(RxWiki News) Ductal carcinoma in situ (DCIS) is the earliest form of breast cancer. Abnormal cells are found inside the milk duct of the breast. Unlike invasive breast cancers, ductal carcinoma in situ has not spread beyond the duct.
Researchers recently learned that radiation after DCIS surgery significantly lowered the chances of the disease returning or becoming invasive.
Radiotherapy, however, did not affect survival, the researchers found.
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This study’s researchers were directed by Nina Bijker, MD, PhD, a physician scientist in the Department of Radiology at the Academic Medical Center in Amsterdam, the Netherlands.
Due to mammography, the rate of DCIS diagnoses has increased dramatically in the past few decades, going from 5.8 cases per 100,000 in 1975 to 32.5 per 100,000 in 2004.
Today, it’s estimated that DCIS makes up as much as 30 percent of the breast cancers detected by mammography.
Treating DCIS typically involves breast conserving surgery in which only the tumor and surrounding tissue are removed. Radiation therapy usually follows surgery to kill any remaining cancer cells and to decrease the chances of recurrence (return).
For this study, the researchers analyzed the long-term impact of radiotherapy on local recurrence and survival in DCIS patients treated with breast conserving surgery.
The researchers conducted a follow-up of the European Organization for Research and Treatment of Cancer 10853 trial in which DCIS patients were randomly assigned to receive radiotherapy following surgery or no further treatment.
Between 1986 and 1996, a total of 1,010 women with DCIS were recruited, with 507 assigned to the radiotherapy group and 503 assigned to receive no more treatment.
The median follow-up was 15.8 years.
During the follow-up, 234 patients had a local recurrence, meaning cancer returned to the same breast; 48 percent of these recurrences were DCIS and 52 percent were invasive breast cancer.
Local recurrence occurred in 149 (30 percent) of the women who did not have adjuvant (after surgery) radiotherapy, compared to 85 (17 percent) of women who did receive radiotherapy.
These figures show that women with DCIS who were treated with radiotherapy had nearly half (48 percent lower) the risk of seeing their cancer return as women who did not undergo radiation treatment.
The researchers also found that after 15 years, 90 percent of participants who had radiation did not have a recurrence, compared to 69 percent of the women who weren’t treated with adjuvant radiotherapy.
The 15-year invasive local recurrence-free survival was 90 percent for the women in the radiotherapy group and 84 percent for the untreated women.
Radiotherapy did not impact survival rates, the researchers discovered.
The 15-year breast cancer-specific survival was 95 percent in the untreated group and 96 percent in the radiation group.
Overall survival was similar as well. At 15 years, 90 percent of the women who did not receive radiation were still alive, as were 88 percent of the patients who did have radiotherapy.
Women in the radiation group who had recurrences had a lower rate of mastectomy (removal of breast) than did women who weren’t treated with radiotherapy (13 percent versus 19 percent, respectively).
David Horvick, MD, a radiation oncologist with 21st Century Oncology of New Jersey who was not involved in this study, told dailyRx News, “This large study with long-term follow-up shows that radiation therapy after lumpectomy for DCIS cuts the risk of recurrence of cancer in half. Radiation was effective is all subgroups and, also, decreased the risk of invasive recurrences and decreased the need for salvage mastectomies [performed after a cancer recurrence]."
This study was published November 10 in the Journal of Clinical Oncology.
The research was supported by a donation from the Kankerbestrijding/KWF from the Netherlands through the EORTC Charitable Trust.
The authors indicated no potential conflicts of interest.