Delay in Radiation Increases Risk for Ipsilateral Breast Cancer

Alexander M. Castellino, PhD

April 20, 2016

Delay in radiation beyond 8 weeks increases the risk for malignant breast cancer recurrence in women who undergo surgery for ductal carcinoma in situ (DCIS), a noninvasive breast abnormality, according to a study presented here at the American Association for Cancer Research 2016 Annual Meeting.

"Women who receive delayed radiation are at a 26% increase risk of recurrence, and those who do not receive any radiation at all are at a 35% increased risk," Ying Liu, MD, PhD, instructor of surgery at the Washington University School of Medicine, St. Louis, Missouri, told Medscape Medical News.

"The study shows it's important for women to understand the benefits of receiving timely radiation therapy after breast-conserving surgery," she added.

The findings are a cautionary tale and come amidst much publicity about overtreatment of DCIS and studies showing that some women can skip radiotherapy, as previously reported by Medscape Medical News.

"This is a nonrandomized study and the association should be interpreted with caution," Clifford Hudis, MD, chief, breast medicine service, Memorial Sloan Kettering Cancer Center, New York City, told Medscape Medical News.

Consequences of Delaying Radiation

Dr Liu and colleagues analyzed data from the Missouri Cancer Registry who were diagnosed with DCIS from 1996 to 2011 and were treated with breast-conserving surgery.

Dr Ying Liu

Radiation therapy delay was defined as the first radiation therapy delivered more than 8 weeks after surgery. "The cutoff time was based on prior literature on risk of recurrence increasing in patients who received delayed radiation after lumpectomy," Dr Liu told Medscape Medical News.

Of the 5916 women in the registry, 53.4% received radiation within 8 weeks of surgery, 17.8% received radiation 8 or more weeks after surgery, and 28.8% did not receive any radiation.

During the follow-up of 72 months, the number of events recorded were as follows: 81 per 20,453 patient-years for patients receiving timely radiation; 33 per 6374 patient-years for patients delaying radiation therapy; and 68 events per 12017 patient-years for patients not receiving radiation therapy at all.

This translates to patients receiving delayed radiation being at a 26% increased risk of developing ipsilateral breast cancer; the risk increased to 33% for patients not receiving any radiation at all.

In a subgroup analysis, black patients were at an 83% increased risk for ipsilateral breast cancer and, compared with privately insured patients, Medicaid patients, or uninsured patients, had a 68% increased risk for breast cancer.

Dr Liu told Medscape Medical News that it is not possible to determine the reasons for delayed radiation. However, poor access to quality care may be a reason, Dr Hudis suggested.

Nuance in Discussion

Dr Hudis went a step further in adding a nuance to the discussion of radiotherapy after breast-conserving surgery in women with DCIS.

"We will accept a higher local or regional recurrence in older women," he said, and highlighted data from study from 2004 known as C9343 — a study from the Cancer and Leukemia Group B, Eastern Cooperative Oncology Group, and the Radiation Therapy Oncology Group (N Engl J Med. 2004;351:971-977).

In this study, 636 women 70 years and older with stage I, estrogen-receptor-positive breast cancer who underwent lumpectomy were randomized to receive tamoxifen (n = 319) or tamoxifen and radiation (n = 317).

The only significant difference between the two groups was in the rate of local or regional recurrence (1% with tamoxifen plus radiation vs 4%with tamoxifen alone; P < .001). Overall 5-year survival rates were similar in the two groups (87% vs 86%).

Yet, according to the study, lumpectomy plus tamoxifen alone was considered a "realistic choice" for these women, Dr Hudis noted.

Dr Hudis pointed out that in these older women, "we make a compromise." Radiation is not considered appropriate for this population. "There is a lack of consistency over time in what we value. We have to agree to what matters," he said.

The study was funded by the Foundation for Barnes-Jewish Hospital and the Breast Cancer Research Foundation. Dr Liu and Dr Hudis have disclosed no relevant financial relationships.

American Association for Cancer Research (AACR) 2016 Annual Meeting: Abstract 2576. Presented April 18, 2016.

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