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Women treated for DCIS have lower all-cause mortality risk
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Women aged older than 50 years who have been treated for ductal carcinoma in situ demonstrated a 10% lower risk for dying of any cause than the general population, according to a study presented at the European Cancer Congress.
“Being diagnosed with DCIS can be extremely distressing, and research indicates that many women overestimate the risks involved and are confused about treatment,” Lotte Elshof, MD, research physician and epidemiologist at Netherlands Cancer Institute, said in a press release. “This study should provide reassurance that a diagnosis of DCIS does not raise the risk for dying.”
Due largely to increased breast screening, each year more than 51,000 women in the United States are diagnosed with DCIS, which differs from breast cancer because it is noninvasive. However, because 15% to 50% of women not treated for DCIS develop invasive breast cancer, surgery and radiation therapy are often recommended. Whole-breast radiation, which is recommended after breast conservation, has been associated with increased risk for cardiac disease and death.
Elshof and colleagues analyzed data from 9,799 Dutch women diagnosed with DCIS between 1989 and 2004 and compared their death rates after 10 years to the expected mortality of the general population.
Of the 1,429 deaths that occurred after a median follow-up of 10 years, 368 were from cardiovascular disease (4%) and 284 were from breast cancer (3%).
Overall, the study population had a significantly lower risk for dying of all causes compared with the general population (standardized mortality ratio [SMR] = 0.9; 95% CI, 0.87-0.96).
Patients treated for DCIS also experienced lower risks for mortality due to diseases of the circulatory (SMR = 0.8, 95% CI, 0.69-0.85), respiratory (SMR = 0.7, 95% CI, 0.60-0.89) and digestive systems (SMR = 0.7, 95% CI, 0.55-0.98); mental and behavioral disorders (SMR = 0.7, 95% CI, 0.52-0.9); and endocrine, nutritional and metabolic diseases (SMR = 0.7, 95% CI, 0.49-0.94).
“It might seem surprising that this group of women actually has a lower mortality rate than the general population,” Elshof said. “However, the vast majority would have been diagnosed via breast screening, which suggests they may be health-conscious and well enough to participate in screening.”
Patients with DCIS had a higher risk for breast cancer death (SMR = 3.3, 95% CI, 2.95-3.74), but lower risks for mortality from lung (SMR = 0.7, 95% CI, 0.58-0.94) and urogenital cancers (SMR = 0.6, 95% CI, 0.45-0.83).
After 15 years of median follow-up, breast cancer–specific mortality rose from the 3% rate observed after 10 years to 3.9%.
The SMR for breast cancer decreased with increasing age, from 23.2 (95% CI, 15.65-33.11) among women aged younger than 40 years, to 1.9 (95% CI, 1.11-3.06) among women aged older than 75 years.
Further, women who developed invasive breast cancer had a much higher breast cancer–specific mortality (SMR = 26.6, 95% CI, 22.08-31.74) than those who did not (SMR = 2, 95% CI, 1.71-2.34).
The study researchers expect to begin collaborating with researchers in the United States and the United Kingdom to increase the size of their study and try to determine why some cases of DCIS progress into invasive breast cancer and others do not.
“Ductal carcinoma in situ can be a worrying and confusing diagnosis for many women, especially due to the word ‘carcinoma,’” Philip Poortmans, MD, PhD, president-elect of the European CanCer Organization (ECCO) and head of the radiation oncology department at Radbound University Medical Center, said in the release. “Although it should be considered as being clearly different from breast cancer, it can progress into breast cancer, even after removal of the entire breast or after breast-conserving therapy consisting of surgery, generally combined with radiation therapy.”
These results provide reassurance for women diagnosed with DCIS because they show women are as likely to be alive 10 years after diagnosis as women who did not have DCIS, Poortmans added.
“However, we have to recognize that in one-fifth of the patients who die, the cause is breast cancer, which is likely to result from progression of the DCIS they were diagnosed with,” he said. “Therefore, we are eagerly waiting for the results of further research to identify the factors — including age, as clearly shown in this study — that contribute to the risk for recurrence and progression from DCIS for each individual patient.
“Remarkably, the increased risk for dying of breast cancer is completely offset by a lower risk for dying from other causes compared to women in the general population,” he added. “This might be explained by the generally better health and socioeconomic status of women who regularly participate in breast cancer screening. This could also be tested in the ongoing research.”– by Chuck Gormley
Reference: Elshof L, et al. Abstract 173. Presented at: European Cancer Congress; Jan. 27-30, 2017; Amsterdam.
Disclosures: The study was funded by Pink Ribbon and the Dutch Cancer Society. The researchers report no relevant financial disclosures.