European shares inch lower ahead of Yellen; Roche rallies

* Pan-European STOXX 600 index down 0.1 percent

* Banks led lower by Spain's Banco Popular, oils down

* Roche boosted by trial success with cancer drug

* Investors cautious before Yellen speech (ADVISORY- Reuters plans to replace intra-day European and UK stock market reports with a Live Markets blog on Eikon - see cpurl://apps.cp./cms/?pageId=livemarkets for site in development. See the bottom of the report for more details) Adds details, prices)

By Danilo Masoni

MILAN, May 27 (Reuters) - European shares fell slightly on Friday, weighed down by weakness in Spanish banks and some oil sector stocks, although Roche soared on positive results from an interim analysis of one of its cancer drugs.

Investors were likely to remain cautious ahead of U.S (Other OTC: UBGXF - news) . GDP data and comments from Federal Reserve Chair Janet Yellen later in the day which could give more clues about the interest rates outlook in the world's largest economy.

"It (Other OTC: ITGL - news) will be crucial to figure out whether Yellen is aligned or not with (recent) indications that the June are July FOMC meetings are live," JCI Capital portfolio manager Alessandro Balsotti said.

The pan-European STOXX Europe 600 index and the FTSEurofirst 300 index were both down around 0.1 percent by 0821 GMT. Both indexes had hit a 4-week high earlier this week.

The STOXX Europe 600 Bank index was the top sectoral faller with a drop of 0.5 percent. Spanish banks continued to be hit by news of a surprise cash call at Banco Popular, which fell more than 4 percent and was the top loser in its sector and on the broader STOXX index.

The STOXX Europe 600 Oil & Gas index fell 0.3 percent, after crude oil prices slipped back below the $50-per-barrel mark. Shares (Berlin: DI6.BE - news) in oil majors Royal Dutch Shell (LSE: RDSB.L - news) , Total (LSE: 524773.L - news) and Eni (LSE: 0N9S.L - news) were all down between 0.1 and 0.7 percent..

Outsourcing group Capita (LSE: CPI.L - news) 's shares fell 1.6 pct, leading losers on Britain's FTSE index, after Exane BNP Paribas cuts to "underperform" from "neutral".

However, Roche rose 3.6 percent after a clinical trial testing its new blood cancer drug Gazyva proved successful, lifting prospects for a new medicine that will be pivotal as the Swiss company fights the threat of biosimilar competition.

Some analyst said the news was as welcome surprise, while Vontobel also lifted its target price on the stock on the Swiss drugmaker to 330 Swiss francs from 309.

Today's European research round-up

ADVISORY- Reuters plans to replace intra-day European and UK stock market reports with a Live Markets blog on Eikon (see cpurl://apps.cp./cms/?pageId=livemarkets for site in development). In a real-time, multimedia format from 0600 London time through the 1630 closing bell, it will include the best of our market reporting, Stocks Buzz service, Eikon graphics, Reuters pictures, eye-catching research and market zeitgeist. Breaking news and dramatic market moves will continue to be alerted to all clients and we will continue to provide a short opening story and comprehensive closing reports.

If you have any thoughts, suggestions or feedback on this, please email mike.dolan@thomsonreuters.com.

Mike Dolan, Markets Editor EMEA. (Reporting by Danilo Masoni)