BOSTON (Bloomberg) — Sharks don't get cancer. Scientists who are interested in understanding the dynamics of cancer, therefore, say the study of sharks may be rewarding.

Similarly, looking at stocks doing well in a sour market can sometimes yield insights. One might get a clue to the market's future leaders or discover individual stocks worth buying.

Of 1,665 US stocks with a market value of $500 million or more, 117 have gained 20 percent or more this year.

The best gainer through February 11, excluding stocks with tiny trading volumes, was Advanced Medical Optics Inc., up 231 percent on a takeover offer from Abbott Laboratories.

The Santa Ana, California, company makes contact lenses, supplies for cataract surgery and other eye products. It is also the world's largest maker of devices used in Lasik eye surgery.

Abbott offered $22 a share in cash on January 12, causing Advanced Medical shares to rise 143 percent that day. Today, the shares are trading near the offer price. But it's worth noting that they commanded a much higher price in the past. In June 2006, for example, they traded at more than $50. Gamco Investors Inc., an investment firm run by Mario Gabelli, disclosed on January 13 that it raised its stake in Advanced Medical Optics to more than 15 percent, from a little over ten percent. The additional stock was acquired on various dates from mid-November through January 12. The January 12 purchases suggest that Gabelli may expect a higher bid to emerge for Advanced Medical.

Personally, I wouldn't count on another bid. At the current price of about $22, Advanced Medical trades at 39 times earnings, an ample multiple. Moreover, debt was 237 percent of equity as of September 30, a debt load large enough to discourage some prudent potential bidders.

Palm Inc., up 154 percent, was the second-biggest gainer, much to my chagrin. After holding Palm for about two years, I sold it in December, shortly before the spurt. Much of what I thought would happen at Palm did occur. A product design team under the leadership of chief executive officer Jonathan Rubinstein has come up with a snappy new smart phone, the Pre.

I sold, though, because Palm's debt had climbed. As of November 30, the company's book value (corporate net worth per share) was negative to the tune of $3.72 per share. I don't feel comfortable, during a recession and financial crisis, holding companies with weak balance sheets.

GT Solar International Inc. of Merrimack, New Hampshire, was another strong performer, up 82 percent. Solar energy companies have been popular for several years, and they got a boost with the election of Barack Obama, who supports developing alternative energy sources.

For the quarter ended December 27, 2008, GT Solar reported sales of $205 million, beating analysts' expectations of $195 million. Earnings came in at 30 cents a share, trumping the expected 24- cent figure. Enviably, the company is debt-free.

At $4.62 a share, I find GT tempting. Analysts think that GT will earn 71 cents in the fiscal year that ends next month. If so, the stock is selling for only seven times earnings, which is my kind of multiple.

InterMune Inc. was the fourth-best gainer, rising 73 percent. The Brisbane, California, biotechnology company reported strong results in trials of a drug for chronic lung disease. It expects to submit Pirfenidone shortly for approval by regulators in the US and Europe.

InterMune, though, is the kind of stock I would be more likely to sell short than to buy. It has reported losses every quarter since it went public in 2000, and its book value was a negative $2.34 a share as of Sept. 30.

I believe that paying for success that has yet to be achieved is a bit like drawing to an inside straight in poker. It can work, but it isn't an optimal strategy. CV Therapeutics Inc. of Palo Alto, California, another biotechnology firm, posted a 68 percent gain. Astellas Pharma Inc. of Japan bid $1 billion for the company in November. CV Therapeutics, which is pinning most of its hopes on a proposed drug for heart pain, spurned the offer.

In late January, Astellas renewed its $16-a-share offer. This time, CV said it would "review developments".

The stock is trading at $15.45. Like InterMune, CV has never reported a profit. Its book value is negative $3.64 a share.

It's no coincidence that three of the five top gainers are in the health-care field. Health care is traditionally a defensive bastion during recessions and bear markets, and it's playing that role this time.

I continue to like the health-care sector, but I prefer the big, established pharmaceutical companies that have long records of profitability and sell for more modest multiples.

Disclosure note: I have no current positions, long or short, for myself or clients, in the stocks discussed in this column.

John Dorfman, chairman of Thunderstorm Capital in Boston, is a columnist for Bloomberg News. The opinions expressed are his own.