* Varian's cash offer a 49 pct premium on Sirtex stock
* Analysts see price as generous, caps tough year for Sirtex
* Sirtex, Varian shares yet to trade since announcement (Recasts, adds Sirtex background and analysts' quotes)
By Tom Westbrook
SYDNEY, Jan 30 (Reuters) - U.S. cancer-treatment company Varian Medical Systems agreed on Tuesday to buy Australian liver-cancer treatment maker Sirtex Medical for $1.3 billion, the latest in a wave of big M&A deals sweeping the global healthcare sector.
Sirtex, whose shares have halved over the past two years, and which swung to a full-year loss after its technology failed in three major tests, recommended the buyout as an "attractive outcome".
California-based Varian's offer of A$28 in cash per share is 49 percent above Sirtex's closing price of A$18.83 on Monday, and comes amid a multibillion dollar shopping spree in the sector as big companies buy their way to growth.
"The bid price is definitely a good premium, I would struggle to see anyone else coming over the top," said Mathan Somasundaram, Market Portfolio Strategist at stockbrocker Blue Ocean Equities, adding the bid was timely.
Sirtex had written down the value of its research and development projects in June after last year's poor study results, sacked its CEO after an internal investigation into his trading of Sirtex shares, and still faces two class action lawsuits over alleged disclosure breaches.
"Whilst we remain confident that the company would continue to have a successful stand-alone future, we believe that the material premium provided by Varian and the certainty of all cash consideration is an attractive outcome for shareholders," Sirtex's Interim Chairman, John Eady, said in a statement.
Varian said in a separate statement the deal is part of its "long-term growth and value creation strategy" and expands its portfolio of radiation medicine.
It comes as a search for growth drives a spike in big biotech deals, pushing global mergers and acquisitions (M&A) in the sector to $26.3 billion for January, far ahead of any comparable tally for the month in over a decade, according to Thomson Reuters data.
French drugmaker Sanofi has led the charge, with its agreed $4.8 billion purchase of Belgian biotech company Ablynx on Monday, a week after it splashed $11.6 billion on U.S. haemophilia expert Bioverativ.
U.S.-based Celgene is paying $9 billion for cancer specialist Juno Therapeutics.
"These companies are entering this space because they're cashed up, they have holes in their pipelines...they're looking for growth and near-term accretive acquisitions," said Derek Jellinek, an analyst at stockbroker Morgans.
"From a shareholder point of view for Sirtex, party on dude, you'd definitely vote for this."
The deal, which was announced outside market trading hours in both Sydney and New York where the two companies are listed, is subject to approval from the Foreign Investment Review Board and other competition authorities.
Varian said it plans to finance the acquisition using cash on hand and proceeds from borrowings, adding that the deal is expected to close in late May 2018. ($1 = 1.2396 Australian dollars) (Reporting by Tom Westbrook in SYDNEY. Additional reporting by Chris Thomas in BENGALURU; Editing by Edwina Gibbs and Muralikumar Anantharaman)