Similar Local Tumor Recurrence Rates With Hypofractionated vs Conventional Radiotherapy for Ductal Carcinoma in Situ
In patients with ductal carcinoma in situ of the breast who underwent breast-conserving surgery, hypofractionated radiation therapy was not significantly associated with an increased risk of any local recurrence when compared with conventional radiation therapy, according to the study findings presented by Lalani et al in the International Journal of Radiation Oncology • Biology • Physics. However, cumulative 10-year local recurrence-free survival rates were slightly higher in women treated with hypofractionated radiation therapy than in those treated with conventional radiation therapy.
The primary objective in the treatment of ductal carcinoma in situ, the most common noninvasive form of breast cancer, is to minimize the risk of local tumor recurrence. This goal is usually accomplished via breast-conserving surgery. However, recent studies have indicated that the addition of whole-breast irradiation may decrease the risk of local tumor recurrence even further. Oncologists have leaned toward the utilization of accelerated hypofractionated radiation therapy regimens, which deliver a lower total dose of radiation over a shorter period of time.
Although there have been studies on the use of accelerated hypofractionated radiation therapy regimens in women with early-stage invasive breast cancer, there have been limited comparative studies comparing that approach and whole-breast radiation therapy. Thus, Lalani and colleagues evaluated the impact of whole-breast irradiation vs accelerated hypofractionated radiation therapy in women with ductal carcinoma in situ.
Study Details
The investigators analyzed the medical records of 1,609 patients, of whom 971 (60%) received conventional radiation regimens and 638 (40%) received accelerated hypofractionated radiation therapy. Medical records were obtained from the Canadian Institute of Health Information database, which were compiled from 1994 to 2003. Patients treated by mastectomy and breast-conserving surgery alone were excluded from the study cohort.
Patients had a median age of 55 years in the conventional regimens cohort and 57 years in the hypofractionated radiation cohort. There was no significant difference in the proportion of women younger than age 45 years at diagnosis (13% vs 11%, P = .20).
Similar Risk Found in Both Cohorts
The risk of local tumor recurrence was similar in both cohorts. At 10 years, 13% of patients who received conventional radiation therapy experienced local tumor recurrence, whereas 10% of patients who received hypofractionated radiation therapy experienced local tumor recurrence. The 5-year and 10-year actuarial local tumor recurrence-free survival rates were 90% and 86% among women treated with conventional radiation therapy and 93% and 89% for those treated with hypofractionated radiation therapy (P = .03).
Predictors of increased risk of local tumor recurrence included age < 45 years at diagnosis (hazard ratio [HR] = 2.6, 95% confidence interval [CI] = 1.8–3.6, P < .0001), the presence of high-grade ductal carcinoma in situ (HR = 3.0, 95% CI = 1.2–7.4, P = .02), the presence of intermediate-grade ductal carcinoma in situ (HR = 2.6, 95% CI = 1.0–6.3, P = .04), and conventional radiation scheme vs hypofractionated radiation therapy (HR = 0.8, 95% CI = 0.6–1.0, P = .03). There was no significant interaction between radiation therapy regimen and age at diagnosis, nuclear grade, or administration of boost radiation.
Closing Thoughts
According to the investigators, hypofractionated radiation therapy was not significantly associated with an increased risk of any local tumor recurrence when compared with conventional radiation therapy. They found that the cumulative 10-year local tumor recurrence-free survival rate was slightly higher in women treated with hypofractionated radiation therapy than in those treated with conventional radiation therapy.
During the time period from which the investigators extracted patient medical records, tamoxifen use was limited. In their study, however, among women older than age 65, only 17% received tamoxifen. Thus, their findings were unlikely to have been confounded by tamoxifen use.
“The efficacy of breast radiation after breast-conserving surgery for ductal carcinoma in situ is well established, but it remains unclear whether different radiation therapy dose fractionation regimens provide similar low rates of local recurrence. In our population cohort, individuals treated with hypofractionated radiation therapy after breast-conserving surgery for ductal carcinoma in situ did not experience an increased risk of local recurrence compared with women treated by a conventional radiation therapy regimen,” the investigators concluded.
Eileen Rakovitch, MD, FRCPC, of the Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Odette Cancer Centre, Toronto, is the corresponding author of this article in the International Journal of Radiation Oncology • Biology • Physics.
This work was supported by funds from the Canadian Cancer Society Research Institute. The authors reported no potential conflicts of interest.
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