Role of Radiation and Imaging in DCIS Explained

TON - January/February 2014 Vol 7 No 1 - Breast Cancer
Phoebe Starr

Management of ductal carcinoma in situ (DCIS) was the focus of 2 studies highlighted at a premeeting Press Cast for the American Society of Clinical Oncology Breast Cancer Symposium held in San Francisco, California.1,2 The studies showed:

  • Radiation to the breast as part of treatment of DCIS does not appear to increase cardiovascular toxicity, including risk of cardiovascular disease (CVD) and death from CVD or other causes
  • Perioperative magnetic resonance imaging (MRI) does not reduce the risk of locoregional recurrence (LRR) or contralateral breast cancer (CBC) in patients with DCIS undergoing surgery as part of their treatment program

Women and their physicians can gain reassurance from the first study that radiation for DCIS does not increase cardiotoxicity, and the second study suggests that MRI should not be part of routine presurgical or surgical planning.

Radiation for DCIS
DCIS is a precancerous lesion that may progress to invasive cancer in a small percentage of patients if left untreated. At present there is no way to identify which patients with DCIS are at risk of progression, so DCIS is typically treated with surgery plus or minus radiation to reduce the risk of LRR.

Concern has been raised about increased cardiotoxicity with radiation to the breast area, and modern protocols have been adjusted to reduce exposure to the breast as well as radiation dose. Using modern techniques, the risk of CVD was not increased in women with DCIS treated with radiotherapy in a large population-based study in the Netherlands compared with women treated with surgery alone and with women in the general population.

According to the authors, this is the first large study to evaluate long-term effects of radiotherapy for DCIS on both the incidence of CVD and associated deaths. However, longer follow-up is needed to establish the cardiovascular safety of radiation with certainty in patients with DCIS, said lead author Naomi B. Boekel, MSc, a PhD student at the Netherlands Cancer Institute in Amsterdam. She said that 5 or 10 more years of follow-up should be sufficient.

The study included 10,468 women younger than 75 years of age diagnosed with DCIS between 1989 and 2004. About 71% had surgery only (43% had mastectomy and the remaining women had lumpectomy), and 28% underwent both surgery and radiotherapy. DCIS survivors had similar death rates, as well as a 30% lower risk of dying of CVD compared with the general population. Patients treated with surgery alone had a similar risk of developing CVD as did those treated with both surgery and radiotherapy (9% vs 8%, respectively); no difference in risk of CVD was observed between patients who received left-sided radiotherapy (which includes a portion of the heart in the radiation field) or right-sided radiotherapy (which does not include the heart in the radiation field)—in these subgroups, the incidence of CVD was 7% versus 8%, respectively.

It is not clear why DCIS survivors had a slightly lower risk of CVD compared with the general population, but Boekel suggested that cancer survivors may be more concerned than the general population about a healthy lifestyle.

MRI in DCIS
Perioperative MRI may not be necessary in all patients undergoing surgery for DCIS, according to results of the second study featured at the Press Cast. The risk of LRR or CBC was not lower in women who underwent MRI around the time of surgery, according to a retrospective study conducted at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City.

Although no official guidelines for MRI in DCIS are available, many medical centers routinely order perioperative MRI with the hope of improving outcomes by finding additional cancers not detected by mammograms or other imaging studies. “Our findings indicate that MRI is not necessary for every patient with DCIS,” stated first author Melissa L. Pilewskie, MD, MSKCC in New York City and Commack, New York. She noted that perioperative MRI may be useful in specific patients with DCIS, such as those with a palpable mass and nipple discharge not found on mammography screening.

The study analyzed rates of LRR and CBC in 2321 women who underwent a lumpectomy between 1997 and 2010 at MSKCC; 596 had an MRI before or immediately after surgery and 1725 did not. At a median follow-up of 59 months, 5-year LRR rates were 8.5% in those who had an MRI versus 7.2% for those who did not. After adjusting for patient characteristics and risk factors associated with recurrence, MRI was still not associated with lower rates of LRR. Additionally, no significant differences were seen in the 5-year rates of CBC (3.5 years in both groups).

At 8 years, the rate of LRR was 14.6% for those women who had an MRI versus 10.2% for those women who did not. The rate of CBC at 8 years was 3.5% and 5.1%, respectively.

MRIs are typically ordered for women who have risk factors for breast cancer, such as younger age or family history. Pilewskie said that this might explain the higher recurrence rates in that group.

References
1. Boekel NB, Schaapveld M, Gietema JA, et al. Cardiovascular morbidity and mortality in patients treated for ductal carcinoma in situ of the breast. J Clin Oncol. 2013;31(suppl 26). Abstract 58.
2. Pilewskie ML, Olcese C, Eaton A, et al. Association of MRI and locoregional recurrence (LRR) rates in ductal carcinoma in situ (DCIS) patients treated with or without radiation therapy (RT). J Clin Oncol. 2013;31(suppl 26). Abstract 57.

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Last modified: March 14, 2014