Women who underwent treatment for ductal carcinoma in situ (DCIS), a noninvasive breast abnormality, were at higher risk of developing malignant breast tumours if they did not receive timely radiation therapy as part of their treatment, according to a study presented at the AACR Annual Meeting 2016.
DCIS is the most common premalignant breast lesion, with over 60,000 women diagnosed each year.
Not all DCIS will develop into invasive cancer, but because it is difficult to predict which cases will become cancerous, most women diagnosed with DCIS undergo treatment for it.
“According to the National Comprehensive Cancer Network guidelines, primary treatment options for DCIS include breast-conserving surgery plus radiation, total mastectomy, and breast- conserving surgery alone,” said the study’s lead author, Ying Liu, MD, PhD, instructor of surgery at Washington University School of Medicine and a research member at Siteman Cancer Center in St. Louis, Missouri. “This study shows that it is important for women to understand the benefits of timely receipt of radiation therapy after breast-conserving surgery.”
Liu and colleagues conducted this study by identifying 5,916 women in the Missouri Cancer Registry who were diagnosed with first primary DCIS between 1996 and 2011 and were treated with breast-conserving surgery.
Of those women, 1,053 (17.8 percent) received radiation therapy eight or more weeks after surgery, which the researchers defined as a delay.
Also, 1,702 (28.8 percent) did not receive any radiation therapy during the first course of treatment.
The remaining 53.4 percent of women received radiation within eight weeks of the surgery.
During the 72-month follow-up period, 3.1 percent of the women developed an ipsilateral breast tumour, which is an invasive or in situ tumour occurring on the same side as the DCIS.
After adjustment for propensity scores based on factors such as age, race, tumour size, and tumour grade, the risk of ipsilateral breast tumours was 26 percent higher for women who had delayed radiation therapy and 35 percent higher for women who did not receive any radiation therapy during the first course of treatment.
Delays were more likely for certain groups
Liu and colleagues identified several groups who were significantly affected by delays in radiation therapy.
African-American women, single women, those who received Medicaid, those whose DCIS tumours were larger, and those who were diagnosed more recently were all more likely to have a delay in treatment.
“Among these groups, African-American women, those on Medicaid, and those with a large DCIS have a higher risk of recurrence, therefore, timeliness of radiation therapy should be improved,” Liu said.
Study data did not fully explain the reasons for delays among certain groups, but Liu said that the quality and accessibility of health care providers and facilities could be one possible cause.
She added that further research could provide insight into the factors influencing delays and help identify ways to encourage women to receive radiation therapy soon after DCIS surgery.
Liu said a limitation of the study is that during the 72 months of average follow-up time, the number of study subjects who developed ipsilateral breast tumours was small.
“Our preliminary finding needs to be confirmed in a large cohort of DCIS patients with a longer follow-up,” she said. “Future studies should also address the contributions of patient choice, healthcare providers, facilities, and neighbourhoods to therapy delay.”
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