Though well-known cancers like breast and prostate cancer are still the most common, America has gotten really good at diagnosing rare cancers, according to a new study. 

This is a significant achievement, because rare cancers can be challenging to diagnose, often resulting in numerous physician visits, misdiagnoses, and substantial delays in diagnosis. Rare cancers have become an area of priority for some researchers and public health advocates because treatment options are often more limited and less effective than for more common cancers.

Yet because they are rare there is less preclinical research and fewer clinical trials for rare cancers - drug companies are not as motivated to study rare cancers if they are going to be vilified for an expensive drug, but when getting a drug to market costs at least a billion dollars, a small market means prices will be high. The US government has promised to streamline both approval and to cut the red tape in ridiculous policies like needing a web of approval and numerous months simply to get a change on a label.

Still, scientists are persisting. And the news is good. Using data from the North American Association of Central Cancer Registries and the Surveillance, Epidemiology, and End Results (SEER) program to comprehensively examine contemporary incidence rates, stage at diagnosis, and survival for more than 100 rare cancers (defined as an incidence of fewer than 6 cases per 100,000 individuals per year) in the United States, the authors found that approximately 20% of patients with cancer in the United States are diagnosed with a rare cancer. Rare cancers make up a larger proportion of cancers diagnosed in Hispanic (24%) and Asian/Pacific Islander (22%) patients compared with non-Hispanic blacks (20%) and non-Hispanic whites (19%). More than two-thirds (71%) of cancers occurring in children and adolescents are rare cancers compared with less than 20% of cancers diagnosed in patients aged 65 years and older.

Among solid tumors, 59% of rare cancers are diagnosed at regional or distant stages compared with 45% of common cancers. In part because of this stage distribution, 5-year relative survival is poorer for patients with a rare cancer compared with those diagnosed with a common cancer among both males (55% vs 75%) and females (60% vs 74%). However, 5-year relative survival is substantially higher for children and adolescents diagnosed with a rare cancer (82%) than for adults (46% for ages 65-79 years).

"Continued efforts are needed to develop interventions for prevention, early detection, and treatment to reduce the burden of rare cancers, write the authors. "Such discoveries can often advance knowledge for all cancers."