Ductal carcinoma in situ (DCIS) is cancer that is limited to the breast ducts and does not invade nearby tissue. The Van Nuys Prognostic Index (VNPI) classifies patients with DCIS to guide decisions on the best treatment option. The index uses patient age, tumour size, tumour growth patterns (histological grade) and the amount of healthy tissue surrounding the tumour after removal (resection margin width) to predict the risk of cancer returning.

After adding together the score from each of these factors, patients are classified into three categories:

  • low-risk (total VNPI¬† score of 4-6) breast conserving surgery (BCS) without radiotherapy is recommended
  • intermediate-risk (total VNPI score of 7-9) BCS with radiotherapy is recommended
  • high-risk (total VNPI score of 10-12) mastectomy is recommended.

VNPI scoring system

AGE

DCIS SIZE (mm)

HISTOLOGICAL GRADE

MARGIN WIDTH (mm)

more than 60 (score 1)

less than 16 (score 1)

1-2, no necrosis (score 1)

10 or more (score 1)

40-60 (score 2)

16-40 (score 2)

1-2, necrosis (score 2)

1-9 (score 2)

less than 40 (score 3)

more than 40 (score 3)

3 (score 3)

less than 1 (score 3)

According to National Breast Cancer Audit figures, most patients (77%) were managed in agreement with the VNPI classification system between 2004 and 2009. However, some patients received treatment that did not follow recommendations:

Low-risk patients

In low-risk patients undergoing BCS, over half also received radiotherapy, despite the lack of evidence that radiotherapy would improve outcomes in this group. These results suggest that some surgeons may have been overly cautious in their post-operative treatment advice.

Some low-risk patients underwent mastectomy (23%); however, this may be due to patient choice.

Intermediate-risk patients

Radiotherapy was not received by 20% of intermediate-risk BCS patients, including:

  • 3% with margins of 10mm or more
  • 15% with margins less than 10mm
  • 2% with cancer cells present at the edge of the removed tissue (involved margins).

A number of studies have questioned the value of radiotherapy in patients with margins larger than 10mm; however, this only accounts for a small proportion of patients in the current study. There is no evidence for withholding radiotherapy in patients with smaller or involved margins, which suggests that these patients may currently be under-treated.

Over one-third of patients in the intermediate-risk group were treated with mastectomy; however, the recommendation that women in this group undergo radiotherapy after breast conservation may have caused some to choose mastectomy instead.

High-risk patients

Almost one third (32%) of high-risk patients underwent BCS, of which the overwhelming majority also received radiotherapy. The VNPI suggests that, as a group, these patients may have been better treated by mastectomy. BCS may not give the patient an acceptable cosmetic outcome as the cancer is more extensive than in lower-risk patients; however, if immediate breast reconstruction is not advised or is unavailable for any reason, this may contribute to a patient choosing BCS over a mastectomy without reconstruction.

The results of the current study indicate that some patients at low-risk of recurrence may have been over-treated and some patients at intermediate- or high-risk of recurrence may have been under-treated. Although there may be reasonable explanations for some of this variation, the data does suggest that there may be room for improvement in the clinical management of DCIS in Australia and New Zealand.