A new study has reported breast cancer relapse rates according to subtype in an effort to evaluate the need for individualized surveillance and follow-up after initial treatment. At least five distinct breast cancer subtypes have been identified using gene expression profiles. These subtypes tend to have specific profiles in terms of relapse patterns, typical metastatic sites, and the risk of progression to stage IV breast cancer. However, the follow-up programs which are currently used do not take into account the differences among subtypes. In the study, the characteristics and outcomes of 1,879 patients with invasive breast cancer during the period 2000 to 2004 were analyzed.
A total of 316 (17%) of the patients relapsed during a median follow-up period of 75 months. HER2 overexpression, triple negative subtype, high histological grade, and TNM stage 3 were identified as independent risk factors for breast cancer recurrence. The authors developed a scoring system based on these risk factors as follows: score 0 = no risk factor; score 1 = 1 risk factor; score 2 = 2 risk factors; and score 3 = 3 risk factors. Patients with a score of 0 to 2 were found to have relatively low risk of relapse, whereas those with a score of 3 were at high risk. The high-risk group was comprised of two subgroups: (1) HER2 positive breast cancer patients with a high histological grade and TNM stage 3; and (2) triple negative breast cancer with a high histological grade and TNM stage 3. The overall relapse rate of the low-risk group was 16%, with a 12% rate of distant metastasis. The relapse rate for the high-risk group was 53%, with a 51% rate of distant metastasis. The median relapse-free survival period for high-risk patients was 49 months (the study follow-up period was not long enough to determine this period for the low-risk group). The majority of recurrences occurred within three years of surgery for high-risk patients. The five-year survival rate among the high-risk patients was 65% compared to 96% for those with low risk. The authors conclude that there is a need to implement individualized surveillance protocols based on breast cancer subtypes and risk of relapse, with more focus on patients with a high risk of relapse.