An update on the role of PET/CT and PET/MRI in ovarian cancer

The Role of Positron Emission Tomography/Magnetic Resonance Imaging in Gynecological Malignancies

Accurate oncological staging for early detection is of utmost importance in patient care and increasing the overall patient survival outcome. Hybrid imaging in the form of positron emission tomography (PET)/computed tomography has been successfully implemented in oncological imaging and, where available, has been used consistently in patients with gynecologic malignancies. The implementation of PET/magnetic resonance imaging (MRI) enables high-quality assessment of gynecological malignancies by combining the diagnostic advantages of metabolic information of PET along with the high-resolution anatomical and functional information from the MRI to provide precise information about staging, recurrence, and metastases. This article will review the various applications of PET/MRI in gynecological cancer.

Imaging before cytoreductive surgery in advanced ovarian cancer patients

Appropriate and accurate pre-operative imaging in epithelial ovarian cancer patients may allow selection of patients that may mostly benefit either from primary cytoreductive surgery or from neoadjuvant chemotherapy. If the patient is considered suitable for upfront surgery, pre-operative imaging may help in planning the surgical approach, to forecast the operating time, and to estimate the need for other consulting specialists. Currently, computed tomography (CT) imaging is the standard of care for pre-operative evaluation of ovarian cancer patients; however, advanced magnetic resonance imaging (MRI) is emerging as a technique that may overcome the limitations of CT imaging, especially for small peritoneal deposits in difficult-to-resect sites. Positron emission tomography (PET)-CT imaging in the pre-operative setting is currently limited, whereas the use of the new hybrid technique PET-MRI is still under evaluation. Since criteria that may preclude optimal cytoreductive surgery may vary, depending on the aggressiveness of the surgical procedure and surgeon skill, multidisciplinary consensus conferences are the ideal platform to evaluate extent of the disease and surgical strategy.

An update on preoperative assessment of the resectability of advanced ovarian cancer

The best prognosis for advanced ovarian cancer is provided by no residual disease after primary cytoreductive surgery. It is thus important to be able to predict resectability that will result in complete cytoreduction, while avoiding unnecessary surgery that may leave residual disease. No single procedure appears to be sufficiently accurate and reliable to predict resectability. The process should include a preoperative workup based on clinical examination, biomarkers, especially tumor markers, and imaging, for which computed tomography, as well as sonography, magnetic resonance imaging and positron-emission tomography, can be used. This workup should provide sufficient information to determine whether complete cytoreduction is possible or if not, to propose neoadjuvant chemotherapy which is preferable in this case. For the remaining patients, laparoscopy is broadly recommended as an ultimate triage step. However, its modalities are still debated, and several scores have been proposed for standardization and improving accuracy. The risk of false negatives requires a final assessment of resectability as the first stage of cytoreductive surgery by laparotomy. Composite models, consisting of several criteria of workup and, sometimes, laparoscopy have been proposed to improve the accuracy of the predictive process. Regardless of the modality, the process appears to be accurate and reliable for predicting residual disease but less so for predicting complete cytoreduction and thus avoiding unnecessary surgery and an inappropriate treatment strategy. Overall, the proposed procedures are heterogeneous, sometimes unvalidated, or do not consider advances in surgery. Future techniques and/or models are still needed to improve the prediction of complete resectability.

Molecular imaging of bone metastases using tumor-targeted tracers

Bone metastasis is a disastrous manifestation of most malignancies, especially in breast, prostate and lung cancers. Since asymptomatic bone metastases are not uncommon, early detection, precise assessment, and localization of them are very important. Various imaging modalities have been employed in the setting of diagnosis of bone metastasis, from plain radiography and bone scintigraphy to SPECT, SPECT/CT, PET/CT, MRI. However, each modality showed its own limitation providing accurate diagnostic performance. In this regard, various tumor-targeted radiotracers have been introduced for molecular imaging of bone metastases using modern hybrid modalities. In this article we review the strength of different cancer-specific radiopharmaceuticals in the detection of bone metastases. As shown in the literature, among various tumor-targeted tracers, 68Ga DOTA-conjugated-peptides, 68Ga PSMA, 18F DOPA, 18F galacto-RGD integrin, 18F FDG, 11C/18F acetate, 11C/18F choline, 111In octreotide, 123/131I MIBG, 99mTc MIBI, and 201Tl have acceptable capabilities in detecting bone metastases depending on the cancer type. However, different study designs and gold standards among reviewed articles should be taken into consideration.

Performance of pre-treatment ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography for detecting metastasis in ovarian cancer: a systematic review and meta-analysis

OBJECTIVE

We describe a systematic review and meta-analysis of the performance of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) for detecting metastasis in ovarian cancer.

METHODS

MEDLINE and Embase were searched for diagnostic accuracy studies that used ¹⁸F-FDG PET or PET/CT for pre-treatment staging, using surgical findings as the reference standard. Sensitivities and specificities were pooled and plotted in a hierarchic summary receiver operating characteristic plot. Potential causes of heterogeneity were explored through sensitivity analyses.

RESULTS

Eight studies with 594 patients were included. The overall pooled sensitivity and specificity for metastasis were 0.72 (95% confidence interval [CI]=0.61-0.81) and 0.93 (95% CI=0.85-0.97), respectively. There was considerable heterogeneity in sensitivity (I²=97.57%) and specificity (I²=96.74%). In sensitivity analyses, studies that used laparotomy as the reference standard showed significantly higher sensitivity and specificity (0.77; 95% CI=0.67-0.87 and 0.96; 95% CI=0.92-0.99, respectively) than those including diagnostic laparoscopy (0.62; 95% CI=0.46-0.77 and 0.84; 95% CI=0.69-0.99, respectively). Higher specificity was shown in studies that confirmed surgical findings by pathologic evaluation (0.95; 95% CI=0.90-0.99) than in a study without pathologic confirmation (0.69; 95% CI=0.24-1.00). Studies with a lower prevalence of the FDG-avid subtype showed higher specificity (0.97; 95% CI=0.94-1.00) than those with a greater prevalence (0.89; 95% CI=0.80-0.97).

CONCLUSION

Pre-treatment ¹⁸F-FDG PET/CT shows moderate sensitivity and high specificity for detecting metastasis in ovarian cancer. With its low false-positive rate, it can help select surgical approaches or alternative treatment options.

Diagnostic value of ultrasound score, color Doppler ultrasound RI and spiral CT for ovarian tumors

Diagnostic value of ultrasound score, color Doppler ultrasound resistance index (RI) and spiral computed tomography (CT) for ovarian tumors was investigated. In total 224 patients pathologically diagnosed with ovarian tumor after operation in Cangzhou Central Hospital were selected, including 120 patients with benign ovarian tumor and 104 patients with malignant ovarian tumor. Patients with benign and malignant tumors were scored according to the ultrasound scoring criteria. The color Doppler ultrasound examination was performed and the corresponding RI was recorded. At the same time, 64-slice spiral CT was performed, and results were compared with the postoperative pathological diagnosis. Also, the sensitivity, specificity and accuracy of the combined application of the three methods were detected. The RI value of benign ovarian tumor was higher than that of malignant ovarian tumor, displaying statistically significant difference (P<0.05). The sensitivity, specificity and accuracy of the combined application of the three methods were 96.49, 90.91 and 93.75%, respectively. Ultrasound scoring, color Doppler ultrasound RI and 64-slice spiral CT have good diagnostic value for ovarian tumor, and the diagnostic accuracy rate of the combined application is higher. Therefore, different examination methods can be selected in clinic according to the different situations.

[Diagnostic value of imaging (ultrasonography, doppler, CT, MR, PET-CT) for the diagnosis of a suspicious ovarian mass and staging of ovarian, tubal or primary peritoneal cancer: Article drafted from the French Guidelines in oncology entitled "Initial management of patients with epithelial ovarian cancer" developed by FRANCOGYN, CNGOF, SFOG, GINECO-ARCAGY under the aegis of CNGOF and endorsed by INCa]

Transvaginal ultrasound is the first-line examination allowing characterizing 80 to 90% of adnexal masses (LP1). If performed by an expert, a subjective analysis is optimal. If performed by a non-expert, combining the use of Simple Rules with subjective analysis can achieve the diagnostic performance of an expert (LP1). Whichever the chosen model (subjective analysis by an expert or combination of the Simple Rules with a subjective analysis by a non-expert), a second-line examination will have to be proposed in the complex or indeterminate cases (about 20% of the masses) (grade A). The best-performing second-line test for characterization is pelvic MRI (LP1). If read by an expert, a pathological hypothesis can or should be suggested (grade D). In case of non-expert reading, the use of the ADNEXMR score allows a reliable assessment of the positive predictive value of malignancy to guide the patient towards the best management (gradeC). For preoperative assessment and evaluation of resectability of ovarian, fallopian tube or primary peritoneal cancer, it is recommended to perform a chest abdomen and pelvis CT with contrast agent injection (LP2, grade B). In the event of a contraindication to the injection of iodinated contrast agent (severe renal insufficiency, GFR <30mL/min), an abdomen and pelvis MRI completed with a non-injected chest CT may be proposed (LP3, grade C). By analogy, the same examinations are recommended to evaluate the disease after neo-adjuvant chemotherapy (LP3, Recommendation grade C). Further studies will be required to determine whether PET-CT provides better lymph node assessment before retroperitoneal and pelvic lymphadenectomy. PET-CT may be used to eliminate lymph node involvement in the absence of suspicious lymph nodes on morphological examination (LP3, grade C). The report should specify the localizations leading to a risk of incomplete cytoreductive surgery and lesions outside the field explored during surgery.

Prognostic value of volume-based metabolic parameters of 18F-FDG PET/CT in ovarian cancer: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis on the prognostic value of ¹⁸F-FDG PET-derived volume-based parameters regarding metabolic tumor volume (MTV) and total lesion glycolysis (TLG) in patients with ovarian cancer.

METHODS

Pubmed and EMBASE databases were searched up to February 12, 2018 for studies which evaluated MTV or TLG as a prognostic factor in ovarian cancer with progression-free (PFS) and overall survival (OS) as the endpoints. Hazard ratios (HRs) were meta-analytically pooled using the random-effects model. Multiple subgroup analyses based on clinicopathological and PET variables were performed.

RESULTS

Eight studies with 473 patients were included. The pooled HRs of MTV and TLG for PFS were 2.50 (95% CI 1.79-3.48; p < 0.00001) and 2.42 (95% CI 1.61-3.65; p < 0.0001), respectively. Regarding OS, the pooled HRs of MTV and TLG were 8.06 (95% CI 4.32-15.05; p < 0.00001) and 7.23 (95% CI 3.38-15.50; p < 0.00001), respectively. Multiple subgroup analyses consistently showed that MTV and TLG were significant prognostic factors for PFS with pooled HRs ranging from 2.35 to 2.58 and from 1.73 to 3.35, respectively.

CONCLUSIONS

MTV and TLG from ¹⁸F-FDG PET were significant prognostic factors in patients with ovarian cancer. Despite the clinical heterogeneity and difference in methodology between the studies, patients with a high MTV or TLG have a higher risk of disease progression or death.

A PET imaging agent for evaluating PARP-1 expression in ovarian cancer

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) inhibitors are effective in a broad population of patients with ovarian cancer; however, resistance caused by low enzyme expression of the drug target PARP-1 remains to be clinically evaluated in this context. We hypothesize that PARP-1 expression is variable in ovarian cancer and can be quantified in primary and metastatic disease using a novel PET imaging agent.

METHODS

We used a translational approach to describe the significance of PET imaging of PARP-1 in ovarian cancer. First, we produced PARP1-KO ovarian cancer cell lines using CRISPR/Cas9 gene editing to test the loss of PARP-1 as a resistance mechanism to all clinically used PARP inhibitors. Next, we performed preclinical microPET imaging studies using ovarian cancer patient-derived xenografts in mouse models. Finally, in a phase I PET imaging clinical trial we explored PET imaging as a regional marker of PARP-1 expression in primary and metastatic disease through correlative tissue histology.

RESULTS

We found that deletion of PARP1 causes resistance to all PARP inhibitors in vitro, and microPET imaging provides proof of concept as an approach to quantify PARP-1 in vivo. Clinically, we observed a spectrum of standard uptake values (SUVs) ranging from 2-12 for PARP-1 in tumors. In addition, we found a positive correlation between PET SUVs and fluorescent immunohistochemistry for PARP-1 (r2 = 0.60).

CONCLUSION

This work confirms the translational potential of a PARP-1 PET imaging agent and supports future clinical trials to test PARP-1 expression as a method to stratify patients for PARP inhibitor therapy.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02637934.

FUNDING

Research reported in this publication was supported by the Department of Defense OC160269, a Basser Center team science grant, NIH National Cancer Institute R01CA174904, a Department of Energy training grant DE-SC0012476, Abramson Cancer Center Radiation Oncology pilot grants, the Marsha Rivkin Foundation, Kaleidoscope of Hope Foundation, and Paul Calabresi K12 Career Development Award 5K12CA076931.

Multimodality reporter gene imaging: Construction strategies and application

Molecular imaging has played an important role in the noninvasive exploration of multiple biological processes. Reporter gene imaging is a key part of molecular imaging. By combining with a reporter probe, a reporter protein can induce the accumulation of specific signals that are detectable by an imaging device to provide indirect information of reporter gene expression in living subjects. There are many types of reporter genes and each corresponding imaging technique has its own advantages and drawbacks. Fused reporter genes or single reporter genes with products detectable by multiple imaging modalities can compensate for the disadvantages and potentiate the advantages of each modality. Reporter gene multimodality imaging could be applied to trace implanted cells, monitor gene therapy, assess endogenous molecular events, screen drugs, etc. Although several types of multimodality imaging apparatus and multimodality reporter genes are available, more sophisticated detectors and multimodality reporter gene systems are needed.

Selected PET radiomic features remain the same

Purpose

We investigated whether PET radiomic features are affected by differences in the scanner, scan protocol, and lesion location using ¹⁸F-FDG PET/CT and PET/MR scans.

Results

SUV, TMR, skewness, kurtosis, entropy, and homogeneity strongly correlated between PET/CT and PET/MR images. SUVs were significantly higher on PET/MR_{0-2 min} and PET/MR_{0-10 min} than on PET/CT in gynecological cancer (p = 0.008 and 0.008, respectively), whereas no significant difference was observed between PET/CT, PET/MR_{0–2 min}, and PET/MR_{0–10 min} images in oral cavity/oropharyngeal cancer. TMRs on PET/CT, PET/MR_{0–2 min}, and PET/MR_{0–10 min} increased in this order in gynecological cancer and oral cavity/oropharyngeal cancer. In contrast to conventional and histogram indices, 4 textural features (entropy, homogeneity, SRE, and LRE) were not significantly different between PET/CT, PET/MR_{0–2 min}, and PET/MR_{0–10 min} images.

Conclusions

¹⁸F-FDG PET radiomic features strongly correlated between PET/CT and PET/MR images. Dixon-based attenuation correction on PET/MR images underestimated tumor tracer uptake more significantly in oral cavity/oropharyngeal cancer than in gynecological cancer. ¹⁸F-FDG PET textural features were affected less by differences in the scanner and scan protocol than conventional and histogram features, possibly due to the resampling process using a medium bin width.

Methods

Eight patients with gynecological cancer and 7 with oral cavity/oropharyngeal cancer underwent a whole-body ¹⁸F-FDG PET/CT scan and regional PET/MR scan in one day. PET/MR scans were performed for 10 minutes in the list mode, and PET/CT and 0–2 min and 0–10 min PET/MR images were reconstructed. The standardized uptake value (SUV), tumor-to-muscle SUV ratio (TMR), skewness, kurtosis, entropy, homogeneity, short-run emphasis (SRE), and long-run emphasis (LRE) were compared between PET/CT, PET/MR_{0-2 min}, and PET/MR_{0-10 min} images.

Fludeoxyglucose F 18 PET/CT Assessment of Ovarian Cancer

Ovarian cancer is one of the most common gynecologic cancers and one of the leading causes of cancer death in women. It is often asymptomatic in early stages, and thus most patients are diagnosed when it is of advanced stage. For these reasons, the role of biomarkers and tomographic imaging is crucial. Fludeoxyglucose F 18 PET/CT is a useful imaging modality in different clinical settings of the disease, overcoming some limits of conventional imaging and influencing prognosis and therapeutic approaches. PET/MR imaging is an emerging modality, and its potential role remains to be explored.

Modified posterior pelvic exenteration for advanced ovarian malignancies: a single-institution study of 35 cases

INTRODUCTION

This study aimed to investigate the possible benefits of a complete cytoreduction in patients with advanced ovarian cancer and concomitant rectal invasion. Furthermore, we evaluated the morbidity associated with radical surgery.

MATERIAL AND METHODS

A retrospective analysis examined 35 women who underwent radical surgery in the form of modified posterior pelvic exenteration. Descriptive statistics, Kaplan-Meier survival curves and log-rank test were used for statistical estimations. Surgical complications were analyzed using the Clavien-Dindo classification.

RESULTS

The analysis of survival in relation to residual disease assessed according to Sugarbaker confirmed an optimistic prognosis in patients with optimal debulking with a mean disease-free survival period of 33.6 months in R0 patients, 19.6 months in R1 patients, and 14.3 months in R2 patients. A statistically significant difference in disease-free survival (p = 0.023) was observed between the R0 (without residual disease) and R1+2 (with residual disease) groups. Surgical complications occurred in 83% of patients, with early postoperative complications being most frequent (65.7%). While grade III-IV complications occurred in 37.7% of all patients, no cases of surgery-associated mortality occurred.

CONCLUSIONS

Modified posterior pelvic exenteration is a highly effective method for achieving optimal debulking in cases of advanced ovarian cancer with the direct invasion of the rectum. Modified posterior pelvic exenteration does not delay the beginning of complementary chemotherapy. However, it is necessary to take into account surgery-related morbidity. As modified posterior pelvic exenteration represents an extremely invasive technique, the surgical plan and perioperative care should be personalized to address the individual medical and surgical conditions of each patient.