Do observational studies exaggerate radiotherapy benefits in breast cancer?

A comparison of observational studies and randomized trials showed as much as a 50% difference in survival hazards for adjuvant radiation therapy in early breast cancer. A meta-analysis of the randomized trials yielded a 15% to 20% reduction in the hazard for disease-specific mortality and about a 10% reduction in overall mortality for radiotherapy following breast-conserving surgery or mastectomy, reported Sarah C. Darby, PhD, of the Clinical Trial Service Unit of Oxford University in London, and colleagues.

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