Inverse correlation between Ki67 expression as a continuous variable and outcomes in luminal HER2-negative breast cancer

Negative progesterone receptor status correlates with increased risk of breast cancer recurrence in luminal B HER2-positive and -negative subtypes

OBJECTIVES

The prognostic significance of the progesterone receptor (PR) has been widely investigated in luminal A and luminal B [human epidermal growth factor receptor 2 (HER2)-] breast cancer subtypes, both of which are estrogen receptor (ER)-positive and HER2-negative. In contrast, few studies have focused on PR status in luminal B (HER2+) tumors. The aim of this study was to evaluate the impact of positive PR status on outcomes in patients with luminal B (HER2-) or luminal B (HER2+) breast cancer.

METHODS

Survival analysis was performed to estimate the likelihood of distant recurrence and death in 469 breast cancer patients with the luminal B (HER2-) or luminal B (HER2+) subtype. The relationship between PR and HER2 status was also assessed.

RESULTS

Of 387 luminal B (HER2-) and 82 luminal B (HER2+) cancers, PR+ was significantly more frequent in the former than the latter (86.3% vs. 61.0%, respectively; P<0.001). In univariate analysis, PR was identified as a significant favorable prognostic factor for distant disease-free survival and overall survival in both subtypes, but in multivariate analysis PR was not an independent prognostic factor.

CONCLUSIONS

After patients with luminal B subtype were divided into two subgroups according to HER2 status, there was evidence of a relatively good prognosis in the PR+ subgroup. Further studies with a larger number of patients are recommended to validate these findings.

Differences in clinicopathologic features and subtype distribution of invasive breast cancer between elderly and non-elderly women

OBJECTIVES

This study aimed to investigate the clinicopathologic features and subtype distribution of invasive breast cancer in elderly women (≥70 years of age).

METHODS

This retrospective study of 1,130 women compared the clinicopathologic characteristics and subtype distribution of invasive breast cancer in elderly (≥70 years) versus non-elderly (<70 years) women. Tumors were classified into five distinct subtypes based on the immunohistochemistry status of estrogen receptor (ER), progesterone receptor (PR), Ki67, and human epidermal growth factor receptor 2 (HER2).

RESULTS

The two patient groups did not differ significantly regarding ER and HER2 status. Breast cancers in elderly women were more likely to have negative PR status (40.4% vs. 32.6%, P=0.033) and low Ki67 expression (62.0% vs. 54.4%, P=0.047) than those in non-elderly women. Elderly women were less likely to undergo axillary lymph node dissection and axillary surgery (P<0.001). Consequently, unknown node status was more common in elderly women than non-elderly women (11.1% vs. 1.4%, respectively, P<0.001), while node involvement was less common in elderly women than non-elderly women (26.9% vs. 37.7%, respectively, P<0.001). There was no significant difference in the distribution of subtypes between the two groups.

CONCLUSIONS

Breast cancers in elderly women were less frequently node positive and more frequently PR negative and with low Ki67 expression than those in non-elderly women. Moreover, there was no difference in subtype distribution between the two age groups.

Differences in clinicopathologic features and subtype distribution of invasive breast cancer between women older and younger than 40 years

OBJECTIVES

We investigated and compared clinicopathologic features and subtype distribution of invasive breast cancer among women <40 and ≥40 years of age.

METHODS

We retrospectively compared clinicopathologic characteristics and subtype distribution of invasive breast cancer in women <40 and ≥40 years of age, in a cohort of 1,130 patients. Subtypes included luminal A (positive for hormone receptors [HR]-estrogen receptor [ER] and/or progesterone receptor [PR]-and negative for human epidermal growth factor receptor 2 [HER2] with low Ki67), luminal B (HER2^-) (HR⁺/HER2^-/Ki67^High), luminal B (HER2⁺) (HR⁺/HER2⁺), HER2-overexpressing (HR^-/HER2⁺), and triple negative (ER^-/PR^-/HER2^-).

RESULTS

Breast cancers in younger women had unfavorable clinicopathologic characteristics, including larger tumors and more frequent node involvement. Subtypes among the 1,130 tumors were luminal A: 36.4%, luminal B (HER2^-): 35.0%, luminal B (HER2⁺): 7.5%, HER2-overexpressing: 7.1%, and triple negative: 14.0%. The age groups significantly differed in subtype distribution (P<0.001). Luminal A subtype was more common in the older group (38.5%) than the younger group (16.2%), and luminal B (HER2^-) was more common in the younger group (52.2%) than in the older group (33.2%; P<0.001).

CONCLUSIONS

Breast cancers in women younger than 40 years have unfavorable clinicopathologic characteristics and are more likely to be luminal B (HER2^-) and less likely to be luminal A than breast cancers in older women.