Incidence trends of ductal carcinoma in situ in New Zealand women between 1999 and 2022.

BACKGROUND

In New Zealand, BreastScreen Aotearoa (BSA), a biennial national breast screening programme, was implemented in 1998. This study examines the incidence trends of ductal carcinoma in situ (DCIS) in New Zealand women from 1999 to 2022.

METHODS

All women with a primary diagnosis of DCIS over the 24-year study period were identified from the New Zealand Cancer Registry and BSA records. Age-standardised incidence rates (ASIR), detection rates (ASDR) and average annual percent changes were calculated.

RESULTS

The annual ASIR was 13.5 per 100,000 New Zealand women, and increased by 0.91% (95% confidence interval (CI): 0.26%, 1.66%) annually. Among women aged 45-69 years during 2006-2022, the annual ASIR was 36.3 for programme-detected DCIS, increasing 1.29% (95%CI: 0.13%, 2.73%) per year, and 14.2 for non-programme-detected DCIS, with no significant changes over the study period. The programme-detected ASIRs were highest for Pacific (38.6), Asian (38.2), and Māori (38.0) women. The programme ASDR was 0.55 per 1000 women screened, with no significant changes over time, and was highest for Asian (0.69), and Māori and Pacific (both at 0.65) women.

CONCLUSION

DCIS incidence increased in New Zealand women from 1999 to 2022, driven by an increase in screening participation, and varied by ethnicity.