Breast cancer could be divided into four subtypes according to hormone status, epidermal growth factor 2 status and Ki-67 expression level. In recent years, it has been widely accepted that treatments for breast cancer should be based on different molecular subtypes. Most studies’ explorations were based on nonspecific breast cancer. But IMPC was a special and rare type of breast cancer, which behaviored more aggressively than invasive ductal breast carcinoma. Previous clinical studies proved that breast cancer with ER and PR positive status was associated with better OS and CSS.5 10 11 Several studies suggested that molecular subtype of breast cancer provided additional prognostic information regarding patient outcomes. 12 11 13 A population based study showed that hormone positive IMPC had a better survival.8 Therefore, in this study we used breast cancer molecular type to analyze the impact of combination HR with Her-2 status on IMPC. Our results indicated that HR-/Her-2- subtype had the most unfavorable prognosis.
As was mentioned above, hormone positive status was associated with better OS and CSS, many studies separately analyzed the effects of hormone receptor and HER2 expression status on IMPC.9 8 In fact, many previous research has proven that molecular subtype can affect prognosis on breast carcinoma.12 14 15 Here in this study, multivariate analysis indicated that only HR-/Her-2- subtype had a worse prognosis on OS and CSS comparing to HR+/HER2- subtype, suggesting that Her-2 expression status might play an important role, especially when both hormone receptor and Her-2 were negative.
Comparing with other three subtypes, HR-/Her-2- IMPC had more aggressive behaviors, for it had larger tumor size and more advanced histological grade and stage. Tumors which performed more aggressively were more possible to receive surgery, chemotherapy and radiotherapy. And further analysis showed that HR-/Her-2- and HR+/Her-2 + subtype had more proportions to receive mastectomy than HR+/Her-2- subtype, this was might because that HR+/Her-2- status IMPC had better biological behaviors.
We conducted a nomogram models to predict 3-year survival rate of IMPC. This tool allowed us to estimate patients’ survival according to individual characteristics. For instance, a HR-/Her-2- IMPC patient who was at 50-year-old, black ethnicity, T4N3M1 stage, receiving surgery and adjuvant therapy, the 3-year overall survival rate was only 50% while at the same condition, 3-year overall survival rate of HR+/Her-2- subtype could reach to about 92%. From this model, we could find that at the same background, chemotherapy and radiotherapy had smaller influence on CSS than on OS. This model made it more clear for clinical doctors to assess survival rate of IMPC patients, particularly evaluating survival rate of different subtype IMPC, thus to help doctors to make more accurate and valuable treatments strategies.
However, this study did not obtain data on specific chemotherapy regimens which might affect prognosis. And we could not obtain data about whether Her-2 positive patients received targeted therapy (Herceptin) or not. Because the patients with Her-2 expression information only started from 2010, we selected breast cancer patients from 2010 to 2015, which might lead to insufficient follow-up time. It is necessary to follow up longer time to verify our findings. When typing breast cancer, the factor of Ki-67 is lacking, a factor that is practical for most breast cancers. And it would be better to acquire data about local recurrence rate (LRR), recurrence-free interinterval (RFI) and distant relapse-free survival (DRFS) data to make a more complete analysis of the four subtypes of IMPC.