One in five cancers diagnosed in U.S. is rare

A new study found 1 in 5 cancers diagnosed in the U.S. is a rare cancer. The details:

• For people 20 years or younger, two out of three cancers diagnosed are rare.
• More Hispanic (24%) and Asian/Pacific Islander (22%) patients are diagnosed with rare cancers compared with non-Hispanic blacks (20%) and non-Hispanic whites (19%).
• The five-year survival rate for rare cancers is poorer than that for common cancers in both males (55% vs. 75%) and females (60% vs. 74%) due to delays in diagnosis and fewer treatment options.

The definition: In the study, a "rare cancer" is defined as one diagnosed with fewer than six cases per 100,000 individuals per year. (There is no universally adopted definition of rare cancer; for instance, the National Cancer Institute defines rare cancers as fewer than 15 cases per 100,000 people per year.) The study examined incidence rates, stage at diagnosis, and survival rates for 181 rare cancers.

Some good news: The five-year relative survival rate is substantially higher (82%) for people younger than 20 diagnosed with a rare cancer than for adults aged 65-79 years (46%). But that's just one measure of cancer patients' health — childhood cancer survivors in particular can experience life-long health effects.

What's next: The proportion of rare cancers is likely to grow because molecular techniques are finding more differences and therefore more classifications of cancers. "Continued efforts are needed to develop interventions for prevention, early detection, and treatment to reduce the burden of rare cancers. Such discoveries can often advance knowledge for all cancers."