s going on, because it can be a little bit of a wave pool in there. I’ve had a lot of experience doing it, so fortunately I went in there knowing what I needed to do.

“The last 15 (meters) hurt really bad, as you could probably see. I had to take two months off of training (for cancer treatment), but that will certainly be there come next year.”

The men’s 400m free relay was one of four medals for the U.S. Sunday, the only gold. The Americans also won a silver and set an American record in the women’s 400m free relay (3:31.02), a silver in the women’s 400m free, and a bronze in the women’s 400m free.

In addition to his gold in the relay, Dressel set an American and World Championship meet record in the semifinals of the men’s 50m butterfly in 22.57. The former meet record, held by Milorad Cavic of Serbia, stood at 22.67. The former American record, held by Dressel, was 22.76.

Dressel is the top seed heading into tomorrow night’s finals. Teammate Michael Andrew will also be swimming in tomorrow night’s finals, qualifying fifth in 22.95.

“It’s a pretty ideal day,” Dressel said. “You can’t ask for everything, but the semifinal of the fly was good. I still don’t know too much of what I’m doing in the fly. I’ve got to figure it out a little bit better. I don’t think the time I went is going to stand to win, so I’ve got to get a little bit quicker in that.

“But the relay was great. All the guys stood up, especially Zach on that split, and Nathan – he just does his job every single time. It’s just that experience. You can’t beat that experience. That’s a tough leg, anchoring that with the Russians coming on quick. I think I have the morning session off tomorrow. Right now I’m going to focus on eating and getting some sleep and then focusing on tomorrow.”

Turning to the women’s 400m free relay, Americans Mallory Comerford, Abbey Weitzeil, Kelsi Dahlia and Simone Manuel were in the hunt the whole way, jockeying for position with a few other teams, including Australia, Canada and Sweden.

Weitzel put the U.S. out in front in the second leg, and while Manuel was able to pass Canada in the final 50 meters for silver, Australia proved too strong, winning gold in a meet record time of 3:30.21. The U.S. took silver. Canada won bronze in 3:31.78.

In the women’s 400m freestyle, Ariarne Titmus of Australia dealt Katie Ledecky her fist loss in that event at a major international competition.

Titmus jumped out to a lead in the first half of the race, only to have Ledecky pull ahead at the 250-meter mark. Ledecky led by half a body length at 300 meters, but couldn’t hold Titmus off down the homestretch. Titmus touched in 3:58.76, followed by Ledecky in 3:59.97. American Leah Smith took bronze in 4:01.29.

Going into tonight’s race, Ledecky held 10 of the top 10 performances of all time in the 400, including the world record of 3:56.46. Titmus’ performance now ranks eighth on that list.

“I’m all right,” Ledecky said. “Obviously it wasn’t the swim I wanted, and it didn’t go as I wanted it to, but I have a lot of racing ahead of me, so I’ve got to move on. I made a move, and came into the last turn and felt like I could barely push off. My legs and arms just kind of tightened up that last 50. She took advantage of that and had a great swim.

“I knew she was going to be really tough, and I know she takes the race out fast, and that I had to be prepared for that. I felt like I stayed pretty calm during the race, but when I made my move, she responded, and when I tightened up, she ran me right down. I’ll rebound off this and get focused on my next races.”

Zane Grothe, the lone American competing in the finals of the men’s 400m freestyle, finished eighth in 3:45.78. Sun Yang of China was first in 3:42.44, followed by Mack Horton of Australia in 3:43.17 and Gabriele Detti of Italy in 3:43.23.

Semi-finals

The men’s 50m butterfly was one of four semi-finals contested Sunday. Swimmers also competed in the semifinals of the women’s 100m butterfly, men’s 100m breaststroke and women’s 200m IM. The top eight swimmers in each event advance to tomorrow night’s finals.

Americans competing in semifinals included Dahlia, who finished seventh in the women’s 100m butterfly in 57.06; Katie McLaughlin, who finished ninth in the women’s 100m butterfly in 57.23; Andrew Wilson, who finished fifth in the men’s 100m breaststroke in 58.95; Melanie Margalis, who finished third in the women’s 200m IM in 2:09.14; and Ella Eastin, who tied for ninth in the women’s 200m IM 2:10.72.

In other noteworthy swims, Great Britain’s Adam Peaty set a world record in the semifinals of the men’s 100m breaststroke in 56.88.