Quarter of Cancer Diagnoses in the EU Are Rare Cancers

Pam Harrison

July 10, 2017

Almost one quarter of all cancer diagnoses in the European Union (EU) from 2000 to 2007 were rare cancers,  with an annual incidence of less than 6 per 100,000 individuals, a population-based study suggests.

Furthermore, the overall incidence of rare cancers has been rising by 0.5% per year since 1999, as has the 5-year relative survival rate for most rare malignancies.

"To our knowledge, this is the largest study that estimates the burden of rare cancer for Europe, including trends in incidence and survival rates," writes lead author Gemma Gatta, MD, Nazionale dei Tumori, Milan, Italy, and members of the project Information Network on Rare Cancers (RARECAREnet).

"This very large population-based study on rare cancers...provides useful information for public health," study authors add.

The study was published online July 4 in the Lancet Oncology.

RARECAREnet members analyzed data from 94 cancer registries representing over 2 million diagnoses of rare cancer in Europe between 2000 and 2007.

"Seven registries...provided additional data for hospitals treating about 220 000 cases diagnosed in 2000-07," the researchers add.

The researchers also analyzed trends in 5-year cancer survival rates between 1999–2001 and 2005–2007.

In total, the group tallied incidence and survival estimates for 198 rare cancers diagnosed in the EU over the study interval.

The "5-year relative survival for all rare cancers was 48.5%...compared with 63.4%...for all common cancers," the team reports.

Furthermore, the relative survival rate over 5 years also increased by 2.9% between 1999–2001 and 2007–2009. The largest increases in 5-year relative survival rates were observed for hematologic malignancies and sarcomas.

Five-year survival rates were lower within families of rare digestive cancers, at only 15.3%, and higher for rare female genital cancers, at 57.7%; rare male genital and urologic cancers, 73.6%; rare skin cancers, 70.2%; and rare hematologic malignancies, 50.5%.

Rare Cancer Treatment

Looking at how rare cancer is treated in the EU, Dr Gatta and colleagues found that the degree of centralization of that treatment varied widely both between cancers and between countries.

For example, mean admission volumes ranged from a high of 82.9 treatments per year for head and neck cancer to under 0.5 treatments per year for choriocarcinoma and some embryonal and endocrine tumors.

"The higher the incidence, the larger the mean admission volume of treating hospitals," the researchers observe. The Netherlands and Slovenia had the highest treatment volumes among the seven countries that provided additional data on the treatment of rare cancers.

Nevertheless, RARECAREnet members concluded that centralization of treatment is clearly needed in order to improve outcomes in the seven countries where this endpoint could be studied.

Survival of patients with a rare cancer could similarly be enhanced with earlier diagnosis, new treatments, and better case management, the authors suggest.

Reliable Data Needed

Commenting on the study in an accompanying editorial, Alastair Munro, MBChB, from the University of St Andrews, United Kingdom, points out that despite researchers' best efforts, there are problems with the quality and the scope of data that are entered into these kinds of registries.

"In a survey, 44 of 123 pathologists said that they encountered fewer than eight rare cancers per year and 14 out of 29 pathologists from eastern Europe rated their pathology standards as average or low," Dr Munro writes.

These discrepancies could markedly influence the incidence of overall cancer in different EU nations — differences that might be genuine but could just as well be artifactual, he suggests.

"It should be a matter for regret that, in the developed world, and despite clinicians' ready access to information technology, we have not successfully established uniform, prospective, population-based registries of patients treated for uncommon cancers, with automatic linkage to reliable data on treatment and outcomes," Dr Munro states.

"Clinicians and epidemiologists should rise to the challenge," he suggests.

The authors and the editorialist have disclosed no relevant financial relationships.

Lancet Oncol. Published online July 4, 2017. Abstract, Editorial

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