While no precise definition of rare cancer exists, rare cancers are frequently described as those with an incidence rate of fewer than 6 cases per 100,000 persons per year (fewer than 15 per 100,000 in the United States). But those numbers don’t come close to recognizing the sweeping impact of rare cancers. An American Cancer Society study published in May found, for example, that rare cancers affected children in outsized proportions.3

“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,” the study stated.

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And, the study continued, rare cancers are frequently diagnosed at later stages, resulting in significantly worse outcomes.

“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%).”

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Barbara Van Hare, BA, director of foundation partnerships at the Rare Cancer Research Foundation in Durham, North Carolina, said that proper diagnosis of rare cancers is often delayed because of lack of knowledge.

“One of the big problems with rare cancers is that many patients are misdiagnosed,” she said. “Lots of patients [are misdiagnosed] multiple times.”

The US Food and Drug Administration (FDA) has, however, fast-tracked approval of some drugs aimed at rare cancers.

“In a survey of 68 oncology drugs gaining [FDA] approval from 1973 through 2006 (excluding hormone therapy), 31 gained marketing authorization without a randomized trial,” a 2015 analysis stated. “For these 31 drugs, a median of two clinical trials (range, one to seven) and only 79 patients (range, 40 to 413) were used per approval. Not surprisingly, the vast majority of approvals were for rare neoplasms.”4

Furthermore, the National Cancer Institute included the study of rare cancers in the mandate of the National Clinical Trials Network (NCTN).

“One of the strengths [of the NCTN] is its size and being able to have thousands of different investigators participating in a single trial,” said Anne Schott, MD, associate director of clinical research at the University of Michigan Comprehensive Cancer Center in Ann Arbor, and deputy chair of SWOG, 1 of 4 adult NCTN groups, in an interview with Cancer Therapy Advisor.

Dr Schott and her co-authors stated in the analysis, the NCTN “launched two basket trials targeting rare subtypes within common histologies.”