* Staff also recommend black box warning

* Drug still approvable - analysts

* Shares fall 5 pct in choppy trading (Adds analyst comment; updates shares)

April 8 (Reuters) - U.S. Food and Drug Administration staff members on Friday questioned whether Clovis Oncology Inc's lung cancer drug was superior to existing treatments and also raised concerns about its safety profile.

The drug, rociletinib, like rival Tagrisso from AstraZeneca Plc , aims to treat a sub-set of patients with advanced non-small cell lung cancer whose disease has worsened despite treatment.

"It's ugly, but we think the drug could still get approved, though timing is up in the air and its competitive position may be severely damaged," Mizuho Securities analyst Eric Criscuolo wrote in a note.

Clovis' shares were down about 5 percent in morning trading, swinging between gains and losses.

A panel of outside advisers to the FDA is scheduled to vote on the drug on Tuesday.

The experts will discuss whether the drug's benefits outweigh risks, and vote if data from an ongoing late-stage study should be submitted before FDA makes its decision.

FDA staff reviewers on Friday recommended that rociletinib carry a black box warning, the strongest warning imposed by the FDA, of increased heart risk on its label.

The labeling should also include monitoring of the patient's heart while under the treatment, the reviewers suggested. (http://1.usa.gov/1WhpSFa)

The drug will likely play second fiddle to Tagrisso, given that its efficacy compares poorly with that of AstraZeneca's treatment, analysts have said.

Clovis, which is seeking an accelerated approval for rociletinib, was asked for more data by the FDA in November, delaying the panel's discussion to April 12 from March 31.

The FDA is not obligated to follow the panel's recommendations, but it usually does. The health regulator is scheduled to decide on rociletinib by June 28.

Up to Thursday's close of $19.17, Clovis shares had fallen about 81 percent since the FDA in November asked for additional data.

(Reporting by Amrutha Penumudi and Natalie Grover in Bengaluru; Editing by Sriraj Kalluvila)