For the first time since researchers began reporting national data on cancer, the statistics in a new report show that the rate of newly diagnosed cancers is declining in America; at the same time, the death rate for all cancers combined continues to fall.

“It’s a validation of the efforts we are making in the fight against cancer,” says Dr. Therese Bevers, medical director of clinical cancer prevention at the M.D. Anderson Cancer Center; she was not involved in the new paper. (See TIME’s study of breast cancer around the world.)

Overall, cancer death rates have been dropping since the early 1990s - the most recent data suggest that death rates have decreased for 10 of the 15 most common causes of cancer death in the U.S. - in large part as a result of earlier screening and better treatments. But this year’s Annual Report to the Nation on the Status of Cancer marks the first concurrent decline in incidence, or the rate of new cancer diagnoses. For both American men and women, the incidence of all cancers combined decreased 0.8% per year from 1999 through 2005. That overall decline was largely driven by men, however: cancer incidence dropped 1.8% per year from 2001 through 2005 for men but just 0.6% per year from 1998 through 2005 for women.

Over roughly the same time period, death rates from all cancers fell in both sexes: 1.8% per year on average from 2002 through 2005. Again, the decline was slightly steeper in men, whose cancer death rate fell 2% a year from 2001 through 2005; in women, the death rate dropped 1.6% per year from 2002 through 2005.

That’s certainly good news. Indeed, the best indicator of progress is a declining death rate. But while the falling incidence rate suggests successful efforts at prevention, the real reasons behind the trend are not as clear-cut. Decreasing cancer rates may reflect a real reduction in cancer; they may also be a result of more frequent and effective screening, which can catch and cure pre-cancer, or they may reflect less frequent use of screens overall.

Although the trends are encouraging on the whole, some of the details of the data are knottier, highlighting gaps in access to health care. Cancer incidence was highest in black men, for instance, compared with men of other races. Among women, overall incidence was highest in white women, in whom the rate of lung cancer increased, while it remained stable in other populations. When parsed by race, cancer death rates were highest in blacks and lowest in Asians and Pacific Islanders. “The decrease in death rates could have been accelerated further by ensuring that all Americans have timely access to prevention measures,” says the report’s lead author, Ahmedin Jemal of the American Cancer Society. “We don’t optimize what we know about cancer prevention and treatment to all segments of the population in the U.S.”

That disparity is especially apparent when it comes to lung cancer. The report showed that lung-cancer incidence and death rates across the country varied widely, depending on the existence of smoking bans and the amount of state taxes on cigarettes. Data show, for example, that California, which was the first state to adopt a public-smoking ban, had the greatest decline in lung-cancer death rates in the U.S. - 2.8% per year from 1996 through 2005, which was twice the decline of many Midwestern and Southern U.S. states. Kentucky, which has low excise taxes on cigarettes and only partial smoking bans, had the country’s highest lung-cancer incidence and mortality rates; it also had the highest percentage of cigarette smokers: nearly 30% of its adult population.

According to Bevers, California saw a decline in lung-cancer incidence even among women, a reversal of the overall trend in lung-cancer rates, which have been steadily increasing in women since 1975. Researchers say the difference in lung-cancer rates between the sexes - incidence has been dropping in men since 1991 - may owe in part to the fact that women in the U.S. began smoking decades later than men.

The annual report, which was produced by the American Cancer Society, the Centers for Disease Control and Prevention and the National Cancer Institute, also underscores the value of screening. Doctors currently have good tests - such as PSA tests, mammograms and colonoscopies - for detecting lung, prostate, breast and colorectal cancers. The death rates for these diseases have dropped, according to recent data. Meanwhile, mortality for liver, esophageal and pancreatic cancers have risen in many populations - and it is probably no coincidence that regular, reliable tests for those conditions don’t exist.

The larger goals, say researchers, are earlier detection, better treatments and, most important, prevention. As more young people get vaccinated for hepatitis B, for instance, liver cancer, which is often a result of infection with the virus, may see its rates begin to drop in the coming years. But that depends on whether patients continue to use the screening methods currently available; other studies show that only about half of American adults get regular preventive care - including regular cancer screens like mammograms, PSA tests and colon exams.