Like many oncologists and cancer researchers, I rolled my eyes when I first heard about Vice President Joe Biden's cancer "moonshot," but not because of the noble goal. I was among the many people who were deeply sorry to hear about the death of the vice president's son Beau from cancer last year. And I, too, have mourned the untimely deaths from the disease of people close to me. Those of us who care for cancer patients would give nearly anything to be able to cure all those with cancer or, at a minimum, to greatly extend their lives. Today, we can sometimes do this, but sadly those circumstances remain far too limited.

But a cancer moonshot evokes a sense of déjà vu. The 1970s ushered in the War on Cancer, which was largely unsuccessful at generating better treatments. In 2003, it was then-National Cancer Institute head Andrew Von Eschenbach assuring then-Sen. Arlen Specter that, for just $600 million a year, we could rid the world of cancer five years ahead of 2015, the target at that time. Now here were Biden and the Obama administration making another tall promise. Did we really need this again?

Then, the specifics emerged. One of Biden's first announcements was that the Food and Drug Administration would speed the approval of promising drug combinations. But thinking you will substantively improve cancer treatment by altering how it is regulated is like thinking you can run a faster mile by buying a new stopwatch. The efficacy of cancer drugs is beyond the FDA's control, and no one doubts it would approve transformative drugs or drug combinations if they appeared. In fact, the FDA has already shown that it is willing to approve nearly any cancer drug that comes before it. A study of 71 drugs approved for solid tumors from 2002 through 2014 showed that the median improvement in survival times was just 2.1 months. If we are going to make real progress against cancer, we must acknowledge that such marginal gains — achieved at the price of substantial cost and toxicity — are just not good enough. We must also acknowledge that no matter what we do with the FDA, it can't produce better medicines.

Another oft-mentioned proposal is harnessing the power of big data. One such idea is to closely examine what therapies have worked for individuals and which unique genetic traits allowed those therapies to work, then extend these findings to other patients. Unfortunately, such an approach is fraught with limits. My colleague Andrae Vandross and I recently reviewed the published reports of patients who have had an exceptional response to a cancer drug. In many instances, we found that these patients responded unusually well not only to the studied drug but also to older ones. In several cases, these people had already survived far longer than the typical patient by the time they received the lauded medication. It is hard, then, to conclude which patients have great outcomes because of a drug and which simply have slow-growing cancers — a phenomenon doctors have recognized for years. But this distinction is the very crux of the big-data approach. Observational data — no matter how "big" — will have difficulty overcoming this challenge.

The other trouble with big data is that if we agree that the outcomes we have now are mediocre (and I think we can agree on that), studying these outcomes in greater detail is unlikely to result in truly transformative approaches. It would be like NASA scientists studying old nautical voyages to figure out how to reach the moon.

Biden has recently offered up two more moonshot ideas: immunotherapy and increasing access to trials. Immunotherapy refers to promising new drugs that harness the body's immune system to fight cancer, and indeed these have generated impressive outcomes for some patients. But with dozens of immunotherapy studies underway, that rocket has already lifted off, and it's unclear what Biden's moonshot can add. And, unfortunately, the bitter reality is that despite immunotherapy's promise, its benefits will probably remain confined to a minority of patients with certain types of cancer. Immunotherapy is unlikely to be a panacea.

Increasing access to cancer trials would be a great thing, but it is hard not to think of it as only a modest step, as well. Perhaps this reflects political reality. With one year left in President Obama's term, and a Congress whose recent achievements make the War on Cancer look like a huge success, the chances of passing meaningful legislation are slim. Obama can still take executive action, but this is likely to yield only modest changes — such as small shifts in funding priorities or lowering minor bureaucratic hurdles. John F. Kennedy called for his moonshot at the beginning of his presidency, not near the end of his term.

But the fundamental problem with a moonshot — a surge of concentrated effort to tackle a single problem — aimed at cancer is that it does not fit the way that medical progress occurs. Scientific discovery is hard to predict, and breakthroughs occur in serendipitous and unexpected ways, arising from diverse disciplines. A serious moonshot would require funding science broadly, consistently and in steadily increasing amounts. This money would go to cancer biology research, but also to physiology, molecular biology, genetics, physics, chemistry, social science, clinical trials, supportive care and on and on. The way in which we will ultimately make progress in fighting cancer, and for that matter Alzheimer's disease, and emphysema, and mental illness, will likely surprise even the most farsighted experts, and may have surprisingly diverse origins.

Such science is not just the best way to improve human health but also the only way. A commitment to funding science generally, and not just fad projects or treatments, in times of both budget surplus and shortfall, would be a true moonshot for the United States. Sadly, this is the one moonshot no one in politics seems to have the courage to fight for.

Dr. Vinay Prasad, a cancer researcher and assistant professor at Oregon Health and Science University, is co-author of the 2015 book "Ending Medical Reversal: Improving Outcomes, Saving Lives." He wrote this article for the Washington Post.