Not only is the headline not what the study concluded, but the data in the paper do not support any such suggestion.
As well, it appears to me that reporter Helen Branswell of The Canadian Press seems to have been swayed by speculation expressed in an accompanying commentary by Dr. Laura Esserman. The claims in that commentary are not supported by the JAMA paper.
The review in JAMA by Dr. Steven Narod and his colleagues certainly does not argue that treatment is not necessary. What they claim to show is that the three different ways that ductal carcinoma in situ, DCIS, has been treated do not seem to differ in their results. These are: 1) The complete surgical removal of the lesion (lumpectomy); 2) lumpectomy followed by irradiation of the breast; and 3) mastectomy.
The JAMA paper claims all three resulted in the same survival rate. It is unclear where “watchful waiting” came from, since all of the women in this review had treatment. None of them underwent “watchful waiting.” They were all treated, yet their rate of death was still twice that of women without DCIS.