A tale of two treatments.

Top Line: There’s been quite the shift in recent decades to less radiation by way of more chemo across several pediatric malignancies.
The Study: A couple of things should give us pause here. First, radiation ain’t like it used to be 50 years ago. Second, is chemo better really? Here’s a case-control study nested in a prospective database of patients surviving at least 5 years from childhood cancers diagnosed between 1970 to 1986. So, no, this isn’t going to tackle concern one. Among over 14K survivors, there were 241 women with subsequent breast cancers (aka cases) and another 1044 women selected as age-matched controls. First of all, the odds of developing breast cancer were increased by a factor of 4 for every 10 Gy to the breast. More interesting, even though it makes sense, this association wasn’t seen if the ovary also received at least 15 Gy. And now we get to concern two. There was also a significant increase in odds of breast cancer in a continuous fashion with every 100 mg/m2 of anthracyclines received. Most interesting, there appeared to be a synergistic impact (in a bad way) of adding an anthracycline to a breast dose of ≥10 Gy, where the odds of breast cancer were increased by nearly 20x. Finally, let’s circle back to concern one. In the radiation epoch captured here, 10 Gy to “the breast” was likely just that. But in the era of highly conformal radiation techniques, very little non-target breast tissue is likely to receive any sizeable proportion of prescription. How much has 100 mg/m2 of anthracyclines changed over the same time period?
TBL: We may be overlooking a tricky balancing of toxicities if we continue to discuss the long term risks of radiation, regardless of technique, in the superlative degree of comparison only. | Veiga, JAMA Pediatr 2019


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