Is 18F-FDG PET/CT Beneficial for Newly Diagnosed Breast Cancer Patients With Low Proportion of ER Expression?

Abstract

Objective: It is unclear whether the receptor status of breast malignancy or the proportion of receptors expression is useful in the interpretation of ¹⁸F-FDG PET/CT. This study's purpose was to analyze whether ¹⁸F-FDG PET/CT was valuable for helping newly diagnosed breast cancer patients find suspected or unsuspected metastasis lesions based on the proportion of receptors expression.

Materials and methods: Eighty newly diagnosed breast cancer patients were divided into six groups, containing N0 (no extraaxillary lymph node metastasis), N1 (extraaxillary lymph node metastasis), M0 (no distant metastasis), and M1 (distant metastasis) groups, C0 (no unsuspected metastasis), and C1 (unsuspected metastasis and treatment plan changed) detected by PET/CT. The main data, including the proportion of receptors ER (estrogen receptor), PR (progesterone receptor), and Her-2 (human epidermal growth factor receptor 2) status, were extracted. Simple correlation and logistic regression were preformed to analyze the association between them.

Results: Patients in N1 group had lower proportion of ER (%) and PR (%) than that in N0 group (ER: 2 [0-80] vs. 80 [15-95]; PR: 1 [0-10] vs. 20 [0-45], p<0.001). Moreover, the proportions of ER and PR were negatively correlated with N1 (ER: [r= -0.339, p= 0.002], PR: [r= -0.247, p= 0.011]) by simple correlation. Also, patients in C1 group had lower proportion of ER (%) and PR (%) than those in C0 group (ER: 10 [0-85] vs. 80 [15-90], p=0.026; PR: 1 [0-10] vs. 20 [0-70], p=0.041), while the distribution of ER and PR between M1 and M0 group had no significant difference. After the adjustment of traditional factors, the negative correlation between the proportion of ER (OR=0.986, 95% CI of OR [0.972-0.999], p=0.016) and C1 was found by logistic regression, cutoff value was 25% (ER) calculated by ROC (Receiver Operating Characteristic) curve (AUC [Area Under Curve]= 0.647, p=0.024).

Conclusion: The proportion of ER in newly diagnosed breast cancer was negatively correlated with unsuspected metastasis detected by ¹⁸F-FDG PET/CT. ¹⁸F-FDG PET/CT might be recommended for newly diagnosed breast cancer patients with single lesions when the ER expression proportion is less than 25% to find unsuspected metastasis lesions and to modify treatment plan contrasted with conventional imaging and clinical examination.

Keywords: 18F-FDG PET/CT; breast cancer; receptor status; the proportion of ER expression; the proportion of PR expression.

Figure 1

Workflow for this study design. N0, no extraaxillary lymph node metastasis; N1, extraaxillary lymph node metastasis; M0, no distant metastasis; M1, distant metastasis; C0, no unsuspected metastasis; C1, unsuspected metastasis and with initial treatment plan changed; ER, estrogen receptor; PR, progesterone receptor; Her-2, human epidermal growth factor receptor 2.

Figure 2

Box plot for the proportion of ER and PR distribution between groups. (A) Box plot for the proportion of ER and PR distribution between N group. (B) Box plot for the proportion of ER and PR distribution between M group. (C) Box plot for the proportion of ER and PR distribution between C group. N0, no extraaxillary lymph node metastasis; N1, extraaxillary lymph node metastasis; C0, no unsuspected metastasis; C1, unsuspected metastasis and with initial treatment plan changed; ER, estrogen receptor; PR, progesterone receptor. *p < 0.001.

Figure 3

ROC curve for proportion of ER-positive expression predicting C1 and N1. Youden Index of N group and C group =25%. N1, extraaxillary lymph node metastasis; C0, no unsuspected metastasis; C1, unsuspected metastasis and with initial treatment plan changed; ER, estrogen receptor; ROC, Receiver Operating Characteristic; AUC, area under curve; CI, confidence interval. P < 0.05 was considered significant.

Figure 4

Example for a newly diagnosed breast cancer patient with unsuspected extraaxillary lymph node metastasis detected by 18F-FDG PET/CT inspection. (A) A MIP picture of a 48-year-old newly diagnosed breast cancer woman detected by an 18F-FDG PET/CT inspection with the proportion of ER at 1%. The blue arrow showed the primary tumor of this patient. The green arrow indicated axillary lymph node metastasis in the left armpit. The red arrow presented extraaxillary lymph node metastasis in the left internal mammary near breastbone. (B) PET/CT fusion image of this woman with primary tumor. The blue arrow showed the primary tumor of this patient. (C) PET/CT fusion image of this woman with axillary lymph node metastasis. The green arrow indicated axillary lymph node metastasis in the left armpit. (D) PET/CT fusion image of this woman with extraaxillary lymph node metastasis. The red arrow presented extraaxillary lymph node metastasis in the left internal mammary near the breastbone. ER, estrogen receptor; MIP, maximum intensity projection, with the proportion of ER lower than 25%.

Figure 5

Example for a newly diagnosed breast cancer patient with unsuspected lung, hilar lymph node, and bone metastases detected by 18F-FDG PET/CT inspection. (A) A MIP picture of a 63-year-old newly diagnosed breast cancer woman detected by an ¹⁸F-FDG PET/CT inspection with the proportion of ER at 10%. The red arrow showed the primary tumor of this patient. The green arrow indicated lung metastasis in the right lung. The yellow arrow presented hilar lymph node metastasis. The blue arrow showed bone metastasis. (B) PET/CT fusion image of this woman with primary tumor. (C) PET/CT fusion image of this woman with lung metastasis and hilar lymph node metastasis. The green arrow indicated lung metastasis, and the yellow arrow presented hilar lymph node metastasis. (D) PET/CT fusion image of this woman with bone metastasis. ER, estrogen receptor; MIP, maximum intensity projection, with the proportion of ER lower than 25%.