The Value Of ¹⁸F-FDG PET-CT In Estimation Of Recurrence And Metastasis Of Breast Cancer

OBJECTIVE: To evaluate the applicable value of ¹⁸F-fluorodeoxyglucose(FDG) PET-CT in the prediction of recurrences and metastases of breast cancer by comparing helical CT, PET with PET-CT.MATERIALS AND METHODS: The analysis was based on 37 cases with breast cancer (37 females, age range 37⁶8y, mean age 51±6.3y) which were collected from December, 2003 to March, 2006. All patients underwent ¹⁸F-FDG PET-CT imaging with GE Discovery PET-CT and helical CT. PET-CT imaging was reconstructed and transferred to the working station (GE Entegra) for images fusion. The scan 2 of the dual-time point ¹⁸F-FDG-PET-CT imaging was at 150– 180 min after the intravenous injection, and the acquisition parameters of the scan 2 were the same as the scan 1 in the PET-CT dual-time point imaging. PET-CT images were evaluated by two experienced nuclear medicine physicians and one radiologist in consensus. The positive diagnosis standards for metastases of the axillary lymph nodes were as the following: the long diameter (L) was greater than 10mm or the short diameter (S) was greater than 5mm, or L/S less than 2, and the fat around the node with high density. Distant lymph node metastasis assessment was based on its size, with a short axis diameter exceeding. But if the lymph nodes were bunchiness or ringlike enhanced, their size can not be emphasized. When the lymph node was accorded to the standarde, the diagnosis was positive, otherwise negative. Two kinds of methods were used to analyze the PET-CT images: (1) Eyeballing analysis: the lesions were divided into two types according to the degrees of radioactivity accumulation. Positive account: ¹⁸F-FDG uptake in lesion was higher than that in surrounding normal tissue; negative account: ¹⁸F-FDG uptakes in lession were similar to or lower than that in surrounding normal tissue. (2) Semiquantitative analysis: The regions of interest (ROI) were placed in lesions, and the average standard uptake value (SUVmean) and the maximum standard uptake value (SUVmax) of the lesions were automatically calculated with the computer software. SUVmean≥2.5 were diagnosed as positive lesions, and SUVmean<2.5 were diagnosed as negative lesions. The SUV changes >10% (ΔSUV%=(SUV₂-(SUV₁)/(SUV₁)×100%) between the first and second scans was as a criterion for abnormal increase or decrease. All lesions were analysed with both eyeballing and semiquantitative analysis.The results of PET-CT, PET and CT were compared with those of the histopathology, biopsy, cytological examination, and clinical follow-up results.The results were statistically analyzed with exact probabilities in 2×2 tables or t-test (SPSS software). P<0.05 was defined as a criterion for significant difference.RESULTS: Recurrences and metastases were confirmed in 27 patients with breast cancer by positively pathological results and clinical follow-up. No recurrences and metastases in the remaining 10 patients.1. The comparison of PET-CT, CT with PET in diagnosis of recurrences and metastases of breast cancerPET-CT showed positive results in 28 patients with breast cancer. 27 patients were diagnosed correctly, and 8 negative PET-CT studies had no recurrences and metastases diseases. The sensitivity, specificity, accuracy, positive and negative predictive value in ¹⁸F-FDG PET-CT prediction in recurrences and metastases of breast cancer was 96.30%, 80.00%, .91.89%, 92.86% and 88.89%.In 27 patients of recurrences and metastases with breast cancer, 17 of them were diagnosed as positive and 10 as negative by helical CT; and in 10 patients of no recurrences and metastases, 7 of them were negative and 3 were positive by helical CT. The sensitivity, specificity, accuracy, positive and negative predictive value in CT prediction in recurrences and metastases of breast cancer was 62.96%, 70.00%, 64.86%, 85.00% and 41.18%.Also,in 27 patients of recurrences and metastases with breast cancer, 21 of them were diagnosed as positive and 6 as negative by PET, and in 10 patients of no recurrences and metastases, 6 of them were negative and 4 were positive by PET. The sensitivity, specificity, accuracy, positive and negative predictive value in PET prediction in recurrences and metastases of breast cancer was 77.76%, 60.00%, 72.97%, 84.00% and 50.00%.There was significant difference in sensitivity, accuracy and negative prediction between PET-CT and CT in prediction of recurrences and metastases of breast cancer (P<0.05). PET-CT and CT did not have significant differences in specificities and positive predictive value (P>0.05). There was a significant difference in accuracy between PET-CT and PET in prediction of recurrences and metastases of breast cancer (P<0.05). PET-CT and PET did not have significant differences in sensitivity, specificities, positive and negative prediction (P>0.05).2. The comparison of PET-CT with CT in diagnosing lymph node metastases55 lymph nodes of 37 patients were detected by helical CT, which 33 lymph nodes were proved positive by histopathology, biopsy, cytological examination, and clinical follow-up, and 22 lymph nodes were negative. 37 of all were diagnosed as positive and 18 as negative by helical CT. The sensitivity, specificity, accuracy, positive and negative predictive value in CT prediction in lymph nodes metastases of breast cancer was 81.82%, 54.55%, 70.91%, 72.97% and 66.67%.64 lymph nodes of 37 patients were detected by PET-CT, which 39 lymph nodes were proved positive by histopathology, biopsy, cytological examination, and clinical follow-up, 25 lymph nodes were negative. 44 of all were diagnosed as positive and 20 as negative by PET-CT. The sensitivity, specificity, accuracy, positive and negative predictive value in ¹⁸F-FDG PET-CT prediction in lymph nodes metastases of breast cancer was 97.44%, 76.00%, 89.06%, 86.36% and 95.00%.There was significant difference in sensitivity, accuracy and negative prediction value between PET-CT and CT in prediction of lymph node metastases of breast cancer (P<0.05). PET-CT and CT did not have significant differences in specificities and positive prediction value (P>0.05). PET-CT is much better than helical CT in predicting whether the it was involved of the lymph nodes that the longest-shortest (SD) less than 5mm, PET-CT and helical CT have equal accuracy in predicting whether the lymph nodes that SD were greater than 5mm were involved cancer.3. The diagnostic value of PET-CT dual-time point imaging14 patients with breast cancer underwent PET-CT dual-time point imaging. Recurrences and metastases were diagnosis in 9 patients. Among them, 5 patients had SUV> 2.5 at (the early imaging) scan 1, and all showed increased at the delayed imaging (scan 2); the other 4 patients had SUVs between 1.5 and 2.5 at scan 1 which showed suspected positive, all of their SUVs increased at time point 2. 5 patients with no recurrences and metastases, only 1 patient with benign lesions had SUV> 2.5 at scan 1, and SUVs increased at time point 2; the other 4 patients that confirmed by clinical follow-up showed suspected positive at early and no change of SUV in scan 2.4. The comparision of PET-CT, CT with PET in diagnosing distant metastases27 patients with breast cancer that were detected distant metastases by positively pathological results and clinical follow-up, PET-CT showed positive results in 26 patients. There were 17 patients with axillary and supraclavicular lymph nodes metastases, 3 patients with pleura metastases, 8 patients with distant lymph nodes and (or) distant organ metastases (including 4 patients with lung and mediastinal lymph nodes metastases, 3 patients with liver, pleural and abdominal lymph nodes metastases, and 1 patient with inguinal lymph nodes metastases,), and 5 patients with bone metastases.17 patients were detected distant metastases by helical CT, and there were 13 patients with axillary and supraclavicular lymph nodes metastases, 1 patient with liver metastases, 4 patients with lung metastases, 2 patients with pleural metastases, 1 patient with abdominal metastases.22 patients were detected distant metastases by PET, and there were 15 patients with axillary and supraclavicular lymph nodes metastases, 2 patients with liver metastases, 4 patients with lung and mediastinal lymph nodes metastases, 3 patients with pleural and abdominal metastases, and 5 patients with bone metastases.The sensitivity in ¹⁸F-FDG PET-CT, CT and PET prediction in recurrences and metastases of breast cancer was 96.30%, 62.96%, .81.48%. There was significant difference in snesitivity between PET-CT and CT in prediction of recurrences and metastases of breast cancer (x2=9.247, P<0.05).CONCLUSIONS: The specificity and positive predictive value in prediction the recurrences and metastases of breast cancer of helical CT are relatively high. It can provide correct information, and it is one of the effective methods in predicting the recurrences and metastases of breast cancer. But the sensitivity, accuracy and negative prediction in prediction of the recurrences and metastases of breast cancer is much lower than those of PET-CT. The sensitivity, specificity, positive predictive value and negative predictive value in prediction the recurrences and metastases of breast cancer of PET are relatively high. But the accuracy in prediction of the recurrences and metastases of breast cancer is much lower than those of PET-CT.PET-CT is more accuracy than CT in diagnosing the positive lymph node metastasis and the false negative value is fewer than that of CT. There are no significant differences in specificities between PET-CT and CT for the lymph node metastases of breast cancer. But PET-CT is much better than helical CT in predicting whether it is involved of the lymph nodes that the SD less than 5mm. PET-CT and helical CT have equal accuracy in predicting whether it is involved the lymph node that SD is greater than 5mm.PET-CT dual-time point imaging appeares to be helpful for differentiating benign lesions from malignant lesions, that the lesions have high uptake of ¹⁸F-FDG at scan 1, and eliminate the interference from ¹⁸F-FDG uptake in normal physiologic formation, post radio-chemotherapy inflammation or scar. It can improve the accuracy in the diagnosis of recurrence and metastasis of breast cancer.In distant metastasis, PET-CT is more sensitive than helical CT in detecting liver metastasis and bone metastasis, but in detecting lung and abdominal metastasis PET-CT and CT have equal accuracy. Compared with CT and PET-CT, PET has low accuracy in detecting lung metastasis and abdominal metastasis.In an overview, Integrated PET-CT scanner realizes the fuse of functional and anatomic imaging in one device, and it is superior to traditional imaging in evaluating curative effect for malignant tumors. For the patients with brast cancer who cannot be confirmed recurrence or metastasis by traditional diagnosis, PET-CT is the best choice.. Compared with CT and PET, PET-CT can provide more information for choosing the best clinical treatment. OBJECTIVE: To establish the method of labeling ATWLPPR with ^99mTc, and the biodistribution of the anti-VEGF peptide in normal mice and the imaging study on tumour bearing nude mice were carried out. The purpose is to evaluate the feasibility of tumour receptor imaging with radiolabelled HYNIC-ATWLPPR in early diagnosis of malignancy.METHODS: ATWLPPR labeling and character analysis of 99Tcm-HYNIC-ATWLPPR: ATWLPPR conjugating the bifunctional chelator-HYNIC was synthesized. The peptide was labeled with 99Tcm through an indirect method using tricine/EDDA as co-ligands. After 30～40 minutes at room temperature, the labeled mixture, named 99Tcm-HYNIC-ATWLPPR was completed. Absorbency at 280 nm and radioactivity were used to identigy peak fractions and count yield. We compared the radiolabeling yield of using different co-ligands for HYNIC conjugation and different activity of radioactivity. The radiolabeling yield, radiochemical purity, and stability of the 99Tcm-HYNIC-ATWLPPPR were assessed.Mice model preparation, biodistribution study and imaging: (1) Biodistribution in normal mice: A total of 25 normal KM mice were used in biodistribution. Immediately after labeling, 1μg of radiolabeled ATWLPPR in 100μl eluent was injected into each mouse via a tail vein. At different time point post-injection, Whole blood samples were collected and the mice were sacrificed by cervical dislocation. The myocardium, liver, spleen, lung, kidney, brain, stomach, intestines, muscle, and bone were harvested, rinsed, weighed and counted on aγcounter. The percent uptake per gram tissue was calculated. (2) In vivo tumour imaging in tumour bearing nude mice: BALB/c A nude mice bearing human breast cancer cancer MCF-7 xenografts were studied. After injection of the radiotracers, static acquisitions imaging were performed at different time point with a gammar camera fitted with a general-purpose low-energy pinprick using a 256×256 matrix with a 20% energy window set at 140 keV. And radioactivity ratios of tumour to contralateral limbs were calculated using ROI technique. (3) Biodistribution in tumour bearing nude mice: Five tumour model nude mice were sacrificed 180min after radiotracer injection. Tumours, blood samples and organs were harvested, rinsed, weighed and counted on aγcounter. (4) Immunohistochemical analysis of tumour histological paraffin section: the expression of VEGF165 was examined by using SP method. And the negative control was set up.RESULTS: ATWLPPR labeling and character analysis of 99Tcm-HYNIC-ATWLPPR: Using tricine, EDDA, and tricine/EDDA as co-ligands, the labeling yield of ^99mTc-HYNIC-ATWLPPR was 77.75%,68.09%,91.531%,80% respectively. When the activities of 99TcmO4- were 185MBq, 74MBq and 37MBq, the radiolabeling yield of 99Tcm-HYNIC-ATWLPPR were 88.06%±1.05%,94.00%±1.25% and 91.61%±2.70%, respectively. The radiochemical purity of the 99Tcm-HYNIC-ATWLPPR was 94.14%±1.75%. After incubation with fresh human serum for 30min and 120min, the radiochemical purities were 91.5% and 90.8%, and analyzed by Sep-Pak C18 column, the radioactivity peak showed no shift to early or late fractions. The reaction mixture was incubated at room temperature for 5h, and the radiochemical purity was 91.35%. Mice model preparation, biodistribution study and imaging: (1) Biodistribution in normal mice: It indicated that the disappearance of radioactivity from plasma was rapid. ^99mTc-HYNIC-ATWLPPR was mainly excreted through kidney and liver. (2) In vivo tumour imaging in tumour bearing nude mice: Tumour lesions were clearly visible 180min after injection and the ratios of tumour/contralateral limbs were 3.758 respectively. The ectent of accumulation increases with time with a peak tumour/contralateral limbs ratio (T/L) of 3.758 at three hours and then decreased to 1.754 at six hours in tumour mice. (3) Biodistribution in tumour bearing nude mice: The radioactivity of tumour nude mice accumulated in the kidney and liver was the highest, and in the brain was the lowest. The radioactivity ratios of tumour/brain and tumour/heart were 22.18 and 4.63, which were the highest. And the radioactivity ratios of tumour/muscle, tumour/skeleton and tumour/blood were 2.85, 1.89 and 1.59. (4) Immunohistochemical analysis of tumour histological paraffin section: the expression of VEGF165 was mainly seen in the endochylema of vascular endothelial cells, and there were brown granulocorpuscle or diffuse distribution. But in the negative control, the endochylema of vascular endothelial cells was not seen staining.CONCLUSION: The labeling method of ATWLPPR conjugated by HYNIC has been proved successful. It is an optimal method with simple steps, high radiolabeling yield and well stability. Radiochemical was mainly excreted through kidney and liver, and high accumulation in the tumour in tumour bearing nude mice. The study of in vivo imaging and biodistribution showed that ^99mTc-HYNIC-ATWLPPR remains fine biological activity, our data suggest ^99mTc-HYNIC-ATWLPPR is a promising tumour radiotracer.