The golden egg.

Top Line: There are lots of reasons to offer adjuvant radiation following lumpectomy for ductal carcinoma in situ (DCIS), but living longer isn’t usually one of them.
The Study: Endpoints for oncology studies come in wide varieties, and we all know the golden egg is overall survival. Too bad there’s no golden goose for DCIS, a pre-invasive breast cancer that virtually by definition can’t kill you. But we’ve known for a long time that lumpectomy followed by radiation cuts the risk of invasive breast recurrence in half. That paired with the old adage “four local recurrences spared, one life saved” means that all we’re really lacking here is number of events. In the current era of big data, can’t someone somewhere get the big numbers we need? Why, yes, yes they can. A huge, huge SEER analysis of >140K patients treated for DCIS between 1998 and 2014 compared, that’s right, breast cancer-specific mortality (BCSM) rates among modalities used. Alas, a “significant” difference emerged: rate of BCSM 15 years after lumpectomy or mastectomy was 2.3% and after lumpectomy + radiation was 1.7%. Now remember, a teeny difference between slightly less teeny numbers can translate to quite an impressive (misleading?) hazard ratio0.75-0.77 in this case. Don’t just take our word for it. Look at the clear separation in Kaplan-Meier curves on the y-axis that spans 0-3% in its entirety. Number needed to treat? 370.
Bottom Line: Go ahead, ramp up your radiation treatments for DCIS because eventually you’re going to save a life. | Giannakeas, JAMA 2018


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