George F. Will is exactly right in saying that President Reagan's illness will save the lives of thousands of potential cancer victims by ending their procrastination in getting tests and treatment for their own cases.

If this were a rational world, it would also end the government's mindless procrastination in dealing with the problem of runaway federal deficits.

Those deficits are the cancer in our economic system, and the longer they are left untreated, the more certain and painful will be the end of our current prosperity.

It must have struck someone that four days after the president's surgery and two days after the diagnosis of colon cancer, Federal Reserve Chairman Paul A. Volcker was issuing the same diagnosis for the economy.

"When you operate on borrowed money to the extent that we have," he said in congressional testimony, "you are living on borrowed time." It is exactly the same point -- indeed, almost a word-for-word paraphrase -- that Walter Mondale made in his Democratic convention acceptance speech a year ago last week and that many others of both parties have made before and since.

There is no serious challenge to that proposition among those businessmen, bankers and economists who look seriously at the picture or, for that matter, among many of the administration and congressional officials who are struggling with it.

Yet Senate Majority Leader Bob Dole, one of those who clearly understands the threat, has said that the government is "surrendering to the deficit."

He expressed that bitter view in criticizing the unwise budget concessions Reagan made just before his hospitalization. The White House has mismanaged this year's budget process, starting with the unrealistic defense spending numbers of last January and continuing up through the cave-in on Social Security cost-of-living adjustments of which Dole complained.

But there is no one so blame-free in this process that he can walk away from responsibility if it collapses -- as it recurrently has threatened to do. For the congressional budget-makers to quit in disagreement would be exactly as indefensible as it would have been for the president's doctors to throw up their hands when they found the new -- and cancerous -- polyp.

The basic strength of the American economy is being sapped by three cancers, closely linked and feeding each other. The first is the budget deficit, brushing $200 billion a year. When added to the existing trillion-dollar-plus national debt, it guarantees that a multiplying share of each year's tax collections will be consumed simply in making runaway interest payments on the debt.

The second cancer is the rising tide of foreign borrowing -- $100 billion a year from now until at least 1990, according to the latest Congressional Research Service estimate. This year that borrowing has made the United States a debtor nation for the first time in 70 years.

By next year, we may be the world's biggest debtor. The rapid growth of that foreign debt almost strips us of control of our own economic future. More and more of our future income will be sent abroad to pay those foreign creditors, and if they put the squeeze on us by withdrawing their funds, we could in truth be "a pitiful, helpless giant."

The third cancer is the steadily worsening foreign trade deficit, estimated by Secretary of Commerce Malcolm Baldrige in the mind-boggling $140-$150 billion range this year. That measures the inability of the American economy to hold its own in international competition. It explains why, in a time of seeming prosperity, we are continuing to lose jobs in manufacturing and seeing industry after industry overwhelmed by foreign competitors.

None of these facts is in dispute -- any more than the president's diagnosis was subject to debate. Yet we continue to be lulled by stock-market highs and summer sloth into thinking there will not be a day of reckoning.

Ignoring these economic cancers is as stupid and criminal as it would have been to say of Ronald Reagan, "Hell, he can't be sick. Look at that tan he's got."

When Reagan's problem was diagnosed, his doctors did not hesitate or procrastinate. They did the surgery. He accepted the pain and discomfiture in order to achieve what should be a cure.

Every diagnosis of our economic cancer leads to the recommendation that the budget deficit must be cut -- with whatever short-term pain and discomfiture -- by dealing with defense, domestic spending, entitlements and taxes.

If Reagan's doctors had shrunk from doing what his life and health required, they would have been denounced and replaced. If this administration and Congress attempt to sneak off on vacation in August without acting on the budget deficit, they deserve no better treatment.

If they -- and we -- can't read the message we've been sent, and summon the will to act on it, we deserve the fate we will surely suffer.