Scott Blackmun resigned as chief executive of the U.S. Olympic Committee on Wednesday, stepping aside so he can tackle his worsening bout with prostate cancer and to allow the federation to move forward under new leadership to address the sex-abuse scandal that has rocked gymnastics and other sports.

The 60-year-old CEO was diagnosed with prostate cancer in January and did not attend the Pyeongchang Games.

Blackmun leaves as calls for his ouster were growing louder — from two U.S. senators and, more notably, from a number of gymnasts and other athletes who said neither he nor the USOC at large reacted properly to cases including those involving Larry Nassar, the doctor who sexually abused members of the U.S. gymnastics team.

The USOC is conducting an independent review of when Blackmun and others learned the details about abuse cases at USA Gymnastics and whether they responded appropriately.

Susanne Lyons, a member of the board, will step down from that position and serve as acting CEO while the search for Blackmun's replacement begins.

At a news conference to kick off the Olympics, chairman Larry Probst said Blackmun had served the USOC with distinction and the board found no reason to relieve him. In an interview with The Associated Press on Wednesday, Probst said Blackmun has since received more information about the treatment he'll need.

"We need a CEO in place who can (tend) to this current situation and work hard to get things back on a positive track," Probst said.

The USOC said it was starting several initiatives, including providing new funding and resources for Nassar victims and others in Olympic sports who have been subject to abuse; sex-abuse cases in swimming, taekwondo and speedskating have also occurred during Blackmun's tenure. The USOC also will review its relationships with national governing bodies of Olympic sports and double funding to the U.S. Center for SafeSport.

John Manly, an attorney representing Nassar victims in a lawsuit that seeks monetary damages and court oversight of USA Gymnastics, said it was victims speaking out about the USOC that forced Blackmun to resign.

"USOC has focused nearly all its efforts on money and medals while the safety of our athletes has taken a back seat," Manly said.

Blackmun's last several years at the helm of USOC have focused on establishing the SafeSport organization, which formed to compel all Olympic sports organizations to use the same rules for reporting and handling abuse cases.

It was a herculean task that involved raising millions of dollars to start an entity independent of the USOC that could police abuse cases in a similar manner as the U.S. Anti-Doping Agency runs the anti-doping system in the United States.

But most of the cases in question occurred before the new protocols came into play. The shocking testimony in January from dozens of gymnasts who were abused by Nassar led to calls for a complete turnover of the USA Gymnastics board, and then for Blackmun's removal.

"The U.S. Olympic Committee must now bring on new leadership determined to deliver answers and accountability regarding how Larry Nassar was able to freely abuse young girls for decades, as well as answers to questions about abuse in other Olympic programs," said U.S. Sen. Jeanne Shaheen, D-N.H.

Blackmun started as CEO just before the 2010 Vancouver Games and settled an organization that had been rife with infighting after the surprise removal of Jim Scherr and his replacement with Stephanie Streeter, who lasted barely a year.

Blackmun patched rocky relationships with national governing bodies and with the International Olympic Committee, renegotiating an agreement over sharing revenues from TV and sponsorship deals that caused problems between the two entities for years.

The reworked deal smoothed the way for the USOC to bring the Olympics back to the United States for the first time since 2002, when it landed the 2028 Games for Los Angeles. Some, however, criticized that deal as a consolation prize; LA really bid for the 2024 Games, which were awarded to Paris, and the IOC ended up granting 2028 to Los Angeles at the same time as the only other candidate for 2024.

Lyons has been on the board since 2010. In January, she was tasked with leading a USOC working group to address failings the Nassar case brought to light.

"The lesson we learned from the Nassar tragedy is, it's a wakeup call for parents, coaches and universities that the work is never done," Lyons said.

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