On World Cancer Day... let's talk about tumors of unknown origin
4th February is World Cancer Day. Founded by the Union for International Cancer Control, its main objective is to raise awareness, both in society and among public bodies, about how much more can and must be done to fight cancer.
Cancer refers to a large group of diseases characterized by the development of abnormal cells, which proliferate without control, and which can appear in any part of the body. Cancer is caused by damage to DNA (genetics) and/or to its regulatory mechanisms (epigenetics). In most cancers, this damage is be caused by external factors, while in some cases hereditary factors also play a part.
Cancer continues to be a leading cause of global morbidity and mortality, with 14.1 million new cases and 8.2 million deaths in 2012, of which 4 million were people aged 30-69 (World Cancer Report 2014, IARC). The largest number of deaths were due to lung, liver, gastric, colorectal, breast and esophageal cancer.
Estimates for the year 2025 predict more than 19 million new cases and more than 11 million global deaths.
In Spain, according to the annual report Cancer Statistics in Spain 2017 (in Spanish), recently published by the Spanish Society of Medical Oncology (SEOM), the incidence of cancer in 2015 has already exceeded the estimates made for the year 2020 by more than a thousand cases, with 247,771 new incidences. The most frequent types of cancer in both sexes were colorectal, prostate, lung, breast and bladder.
This increase is mainly due to the country's demographic characteristics (population growth and aging), early detection techniques and unhealthy lifestyle habits, especially tobacco and alcohol consumption, obesity and sedentary lifestyle. These lifestyle factors can significantly increase the risk of cancer but are, in turn, potentially modifiable.
Thanks to advances in cancer treatment, although the prognosis and treatment of various types of cancer can be very different, the survival and overall quality of life of patients in recent years has increased. About 50% of patients diagnosed with cancer in Spain live for more than five years.
One form which is little known to the general public is cancer of unknown primary (CUP). It is defined by the presence of a histologically confirmed metastasis whose site of primary origin is unknown, despite a detailed and standardized diagnostic study.
CUP represents between 3 and 5% of all malignant tumors of both sexes, and is the tenth most common tumor worldwide, with an incidence similar to or even greater than that of pancreatic gastric cancer. It is the fourth most common cause of cancer death in both men and women.
The majority of patients with CUP present an advanced stage of the disease and therefore have a poor prognosis. In addition, the absence of a clear diagnosis of the origin of the tumor makes it harder to establish the most effective treatment for these patients. An empirical, less specific, more toxic approach is usually followed, with a subsequent reduction in the likelihood of survival.
However, new diagnostic tools have emerged in recent years to better understand CUP, such as more specific gene expression profiles, some of which are more sensitive than standard methods in identifying the origin of the tumour.
Going into genetics in more depth, recent discoveries linking epigenetic modification - DNA methylation - and cancer have been applied to developing a platform to determine the origin of a CUP tumor with great accuracy and precision. A collaboration between the Epigenetics and Cancer Biology program at the Bellvitge Biomedical Research Institute (IDIBELL), led by Dr. Manel Esteller, and Ferrer have created such a platform for professionals which is already available in Spain.
These advances in new diagnostic techniques can help the specialist to define more specific therapies for these patients, which can in turn lead to better outcomes and prognoses.