Since learning last month that her cancer had returned, Mandi Schwartz ’11 and her family have elected to stop medical treatment of her aggressive leukemia.

The women’s hockey player’s 25-month battle with cancer took a drastic turn in mid-December. Schwartzlearned of her relapse on Dec. 17 — approximately 85 daysafter a potentially life-saving stem cell transplant, and just two weeks shy of the point at which the average transplant patient is well enough to return home. She resumed treatment for less than a month before announcing Jan. 6 that she would not continue the therapy.

“I’d honestly like to tell [the Yale community] a lot but my heart right now isn’t,” said Mandi’s father, Rick Schwartz, in a phone interview Sunday. “I just feel awful. I’m lost for words, really.”

On the morning of Dec. 17, Mandi and the Schwartz family composed a letter of thanks to those who have supported Mandi throughout her fight with cancer,expressing the family’s hope that Mandi was on the path to recovery. Their hopes were dashed after receiving bone marrow biopsy results that afternoon revealing the leukemia’s return.

In an update sent to Yale Athletics soon after receiving the results, Mandi’s family said the diagnosis was “like we’ve just hit a brick wall at one hundred miles an hour.” Mandi immediately resumed chemotherapy in Seattle as part of a research study for leukemia patients who relapsedfollowing a transplant.

The hockey player returned home on Dec. 29 to continue treatment in her hometown of Regina, Saskatchewan. Mandi would have received doses ofAzacitadine, thedrug used in the study, for seven straight days every month for a six- to eight-month period, but the family wrote on that the therapy was unable to quell the cancer. The Schwartzes announced on Jan. 6 that Mandi’s latest test showed her bone marrow contained 36 times the amount of leukemia blasts — abnormal, immature white blood cells that hamper the production of normal blood cells — found in her body when her cancer reappeared in December.

Mother Carol Schwartz said the entire Schwartz family — including Mandi’s fiancé, Kaylem Prefontaine — congregated in Regina this weekend to celebrate the 21st birthday of Mandi’s brother, Rylan. When the Schwartzes took family photos at the birthday celebration this weekend, Carol said, Mandi was “still smiling.”

Carol said family and friends have surrounded her daughter, who is “overall trying to hang in there and trying to be strong so that the people around her are strong as well.”

“We’re just trying to take it day by day, ask her who somebody she wants to see is, or who somebody is she wants to talk to,” Carol said in a phone interview Sunday. “There have been a lot of prayers.”

Samantha MacLean ’11, the women’s hockey team captain, said the seniors on the team planned to visit Mandi the weekend before Martin Luther King, Jr. Day. They cancelled the trip after Mandi told them that her treatment was progressing poorly and the visit was not a good idea, MacLean said.

“It’s hard because we don’t really know what to do at this point,” MacLean said. “Before we had the bone marrow drives and were raising money and stuff, but now we don’t know what to do anymore.”

Former women’s hockey coach Hilary Witt said there is little Mandi’s supporters can do other than pray, but Witt expressed confidence in Mandi’s resolve to beat cancer.

“Mandi’s a fighter,” Witt said. “She’s not going to give up her fight. That kid has battled hard for 25 months and she’s not going to give up now.”

The women’s hockey team has rallied around Mandi since her diagnosis, leading a national movement to raise funds and awareness for Mandi and other leukemia patients. Yale held its second annual bone marrow drive in April 2010 and registered 921 potential donors — far exceeding the 704 donors who joined the registry during the 2009 drive.