Definition of rare cancers

In Japan, rare cancers are defined as those with a morbidity (incidence rate) of 6/100,000 according to the Ministry of Health, Labour and Welfare*1.

Due to the limited number of patients dispersed around the country, medical care and treatment at the right time for rare cancer patients are more challenging than for other cancers.
MHLW also takes the following 3 criteria to confirm the definition of each rare cancer:

  1. lack of established standard diagnostic and therapeutic methods
  2. limited progress in research and development, as well as limited availability of clinical studies
  3. delay in establishment medical treatment system

Even though each type of rare cancer is rare, the sum of all rare cancers accounts for about 2 out of 10 new cancers diagnosed..
As comparison, rare cancers in Europe account for 15% of all cancers*2.
In addition, numbers for pediatric and AYA generation rare cancers are larger than other generations.

*1 Japanese version: 「希少がん医療・支援のあり方に関する検討会報告書」厚生労働省 Aug. 2015 (PDF)
*2 “Rare cancers are not so rare: The rare cancer burden in Europe” EUROPEAN JOURNAL OF CANCER 47 2011 (PDF)

Types of rare cancers

There is currently no accurate list in the country as to what type of cancer hits rare cancer. As data collection of “nation cancer registration” started in 2017, an accurate list should become available in the near future.

The “Tier 2” of the “List of Rare Cancers” published by RARECARENet*3 in Europe is a useful reference to allow the evaluation whether a cancer is a rare cancer.

This classification is also used as reference by the Ministry of Health, Labor and Welfare ‘s Study Group on Rare Cancer Medicine and Support”.

In addition, the Rare Cancer Center at the National Cancer Center of Japan is currently proposing a list of Rare Cancers (in Japanese)*4.

For further information on Rare Cancers history and current status, please refer to “Rare Cancers in Japan”*5.

*3 “List of Rare Cancers” by RARECARENet
*4 希少がんセンターのサイトにある「さまざまな希少がんの解説」
*5 “Rare Cancers in Japan, A. Kawai, Nov. 2017