Colorectal cancer (CRC) is the second most common cancer in men and the third most common cancer in women worldwide. Survival after CRC diagnosis is increasing thanks to early detection and better treatments.
The variation of lifestyle
Large variations in survival exist among CRC patients that might be related to differences in lifestyle. Abundant research has shown that CRC risk is influenced by lifestyle characteristics such as smoking, high alcohol consumption, diets low in fibre and rich in processed meats, low physical activity and high body fatness.
In 2007, the World Cancer Research Fund/American Institute of Cancer Research (WCRF/AICR) evaluated the existing scientific evidence on the link of cancers with diet, physical activity and body fatness with the aim of deriving lifestyle recommendations for cancer prevention.
What are the recommendations?
The ten recommendations created include the maintenance of a healthy body weight throughout lifetime, being physically active, eating mostly a plant-based diet, avoiding the consumption of highly preserved foods, preserved meats, sugary drinks and other foods that promote weight gain, and drinking alcohol in moderation, if any.
A special recommendation for mothers to aim to exclusively breastfeed their children up to six months was included, and for cancer survivors to follow the recommendations for cancer prevention. The latter was based in the data on cancer prevention, because studies on the link of dietary and lifestyle factors on cancer survival were still scarce.
Developing an index score
A few years ago, a team of researchers, led by Dr. Teresa Norat, developed an index score to reflect adherence to the WCRF/AICR recommendation that could be applicable in epidemiological studies.
The first studies were conducted within the large European Prospective Investigation into Cancer and Nutrition (EPIC). This is a prospective study of over half a million participants across ten European countries with the aim of ascertaining how lifestyle, metabolic and genetic factors may influence the risk of developing cancer and other chronic diseases.
Their lifestyle and other characteristics were collected through questionnaires or measured. The study participants have been followed up for ascertainment of all new cancer diagnosis and causes of deaths.
What did the results show?
The study showed that participants with higher WCRF/AICR index scores, reflecting a lifestyle in concordance with the WCRF/AICR recommendations, had 18% lower risk of having any type of cancer, 27% lower risk of CRC, and lived longer than participants with the lowest scores.
Other research has later confirmed our first findings: despite differences in study populations, overall greater adherence with the WCRF/AICR recommendations predicts a lower cancer risk.
One of the research questions recently explored in EPIC is whether people with lifestyle in concordance with the WCRF/AICR recommendations live longer after cancer diagnosis than people whose lifestyle is less concordant with the recommendations for cancer prevention.
CRC patients with a higher WCRF/AICR score had 30% lower risk of dying from CRC compared to those with lower adherence.
We calculated the WCRF/AICR score in 3,292 EPIC participants that had been diagnosed with CRC 6.4 years later on average. The score was constructed using data on lifestyle and body weight assessed before cancer diagnosis. About four years after CRC diagnosis, 1,113 patients had died, from which 872 deaths were due to CRC.
We observed that CRC patients with a higher WCRF/AICR score (higher adherence to the recommendations before cancer diagnosis) had 30% lower risk of dying from CRC compared to those with lower adherence.
When we looked specifically at each recommendation, having a healthy body weight (not being obese or overweight), and having a diet rich in plant foods were the factors that better predicted survival in these CRC patients. Our analysis also took into account smoking habits of the study participants.
We acknowledge that this study has several limitations. First, lifestyle and body weight were assessed only at enrolment in EPIC, before cancer diagnosis, and may have changed during follow-up, especially after cancer diagnosis. Also, we could not investigate whether lifestyle or weight changes after cancer diagnosis could improve survival; neither had we investigated lifestyle in patients during cancer treatment.
Improving the chances
In spite of these limitations, our research has important implications. We have shown that a healthy lifestyle during adulthood, in line with the WCRF/AICR recommendations may contribute to cancer prevention and increase survival after CRC diagnosis.
In the words of our colleague Dr Giota Mitrou, Head of Research Funding & Science External Relations at World Cancer Research Fund International: “This research confirms what we have been saying for some time about the crucial role of diet, nutrition and physical activity in preventing bowel cancer.
“The research shows that people whose lifestyles were broadly in line with the cancer prevention recommendations before being diagnosed with bowel cancer had a greater chance of surviving bowel cancer.
“Latest figures show that half of us may get cancer in our lifetime, but the truth is we will not be able to treat our way out of this epidemic without investing in cancer prevention research and using the evidence to implement public health interventions that help prevent cancer”.