NEW YORK (TheStreet) -- Shares of Tesaro (TSRO) - Get Report have been skyrocketing after the bio-pharmaceutical company reported positive results of its experimental ovarian cancer drug study, and Dr. Marc Siegel discussed why on Fox Business News' "Varney & Company" Thursday.

At the point when the vast majority of people are diagnosed with ovarian cancer, the disease has already spread throughout the body, Siegel explained.

"The good news is there's a chemotherapy out there that knocks it back 80% to 90% of the time and you get rid of it," Siegel said. However, after the treatment, the cancer will recur within two years in most cases.

A new drug by Tesaro, a daily pill with "minimal side effects," stops the cancer from recurring three out of four times, according to Siegel.

"That's very dramatic," he commented.

The one side effect reported with the drug is that it knocks a person's blood count down, "so you have to get your blood checked," Siegel noted.

"Cancer loves to repair DNA," Siegel said when asked how the drug works.

"It loves to get inside the cell and repair the cell so it grows, grows, grows. This drug stops it from doing that," Siegel announced, "So, I think I know why the stock went up."

Tesaro's drug is the "new phase of cancer treatment." It carries less side effects at a more effective rate, Siegel concluded.

Shares of Tesaro are rising by 2.07% to $79 late this morning.

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