How is DCIS being treated in Australia and New Zealand?

Ductal carcinoma in situ (DCIS) is the presence of abnormal cells in the breast ducts or glands. DCIS, unlike invasive breast cancer, does not spread to the rest of the body, hence, the number of deaths from DCIS are low.

Since the introduction of breast screening programs and improvements in screening technology, cases of DCIS have been increasing, making up 14% of all breast cancers. The percentage is even higher (20-25%) when looking only at cancer found through breast screening.

This study looked at management of DCIS in Australia and New Zealand from 2007 to 2016. Most DCIS cases were among women in the target ages of breast screening programs for each country (50-74 in Aus vs 45­­­­­-69 in NZ). Treatment did not appear to change over this decade.

Overall, breast conserving surgery (BCS) was the most common surgery type. In women over 50 years of age, BCS followed by radiation therapy was more common than mastectomy. However, in women younger than 40 years, mastectomy was the most common surgery, as this group of women are more likely to go on to develop invasive breast cancer. There is no indication that outcomes are improved from the more invasive treatment given to these women.

Mastectomy is more common for women with larger tumours or high-grade DCIS. Although these are factors in decision-making on treatment, they will not perfectly predict whether a patient who had a DCIS tumour will later develop invasive breast cancer.

A large proportion of women with DCIS received sentinel node biopsy (SNB), and this has increased over time. Guidelines for management of women with pure DCIS do give reasons for considering SNB. However, there are still a significant proportion of cases where it is unclear whether it should have been received.

Over-treatment is a risk for DCIS cases. Future recommendations include:

• Clearer guidelines for use of SNBs in women with pure DCIS
• Information for specialists on how to de-escalate management
• Inclusion of biological markers in the BreastSurgANZ Quality Audit, as they will become more frequently used in decision-making on treatment
• Formal bi-national registry to assess different DCIS therapy for effectiveness, cost versus benefit, and patient satisfaction.

Omling, S., Houssami, N., McGeechan, K., Zackrisson, S., Jacklyn, G., Walters, D., Barratt, A. and Farber, R. (2021), The management of women with ductal carcinoma in situ of the breast in Australia and New Zealand between 2007 and 2016. ANZ Journal of Surgery, 91: 1784-1791. https://doi.org/10.1111/ans.16970