Few biotechs have raced ahead in 2014 like Gilead Sciences (NASDAQ:GILD)has. The company's stock has soared around 50% so far this year. Gilead's red-hot hepatitis-C franchise is energizing investors. It received regulatory approval for its first oncology drug in July.

But can Gilead keep galloping forward? Here are three key things the company needs to do when it reports third-quarter financial results after market close on Tuesday.

Source: Gilead Sciences.

1. Win the Sovaldi expectations game
There's no question that Gilead's hepatitis-C drug Sovaldi generated great numbers in the third quarter. In the first quarter, sales for the drug totaled more than $2.74 billion. That figure jumped to $3.48 billion in the second quarter. It's a foregone conclusion that Sovaldi should perform even better in the most recent quarter.

The challenge for Gilead is that these impressive results stoke high expectations from investors. It's possible that a solid quarter could still not be enough to satisfy some observers. Gilead's CFO Robin Washington cautioned in the company's second-quarter conference call that accurately predicting sales for its hep-C franchise is "very difficult."

On the other hand, expectations might not be high enough for Sovaldi. Some have worried that a potential payer backlash could impact sales for the drug. So far, though, that hasn't slowed Gilead's momentum. COO John Milligan noted in July that the company was seeing positive movement in the payer community with more dollars budgeted for Sovaldi in the second half of the year. Could an upside surprise be in store for the third quarter? Maybe so. 

2. Maintain HIV juggernaut momentum
While the hepatitis-C market is garnering most of the buzz for Gilead these days, the company's prior success was driven primarily by its HIV drugs. Gilead's HIV franchise continues to be a juggernaut, with nine in 10 U.S. patients new to HIV treatment prescribed to one of Gilead's drugs in the second quarter.

HIV is still a critical component of Gilead's story. The company's five HIV drugs combined for revenue of $2.5 billion in the second quarter. A sluggish third quarter from these drugs could potentially offset positives from Sovaldi.

Is such a slowdown likely to happen? Probably not. While Atripla and Truvada aren't in high-growth mode, Stribild and Complera/Eviplera sales are booming. Nonetheless, Gilead's HIV franchise performance in the third quarter bears watching. 

3. Control operating cost increases
Perhaps the most important thing to watch with Gilead outside of Sovaldi's sales, however, is how much operating costs shot up during the third quarter. Gilead noted in its last earnings conference call that costs are expected to rise during the second half of the year.

Source: Gilead Sciences 

The launch of Sovaldi and ramp-up to launch its successor hep-C combo, Harvoni, no doubt contributed to higher operating costs. Gilead also has been spending to launch its first oncology drug, Zydelig, which received FDA approval in July to treat patients with relapsed chronic lymphocytic leukemia in combination with Roche's Rituxan.

Gilead also expects higher costs related to research and development during the second half of 2014. The biotech has clinical studies underway in hepatitis-C, HIV, inflammation and respiratory therapeutic areas. It's possible that all of this higher spending could be enough to cause some to be disappointed in Gilead's bottom line for the third quarter. 

Horse races and marathons
Any of the above three factors could make a difference in how Gilead's stock fluctuates in the short term. However, investing is more like a marathon than a horse race. It's the long term that matters.

Gilead's stock could climb -- or fall -- by several percentage points after the company's third-quarter results. Remember, though, that this same stock is up around 1,200% during the last 10 years. Thinking with a marathon perspective rather than a horse race perspective is the best winning strategy.