Temporal Trends of Sex Disparity in Incidence and Survival of Colorectal Cancer: Variations by Anatomical Site and Age at Diagnosis

Abstract

Purpose

The incidence of colorectal cancer (CRC) varies by age, sex, and anatomical subsite. Few studies have examined the temporal trends of age-specific sex disparity in incidence and survival by age at diagnosis and anatomical site.

Patients and Methods

The study was performed on all incident cases of CRC, using data derived from the nationwide Swedish Cancer Register between 1960 and 2014, including right-sided colon cancer (RCC), left-sided colon cancer (LCC), and rectal cancer. Male-to-female age-standardized incidence rate ratio (IRR) and male-to-female five-year survival rate ratio (SRR) were calculated as the main indicators. Furthermore, we performed joinpoint regression analyses to estimate average annual percentage change.

Results

The overall male-to-female IRR was 1.05 for RCC, 1.31 for LCC, and 1.66 for rectal cancer. Male-to-female IRR increased steadily for RCC by an average of 0.4% per year until the mid-1990s and then decreased gradually by an average of 1.0% per year. LCC patients showed an increase of 0.6% per year since the mid-1970s. For rectal cancer, a non-significant random fluctuation was noted during the study period. The temporal trends of male-to-female IRR varied by age at diagnosis. The male-to-female SRR was 0.87 for RCC, 0.88 for LCC, and 0.86 for rectal cancer, which remained relatively stable during the study period.

Conclusion

Sex disparity of CRC is age-, period-, and anatomical subsite-dependent. Further studies are needed to investigate the underlying contributing factors.

Keywords:

• colorectal cancer
• sex disparity
• incidence
• survival
• temporal trend

Acknowledgments

The authors wish to thank the CPF’s science editor Patrick Reilly for his valuable comments on the text. This work was supported by grants awarded to Dr. Jianguang Ji by the Swedish Research Council (2016-02373) and Cancerfonden (2017 CAN2017/340) and The Crafoord Foundation, to Professor Kristina Sundquist and to Professor Jan Sundquist by the Swedish Research Council (2018-02400 and 2016-01176, respectively), to Jan Sundquist, Kristina Sundquist, and Jianguang Ji by ALF funding from Region Skåne. The funding agencies had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript. The researchers were independent of the funding agencies.

Disclosure

The authors report no conflicts of interest in this work.