Shares of Novocure (NVCR 1.31%) jumped 18.3% this week, according to data from S&P Global Market Intelligence, after the company announced encouraging results from a phase 3 study of its Tumor Treating Fields (TTFields) therapy for treating brain metastases from non-small-cell lung cancer.

A "potentially practice changing" therapy

In a press release Wednesday, Novocure announced that its phase 3 METIS clinical trial met its primary endpoint by "demonstrating a statstically significant improvement in time to intracranialprogression" for patients treated with TTFields therpamy and supportive care compared to supportive care alone.

More specifically, Novocure says that patients receiving TTFields therapy in addition to supportive care in the late-stage study had a median time to intracranial progression of 21.9 months -- far improved from the 11.3 months for those treated only with supportive care such as nausea medications, steroids, and/or anticoagulants.

"In this international, multicenter, phase 3 trial, the use of TTFields therapy significantly delayed time to brain relapse, with associated improvement in quality of life and stable cognition," explained Minesh Mehta, chief of radiation oncology and deputy director at Miami Cancer Institute. "This is a major benefit and is potentially practice changing."

What's next for Novocure investors?

Novocure added that a preliminary analysis of key secondary endpoints -- including time to neurocognitive failure, overall survival, and radiological response rate -- showed no demonstration of statistical significance. Lesser secondary endpoints including time to distant progression and quality of life showed more "positive trends" favoring treatment.

Nonetheless, it's a big win for Novocure's TTFields therapy to meet its primary endpoints in this brain metastases study -- especially considering the therapy previously failed to meet a primary endpoint in a separate trial for treating platinum-resistant ovarian cancer. With shares down more than 70% over the past year, it's no surprise to see the cancer stock partially rebounding in response.