CHICAGO ( TheStreet) -- The five most important slides from this weekend's American Society of Clinical Oncology (ASCO) annual meeting -- where the anti-PD-1 therapies from Bristol-Myers Squibb ( BMY) and Merck ( MRK) stole the show. This isn't a chart of real data but it's the best slide of the ASCO meeting because it explains why cancer immunotherapy is winning over targeted therapies, particularly in melanoma. It's the long survival tail! Targeted therapies work fast but responses tend to be transient as cancer cells develop resistance. This means that early, impressive survival benefit aren't sustainable. Cancer immunotherapy, on the other hand, works slower. It takes time for the patient's immune system to identify and kill cancer cells. But once a patient's T-cells get a taste for cancer cells, their appetite is insatiable. That means tumor responses that are more durable and (hopefully) sustained and prolonged survival. This is the summary slide of the tumor response data seen with Merck's anti-PD-1 therapy lambrolizumab in patients with advanced melanoma. Treatment with lambrolizumab results in 38 percent of melanoma patients overall having significant tumor shrinkage. In the best-performing dose group, 52 percent of patients responded. Stunningly good results -- some of the best ever -- which is why a theater jam-packed with cancer experts Sunday were buzzing. During a Q&A session, one member of the audience commented (half-jokingly) that the lambrolizumab data were so convincing, the drug should just be approved now without any further clinical trials necessary. This chart illustrates the durability of responses resulting from Merck's lambrolizumab therapy. See all those right-facing arrows? Those are patients still responding to treatment after 50, 60, even 70 weeks. More specifically, 81 percent of patients who had a response were still in the study receiving treatment with lambrolizumab at the time of the analysis. Amazing. This slide helps explain why investors are treating Bristol-Myers like a biotech stock, with shares up more than 40 percent this year. Nivolumab has the potential to be a blockbuster melanoma drug, but even more enticing is the potential for the drug to re-write the lung cancer treatment playbook. Melanoma is a big commercial market but lung cancer is huge -- and Bristol-Myers is already enrolling lung cancer patients in three clinical trials that could be used to support approval. Not to be outdone, Merck also announced plans to start late-stage studies of lambrolizumab in melanoma and lung cancer in the third quarter. More long-tail survival data, these from nivolumab in melanoma. Impressive. -- Reported by Adam Feuerstein in Chicago. Follow Adam Feuerstein on Twitter.