Nightly News   |  May 15, 2013

Immunotherapy targets cancer cells with remarkable results

Cancer cells typically put up a chemical shield to protect against the body’s disease-fighting T cells. But immunotherapy can break down the shield and let the T cells get to work. NBC’s Robert Bazell reports.

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>>> as we mentioned, important, very encouraging news in the fight against cancer. specifically here, melanoma. far too common and it can be far too deadly when it is not caught in time. a new treatment approach is getting excellent results we are told and could be used to fight different cancers. we get our report on this tonight from our chief science correspondent robert bazell .

>> there it is. nicely done.

>> reporter: mary elizabeth williams is 47. in 2010 she got a diagnosis of stage four melanoma that had spread through her body.

>> it was the beginning of the school year for my kids. suddenly i didn't know if i was going to be there for the end of the school year.

>> reporter: williams got a new therapy that worked so well in a few months she got the best possible news.

>> he told me that my cancer was completely gone. i was so stunned and surprised.

>> reporter: unlike chemotherapy which directly kills cancer cells , immunotherapy works on killer t cells that devour bacteria and viruses. cancer cells put up a chemical shield to protect against t cells. the therapy breaks down that shield and the cells go to work. yervoy helps 10% of melanoma studies. doctors combined wit a second drug that hits a different target on t cells allowing them to kill more cancer.

>> i'm tremendously excited. we are seeing more than half of patients having significant regressions of their advanced melanoma.

>> how are you doing?

>> reporter: it's not just melanoma. because of similar drugs david gobin has seen his lung cancer disappear.

>> i can do a lot of things i couldn't before.

>> reporter: and ken kirkwood's cancer is gone. some believes this is one of the most -- curing patients in a new way. many similar experimental drugs are being tested and other combinations could work better. the drugs have side effects and will be very expensive there is no doubt they will save many lives. robert bazell , nbc news, new york.