Background: Although histologic grade has previously been described as a predictor of distant failure, it is uncertain whether histologic grade should be used to decide which patients should undergo axillary lymph node dissection and whether grade should be considered as a selection factor for breast-conserving therapy.
Methods: The authors retrospectively analyzed data from 1081 patients with American Joint Committee on Cancer Stage I or II infiltrating ductal carcinoma treated with breast-conserving therapy at the Joint Center for Radiation Therapy between 1970 and 1986. All patients had pathology slides reviewed by one of two study pathologists. Using the Elston modification of the Bloom-Richardson grading system, patients were divided by histologic grade into 3 groups (219 with Grade I, 482 with Grade II, and 380 with Grade III). The median follow-up time for 716 survivors was 134 months. The incidence of various pathologic features was examined with respect to histologic grade. In addition, the 10-year crude rates of failure (by first site) were examined as they related to grade. A polychotomous logistic regression model was used to determine the effect of grade on local and distant failure.
Results: High grade tumors tended to be larger, to exhibit more mononuclear cellular reaction and necrosis, and were more likely to be estrogen receptor negative. Patients with high grade tumors were also younger than those with lower grade tumors. The incidence of an extensive intraductal component and lymphatic vessel invasion did not vary significantly by histologic grade. The incidence of pathologic lymph node metastases also did not vary by grade, even when stratified by tumor size. In both univariable and multivariable analyses, the 10-year crude rate of local recurrence was not related to histologic grade (P = 0.44). Distant recurrence rates, however, were significantly higher as grade increased (p = 0.002).
Conclusions: Higher histologic grade predicted an increased incidence of distant recurrence, but not a greater likelihood of axillary lymph node metastases or local recurrence after breast-conserving therapy. The authors conclude that grade should not be used to make decisions regarding local management.