New Study Comparing Breast Cancer-specific Survival Rate of Patients Receiving Breast-conserving Treatment or a Mastectomy

Breast Cancer

Researchers from Erasmus Mc, Iknl Netherlands Comprehensive Cancer Organisation and the University of Twente Presented Their Findings from Research into the Treatment of Patients with Breast Cancer That Has Not Spread to Another Part of the Body Other than the Regional Lymph Nodes of the Breast.

They have concluded that in the future, some patients may benefit more from breast-conserving treatment. This research builds on previous research, but also takes into account causes of death and subgroups such as patients with concurrent diseases.

High Survival Rate

Professor Sabine Siesling from IKNL Netherlands Comprehensive Cancer Organisation and the University of Twente worked together with clinical research physician Mirelle Lagendijk from the department of Surgical Oncology at the Erasmus MC Cancer Institute in Rotterdam, Marissa van Maaren (IKNL) and medical specialists from other hospitals. They studied data gathered from almost 130,000 breast cancer patients. “We learned that the number of patients still alive ten years after receiving breast-conserving treatment was 25% higher than the survival rate of patients who had undergone a mastectomy. This applies to both breast cancer-specific survival and survival in general. This higher survival rate can mostly be observed in patients who did not receive chemotherapy, in patients over 50 and in patients with concurrent diseases (comorbidity).

New Element in Decision-making Process

“The findings obtained through this research are mainly valuable in providing new patients with more information they can use in making treatment decisions”, Prof. Siesling explains. Researchers would like to emphasize that these results in no way mean that a mastectomy is a bad choice or that it could be a bad decision. Treatment decisions are made based on more factors than survival rate alone. Mastectomy may still be the preferred  treatment in a number of cases: where radiation therapy is not possible or advisable (e.g. due to a higher risk of adverse effects); where social or psychological factors make radiation therapy impractical; or where the aesthetic outcome of breast-conserving surgery is expected to be unfavourable. Prof. Siesling explains: “Our study helps determine which patients may benefit more in future from breast-conserving treatment, and confirms for other groups that breast-conserving treatment is as good an option as a mastectomy.”

Comparing Groups

The research scientists studied national survival rates from a group of 130,000 patients divided into two sub-groups: patients in the first group had been diagnosed between 1999 and 2005 and patients in the second group had been diagnosed between 2006 and 2012. Information from the first group was used to determine the long-term effects, and information from the second group was used to evaluate modern, more advanced diagnostic methods and treatments. The patients were selected from the NKR Dutch Cancer Registration database that had no metastasis (spreading of the cancer to other organs, with the exception of lymph glands in the region of the breast). The cause of death information was obtained through figures released by Statistics Netherlands (CBS). The results were presented during the European Oncology Conference organised by the European CanCer Organisation in Amsterdam (ECCO 2017). Prof. Siesling: “In our research we compared a number of groups, taking into account factors such as age, stage of breast cancer, comorbidity, hormone receptor status, HER2 status and drug treatments (chemotherapy and endocrine therapy). Using this information we were able to identify the subgroups that may benefit the most from breast-conserving treatment in future.”

In-depth Follow-up to Previous Study

Previous studies, mainly initiated in the 1980s, showed that survival rates for breast cancer patients using both forms of treatment were equal. These studies tended to leave out older patients or patients with comorbidity. Current diagnostics and treatment including surgery, radiation, chemotherapy and hormonal therapy have greatly improved in the last thirty years. This is why there was a need for new insights.

A number of more recent studies that were based on information from daily practice, including research by Van Maaren, Saadatmand, Siesling and colleagues, have already shown that breast-conserving treatments may offer survival advantages. In these studies, however, (a combination of) data on long-term follow-up was missing , or information about specific medical treatment, or a classification into for example age groups was unavailable. Information about cause of death was also missing, which is necessary to determine breast-cancer specific survival. The research scientists say this is necessary to enable a more  even comparison for the two treatment groups.

Although this new study was based on historic or retrospective data using highly detailed information, researcher scientists are not able to completely exclude any disruptive variables that were not included. Research scientists say that they have so far been unable to find an explanation for the differences found, but that the results will help future patients make important decisions about their own healthcare.