Impact of Radiation Therapy on Breast Conservation in DCIS
With greater use of screening mammography, the incidence of pre-invasive breast carcinoma or ductal carcinoma in situ (DCIS) has increased by 560% over the past 35 years. By the year 2020, more than one million women will be living with a DCIS diagnosis. Despite the large number of women affected, the optimal treatment strategy for DCIS is not known. DCIS does not spread to the lymph nodes or other sites in the body, but if left untreated, it can progress to invasive breast cancer. Mastectomy, or removal of the breast, had been the standard of care for treatment of DCIS and is curative in almost all patients; however, it is an extreme surgery for a diagnosis that may not progress to invasive breast cancer.
Currently, over 70% of women with DCIS receive breast-conserving surgery, but they then have a risk of being diagnosed with a second cancer in the same breast. Some women with DCIS undergo radiation therapy delivered to the breast after breast-conserving surgery to decrease the risk of another diagnosis in the affected breast. But, if a woman undergoes radiation for DCIS and then has a second diagnosis in the same breast, she will need a mastectomy because radiation can only be given once due to limits of normal tissue tolerance. Therefore, radiation therapy may also reduce the long-term likelihood of breast conservation.
The important outcome of lifetime breast conservation with or without radiation has not been studied, resulting in patients and physicians choosing treatment without complete information about expected treatment outcomes. Across the United States, the use of radiation therapy for DCIS varies by region of the country. Instead, the choice to add radiation should vary according to the values and preferences of each DCIS patient.
To enable informed decision making by DCIS patients, we seek to provide individualized data about outcomes following breast-conserving surgery with and without radiation therapy—in terms of recurrence, disease-free and overall survival, and likelihood of long-term breast conservation. To do this, we are studying patient-specific risk factors for having a new breast cancer after DCIS and the likelihood of breast-conserving surgery versus mastectomy if a woman has a second cancer diagnosis after DCIS and has not received radiation upfront, using four large data sets.
The results of these analyses will then be combined into a model that will generate individually tailored predictions of the long-term likelihood of breast conservation with and without radiation therapy for DCIS. So that patients and physicians can access the results of the model, we will then design a web-based decision aid to present the trade-offs and compare expected treatment outcomes with and without radiation therapy.
This decision aid will enable patients and their physicians to choose the treatment most consonant with patient preferences, and it will improve both the quality of decision making and quality of life for patients diagnosed with DCIS.