Research has shown a link between antibiotic usage and a higher risk of colon cancer. India is one of the world's biggest users of antibiotics and as per the statistics, it cannot be denied that antibiotics are the possible contributors to colon cancer in the country.

The research

New research has established a link between antibiotic usage and a higher risk of colon cancer. The most recent statistics came from a study of the Swedish population. The researchers examined data from more than 40,000 individuals with colorectal cancer and 200,000 cancer-free controls.

Antibiotic usage was classified as no use (no antibiotics were reported being used throughout the research period), low use (1–10 days), moderate use (11–60 days), high use (61–180 days), and extremely high use (>180 days). The research, headed by Sophia Harlid, PhD, of Ume University's Department of Radiation Sciences and Oncology in Ume, Sweden, was published online on September 1 in the National Cancer Institute's Journal.

Antibiotic usage and colon cancer

The findings corroborate those of previous Scottish research, which showed that a history of antibiotic usage increased the chance of getting colon cancer by 49 per cent in people younger than 50, but not rectal cancer.

The new Swedish data, scientists said, "confirm previous findings and offer fresh insights into site-specific carcinogenesis, as well as indirect support for the involvement of gut microbiota, because the favourable correlations between antibiotic usage and proximal colon cancer started at the lowest levels of antibiotic use, they may provide a rationale for clinical practise to reduce antibiotic prescriptions."

The researchers argue in their paper that the higher risk may be due to antibiotics' "disruptive impact" on the gut microbiota. The elevated risk of cancer in the proximal colon but not farther down the alimentary tract, the authors wrote, "is consistent with a strong microbial effect in the proximal colon and a decreasing concentration of short-chain fatty acids along the colon." This leads to a "significant increase in bacterial activity, biofilm formation, and fermentation in the proximal colon and rectum as compared to the distal colon and rectum."

The main findings of the study

1. The researchers conducted an analysis of complete-population data from Swedish national registries from July 1, 2005, to December 31, 2016. They compared case patients diagnosed with colorectal cancer between January 1, 2010 and December 31, 2016, in a 1:5 ratio with cancer-free controls. The Swedish Prescribed Drug Register was used to obtain data on antibiotic usage.
2. Additionally, socioeconomic characteristics and healthcare use were collected from the Swedish Inpatient Register and the Longitudinal Integration Database for Health Insurance and Labor Market Studies.
3. The researchers found 40,545 patients with colorectal cancer and 202,720 healthy controls. Men made up slightly more than half (52.9 percent) of the subjects, and the average age at cancer diagnosis was 72 years. 36.4 percent of the cases included proximal colon cancers, 29.3 percent involved distal colon cancers, and 33.0 percent involved rectal malignancies.
4. Control patients were more likely than case-patients to have been given no antibiotics, at 22.4 percent versus 18.7 percent. Case patients were significantly more likely than controls to have taken antibiotics for more than two months, 20.8 percent versus 19.3 percent (P.001).
5. Antibiotic usage was shown to be positively related to colorectal cancer in general. The odds ratio for moderate usage was 1.15 when compared to no use, and 1.17 when compared to extremely high use (P.001 for trend).
6. By excluding all antibiotic usage in the two years before a colorectal cancer diagnosis, the relationship was diminished to the point that it was no longer significant for extremely high versus no antibiotic use. The researchers discovered that the dose-response connection between antibiotic usage and colorectal cancer was mainly limited to proximal colon cancer, with an odds ratio of 1.09 for moderate use and 1.17 for very high use in contrast to no use (P.001 for trend).
7. The association was "near to nil" for distal colon cancer. There was a modest negative association between rectal cancer and antibiotic usage, with an odds ratio of 0.96 for moderate use and 0.91 for extremely high use compared to no use (P.001 for trend). This connection was seen in women exclusively, while the others were observed in men and women alike.

Situation in India

In India, rates of colorectal cancer are increasing. While absolute rates are modest in the Indian population, increasing rates contribute to India's rising cancer morbidity. The increasing rates may be linked to changing lifestyles that include a high-calorie, low-fibre diet, an excessive intake of red meat and processed foods, and inactivity.

India is one of the world's biggest users of antibiotics. And its abuse and overuse are widespread. One cannot dispute that antibiotics may have contributed to the increasing trend of colon cancer in India.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author is a practising super specialist from New Delhi.