Bristol-Myers Squibb Co's shares rose more than 8 percent on Monday after news over the weekend that its experimental drug ipilimumab extended survival in patients with deadly skin cancer.

Bristol's ipilimumab added an average of four months to the lives of patients with advanced melanoma, according to data released at a major cancer meeting, marking a huge advance in a disease littered with failures.

Celgene Corp shares also rose more than 4 percent after data from the meeting on its multiple myeloma drug Revlimid showed that when taken as maintenance therapy following stem-cell transplantation, it reduced the risk of disease progression more than 50 percent.

Sanford Bernstein analyst Geoff Porges said the eagerly anticipated presentations at the meeting on Revlimid did not disappoint ... showing a conclusive improvement and Jefferies analysts upgraded Celgene shares to buy from hold.

However, shares of smaller biotechnology companies Delcath Systems Inc , ArQule Inc , Celldex Therapeutics and Pharmacyclics Inc each slumped more than 10 percent after data on their respective products were released at the American Society of Clinical Oncology (ASCO) meeting in Chicago.

Delcath shares fell nearly 25 percent after its drug delivery system was shown to help melanoma patients whose cancer had spread to their liver, live more than three times as long as patients treated with best available care.

The Delcath study was criticized during the meeting over its lack of demonstrated survival benefit, its design and over questions of how many patients could benefit, according to Cowen & Co analyst Sara Michelmore. Michelmore said in a research note that the criticism did not alter her opinion on the treatment's potential but acknowledged it may be attracting investor attention.

ArQule's experimental drug ARQ197 showed that it was most effective in certain types of lung cancer tumors, but investors apparently were not impressed. Its shares fell 13 percent.

The stock declines cut into yearly gains for Delcath and ArQule, which have seen their shares soar in recent months on initial positive results for their respective products.

The success of Bristol's ipilimumab heralded a new era of cancer immunotherapy -- drugs that enlist the help of the immune system to fight the disease, researchers said on Saturday.

Credit Suisse analyst Catherine Arnold raised her forecast for the drug's sales to $720 million in 2015, from $500 million on the strength of the data.

While some regulatory risk still exists ... at minimum the probability of success for the drug reaching the market has now increased, Arnold said in a research note.

Goldman Sachs analyst Jami Rubin raised Bristol to buy from neutral, calling ipilimumab the first pipeline drug in the pharma sector that has the potential to re-rate the way investors perceive pharma terminal growth rates.

Industry analysts at Jefferies said the success underscored the drug's $1 billion-plus sales potential, although questions remain about adverse events. There is also a potential competitor on the horizon in the form of Roche's experimental treatment PLX4032.

Pfizer's shares slid 0.7 percent after the world's largest drugmaker's experimental medicine crizotinib showed it shrank lung cancer tumors in more than half of treated patients.

Leerink Swann analysts called the results impressive but said the initial opportunity for the treatment was modest because a relatively small number of patients are estimated to have the genetic mutation targeted by the drug.

Novartis AG shares slipped 0.3 percent following news about two rivals to its leukemia drug Gleevec -- a competitor called from Sprycel from Bristol-Myers and Novartis's own follow-on product Tasigna.

Data at ASCO showed patients on both the new drugs did better than those on Gleevec.

Morgan Stanley analysts said Tasigna appeared to have the edge, with superior safety and efficacy over Sprycel.

Roche Holding AG -- which along with Novartis had the most data being shown at the world's top cancer meeting -- reported results of a high-profile clinical study showing the benefits of its blockbuster drug Avastin in ovarian cancer.

However, the impact was limited since the company had previously announced the ovarian study had been positive and some investors were also concerned about questions by an outside expert at ASCO about the design of the study and its findings. Roche stock fell 1.2 percent.

Among biotech stocks, British minnow Antisoma , whose stock plunged 70 percent in March when a lung cancer drug it was developing with Novartis failed in a Phase III trial, saw a partial revival in its fortunes on hopes for other drugs in earlier-stage development.

Shares in Antisoma, which presented updates on both AS1413 and AS1411 at ASCO, rose 21 percent. (Reporting by Ben Hirschler in London and Lewis Krauskopf in New York; Editing by Karen Foster and Maureen Bavdek)

Cancer Medicine