Madrid, 20 March 2024. With more than 44,000 new cases, colon and rectal cancers will be those most frequently diagnosed in Spain in 20241 and are the second most common cause of cancer death in our country. The 5-year overall survival rate for people with colorectal cancer (CRC) is around 65%2. However, the rate can vary depending on various factors, especially the stage of the disease, with a 5-year survival rate of 90% in people with early-stage colorectal cancer compared with approximately 10% once metastases occur. This means that colorectal cancer detected early is potentially curable in 9 out of 10 patients2.
The absence of symptoms in the early stages is the main reason why many patients do not consult their doctor until such symptoms occur and diagnosis is more frequent when the disease has reached stages that are more advanced. Early diagnosis through screening tests is therefore essential and it will help save lives. In fact, according to Dr. José Ignacio Martín Valadés, Head of the Digestive Tumours Department at MD Anderson Cancer Center Madrid, figures suggest that the correct implementation of screening tests could reduce annual deaths from CRC by approximately a third.
"Screening tests in colorectal cancer allow more frequent diagnosis of the disease in its initial stages, when the disease is usually asymptomatic and the probability of cure is highest, or even in precancerous stages, when the endoscopic removal of the premalignant lesion will actually prevent the development of CRC," says the specialist.
Evolution of CRC screening tests: detection of tumour DNA in faeces
Faecal occult blood tests (FOBT) have been evolving and improving over the years. In the past, we employed a chemical guaiac blood test, which required prior dietary restrictions and the taking of several samples. Nowadays we can perform an immunohistochemical test that uses antibodies to detect blood (FIT), providing greater sensitivity and specificity than the guaiac test. In addition, one does not need to vary the diet and it only requires a single sample. There are currently other tests to detect tumour DNA in faeces, which, according to the specialist, "improve the results of previous methods”.
In the context of the above, Dr. Martín Valadés highlighted that the New England Journal of Medicine recently published results of the BLUE-C study, which compared a next-generation combined test for the detection of tumour DNA and faecal haemoglobin against the traditional test for the detection of haemoglobin in faeces (FIT). On a sample of more than 20,000 individuals, the new test demonstrated CRC detection sensitivity of 93.9% with a specificity of 90.6%3.
As regards blood tests, he emphasized that their potential benefit would be based on not needing to obtain a stool sample as we can actually utilize any other blood test prescription, bearing in mind that a positive result (as with tests performed on stools) would still require a subsequent colonoscopy. On the other hand, the same article also published the results of the ECLIPSE study, based on the detection of circulating tumour DNA in blood from a sample of almost 7,900 people. The sensitivity of the test for the detection of CRC was 83.1% and the specificity for the detection of advanced neoplasia (CRC or advanced precancerous lesion) was 89.6%4.
Our expert went on to conclude that: “in all events, although it is desirable that the new screening tests for the early detection of CRC are accompanied by an increased adherence to their findings, it is still necessary to confirm this hypothesis. We first need to evaluate whether the cost-benefit of the new tests justifies their implementation and determine the periodicity at which they should be carried out,"
An increase in CCR case among younger patients
Currently, the recommended screening programs are largely directed at the medium-risk population; in other words the 50-69 age group, without specific personal or family history CCR risk factors (apart from their age), through non-invasive bi-annual FOBT, followed by colonoscopy in the event of a positive result5.
However, Martín Valadés points to the fact that, in recent years, there has been an increase in cases of CRC in younger patients and as a result, various medical societies are evaluating the option of advancing the initial age for screening to 45. "On the other hand” he adds, “age is still considered one of the main risk factors associated with CRC, so in the same way one might be inclined to consider increasing the age for screening tests to 75."
Awareness of and participation in CCR screening tests in Spain
Based on a study by the Spanish Association Against Cancer (AECC) via surveys conducted in 2022 on the target population for CCR screening tests, more than 80% of those surveyed knew about or had at least heard of these screening tests, particularly those involving FOBT. However, there were still 13% of who claimed to have no knowledge at all6.
Despite this, according to a report published in 2021, the 2020 screening program extended to 13 of Spain’s 17 regions with a participation rate of 46.1%, although there was a significant variability in coverage between the different regions7.
"Of course, the goal is to achieve 100% coverage of the target population. Although the actual participation rate exceeds the acceptable minimum of 45% recommended by the European Quality Guide for CCR8 screening, it is still a long way short of the 65% target set as part of the National Health System's Cancer Strategy5," added Dr. Martín Valadés in response to these figures.
“CRC screening save lives. Although new tests and methods have been developed and will likely be introduced over the coming years, the best test is still the one actually performed", concluded the head of the Digestive Tumours Department at MD Anderson Madrid.
References:
1. Sociedad Española de Oncología Médica – SEOM - Las cifras del cáncer en España. Disponible en: https://www.seom.org/images/LAS_CIFRAS_2024.pdf
2. Pronóstico del cáncer de colon. (s. f.). Disponible en: https://www.contraelcancer.es/es/todo-sobre-cancer/tipos-cancer/cancer-colon/evolucion-cancer-colon. Último acceso: marzo 2024
3. Imperiale TF et al . Next-Generation Multitarget Stool DNA Test for Colorectal Cancer Screening. N Engl J Med 2024; 390:984-993
4. Chung DC et al . A Cell-free DNA Blood-Based Test for Colorectal Cancer Screening. N Engl J Med 2024; 390:973-983
5. Estrategia en Cáncer del Sistema Nacional de Salud. Ministerio de Sanidad. 2021. Disponible en: https://www.mscbs.gob.es
6. Estudio sobre los programas de cribado de cáncer colorrectal. Observatorio del Cáncer de la Asociación Española Contra el Cáncer. Disponible en: https://observatorio.contraelcancer.es
7. Molina-Barceló, A. et al. Desigualdades de acceso a los programas de cribado del cáncer en España y cómo reducirlas: Datos de 2013 y 2020.; Rev Esp. Salud Publica. 2021, 95, e202101017.
8. Segnan N et al. European guidelines for quality assurance in colorectal cancer screening and diagnosis. First edition. Luxembourg, Office for Official Publications of the European Communities, 2010.