Women with what is referred to as "triple-negative" breast cancer are more likely than other women with breast cancer to experience a relapse, a new study by Canadian researchers shows.

Triple-negative breast cancers are estrogen receptor-negative, progesterone receptor-negative, and HER2-negative.

The study shows women with triple-negative breast cancer were almost twice as likely to develop distant relapse even after accounting for other factors related to relapse such as tumour size and involvement of lymph nodes. 

"To confirm both the aggressive nature of triple-negative breast cancers regardless of other tumour features, and the distinct pattern of relapse will help identify those patients who need aggressive treatment up front," said Dr. Rebecca Dent, a medical oncologist at Sunnybrook's Odette Cancer Centre.

Dent collaborated on the study with Dr. Steven Narod at Women's College Hospital.

Their study found that the pattern of relapse had a rapidly rising rate in the first two years following diagnosis and a peak at two to three years followed by a decline over the next five.

Lower risk of longer-term recurrence

Unlike other breast cancers where the risk of relapse and death remained throughout the entire study period, most triple-negative breast cancer patients who had no evidence of progression after eight years, did not recur thereafter. 

Despite having a high risk of early recurrence, the study indicates that triple-negative breast cancer patients who remain disease-free for eight years are unlikely to die of breast cancer and may be "cured" of their disease. 

In those who relapsed, the median survival time from relapse to death was nine months, compared to 20 months for other types of breast cancer.

The study also identified specific characteristics of triple-negative breast cancers.

The mean age of diagnosis, 53, was younger compared to that of other breast cancers, which was age 58.

Tumours were larger and of higher grade, with 66 per cent of triple-negative breast cancer having high grade tumours compared to 28 per cent in other breast cancers.

Mean tumour size was also larger in triple negative breast cancer patients. Only 36 per cent of triple-negative tumours were less than two centimetres, compared to 63 per cent of other breast cancers.

"The overall goal is to identify new targeted therapies to improve the outcomes for this younger group of women with breast cancer just as we identified [Herceptin] for women with HER2-positive breast cancer," said Dent.

Researchers evaluated 1,601 patients diagnosed with invasive breast cancer from 1987 to 1997. Of those patients, 180 were identified as having triple-negative breast cancer. All patients were followed for a median of eight years and up to 17 years from diagnosis. 

The results of the study are published in the journal Clinical Cancer Research.