FDG-PET/CT: New horizons in anal cancer

Multimodality imaging findings of infection-induced tumors

Several infections can predispose to certain malignancies in different body parts. These infections include viral, bacterial, and fungal pathogens. Imaging plays a vital role in the diagnosis, staging, and management of these neoplastic conditions. Furthermore, it can help in differentiating infection-related non-neoplastic processes that can mimic malignancies. Both radiologists and clinicians should be familiar with these conditions. This review discusses the epidemiology, pathogenesis, and imaging features of infection-related tumors.

Treatment outcome after radiochemotherapy in anal cancer patients staged with 18F-FDG-PET-CT

BACKGROUND

Anal cancer (AC) is a malignancy with increasing incidence and commonly treated with radiochemotherapy. Positron-emission tomography-computed tomography (PET/CT) has been shown to improve treatment outcome in various oncological diseases, however, for AC long-term outcome data is sparse. The aim of the present study is therefore to report outcomes in our cohort of PET/CT staged AC patients treated with radiochemotherapy.

METHODS

Patients with AC who were treated with radiochemotherapy in curative intent were included in this retrospective study if a PET/CT scan was performed pre-therapeutically. Information from PET/CT was considered for nodal and primary target volume definition. Radiotherapy dose to the primary tumor was 50-66 Gy and concomitant chemotherapy included 5-fluorouracil and mitomycin-C. The uptake of 18F-fluorodeoxyglucose (FDG) was quantified using 50%-isocontour volumes of interests (VOIs) and measuring the standardized uptake value (SUV) and the metabolic tumor volume (MTV).18F-FDG uptake was correlated with baseline clinical parameters and long-term oncological outcome. Survival estimates were determined according to Kaplan-Meier.

RESULTS

A total of 60 patients were included in this study. Estimates for three-year overall survival (OS) and disease free survival (DFS) were 94.5% and 80%. Five patients developed local (n = 2) or locoregional and local (n = 3) failure. Baseline PET/CT related parameters correlated with primary tumor stage, nodal stage and tumor grading. DFS was independent of T-stage, N-stage and baseline 18F-FDG-uptake.

CONCLUSION

In this cohort of PET/CT staged AC patients, excellent outcomes for DFS were seen. PET-based markers of tumor burden correlate with local stage of AC, however, are not of prognostic relevance for disease-free survival.

The Utility of PET/Computed Tomography for Radiation Oncology Planning, Surveillance, and Prognosis Prediction of Gastrointestinal Tumors

At present, the strongest evidence for the use of PET/computed tomography (CT) in gastrointestinal (GI) malignancies is to rule out distant metastatic disease at diagnosis, radiation treatment planning for anal malignancies, and disease recurrence monitoring in colorectal and anal malignancies. Use of PET/CT for GI malignancies continues to evolve over time, with new studies evaluating prognostic abilities of PET/CT and with increasing sensitivity and spatial resolution of more modern PET/CT scanners. The authors encourage future applications and prospective evaluation of the use of PET/CT in the staging, prognostication, and recurrence prediction for GI malignancies.

Prediction of Anal Cancer Recurrence After Chemoradiotherapy Using Quantitative Image Features Extracted From Serial 18F-FDG PET/CT

We extracted image features from serial ¹⁸F-labeled fluorodeoxyglucose (FDG) positron emission tomography (PET) / computed tomography (CT) scans of anal cancer patients for the prediction of tumor recurrence after chemoradiation therapy (CRT). Seventeen patients (4 recurrent and 13 non-recurrent) underwent three PET/CT scans at baseline (Pre-CRT), in the middle of the treatment (Mid-CRT) and post-treatment (Post-CRT) were included. For each patient, Mid-CRT and Post-CRT scans were aligned to Pre-CRT scan. Comprehensive image features were extracted from CT and PET (SUV) images within manually delineated gross tumor volume, including geometry features, intensity features and texture features. The difference of feature values between two time points were also computed and analyzed. We employed univariate logistic regression model, multivariate model, and naïve Bayesian classifier to analyze the image features and identify useful tumor recurrent predictors. The area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the accuracy of the prediction. In univariate analysis, six geometry, three intensity, and six texture features were identified as significant predictors of tumor recurrence. A geometry feature of Roundness between Post-CRT and Pre-CRT CTs was identified as the most important predictor with an AUC value of 1.00 by multivariate logistic regression model. The difference of Number of Pixels on Border (geometry feature) between Post-CRT and Pre-CRT SUVs and Elongation (geometry feature) of Post-CRT CT were identified as the most useful feature set (AUC = 1.00) by naïve Bayesian classifier. To investigate the early prediction ability, we used features only from Pre-CRT and Mid-CRT scans. Orientation (geometry feature) of Pre-CRT SUV, Mean (intensity feature) of Pre-CRT CT, and Mean of Long Run High Gray Level Emphasis (LRHGLE) (texture feature) of Pre-CRT CT were identified as the most important feature set (AUC = 1.00) by multivariate logistic regression model. Standard deviation (intensity feature) of Mid-CRT SUV and difference of Mean of LRHGLE (texture feature) between Mid-CRT and Pre-CRT SUVs were identified as the most important feature set (AUC = 0.86) by naïve Bayesian classifier. The experimental results demonstrated the potential of serial PET/CT scans in early prediction of anal tumor recurrence.

Prognostic utility of pre- and post-treatment FDG-PET parameters in anal squamous cell carcinoma

BACKGROUND AND PURPOSE

We prospectively assessed the contributions of PET to initial staging, early detection of treatment failures, and prognostication in patients with anal squamous cell carcinoma (ASCC).

MATERIALS AND METHODS

Consecutive patients with ASCC referred for radical chemoradiotherapy (CRT) consented to undergo FDG-PET imaging pre-treatment and at 3 and 6 months post-treatment. Clinicopathologic data were collected and CT and PET imaging reviewed for contribution to staging and recurrence detection. Maximum standardized uptake value (SUVmax), peak standardized uptake value (SUVpeak), metabolic tumour volume (MTV), and total lesion glycolysis (TLG) were assessed for association with progression-free survival (PFS), cause-specific survival (CSS), and overall survival (OS) using the Kaplan-Meier and Cox regression models.

RESULTS

Between 2009 and 2016, 73 patients with clinical stages I-IIIB ASCC completed curative-intent CRT. Median follow-up was 48 months. 14 patients died and 18 patients experienced disease progression. 4-year PFS, CSS, and OS were 73%, 87%, and 84%, respectively. A pre-treatment MTV >35 cm³ predicted for worse PFS (p = 0.011) and CSS (p = 0.024) on univariate and multivariate analyses, employing an MTV definition of voxels ≥25% of SUVmax. Higher 6-month post-treatment SUVmax and SUVpeak predicted for worse PFS and OS (p ≤ 0.011). Pre-treatment SUVmax, SUVpeak, and TLG, and 3-month post-treatment SUVmax and SUVpeak did not significantly correlate with survival outcomes.

CONCLUSIONS

Our findings support that pre-treatment MTV provides meaningful prognostic information, with suggestion that an MTV delineation threshold of voxels ≥25% of SUVmax is appropriate in the anal region. Post treatment, the combination of clinical examination and PET effectively detected all treatment failures. Higher 6-month post-treatment SUVmax and SUVpeak predicted worse PFS and OS; however, the optimal timing of post-treatment PET imaging remains unclear.

HIV-related Malignancies and Mimics: Imaging Findings and Management

The risk of developing malignancy is higher in patients with human immunodeficiency virus (HIV) infection than in non-HIV-infected patients. Several factors including immunosuppression, viral coinfection, and high-risk lifestyle choices lead to higher rates of cancer in the HIV-infected population. A subset of HIV-related malignancies are considered to be acquired immunodeficiency syndrome (AIDS)-defining malignancies, as their presence confirms the diagnosis of AIDS in an HIV-infected patient. The introduction of highly active antiretroviral therapy (HAART) has led to a significant drop in the rate of AIDS-defining malignancies, including Kaposi sarcoma, non-Hodgkin lymphoma, and invasive cervical carcinoma. However, non-AIDS-defining malignancies (eg, Hodgkin lymphoma, lung cancer, hepatocellular carcinoma, and head and neck cancers) now account for an increasing number of cancer cases diagnosed in HIV-infected patients. Although the number has decreased, AIDS-defining malignancies account for 15%-19% of all deaths in HIV-infected patients in the post-HAART era. Most HIV-related malignancies in HIV-infected patients manifest at an earlier age with a more aggressive course than that of non-HIV-related malignancies. Understanding common HIV-related malignancies and their specific imaging features is crucial for making an accurate and early diagnosis, which impacts management. Owing to the weakened immune system of HIV-infected patients, other entities such as various infections, particularly opportunistic infections, are prevalent in these patients. These processes can have confounding clinical and imaging manifestations that mimic malignancy. This article reviews the most common AIDS-defining and non-AIDS-defining malignancies, the role of imaging in their diagnosis, and the imaging mimics of malignancies in HIV-infected patients. ^©RSNA, 2018.

Positron emission tomography and computed tomographic (PET/CT) imaging for radiation therapy planning in anal cancer: A systematic review and meta-analysis

To improve the accuracy of chemoradiation therapy in anal cancer patients PET/CT is frequently used in the planning of radiation therapy. A systematic review was performed to assess impact on survival, quality of life, symptom score, change in target definition and treatment intention. Systematic literature searches were conducted in Medline, EMBASE, the Cochrane Library, and Centre for Reviews and Dissemination. Ten cross-sectional studies were identified. No data were available on survival or quality of life. The summary estimate of the proportion of patients in which PET/CT had an impact on the target definition, was 23% (95% CI 16;33). The corresponding summary estimate of a change in treatment intent from curative to palliative was 3% (95% CI 2;6). Almost one in four patients had a change in target definition, which supports the use of PET/CT in radiation therapy planning, but the consequence regarding survival and quality of life is still uncertain.

PET imaging in anal canal cancer: a systematic review and meta-analysis

OBJECTIVE

The aim of this study was to systematically review the literature to synthesize and summarize the evidence surrounding the clinical utility of positron emission tomography (PET) imaging in patients with anal canal cancer.

METHODS

The literature was searched using MEDLINE, EMBASE and Cochrane Database of Systematic Reviews databases. Studies comparing PET or PET/CT with conventional imaging in the staging, response evaluation and follow-up of anal canal cancer were deemed eligible for inclusion.

RESULTS

17 studies met the inclusion criteria. For the detection of primary tumour in situ, the pooled sensitivity was 99% for PET or PET/CT and 67% for CT. For the detection of inguinal lymph nodes, PET/CT had an overall sensitivity of 93% and specificity of 76%. PET or PET/CT upstaged 5.1 to 37.5% of patients and downstaged 8.2 to 26.7% of patients. Treatment plans were modified in 12.5 to 59.3% of patients, which consisted mainly of radiotherapy dose or field changes. Complete response on PET or PET/CT is a good prognostic factor for overall and progression-free survival.

CONCLUSIONS

PET/CT seems to add value to conventional imaging in the initial staging of patients with T2-4 disease but further high-quality research is required to validate this. There is insufficient evidence at this time to recommend a routine use of PET/CT in the assessment of treatment response or follow-up. Advances in knowledge: PET/CT appears to alter the disease stage and management in a meaningful number of patients to justify its use as part of staging investigations in locally advanced cases.

Negative 18F-FDG-PET-CT may exclude residual or recurrent disease in anal cancer

OBJECTIVES

The incidence of anal cancer is increasing in Western countries. Fluorine-18 fluorodeoxyglucose (F-FDG) PET-computed tomography (CT) is used in the assessment of anal cancer, but its routine use is not established. The aim of this study was to assess the value of F-FDG-PET-CT in staging and post-treatment assessment in anal cancer and to determine its impact on management.

METHODS

This was a retrospective analysis of patients with anal cancer treated at the Sussex Cancer Centre who underwent PET-CT between November 2004 and September 2014. Information was retrieved from patient notes and the local cancer register, and verified by referring consultants in all cases.

RESULTS

A total of 75 PET-CT scans in 52 patients were identified, representing 38.5% of patients diagnosed with anal cancer during this period. There were 24 staging scans and 51 post-treatment scans. Management was altered following 45.8% of staging scans and 56.0% of all scans, mostly changing treatment type or radiotherapy volume. Out of 28 positive post-treatment scans, 71.4% were true positives, 7.1% were false positives and 21.4% showed nonspecific uptake. Of the 23 negative post-treatment scans, all remained disease free at clinical/radiological follow-up (median follow-up 25 months). The sensitivity and specificity of post-treatment PET-CT were 100 and 74%, respectively. Negative predictive and positive predictive values were 100 and 71%, respectively.

CONCLUSION

Evidence is evolving for the use of PET-CT in anal cancer. Because of a high negative predictive value, our series shows that PET-CT can be used in the assessment of treatment response to exclude residual/recurrent disease.

Effect of AIDS on women who have sex-determined health issues

Worldwide, women account for a growing percentage of human immunodeficiency virus (HIV)-infected patients and more than half of all HIV infections. For many years, morphologic imaging methods were the main approaches employed to investigate HIV and its complications. However, during the past decade, advancements in PET and SPECT imaging technologies opened new possibilities for improved understanding of the pathophysiological processes in HIV. Diagnosis of early HIV-associated neurocognitive disorders (HAND) is important, as many of its symptoms can be caused by other conditions common to people with HIV/AIDS. Presently, there are no PET and SPECT tracers or combination of markers for HAND, hence novel HAND-specific tracers are needed if nuclear medicine is to play a role in solving the problem of the HAND "epidemic." As both highly active antiretroviral therapy (HAART)-induced lipoatrophy and cardiovascular diseases are characterized by ongoing inflammation, FDG-PET/CT imaging may represent an important imaging technique for better understanding the metabolic risk in HIV-infected women on HAART. HIV-infected women are at increased risk for the development of human papilloma virus-associated neoplasms such as cervical and anal carcinomas; these aggressive tumors could be treated better with integration of FDG-PET as part of the standard pretreatment workup. A similar value of FDG-PET may be realized in women with HIV-associated Kaposi sarcoma, as they have more extensive cutaneous disease than men do. In the era of HAART, the incidence and local invasiveness of breast cancer may change, thus creating a need to redefine the pathophysiology of breast cancer in HIV-positive women. Finally, mammary tuberculosis, occasionally the presenting symptom in HIV-infected women, may present with nonspecific clinical, radiological, and histologic findings. In these women, FDG-PET can be of value to detect the lesion for a representative biopsy, staging to exclude pulmonary and other extrapulmonary lesions, and also for therapy monitoring.

FDG PET/CT in the management of colorectal and anal cancers

OBJECTIVE

CT remains the imaging modality of choice in the diagnosis of colorectal cancer (CRC) and anal cancer. However, advances in imaging have expanded the role of MRI and PET/CT. This article focuses on the evolving role of FDG PET/CT in the diagnosis, radiation therapy planning, therapy assessment, and posttherapy monitoring of CRC and anal cancer.

CONCLUSION

FDG PET/CT is a valuable imaging modality that impacts the clinical management of patients with CRC and those with anal cancer.

Diagnostic performance of positron emission tomography/computed tomography using fluorine-18 fluorodeoxyglucose in detecting locoregional nodal involvement in patients with anal canal cancer: a systematic review and meta-analysis

Purpose. The diagnostic performance of positron emission tomography using ¹⁸F-fluorodeoxyglucose (FDG-PET) in detecting nodal involvement in patients with anal canal cancer (ACC) has been investigated by several studies with conflicting results. The aim of our study is to systematically review and meta-analyze published data about this topic. Methods. A comprehensive computer literature search of PubMed/MEDLINE, Scopus, and Embase databases was carried out on July 10 to find relevant articles concerning the diagnostic performance of FDG-PET in detecting locoregional nodal involvement in patients with ACC. No language restriction was used. Pooled diagnostic performance on a lesion-based analysis was calculated. Results. Seven retrospective and five prospective studies have been reviewed. Six studies allowed assessing pooled sensitivity; five studies allowed assessing pooled specificity. Sensitivity and specificity values of FDG-PET/CT on a lesion-based analysis ranged from 31 to 100% and from 53 to 98%, with pooled estimates of 56% (95% CI: 45–67%) and 90% (95% CI: 86–93%), respectively. Conclusions. Our meta-analysis demonstrates that FDG-PET is a specific diagnostic tool in detecting locoregional lymph node involvement in patients with ACC. Low sensitivity is a major concern; however, higher sensitivity could be reached combining FDG-PET with MR scan.

[Positron emission tomography for volume delineation of pelvic nodal involvement]

Radiotherapy planification has recently known important developments, with the rise of new technologies, such as conformational radiation therapy, intensity-modulated radiation therapy (IMRT) or stereotaxic radiation therapy. Delineation of target volumes has become primordial. Hybrid imaging by positron emission tomography associated to computed tomography scanner (PET-CT) gives an access to functional and morphological information. Radiotherapist and nuclear physicians working closely have the potential to allow a more optimal delineation, and a better preservation of organs at risk. During the past few years, this has been explored by many articles, and we propose a literature review organized by localization, about the use of PET-CT for pelvic nodes delineation.

Imaging of anal carcinoma

OBJECTIVE

The purpose of this article is to review the role of imaging in the management of patients with anal cancer. The relevant anatomy, imaging techniques, and interpretation of images of patients before and after therapy will be discussed.

CONCLUSION

Anal carcinomas are uncommon but increasing in frequency. Radiologists must recognize typical patterns of disease at initial evaluation, posttherapy appearances, and when to suspect residual or recurrent disease to guide clinicians and achieve optimal patient outcome.

Role of positron emission tomography-computed tomography in the management of anal cancer

PURPOSE

Pre- and post-treatment staging of anal cancer are often inaccurate. The role of positron emission tomograpy-computed tomography (PET-CT) in anal cancer is yet to be defined. The aim of the study was to compare PET-CT with CT scan, sentinel node biopsy results of inguinal lymph nodes, and anal biopsy results in staging and in follow-up of anal cancer.

METHODS AND MATERIALS

Fifty-three consecutive patients diagnosed with anal cancer underwent PET-CT. Results were compared with computed tomography (CT), performed in 40 patients, and with sentinel node biopsy (SNB) (41 patients) at pretreatment workup. Early follow-up consisted of a digital rectal examination, an anoscopy, a PET-CT scan, and anal biopsies performed at 1 and 3 months after the end of treatment. Data sets were then compared.

RESULTS

At pretreatment assessment, anal cancer was identified by PET-CT in 47 patients (88.7%) and by CT in 30 patients (75%). The detection rates rose to 97.9% with PET-CT and to 82.9% with CT (P=.042) when the 5 patients who had undergone surgery prior to this assessment and whose margins were positive at histological examination were censored. Perirectal and/or pelvic nodes were considered metastatic by PET-CT in 14 of 53 patients (26.4%) and by CT in 7 of 40 patients (17.5%). SNB was superior to both PET-CT and CT in detecting inguinal lymph nodes. PET-CT upstaged 37.5% of patients and downstaged 25% of patients. Radiation fields were changed in 12.6% of patients. PET-CT at 3 months was more accurate than PET-CT at 1 month in evaluating outcomes after chemoradiation therapy treatment: sensitivity was 100% vs 66.6%, and specificity was 97.4% vs 92.5%, respectively. Median follow-up was 20.3 months.

CONCLUSIONS

In this series, PET-CT detected the primary tumor more often than CT. Staging of perirectal/pelvic or inguinal lymph nodes was better with PET-CT. SNB was more accurate in staging inguinal lymph nodes.

Impact of FDG PET/CT in the staging and the follow-up of anal carcinoma

PURPOSE

The purpose of the study was to assess the diagnostic performance of positron emission tomography/computed tomography and fluorodeoxyglucose (18F) (FDG PET/CT) for the staging and the follow-up of anal carcinoma, and to evaluate the impact of FDG PET/CT on patient management.

MATERIALS AND METHODS

Patients with anal carcinoma were referred to our department from October 2004 until July 2008. The diagnostic performance was evaluated on a perexamination basis and on a per-site basis, together with impact of PET/CT on patient management. The standard of truth was histology when available and, in all cases, follow-up data during at least 6 months.

RESULTS

Fifty-eight FDG PET/CT performed in 44 patients were analysed—22 for initial staging and 36 during follow-up. The detection rate of non-excised tumours on initial examination was 93%. During post-treatment follow-up, FDG PET/CT had, on a per-examination basis, sensitivity for the detection of persistent or recurrent disease of 93% and specificity of 81%, and on a per-site basis, 86% and 97%, respectively. Its negative predictive value was 94% on a per-examination basis and 98% on a per-site basis. FDG PET/CT had an impact on management in nine patients out of 44 (20%), which was relevant in eight of them (89%).

CONCLUSION

FDG PET/CT is an accurate imaging modality in anal cancer. It has an interesting added value during post-treatment follow-up, especially when persistence or recurrence of disease is suspected. Further studies are needed to evaluate whether surveillance by means of FDG PET/CT might have a positive impact on overall survival.