Opium use and risk of colorectal cancer: a multi-center case-referent study in Iran

Abstract

Background

Opium use has been associated with an increased risk of cancers of the lung, oesophagus, and pancreas, and it was recently classified by the International Agency for Cancer Research as carcinogenic to humans. It is not clear whether opium also increases the risk of colorectal cancer (CRC). The aim of our study was to assess the association between various metrics of opium use and the risk of CRC.

Methods

This case-referent study from seven provinces in Iran comprised 848 CRC cases and 3215 referents. Data on opium use (duration, amount, frequency) and potential confounders were collected by trained interviewers. Multivariable unconditional logistic regression models were used to measure odds ratios (OR) adjusted for age, gender, province, marital status, family history of CRC-linked cancers, consumption of red meat, fruits and vegetables, body shape, occupational physical activity, and socioeconomic status.

Results

Regular opium consumption was not associated with the risk of CRC (OR 0.9, 95% confidence interval, CI: 0.7, 1.2) compared to subjects who never used opium. However, frequent opium use more than twice a day was associated with an increased risk of CRC compared to non-users of opium (OR: 2.0, 95% CI: 1.1, 3.8; p for quadratic trend 0.008).

Conclusion

There seems to be no overall association between opium use and CRC, but the risk of CRC might be increased among persons who use opium many times a day.

Keywords:

• IROPICAN
• opium
• colon cancer
• rectum

Authors’ contributions

MH did the literature review. HR, AN, MGH, MM, EM, RS, MS, BH, MB, RA, VA, SSH, AN, FN, AM, and AR contributed to data collection. FZ, RM, and MN provided clinical consultation. MH, HP, AR, RM, PB, EW, FK, KZ, and EP designed the study. MH and EP did the data analysis, interpreted data, and prepared the manuscript draft. All authors critically appraised the drafts of the manuscript and approved the final version. KZ is the guarantor of the study.

Authors’ disclaimer

Where authors are identified as personnel of the International Agency for Research on Cancer/World Health Organization, the authors alone are responsible for the views expressed in this article, and they do not necessarily represent the decisions, policies, or views of the International Agency for Research on Cancer/World Health Organization.

Ethical approval

The study was approved by the Ethics Committee of the National Institute of Medical Research Development (NIMAD) in Iran (Code: IR.NIMAD.REC.1394.027).

Consent to participate

Written informed consent was obtained from the parents.

Disclosure statement

There is no competing interest between authors.

Data availability statement

The data underlying this article cannot be shared publicly due to privacy of individuals that participated in the study. The data may be shared on reasonable request to the corresponding author.

Additional information

Funding

The IROPICAN study was funded by the National Institute for Medical Research Development (NIMAD), Iran (grant number: 940045). The IROPICAN study was funded by the National Institute for Medical Research Development (NIMAD), Iran (grant number: 940045). Also, this PhD paper was granted by the Cancer Society of Finland, and by the Orion Research Foundation (grant number: 2D30019).