The Efficacy of Low-Kilovoltage X-Rays Intraoperative Radiation as Boost for Breast Cancer: A Systematic Review and Meta-Analysis

Table 2

Assessment of the case-control study with the Newcastle-Ottawa Scale (NOS).

Study	Selection				Comparability	Exposure			Quality score
	Adequate definition	Representative cases	Selection of controls	Definition of controls		Ascertainment of exposure	Same method of ascertainment	Nonresponse rate
Vaidya et al.	★	★	★	★	★☆	★	★	★	★★★★★★★★

Comparability variables: 1 = age; 2 = tumor size; 3 = lymph node status; 4 = tumor grade; 5 = hormone receptor status; 6 = HER2 status. If all characteristics were comparable, two stars; if two or three characteristics were comparable, one star; otherwise, no star.