Adjuvant radiotherapy may improve DCIS outcomes
medwireNews: Canadian researchers have found that the use of radiotherapy after surgery for ductal carcinoma in situ (DCIS) leads to an improvement in breast cancer-specific survival, possibly due to its systemic effects.
Their analysis of 140,366 women with primary DCIS – included in the Surveillance, Epidemiology, and End Results database – found “a small but significant” reduction in breast cancer mortality among those who underwent lumpectomy and radiotherapy compared with either lumpectomy or mastectomy alone.
Adjuvant radiation was associated with a significant 23% reduction in the risk for death at 15 years versus lumpectomy alone after adjusting for factors including year of diagnosis and tumor grade, although the researchers note that this translates into an absolute risk reduction of just 0.27%.
Steven Narod and colleagues at the Women’s College Research Institute in Toronto, Ontario, therefore suggest “it is doubtful whether a benefit of this size is large enough to warrant radiotherapy,” adding “it would be necessary to treat 370 women to save [one] life.”
In a commentary accompanying the research in JAMA Network Open, Mira Goldberg and Timothy Whelan, from McMaster University in Hamilton, Ontario, agree that “the potential absolute benefit of radiotherapy was quite small.”
They add: “Such data continue to support a strategy in patients with DCIS of omitting radiotherapy after lumpectomy in low-risk patients, especially when one considers the negative effects of treatment: 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.”
Of the study participants, 46.5% were treated with lumpectomy plus radiotherapy, 25.0% with lumpectomy alone, and 28.5% with mastectomy; the corresponding actuarial 15-year breast cancer-specific mortality rates were 1.74%, 2.33%, and 2.26%.
In addition to the benefit over lumpectomy alone, combining the procedure with radiotherapy was also associated with a significant survival advantage relative to mastectomy, with an adjusted hazard ratio for death of 0.75.
There was no significant difference between women who received lumpectomy alone and mastectomy alone.
The study authors say the survival benefits of radiotherapy “cannot be explained by improving local control” and suggest that “radiation to the breast acts as a systemic therapy to eradicate subclinical latent metastases.”
They maintain: “If a patient dies of breast cancer following DCIS, it is reasonable to conclude that undetected metastatic deposits were present at the time of diagnosis, and that may lead to generalized metastatic clinical disease and death.”
By Anita Chakraverty
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