The role of [(18)F]FDG-PET/CT in staging and treatment planning for volumetric modulated Rapidarc radiotherapy in cervical cancer: experience of the European Institute of Oncology, Milan, Italy

Dynamic FDG PET/CT for differentiating focal pelvic uptake in patients with gynecological cancer

This study aimed to evaluate the ability of serial whole-body dynamic PET/CT to differentiate physiological from abnormal 18F-FDG uptake in the abdomen and pelvis of gynecological cancer patients. We conducted a retrospective study of 61 18F-FDG PET/CT examinations for suspected gynecological malignancies or metastases between March 2018 and January 2020. Our protocol included four-phase dynamic whole-body scans. High-uptake foci with SUVmax > 2.5 in the abdominopelvic region caudal to the renal portal were picked up and visually evaluated as "changed" (disappeared during any phase or morphological changes in more than half of the foci) or "unchanged" in motion on the serial dynamic images. Focal 18F-FDG uptake was observed in 84 foci. Of the 58 foci determined pathologically or clinically to have pathological uptake, no change was observed on serial dynamic imaging in 54 foci (sensitivity, 93%). Of the 26 foci of physiological uptake, temporal changes in uptake were observed in 20 foci using dynamic imaging (specificity, 77%). The positive and negative predictive values were 90% and 83%, respectively, with an accuracy of 88%. Dynamic whole-body 18F-FDG PET/CT imaging allows for differentiation between pathological and physiological uptake in the abdominopelvic region of patients with gynecological cancer.

Molecular Imaging and the PD-L1 Pathway: From Bench to Clinic

Programmed death-1 (PD-1) and programmed death ligand 1 (PD-L1) inhibitors target the important molecular interplay between PD-1 and PD-L1, a key pathway contributing to immune evasion in the tumor microenvironment (TME). Long-term clinical benefit has been observed in patients receiving PD-(L)1 inhibitors, alone and in combination with other treatments, across multiple tumor types. PD-L1 expression has been associated with response to immune checkpoint inhibitors, and treatment strategies are often guided by immunohistochemistry-based diagnostic tests assessing expression of PD-L1. However, challenges related to the implementation, interpretation, and clinical utility of PD-L1 diagnostic tests have led to an increasing number of preclinical and clinical studies exploring interrogation of the TME by real-time imaging of PD-(L)1 expression by positron emission tomography (PET). PET imaging utilizes radiolabeled molecules to non-invasively assess PD-(L)1 expression spatially and temporally. Several PD-(L)1 PET tracers have been tested in preclinical and clinical studies, with clinical trials in progress to assess their use in a number of cancer types. This review will showcase the development of PD-(L)1 PET tracers from preclinical studies through to clinical use, and will explore the opportunities in drug development and possible future clinical implementation.

High precision radiotherapy including intensity-modulated radiation therapy and pulsed-dose-rate brachytherapy for cervical cancer: a retrospective monoinstitutional study

Purpose

To analyse the survival outcomes and toxicity profile of patients treated with pulsed-dose-rate (PDR) brachytherapy (BT) after intensity-modulated radiation therapy (IMRT) for uterine cervical cancer in a single institution.

Material and methods

Between March 2011 and December 2014, 50 patients with histologically proven stages IB1-IVB cervical cancer were treated with IMRT followed by PDR-BT boost. Radiation treatment consisted of IMRT to pelvic with or without paraaortic lymph nodes to a total dose of 45-50.4 Gy. Weekly concomitant chemotherapy was administered to 45 patients. PDR-BT boost was delivered with a median dose of 30 Gy to the high-risk clinical target volume (HR-CTV) after a median time of 14 days since IMRT. Acute and late toxicity were evaluated by Radiation Therapy Oncology Group (RTOG) - European Organization for Research and Treatment of Cancer (EORTC) scoring criteria and Subjective Objective Management Analytic-Late Effects of Normal Tissues (SOMA-LENT) criteria.

Results

Two patients had tumour persistence at 6 months after the end of BT. After a median follow-up of 33 months, 6 distant metastases with or without regional relapse were observed. The 1- and 5-year progression-free survival was 83% (95% CI: 69-91%) and 76% (95% CI: 61-86%), whereas the 3- and 5-year overall survival was 91% (95% CI: 78-97%) and 76% (95% CI: 56-88%), respectively. Urinary and rectal toxicity higher than grade 2 was observed in 6.3% and 17% of patients, respectively. Five patients (10.6%) had grade 4 gastrointestinal toxicity requiring colostomy.

Conclusions

Our study confirms that the combination of IMRT and PDR-BT can be considered an effective treatment for cervical cancer, ensuring high local control, despite the high percentage of locally advanced disease.

Positron emission tomography for staging locally advanced cervical cancer and assessing intensity modulated radiotherapy approach

AIMS

To evaluate toxicity and outcome of concomitant chemotherapy and intensity modulated radiotherapy (IMRT) with 18-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸FDG-PET/CT) based simultaneous integrated boost (SIB) of locally advanced cervical cancer (LACC).

METHODS

Patients with LACC underwent chemo-radiation with IMRT and SIB. Staging and follow-up were performed with clinical evaluation and CT, MRI, ¹⁸FDG-PET/CT. SIB was done on positive nodes with ¹⁸FDG-PET/CT based planning. CT-based planning high-dose-rate brachytherapy (HDR-BT) was delivered as subsequent boost to the primary tumor. Cisplatin concomitant chemotherapy was administered during IMRT.

RESULTS

Fourteen patients with cervical cancer were prospectively recruited between August 2014 and June 2017, 13 (93%) had a LACC, one (7%) patient was not evaluable because ¹⁸FDG-PET/CT evidenced metastases to the liver undetected by previous CT/MRI. Patients had a median age of 59 years, a median Karnofsky performance status of 100%, and a prevalence of squamous cell carcinoma histology (85%). SIB was delivered on 23 positive lymph nodes. IMRT median dose to the pelvis was 48.6 Gy in 27 fractions, SIB median dose 54 Gy in 27 fractions, HDR-BT boost median dose 21 Gy in 3 fractions. After a median follow-up of 30 months, 2-year local control and distant control were 86% and 86%, respectively. There were no grade 4 acute and/or late toxicities.

CONCLUSIONS

The ¹⁸FDG-PET/CT influenced stage assessment and RT treatment planning due to its high specificity in distant metastases and nodal involvement detection. The IMRT with SIB for positive nodes was an effective therapy with acceptable toxicity in LACC.

Prognostic value of posttreatment 18F-FDG PET/CT and predictors of metabolic response to therapy in patients with locally advanced cervical cancer treated with concomitant chemoradiation therapy: an analysis of intensity- and volume-based PET parameters

PURPOSE

To investigate the prognostic value of posttreatment 18F-FDG PET/CT in patients with locally advanced cervical cancer (LACC) treated with concomitant chemoradiation therapy (CCRT). The secondary aim was to assess the possible role of intensity-based and volume-based PET parameters including SUVmax, SUVmean, MTV and TLG, and clinical parameters including age, pathology, FIGO stage and nodal involvement as factors predicting response to treatment.

METHODS

This retrospective study included 82 patients affected by LACC treated with CCRT. All patients underwent 18F-FDG PET/CT both before and after treatment. The posttreatment PET/CT scans were used to classify patients as complete metabolic responders (CMR) or non-complete metabolic responders (N-CMR) according to the EORTC criteria. Kaplan-Meier analysis was used to evaluate differences in overall survival (OS) between the CMR and N-CMR groups. Student's t test, Pearson's chi-squared test and logistic regression were used to investigate the possible value of PET and clinical parameters as predictors of metabolic response to therapy.

RESULTS

Kaplan-Meier analysis showed a highly significant difference in OS between the CMR and N-CMR groups (log-rank test p < 0.0001). Significant independent predictors of response to therapy were MTV (p = 0.019, odds ratio = 1.015, 95% CI = 1.002-1.028, Nagelkerke R2 = 0.110), TLG (p = 0.045, odds ratio = 1.001, 95% CI = 1.000-1.002, Nagelkerke R2 = 0.081) and nodal involvement (p = 0.088, odds ratio = 2.361, 95% CI = 0.879-6.343, Nagelkerke R2 = 0.051).

CONCLUSION

18F-FDG PET/CT-based response assessment using the EORTC criteria reliably predicts OS in LACC patients treated with CCRT. In our cohort of patients, pretreatment MTV and TLG and nodal involvement were predictors of response to therapy. MTV was the best predictor of response. However, its additional risk value seems to be low (MTV odds ratio = 1.015).

Evaluating the Use of 18F-FDG PET CT for External Beam Radiotherapy Planning in Gynaecological Malignancies

PURPOSE OF REVIEW

To evaluate the evidence for the use of fluorine-18-fluorodeoyglucose (18F-FDG) PET CT in external beam radiotherapy planning for treatment of gynaecological malignancies.

RECENT FINDINGS

Our review confirms that the incorporation of 18F-FDG PET CT during radiotherapy planning may decrease inter-observer variability during target delineation. It can also provide useful functional information regarding the tumour, which may facilitate the development of techniques for dose escalation and 'dose painting' not only for primary disease, especially in cervical cancer, but also nodal metastasis. The utilisation of this functional modality in external beam radiotherapy planning, particularly in locally advanced cervical malignancy, is an exciting topic that warrants further prospective research. Perhaps the most valuable role may be the potential to deliver dose escalation to 18F-FDG PET CT avid targets previously limited by organ at risk constraints, now that we have significantly more advanced radiotherapy planning tools at our disposal.

Normal Variants and Pitfalls Encountered in PET Assessment of Gynecologic Malignancies

Combined PET/computed tomography is used for oncological indications. PET/computed tomography benefits from the metabolic information of PET and the anatomic localization of computed tomography. The integrated scanner provides data with accurate registration of anatomy and molecular information. Many physiologic conditions, normal variants, and benign lesions within the pelvis and the body can cause confusion and uncertainty. False-negative results owing to low 18F-fluorodeoxyglucose uptake from the tumor can produce diagnostic challenges and inaccurate conclusions. This article reviews normal variants and potential pitfalls encountered in PET assessment of gynecologic malignancies to provide useful information for the referring and reporting physicians.

[18F]-2-Fluoro-2-Deoxy-D-glucose-PET Assessment of Cervical Cancer

This article provides an overview of PET in cervical cancer, primarily with regard to the use of ¹⁸F-2-fluoro-2-deoxy-d-glucose-PET/computed tomography. A brief discussion of upcoming technologies, such as PET/MR imaging, is presented.

Appropriate magnetic resonance imaging techniques for gross tumor volume delineation in external beam radiation therapy of locally advanced cervical cancer

Background

Accurate delineation of the gross tumor volumes (GTV) is a prerequisite for precise radiotherapy planning and delivery. Different MRI sequences have different advantages and limitations in their ability to discriminate primary cervical tumor from normal tissue. The purpose of this work is to determine appropriate MRI techniques for GTV delineation for external-beam radiation therapy of locally advanced cervical cancer (LACC).

Materials and Methods

GTVs were delineated on the MRI, CT, and PET images acquired for 23 LACC patients in treatment positions to obtain GTVs on CT (GTV-CT), on various MRI sequences including T1 (GTV-T1), T2 (GTV-T2), T1 with fat suppression and contrast (GTV-T1F+), DWI-ADC (GTV-ADC) and on PET were generated using the threshold of 40% of maximum SUV (GTV-SUV40%) as well as SUV of 2.5 (GTV-SUV2.5). MRI, CT and PET were registered for comparison. The GTVs defined by MRI were compared using the overlap ratio (OR) and relative volume ratio (RVR). The union of GTV-T2 and GTV-ADC was generated to represent the MRI-based GTV (GTV-MRI).

Results

The differences between GTV-T2 and other MRI GTVs are significant (P < 0.05). The average ORs for GTV-T1, GTV-T1F+, and GTV-ADC related to GTV-T2 were 86.3%, 81.6%, and 61.6% with the corresponding average RVRs 113.8%, 112.3% and 77.2%, respectively. There is no significant difference between GTV-T1 and GTV-T1F+. GTV-ADC was generally smaller than GTV-T2, however, encompassed suspicious regions that are uncovered in GTV-T2 (up to 16% of GTV-T2) because of different imaging mechanisms. There was significant difference between GTV-MRI, GTV-SUV2.5, GTV-SUV40%, and GTV-CT. On average, GTV-MRI is 18.4% smaller than GTV-CT.

Conclusions

MRI provides improved visualization of disease over CT or PET for cervical cancer. The GTV from the union of GTV-T2 and GTV-ADC provides a reasonable GTV including tumor region defined anatomically and functionally with MRI and substantially reduces the conventional GTV defined on CT.

The role of 18F-FDG PET CT in common gynaecological malignancies

[fluorine-18]-fluoro-2-deoxy-D-glucose positron emission tomography (¹⁸F-FDG PET CT) has increasing clinical applications supplementing conventional TVUS, CT and MRI imaging in assessing ovarian, cervical and endometrial cancer. The published literature on the applications of ¹⁸F-FDG PET CT shows its use can have significant impact on patient management by improving staging of the cancers, influencing patient selection for treatment and in detecting early recurrent disease. However, the increasing clinical use of PET CT does not always align with the guidelines, recommendations or expert opinion in the use of PET CT. This article summarizes the existing evidence base for the established clinical applications and the emerging roles for ¹⁸F-FDG PET CT in the common gynaecological malignancies.

Multiparametric [18F]Fluorodeoxyglucose/ [18F]Fluoromisonidazole Positron Emission Tomography/ Magnetic Resonance Imaging of Locally Advanced Cervical Cancer for the Non-Invasive Detection of Tumor Heterogeneity: A Pilot Study

Objectives

To investigate fused multiparametric positron emission tomography/magnetic resonance imaging (MP PET/MRI) at 3T in patients with locally advanced cervical cancer, using high-resolution T2-weighted, contrast-enhanced MRI (CE-MRI), diffusion-weighted imaging (DWI), and the radiotracers [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) and [¹⁸F]fluoromisonidazol ([¹⁸F]FMISO) for the non-invasive detection of tumor heterogeneity for an improved planning of chemo-radiation therapy (CRT).

Materials and Methods

Sixteen patients with locally advanced cervix were enrolled in this IRB approved and were examined with fused MP [¹⁸F]FDG/ [¹⁸F]FMISO PET/MRI and in eleven patients complete data sets were acquired. MP PET/MRI was assessed for tumor volume, enhancement (EH)-kinetics, diffusivity, and [¹⁸F]FDG/ [¹⁸F]FMISO-avidity. Descriptive statistics and voxel-by-voxel analysis of MRI and PET parameters were performed. Correlations were assessed using multiple correlation analysis.

Results

All tumors displayed imaging parameters concordant with cervix cancer, i.e. type II/III EH-kinetics, restricted diffusivity (median ADC 0.80x10^-3mm²/sec), [¹⁸F]FDG- (median SUV_max16.2) and [¹⁸F]FMISO-avidity (median SUV_max3.1). In all patients, [¹⁸F]FMISO PET identified the hypoxic tumor subvolume, which was independent of tumor volume. A voxel-by-voxel analysis revealed only weak correlations between the MRI and PET parameters (0.05–0.22), indicating that each individual parameter yields independent information and the presence of tumor heterogeneity.

Conclusion

MP [¹⁸F]FDG/ [¹⁸F]FMISO PET/MRI in patients with cervical cancer facilitates the acquisition of independent predictive and prognostic imaging parameters. MP [¹⁸F]FDG/ [¹⁸F]FMISO PET/MRI enables insights into tumor biology on multiple levels and provides information on tumor heterogeneity, which has the potential to improve the planning of CRT.

Image-guided radiotherapy and -brachytherapy for cervical cancer

Conventional radiotherapy for cervical cancer relies on clinical examination, 3-dimensional conformal radiotherapy (3D-CRT), and 2-dimensional intracavitary brachytherapy. Excellent local control and survival have been obtained for small early stage cervical cancer with definitive radiotherapy. For bulky and locally advanced disease, the addition of chemotherapy has improved the prognosis but toxicity remains significant. New imaging technology such as positron-emission tomography and magnetic resonance imaging has improved tumor delineation for radiotherapy planning. Image-guided radiotherapy (IGRT) may decrease treatment toxicity of whole pelvic radiation because of its potential for bone marrow, bowel, and bladder sparring. Tumor shrinkage during whole pelvic IGRT may optimize image-guided brachytherapy (IGBT), allowing for better local control and reduced toxicity for patients with cervical cancer. IGRT and IGBT should be integrated in future prospective studies for cervical cancer.