Small Benefit Seen in Adding Radiation to DCIS Plan for Breast Cancer

Patients with ductal carcinoma in situ (DCIS) are often treated with radiation after lumpectomy, although it has remained unclear whether this can reduce the risk of dying from this noninvasive form of breast cancer. A new study published Friday said that the combination of the 2 treatments was associated with a small benefit in reduced risk of breast cancer death compared with lumpectomy or mastectomy alone. The observational study of more than 140,000 women was published in JAMA Network Open.

The study looked at women with DCIS between 1998 and 2014, comparing lumpectomy plus radiation versus lumpectomy alone, lumpectomy versus mastectomy, and lumpectomy plus radiation versus mastectomy.¹ The cohort was mostly white, with a mean age of 58.8.

Information on age and year of diagnosis, ethnicity, income, tumor size, tumor grade, estrogen receptor status, all treatments (surgery and radiation), and outcomes, measured as invasive local recurrence and death from breast cancer within 15 years.

Of the 140,366 patients, 35,070 (25%) were treated with lumpectomy alone, 65,301 (46.5%) were treated with lumpectomy and radiotherapy, and 39,995 (28.5%) were treated with mastectomy.

The adjusted hazard ratios for death were 0.77 (95% CI, 0.67-0.88) for lumpectomy and radiotherapy versus lumpectomy alone (29,465 propensity-matched pairs), 0.91 (95% CI, 0.78-1.05) for mastectomy alone versus lumpectomy alone (20,832 propensity-matched pairs), and 0.75 (95% CI, 0.65-0.87) for lumpectomy and radiotherapy versus mastectomy (29,865 propensity-matched pairs).

An accompanying commentary said the results support omitting radiotherapy after lumpectomy in low-risk patients, given the cost and inconvenience of 5 to 6 weeks of daily treatments, acute adverse effects such as breast pain and fatigue, and potential long-term toxic effects of cardiac disease and second cancers.² The risk of breast cancer mortality in patients with DCIS was very low, and the potential absolute benefit of radiotherapy was small.

The absolute risk reduction was 0.27%, making it necessary to treat 370 women to save 1 life. Patients who had lumpectomy plus radiation had more local recurrences than those who had mastectomy, but had fewer deaths.

The actuarial 15-year breast cancer mortality rate was 2.33% for patients treated with lumpectomy alone, 1.74% for patients treated with lumpectomy and radiation, and 2.26% for patients treated with mastectomy.

The researchers said the results suggest that the survival benefit of radiation is likely not due to local control, but rather to systemic effects.

DCIS is generally identified in asymptomatic women in the context of mammography. In about 15% of cases of DCIS treated with breast-conserving surgery, the woman will experience an in-breast invasive recurrence in the same breast within 15 years.

In about 6% of cases, women with DCIS will develop a contralateral invasive breast cancer within 15 years. In about 3% of cases, women with DCIS will die of breast cancer within 15 years. The risk of death from breast cancer increases greatly after an in-breast invasive recurrence; however, about 50% of women who die of breast cancer after DCIS have no record of an invasive recurrence.

There were some limits to the study—for example, the possibility remains that the decision to undergo radiotherapy was associated with other favorable factors. Also, investigators didn't have information on tamoxifen use, and some data were missing.

References

1. Giannakeas V, Sopik V, Narod SA. Association of radiotherapy with survival in women treated for ductal carcinoma in situ with lumpectomy or mastectomy. JAMA Network Open. 2018;1(4):e181100. doi:10.1001/jamanetworkopen.2018.1100.

2. Goldberg M, Whelan TJ. Systemic effects of radiotherapy in ductal carcinoma in situ. JAMA Network Open. 2018;1(4):e181102. doi:10.1001/jamanetworkopen.2018.1102.