Statistics now being processed at the National Cancer Institute portend new and wrenching strains in the long-quiescent but potentially volatile politics of cancer.

Preliminary analysis of these numbers indicate that the so-called war on cancer, now in its seventh year, has failed to produce any sharp increase in the survival rates for the most common types of cancer. Nonetheless, the institute's newly collected data show that therapeutic progress is slowly but steadily being achieved. The gains are, so to speak, in inches rather than in the miles that were expected in 1970, when Congress, egged on by the cancer lobby, resolved that cancer should be cured by 1976 "as an appropriate commemoration" of the nation's bicentennial.

Since then, not only has the disease eluded the "magic bullet" approach, but the incidence of cancer has actually increased -- despite the self-serving nonsense issued by apologists for industrial pollution. As Dr. Marvin A. Schneiderman, for many years the institute's chief of statistics, told Congress earlier this year, "Even when the smoking-related lung cancers are removed from the incidence data, there were still increases in incidence from 1969 to 1976."

Thus, the grim news is that there's more of it, while the rate of successful treatment is getting better, if only at a discouragingly slow pace. In comparisons of five-year survival rates for cancers initially diagnosed in 1960-63 and 1970-73, the institute's latest figures show that survival rates for breast cancer are up, from 63 percent to 68 percent; even for highly intractable lung cancer, there has been a slight improvement, from 8 percent to 10 percent; for cancer of the rectum, survival figures are up from 39 percent to 45 percent.

A flock of statistical qualifications and cautions accompanies these preliminary findings: the figures are for whites (those for blacks, who generally suffer higher cancer incidence and mortality rates, are yet to be processed); these are total figures and fail to distinguish disease stage or treatment; and, finally, when the latest figures are viewed against a baseline more recent than 1960-63, improvements persist, but they are smaller. Even so, two of the institute's senior biostatisticians, Earl S. Pollack and Max H. Myers, feel that the favorable changes are unusually large and are not due to analytical oversights or statistical quirks.

What these statistics mean, then, is that the foolishly promised blitz against cancer has still not materialized and that, until that unforeseeable time when the biological mechanisms of cancer are understood, we had better reconcile ourselves to a medical equivalent of trench warfare. The difficulty, however, is that just when the U.S. government ought to be settling in for a long and costly haul, a thoughtless disarray is becoming evident in the politics of cancer.

After years of financial forced-feeding, the budget of the cancer institute has abruptly leveled off -- actually gone down in inflation-eroded purchasing power -- at the very time that the institute's programs around the country are hungrier than ever for support. The president, who, not without justification, is skeptical toward grandiose research projects, said in his science-policy message early this year that "as we have learned from the emphasis on cancer over the last decade, advances depend on new discoveries whose rate cannot be predicted." From which he concluded that the cancer institute could get on without even a cost-of-living budget increase -- a decision that Congress amended to allow for a bit of a rise in spending.

The reality, however, is that the promise-filled war on cancer is now the victim of false expectations. The "new discoveries" to which Carter referred carry the suggestion of the great scientific breakthroughs that were foreseen in the early 1970s, if only the money were made available. Regrettably, there have been very few breakthroughs, and none of them, so far as is known, of general therapeutic value. Meanwhile, with the government's cancer-research spending more or less in the doldrums-- even $1 billion a year doesn't go far in this line of research-- various sectors of the cancer industry are intensifying their squabbles for shares. Thus, academic basic researchers bitterly complain about the share that's dished out in industrial contracts-- to the detriment, they insist, of university-based science. And the doctors who study the effects of new drugs say that clinical research is being short-changed. Meanwhile, after repeated blasts from Congress, the cancer institute is at last moving into the long-neglected field of preventive research. This is a welcome development, but it means that an already stretched budget will have to be stretched even more.

Humanity and sound medical strategy now call for putting this program on a long-term, steady financial basis that fully recognizes that inch-by-inch success is the best that we can hope for at present.

The delayed arrival of a miracle ought not to be a reason for disavowing the importance of small gains. Also, cancer budgets and strategies ought to be kept out of national politics. Let it be recalled that the present National Cancer Program was conceived against a 1971 competition between Richard Nixon and Edward Kennedy over who would become the national champion of cancer research. And at one point, when a "NASA for cancer" was being touted, a supportive plea from Ann Landers produced a letter barrage that remains legendary on Capitol Hill. That bad idea was defeated, but not by much.