Cancer Trends 29 - Breast cancer

The latest trends report just published by the National Cancer Registry shows that the chances of a woman developing malignant breast cancer before her 75^th birthday currently stands at about 1 in 10.

Breast cancer is the most common malignant tumour diagnosed in Irish women, with 2,883 cases diagnosed each year on average during 2011-2013. This represents almost one third of all major malignancies diagnosed in women. The incidence rate increased significantly between 1994 and 2013, by c.1.5% annually. The trend has been influenced somewhat by the introduction of screening (BreastCheck programme) from 2000 onwards.

Although survival from breast cancer is high (currently 82% five-year survival), it is the 2^nd most common cause of cancer death in women (after lung cancer). On average, 690 deaths per year were attributed to breast cancer during 2011-2012, accounting for 17% of all cancer deaths in Irish women. Nevertheless, the mortality rate has declined significantly by about 2% per year since 1994.

The trends for increasing survival and decreasing mortality are largely due to improvement in treatment. Most breast cancers are treated with a combination of modalities – surgery, radiotherapy, hormone therapy, chemotherapy and/or immunotherapy. Most patients have surgical treatment (c.85%), and there has been a strong trend towards greater use of breast-conserving surgery (BCS, ‘lumpectomy’) in combination with radiotherapy. Compared with mastectomy (removal of the breast), BCS allows faster recovery without the need for breast reconstruction. BCS now accounts for about two thirds of all surgical treatments for breast cancer.

The proportions of patients receiving radiotherapy have increased from 62% in 1999-2003 to 69% in 2009-2013, and hormone therapy from 49% to 55% over the same period.

HER2+ (positive) tumours have poorer prognosis. Most breast cancers are now tested for HER2 status, and a high proportion of HER2+ cases received the monoclonal antibody trastuzumab, which reduces the risk of recurrence and death.  About 15% Irish cases diagnosed during 2011-2013 were HER2+ and, of these, 65% received trastuzumab. These figures are broadly in line with the level of uptake in the UK and confirm that Irish patients have good access to this drug.

Commenting on the report’s findings, Dr Harry Comber, Interim Director of the National Cancer Registry noted: “Although the incidence rate of breast cancer continues to increase – partly influenced by improvements in screening – it is reassuring that the mortality rate continues to fall. Detailed collection of treatment data by the Registry also confirmed strong trends towards wider use of effective and appropriate treatment for this cancer.”