UPDATE 2-AstraZeneca profit outlook disappoints, despite drug sales growth

* Sees low single-digit percentage 2018 drug sales growth

* 2018 core EPS guidance $3.30-3.50 vs consensus $3.61

* CEO says drugmaker "steadily turning a corner" (Updates with market reaction)

LONDON, Feb 2 (Reuters) - AstraZeneca expects to return to drug sales growth in 2018 as new medicines win market share and the group puts patent losses behind it, although the need to invest in launches will weigh on profit.

After a 5 percent fall in 2017, the company said on Friday that product sales this year should grow at a low single-figure percentage rate and produce core earnings per share (EPS) of $3.30 to $3.50 - less than current market consensus of $3.61.

AstraZeneca has been through the drug industry's biggest ever cliff of patent expiries in recent years, which wiped out more than half of its sales, but Chief Executive Pascal Soriot said it was "steadily turning a corner."

Although fourth-quarter profits came in better than analysts had expected, helped by one-off tax gains and growing revenue, the weak profit guidance for the current year unnerved investors and the shares fell 2 percent in early trade.

Revenue was boosted by "externalization" deals, involving asset sales and collaborations, which some analysts have criticized as unduly flattering results. Such deals contributed $2.3 billion in 2017 out of total revenue of $22.5 billion.

AstraZeneca has some notable new product successes recently, with oncology pills Tagrisso and Lynparza both doing well and progress in other areas, including novel treatments for lung disorders.

Its heart drug Brilinta and Farxiga for diabetes have also both just breached the $1 billion annual sales mark.

Still, the pace of its turnaround remains uncertain pending further clinical trial read-outs in the multibillion-dollar cancer immunotherapy market, where AstraZeneca is going head to head with industry giants like Merck & Co, Bristol-Myers Squibb and Roche.

AstraZeneca suffered the biggest daily fall in its shares last July, following disappointing initial results from a lung cancer trial dubbed Mystic. Since then the shares have rallied, helped by good news from two other studies.

Further data from the Mystic trial is due in the first half of this year.

Fourth-quarter core EPS, which excludes some items, increased 7 percent to $1.30 cents on revenue of $5.78 billion. Analysts, on average, had forecast earnings of 84 cents on revenue of $5.46 billion, Thomson Reuters data showed. (Reporting by Ben Hirschler; editing by Jason Neely/Keith Weir)