What happened

Shares of NovoCure (NVCR -0.55%), which makes the Optune device for treating cancer with electric fields, popped 20.5% in May, according to data from S&P Global Market Intelligence.

More specifically, the company's technology is called tumor treating fields and is used to treat solid tumors.

NovoCure stock's performance is even more electrifying than it might seem at initial glance, given the S&P 500, including dividends, dropped 6.4% last month.

Man sitting at desk wearing NovoCure's Optune, which appears like netting on his head and includes an over-the-shoulder attachment to the head device.

Image source: NovoCure.

So what

We can attribute NovoCure stock's strong performance last month to two main catalysts. The first was the company's May 2 release of first-quarter 2019 results, which pleased investors. Shares popped 9.6% on the day following the earnings release.

In Q1, NovoCure, which is based in Jersey (the Channel Islands), posted revenue of $73.3 million, representing growth of 41% year over year. Growth was driven by brisk sales of Optune in the United States and across the company's international markets, including Germany, Austria, and Japan, to treat adults with glioblastoma, the most common primary brain cancer in adults and one of the most difficult cancer types to treat. The company's profitability also moved in the right direction, with its net loss falling 41% to $12.2 million. 

The second notable catalyst was NovoCure's announcement on May 23 that it had won approval by the Food and Drug Administration to use Optune to treat malignant pleural mesothelioma. This is an aggressive and rare form of cancer primarily caused by inhaling asbestos fibers into the lungs. Shares gained 7.3% on the day following this news. 

NVCR Chart

Data by YCharts.

NovoCure stock has been moving higher for some time, driven by investor optimism about the company's growth potential. While it's been on a roller-coaster ride in 2019, it's nonetheless up a whopping 63.8% this year through June 5.

NVCR Chart

Data by YCharts.

Now what

Along with just receiving FDA approval to treat mesothelioma, NovoCure has other potential new catalysts for growth on the horizon this year. Notably, this includes a launch of Optune in China, which could approve the device to treat GBM this year, Chairman Bill Doyle said on the Q1 earnings call.