Role of 18F-FDG PET/CT in Posttreatment Evaluation of Anal Carcinoma

Imaging Features of Anal Carcinoma after Chemoradiation

Anal cancer is a rare malignancy that is primarily treated with chemoradiation therapy (CRT). Clinical examination of the anal canal after CRT is often limited owing to the patient's discomfort. Therefore, radiologic surveillance plays a fundamental role in treatment response assessment. Currently recommended imaging modalities for posttreatment follow-up include pelvic MRI for local response evaluation and CT for evaluation of possible distant metastases. Patients who demonstrate a complete treatment response undergo regular clinical and imaging surveillance. Cases demonstrating an equivocal treatment response, an incomplete response, or disease progression should be streamlined for biopsy confirmation of the suspicious site and considered for salvage abdominoperineal resection. Radiologic differentiation of post-CRT inflammatory changes versus residual tumor, particularly in the early post-CRT period, can be challenging. However, careful interrogation of T2-weighted MR images correlated with matching diffusion-weighted and apparent diffusion coefficient images can increase reader confidence. The role of fluorine 18-fluorodeoxyglucose (FDG) PET/CT in assessing the response to anal cancer treatment is a debated topic. However, emerging research suggests that FDG PET/CT is complementary to pelvic MRI for accurate treatment response assessment, providing additional metabolic information. In this article, the authors provide a comprehensive review of the post-CRT imaging appearances of anal cancer, including examples from the spectrum of disease responses and therapy-related complications, and describe the strengths and limitations of pelvic MRI and FDG PET/CT. The authors also share the pearls and pitfalls in differentiating residual tumor from posttreatment inflammatory mimics. ©RSNA, 2025 Supplemental material is available for this article.

Prognostic Value of 18F-FDG PET/CT Assessment After Radiotherapy of Squamous Cell Carcinoma of the Anus in Patients from the National Multicentric Cohort FFCD-ANABASE

This study aimed to evaluate the prognostic value of 18F-FDG PET/CT qualitative assessment in terms of recurrence-free survival (RFS), colostomy-free survival (CFS), and overall survival (OS) after radiation therapy (RT) of squamous cell carcinoma of the anus (SCCA). Secondary objectives were to evaluate the prognostic value of baseline and posttherapeutic quantitative 18F-FDG PET/CT parameters in terms of RFS, CFS, and OS. Methods: We included all consecutive patients from the French multicentric cohort FFCD-ANABASE who had undergone 18F-FDG PET/CT at baseline and 4-6 mo after RT or chemoradiotherapy for a localized SCCA. Qualitative assessments separated patients with complete metabolic response (CMR) and non-CMR. Quantitative parameters were measured on baseline and posttreatment 18F-FDG PET/CT. RFS, CFS, and OS were analyzed using the Kaplan-Meier method. Associations among qualitative assessments, quantitative parameters, and RFS, CFS, and OS were analyzed using univariate and multivariate Cox regression. Results: Among 1,015 patients treated between January 2015 and April 2020, 388 patients (300 women and 88 men) from 36 centers had undergone 18F-FDG PET/CT at diagnosis and after treatment. The median age was 65 y (range, 32-90 y); 147 patients (37.9%) had an early-stage tumor and 241 patients (62.1%) had a locally advanced-stage tumor; 59 patients (15.2%) received RT, and 329 (84.8%) received chemoradiotherapy. The median follow-up was 35.5 mo (95% CI, 32.8-36.6 mo). Patients with CMR had better 3-y RFS, CFS, and OS, at 84.2% (95% CI, 77.8%-88.9%), 84.7% (95% CI, 77.2%-89.3%), and 88.6% (95% CI, 82.5%-92.7%), respectively, than did non-CMR patients, at 42.1% (95% CI, 33.4%-50.6%), 47.9% (95% CI, 38.1%-56.8%), and 63.5 (95% CI, 53.2%-72.1%), respectively (P < 0.0001). Quantitative parameters were available for 154 patients from 3 centers. The following parameters were statistically significantly associated with 3-y RFS: baseline SUVmax (primitive tumor [T]) (hazard ratio [HR], 1.05 [95% CI, 1.01-1.1; P = 0.018]), SUVpeak (T) (HR, 1.09 [95% CI, 1.02-1.15; P = 0.007]), MTV 41% (T) (HR, 1.02 [95% CI, 1-1.03; P = 0.023]), MTV 41% (lymph node [N]) (HR, 1.06 [95% CI, 1.03-1.1; P < 0.001]), MTV 41% (T + N) (HR, 1.02 [95% CI, 1-1.03; P = 0.005]), and posttreatment SUVmax (HR, 1.21 [95% CI, 1.09-1.34; P < 0.001]). Conclusion: Treatment response assessed by 18F-FDG PET/CT after RT for SCCA has a significant prognostic value.18F-FDG PET/CT could be useful for adapting follow-up, especially for patients with locally advanced-stage tumors. Quantitative parameters could permit identification of patients with a worse prognosis but should be evaluated in further trials.

Diffusion-weighted magnetic resonance imaging as an early prognostic marker of chemoradiotherapy response in squamous cell carcinoma of the anus: An individual patient data meta-analysis

Background and purpose

Squamous cell carcinoma of the anus (SCCA) can recur after chemoradiotherapy (CRT). Early prediction of treatment response is crucial for individualising treatment. Existing data on radiological biomarkers is limited and contradictory. We performed an individual patient data meta-analysis (IPM) of four prospective trials investigating whether diffusion-weighted (DW) magnetic resonance imaging (MRI) in weeks two to three of CRT predicts treatment failure in SCCA.

Material and methods

Individual patient data from four trials, including paired DW-MRI at baseline and during CRT, were combined into one dataset. The association between ADC volume histogram parameters and treatment failure (locoregional and any failure) was assessed using logistic regression. Pre-defined analysis included categorising patients into a change in the mean ADC of the delineated tumour volume above and below 20%.

Results

The study found that among all included 142 patients, 11.3 % (n = 16) had a locoregional treatment failure. An ADC mean change of <20 % and >20 % resulted in a locoregional failure rate of 16.7 % and 8.0 %, respectively. However, no other ADC-based histogram parameter was associated with locoregional or any treatment failure.

Conclusions

DW-MRI standard parameters, as an isolated biomarker, were not found to be associated with increased odds of treatment failure in SCCA in this IPM. Radiological biomarker investigations involve multiple steps and can result in heterogeneous data. In future, it is crucial to include radiological biomarkers in large prospective trials to minimize heterogeneity and maximize learning.

[18F]-FDG PET in anal canal cancer: a systematic review and meta-analysis

PURPOSE

To provide comprehensive data on the diagnostic and prognostic value of [18F]-FDG PET (PET) in anal canal cancer patients.

METHODS

This study was designed following the PRISMA-DTA guidelines. For the meta-analysis, published original articles (until December 2022) that met the following criteria were included: Evaluated PET for locoregional and/or distant disease detection in patients with histopathology-proven anal canal cancer; Compared PET with a valid reference standard; Provided crude data to calculate meta-analytic estimates. Diagnostic measurements from subgroups were calculated in evaluating primary tumour detection, T stage, lymph node and distant metastases. Articles providing prognostic information on PET were also reported as a systematic review. For pooled meta-analytic calculations, the hierarchical method was used. The bivariate model was conducted to find the summary estimates. Analyses were performed using STATA 16.

RESULTS

After the screening, 28 studies were eligible to enter the meta-analytic calculations, and data from 15 were reported descriptively. For distinguishing T3/T4 from other T-stages, PET had pooled sensitivity and specificity of 91%(95%CI:72%-97%) and 96%(95%CI:88%-98%), respectively. The sensitivity and specificity for detecting metastatic (regional and/or distant) disease were 100% (95%CI:82%-100%) and 95% (95%CI:90%-98%), respectively. For therapy response assessment, the sensitivity and specificity of PET were 96%(95%CI:78%-99%) and 86%(95%CI:75%-93%), respectively. Higher pre-treatment total metabolic tumour volume was predictive of poorer survival. Conversely, for those achieving complete metabolic response, the 2-year PFS was 94%(95%CI:91%-97%) versus 51%(95%CI:42%-59%) for others (p-value < 0.001).

CONCLUSION

PET may be a useful tool for anal canal cancer therapy planning and provides valuable prognostic information.

Risk factors and outcome following salvage surgery for squamous cell carcinoma of the anus

BACKGROUND

Chemoradiotherapy is the primary treatment for anal cancer. 15-33% of patients will have persistent or recurrent disease after treatment requiring salvage surgery. Relapse after surgery, postoperative complications, and mortality as well as possible risk factors are not fully understood due to the rareness of the disease. The aim of the study was to report outcomes after salvage surgery as well as evaluate risk factors for postoperative complications, cancer relapse and survival.

METHODS

Data were retrospectively collected from electronical patients charts and pathology reports from all patients undergoing salvage surgery from July 1st, 2011 to July 1st, 2021 at the Department of Surgery, Aarhus University Hospital, Denmark.

RESULTS

A total of 98 patients were included in the study. The 5-year overall survival was 61.8%. Relapse after surgery occurred in 36.7% of patients and was significantly associated with R1-resection (HR = 4.4) and preoperative nodal metastases (HR = 4.5). Negative prognostic factors for survival were found to be R1-resection (HR = 3.2), preoperative nodal metastases (HR = 2.9), and male gender (HR = 0.5). There was no association found between complications and survival (HR 1.2). None of the possible risk factors were associated with major postoperative complications.

CONCLUSIONS

An acceptable overall survival after surgery was found. Survival and relapse-free survival was negatively associated with R1 resections and positive preoperative lymph nodes. Complications did not influence long-term survival.

A Prospective Study of Chemoradiotherapy as Primary Treatment in Patients With Locoregionally Advanced Penile Carcinoma

PURPOSE

Neoadjuvant chemotherapy followed by surgery for locoregionally advanced penile carcinoma (LAPSCC) is associated with severe toxicity and a 1-year survival probability of ∼50%. We aimed to evaluate the safety and efficacy of chemoradiotherapy (CRT) as the primary treatment for LAPSCC and the association of high-risk human papillomavirus (hrHPV) with the outcome.

METHODS AND MATERIALS

This was a prospective, single-center, single-arm study of CRT in LAPSCC, defined as a large/inoperable primary tumor, large palpable nodes, suspicion of extranodal extension or pelvic nodal involvement, and no distant metastases. CRT consisted of 49.5 Gy (33 × 1.5 Gy) on affected inguinal and pelvic areas combined with intravenous mitomycin C on day 1 and capecitabine on radiation days. Primary tumors and positron emission tomography/computed tomography-positive deposits received a boost of 59.4 Gy (33 × 1.8 Gy). The response was evaluated by 18F-fluorodeoxyglucose positron emission tomography/computed tomography. If feasible, patients with residual/recurrent disease underwent salvage surgery. The primary endpoint was 1-year progression-free survival (PFS), reached when 1-year PFS was ≥50%. Other endpoints were 2-year PFS, overall survival, and toxicity rates. Kaplan-Meier survival curves were compared using the log-rank test.

RESULTS

Thirty-three patients were included: 29 (88%) with stage IV disease (T4 any-N M0 and/or any-T N3 M0) and 8 (24%) with hrHPV-positive disease. Median follow-up was 41 months. Thirty-two completed CRT. Eleven (33%) experienced ≥1 grade 3 treatment-related adverse event. There were no grade 4 or 5 treatment-related events. Twenty-four patients (73%) responded, including 13 (39%) complete responses. Nine patients (27%) underwent salvage surgery, and an additional 8 patients underwent later surgery (together 52%). One- and 2-year PFS were 34% and 31%, respectively. One- and 2-year overall survival were 73% and 46%, respectively. No significant difference between patients with hrHPV-positive and -negative tumors was observed.

CONCLUSIONS

CRT is a viable treatment option for LAPSCC with acceptable toxicity. CRT can result in an enduring response. If patients have residual tumor, salvage surgery is feasible. HrHPV status was not associated with outcomes.

Combined PET-CT and MRI for response evaluation in patients with squamous cell anal carcinoma treated with curative-intent chemoradiotherapy

OBJECTIVES

To assess the effectiveness of fluorine-18 fluorodeoxyglucose (FDG) positron-emission tomography-computed tomography (PET-CT) and magnetic resonance imaging (MRI) for response assessment post curative-intent chemoradiotherapy (CRT) in anal squamous cell carcinoma (ASCC).

METHODS

Consecutive ASCC patients treated with curative-intent CRT at a single centre between January 2018 and April 2020 were retrospectively identified. Clinical meta-data including progression-free survival (PFS) and overall survival (OS) outcomes were collated. Three radiologists evaluated PET-CT and MRI using qualitative response assessment criteria and agreed in consensus. Two-proportion z test was used to compare diagnostic performance metrics (sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy). Kaplan-Meier analysis (Mantel-Cox log-rank) was performed.

RESULTS

MRI (accuracy 76%, PPV 44.8%, NPV 95.7%) and PET-CT (accuracy 69.3%, PPV 36.7%, NPV 91.1%) performance metrics were similar; when combined, there were statistically significant improvements (accuracy 94.7%, PPV 78.9%, NPV 100%). Kaplan-Meier analysis demonstrated significant differences in PFS between responders and non-responders at PET-CT (p = 0.007), MRI (p = 0.005), and consensus evaluation (p < 0.001). Cox regression analysis of PFS demonstrated a lower hazard ratio (HR) and narrower 95% confidence intervals for consensus findings (HR = 0.093, p < 0.001). Seventy-five patients, of which 52 (69.3%) were females, with median follow-up of 17.8 months (range 5-32.6) were included. Fifteen of the 75 (20%) had persistent anorectal and/or nodal disease after CRT. Three patients died, median time to death 6.2 months (range 5-18.3).

CONCLUSION

Combined PET-CT and MRI response assessment post-CRT better predicts subsequent outcome than either modality alone. This could have valuable clinical benefits by guiding personalised risk-adapted patient follow-up.

KEY POINTS

• MRI and PET-CT performance metrics for assessing response following chemoradiotherapy (CRT) in patients with anal squamous cell carcinoma (ASCC) were similar. • Combined MRI and PET-CT treatment response assessment 3 months after CRT in patients with ASCC was demonstrated to be superior to either modality alone. • A combined MRI and PET-CT assessment 3 months after CRT in patients with ASCC has the potential to improve accuracy and guide optimal patient management with a greater ability to predict outcome than either modality alone.

Anorectal pathology in the HIV population: a guide for radiologists

Patients with human immunodeficiency virus (HIV) can present with a wide range of different acute and chronic pathologies. Anorectal conditions are particularly common in this unique patient population, including pathologies, such as proctitis, anorectal abscess, anorectal fistula, and anal squamous cell carcinoma. The radiologist plays a critical role in the assessment of these common forms of anorectal disease, as these conditions can present with various findings on imaging assessment. Pelvic CT, MRI, and FDG-PET/CT are among the most common modalities used for assessment of anorectal disease in the HIV patient population. Knowledge of the fundamental clinical and imaging findings associated with these pathologies in HIV patients is critical for radiologists.

Variants and Pitfalls in PET/CT Imaging of Gastrointestinal Cancers

In the past two decades, PET/CT has become an essential modality in oncology increasingly used in the management of gastrointestinal (GI) cancers. Most PET/CT tracers used in clinical practice show some degree of GI uptake. This uptake is quite variable and knowledge of common patterns of biodistribution of various radiotracers is helpful in clinical practice. 18F-Fluoro-Deoxy-Glucose (FDG) is the most commonly used radiotracer and has quite a variable uptake within the bowel. 68Ga-Prostate specific membrane antigen (PSMA) shows intense uptake within the proximal small bowel loops. 11C-methyl-L-methionine (MET) shows high accumulation within the bowels, which makes it difficult to assess bowel or pelvic diseases. One must also be aware of technical artifacts causing difficulties in interpretations, such as high attenuation oral contrast material within the bowel lumen or misregistration artifact due to patient movements. It is imperative to know the common variants and benign diseases that can mimic malignant pathologies. Intense FDG uptake within the esophagus and stomach may be a normal variant or may be associated with benign conditions such as esophagitis, reflux disease, or gastritis. Metformin can cause diffuse intense uptake throughout the bowel loops. Intense physiologic uptake can also be seen within the anal canal. Segmental bowel uptake can be seen in inflammatory bowel disease, radiation, or medication induced enteritis/colitis or infection. Diagnosis of appendicitis or diverticular disease requires CT correlation, as normal appendix or diverticulum can show intense uptake. Certain malignant pathologies are known to have only low FDG uptake, such as early-stage esophageal adenocarcinoma, mucinous tumors, indolent lymphomas, and multicystic mesotheliomas. Response assessment, particularly in the neoadjuvant setting, can be limited by post-treatment inflammatory changes. Post-operative complications such as abscess or fistula formation can also show intense uptake and may obscure underlying malignant pathology. In the absence of clinical suspicion or rising tumor marker, the role of FDG PET/CT in routine surveillance of patients with GI malignancy is not clear.

Role of 18F-FDG PET-derived parameters for predicting complete response to chemoradiotherapy in squamous cell anal carcinoma

PURPOSE

We aimed to evaluate the accuracy of metabolic parameters, calculated on pretreatment positron emission computed tomography (PET/CT) with fluorodeoxyglucose (F-FDG), for predicting complete response to chemoradiotherapy (CRT) of patients affected by squamous cell anal carcinoma (SCAC).

PATIENTS AND METHODS

Clinical records of 20 patients affected by SCAC and treated with CRT were retrospectively evaluated. F-FDG PET/CT was performed at time 0 (baseline) and time 1 (12 weeks after CRT). The following parameters were extracted from PET at time 0: standardized uptake values (SUVmax and SUVmean), metabolic tumor volume (MTV) and total lesion glycolysis (TLG). Response was assessed according to PET response criteria in solid tumors and classified as complete metabolic response (CMR), partial metabolic response (PMR) and progressive metabolic disease (PMD). Receiver operating characteristic analysis was performed to analyze the predictive value of each PET-derived parameter on CMR.

RESULTS

Sixteen patients were finally enrolled. All presented increased F-FDG uptake in the primary tumor and 11 (68.7%) also showed metastatic lymph nodes. At PET/CT performed at time 1, 11 subjects (68.7%) presented CMR, three (18.7%) had PMR and the remaining two (12.5%) showed PMD (i.e. hepatic metastases). Among baseline PET-derived parameters, both MTV and TLG efficiently predicted response to CRT with an area under the curve of 0.9 (cutoff 62.3 cm, sensitivity 80%, specificity 100%, P = <0.0001) and 0.87 (cutoff 654.1 g, sensitivity 80%, specificity 100%, P = 0.004), respectively.

CONCLUSION

Among PET-derived parameters, both MTV and TLG presented a high predictive value on subjects' outcome after CRT.

Use of advanced PET-volume metrics predicts risk of local recurrence and overall survival in anal cancer

Objective

Anal cancer is an uncommon malignancy with the primary treatment for localized disease being concurrent radiation and chemotherapy. Pre-treatment PET/CT is useful for target delineation, with minimal exploration of its use in prognostication. In the post-treatment setting there is growing evidence for advanced PET metrics in assessment of treatment response, and early identification of recurrence essential for successful salvage, however this data is limited to small series.

Methods

Patient with non-metastatic anal cancer from a single institution were retrospectively reviewed for receipt of pre- and post-treatment PET/CTs. PET data was co-registered with radiation therapy planning CT scans for precise longitudinal assessment of advanced PET metrics including SUV_max, metabolic tumor volume (MTV), and total lesion glycolysis (TLG), for assessment with treatment outcomes. Treatment outcomes included local recurrence (LR), progression free survival (PFS), and overall survival (OS), as defined from the completed radiation therapy to the time of the event. Cox proportional hazard modeling with inverse probability weighting (IPW) using the propensity score based on age, BMI, T-stage, and radiation therapy dose were utilized for assessment of these metrics.

Results

From 2008 to 2017 there were 72 patients who had pre-treatment PET/CT, 61 (85%) had a single follow up PET/CT, and 35 (49%) had two follow up PET/CTs. The median clinical follow-up time was 25 months (IQR: 13–52) with a median imaging follow up time of 16 months (IQR: 7–29). On pre-treatment PET/CT higher MTV_2.5 and TLG were significantly associated with higher risk of local recurrence (HR 1.11, 95% CI: 1.06–1.16, p<0.001; and HR 1.12, 95% CI: 1.05–1.19, p<0.001), and worse PFS (HR 1.09, 95% CI: 1.04–1.13, p<0.001; and HR 1.09, 95% CI: 1.03–1.12, p = 0.003) and OS (HR 1.09, 95% CI: 1.04–1.16, p = 0.001; and HR 1.11, 95% CI: 1.04–1.20, p = 0.004). IPW-adjusted pre-treatment PET/CT showed higher MTV_2.5 (HR 1.09, 95% CI: 1.02–1.17, p = 0.012) and TLG (HR 1.10, 95% CI: 1.00–1.20, p = 0.048) were significantly associated with worse PFS, and post-treatment MTV_2.5 was borderline significant (HR 1.16, 95% CI: 1.00–1.35, p = 0.052).

Conclusion

Advanced PET metrics, including higher MTV_2.5 and TLG, in the pre-treatment and post-treatment setting are significantly associated with elevated rates of local recurrence, and worse PFS and OS. This adds to the growing body of literature that PET/CT for patient with ASCC should be considered for prognostication, and additionally is a useful tool for consideration of early salvage or clinical trial of adjuvant therapies.

Determining Optimal Follow-up for Patients With Anal Cancer Following Chemoradiation

BACKGROUND

US health care is increasingly defined by over expenditure and inefficiency. Optimizing patient follow-up is critical, especially in cancers treated with high control rates. To optimize patient care, this study assessed time to disease recurrence or toxicity in patients with anal carcinoma.

MATERIALS AND METHODS

In total, 140 patients with biopsy-proven, nonmetastatic anal carcinoma, treated with chemoradiation utilizing intensity-modulated radiation therapy, were identified from our institutional database. This retrospective study evaluated local recurrence (LR), distant metastasis (DM), overall survival (OS), and late ≥grade 3 toxicity (LG3T). Patients were followed posttreatment every 3 months for 2 years, every 6 months in years 3 to 5, then yearly thereafter per NCCN recommendations.

RESULTS

The median age and follow-up was 58 years and 27 months, respectively. Patients were categorized into high (n=61; 44%) and low (n=77; 55%) risk groups based on stage. The 2-year LC, DMFS, and OS were 93%, 94%, and 89% and 5-year LC, DMFS, OS were 92%, 87%, and 85%, respectively. Overall, there were 29 events (9 LR, 11 DM, and 9 LG3T), with 62% of events occurring within year 1 and 79% within 2 years. Stratified by event type, at 2 years 89% of LR, 64% of DM, and 89% LG3T were identified. At the remaining follow-up points, the event incidence rate was 1.3%.

CONCLUSION

With the majority of recurrences/toxicities occurring within the first 2 years, a reduction in follow-up during years 3 to 5 may provide adequate surveillance. Revisions of the current recommendations could maximize resources while improving patient quality of life.

Roles of PET/Computed Tomography in the Evaluation of Neuroblastoma

Neuroblastoma is one of the most common pediatric malignant tumors. Functional imaging plays an important role in the diagnosis, staging, and therapy response monitoring of neuroblastoma. Although metaiodobenzylguanidine scan with single-photon emission computed tomography/computed tomography remains the mainstay in functional imaging of the neuroblastomas, PET/CT has begun to show increased utility in this clinical setting.

Recent advances of PET imaging in clinical radiation oncology

Radiotherapy and radiation oncology play a key role in the clinical management of patients suffering from oncological diseases. In clinical routine, anatomic imaging such as contrast-enhanced CT and MRI are widely available and are usually used to improve the target volume delineation for subsequent radiotherapy. Moreover, these modalities are also used for treatment monitoring after radiotherapy. However, some diagnostic questions cannot be sufficiently addressed by the mere use standard morphological imaging. Therefore, positron emission tomography (PET) imaging gains increasing clinical significance in the management of oncological patients undergoing radiotherapy, as PET allows the visualization and quantification of tumoral features on a molecular level beyond the mere morphological extent shown by conventional imaging, such as tumor metabolism or receptor expression. The tumor metabolism or receptor expression information derived from PET can be used as tool for visualization of tumor extent, for assessing response during and after therapy, for prediction of patterns of failure and for definition of the volume in need of dose-escalation. This review focuses on recent and current advances of PET imaging within the field of clinical radiotherapy / radiation oncology in several oncological entities (neuro-oncology, head & neck cancer, lung cancer, gastrointestinal tumors and prostate cancer) with particular emphasis on radiotherapy planning, response assessment after radiotherapy and prognostication.

HYPHYCA: a prospective study in 613 patients conducting a comprehensive analysis for predictive factors of physiological 18F-FDG anal uptake

Background

Anal cancer is a relatively rare tumor of which incidence increases in developed countries. ¹⁸F-FDG PET has been increasingly used for its post radio-chemotherapy evaluation. However, several authors have reported the risk of local false-positive findings leading to low specificity and positive predictive values. These false-positive results could be due to post-radiotherapy inflammation or infection but certainly also to physiological anal canal uptake that is observed on a regular basis in clinical practice. The purpose of this prospective study (NCT03506529; HYPHYCA) was therefore to seek predictive factors of physiological anal canal hypermetabolism.

Materials and methods

Over a 2-month period, patients aged 18 years old and more, referred for ¹⁸F-FDG PET-CT at two EARL-accredited PET centers were included, after obtaining their informed and written consent. They were asked to fill in a questionnaire including seven closed questions about usual intestinal transit, ongoing medications relative to intestinal transit, history of digestive, and anal and/or pelvic diseases. Age, gender, and body mass index (BMI) were recorded. A single nuclear medicine physician visually and quantitatively analyzed anal canal uptake (SUV_{max_EARL}) and assessed visual rectal content (air, feces, or both) and the largest rectal diameter (mm).

Results

Six hundred and thirteen patients were included (sex ratio F/M = 0.99) and 545 (89%) questionnaires were entirely completed. Significantly more males presented anal canal hypermetabolism (sex ratio (M/F) = 1.18 versus 0.85, p = 0.048). Moreover, patients with anal canal hypermetabolism had higher BMI (27.6 (5.7) kg/m² versus 23.9 (4.5) kg/m², p < 0.0001), higher rate of hemorrhoid history (43% versus 27%, p = 0.016), and higher rate of rectum filled with only feces (21% versus 12%, p = 0.019) as compared to patients with no anal canal uptake. On logistic regression, all these variables were found to be independent predictors of the occurrence of an anal canal hypermetabolism. Odds ratio were 1.16 (1.12–1.20) per unit of BMI (kg/m²) (p < 0.0001), 1.48 (1.04–2.11) for males (p = 0.030), 1.64 (1.10–2.45) for hemorrhoids history (p = 0.016), and 1.94 (1.147–3.22) for the rectum filled with only feces (p = 0.010).

Conclusion

According to our study, the predictive factors of physiological anal canal hypermetabolism are high BMI, male gender, hemorrhoid history, and rectum filled with only feces. This may pave the way to a more specific interpretation of post radio-chemotherapy PET evaluations of anal canal cancer, provided that other studies are conducted in this specific population.

Trial registration

This prospective study was registered at Clinicaltrial.gov: NCT03506529; HYPHYCA on April 24, 2018

FDG-PET parameters predict for recurrence in anal cancer - results from a prospective, multicentre clinical trial

Background

To investigate the prognostic significance of positron emission tomography (PET) parameters from F-18 fluorodeoxyglucose (FDG) PET scans performed pre- and post- chemo-radiotherapy (CRT) for squamous cell carcinoma of the anal canal (AC).

Methods

From January 2013 to January 2017, 19 patients with non-metastatic AC enrolled on a prospective trial underwent FDG-PET/CT imaging before and 12 weeks following CRT. A computer-generated volume of interest (VOI) was snapped around the primary tumour using six different standard uptake value (SUV) thresholds and the following parameters were extracted: SUV max, mean, median, standard deviation and peak as well as metabolic tumour volume (MTV) and total lesion glycolysis. Exact logistic regression and ROC AUC analyses were performed for each metric at each timepoint.

Results

With a median follow up of 15.8 months, 3/19 patients had a local recurrence and 5/19 had any recurrence. On post-CRT PET, the median SUV within a VOI bounded by an SUV of 3 correlated with local recurrence (p < 0.01) and demonstrated excellent discrimination (ROC AUC 1.00, perfect separation was achieved at a median SUV of 3.38). The mean SUV at this threshold did not quite reach significance for prediction of local recurrence (p = 0.06) but demonstrated excellent discrimination (ROC AUC 0.91). The MTV bounded by a threshold of 41% SUVmax on the pre-CRT PET predicted for any recurrence (p = 0.03) and showed excellent discrimination (ROC AUC 0.89).

Conclusions

FDG-PET parameters are predictive of recurrence in AC. FDG-PET may represent a valuable tool for prognostication and response assessment in AC.

Trial registration

ANZCTR, ACTRN12614001219673. Registered 19 November 2014 - Retrospectively registered.

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.

Anal cancer chemoradiotherapy outcome prediction using 18F-fluorodeoxyglucose positron emission tomography and clinicopathological factors

OBJECTIVE

To assess the role of [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET), obtained before and during chemoradiotherapy, in predicting locoregional failure relative to clinicopathological factors for patients with anal cancer.

METHODS

93 patients with anal squamous cell carcinoma treated with chemoradiotherapy were included in a prospective observational study (NCT01937780). FDG-PET/CT was performed for all patients before treatment, and for a subgroup (n = 39) also 2 weeks into treatment. FDG-PET was evaluated with standardized uptake values (SUV_{max/peak/mean}), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and a proposed Z-normalized combination of MTV and SUV_peak (ZMP). The objective was to predict locoregional failure using FDG-PET, tumor and lymph node stage, gross tumor volume (GTV) and human papilloma virus (HPV) status in univariate and bivariate Cox regression analysis.

RESULTS

N3 lymph node stage, HPV negative tumor, GTV, MTV, TLG and ZMP were in univariate analysis significant predictors of locoregional failure (p < 0.01), while SUV_{max/peak/mean} were not (p > 0.2). In bivariate analysis HPV status was the most independent predictor in combinations with N3 stage, ZMP, TLG, and MTV (p < 0.02). The FDG-PET parameters at 2 weeks into radiotherapy decreased by 30-40 % of the initial values, but neither absolute nor relative decrease improved the prediction models.

CONCLUSION

Pre-treatment PET parameters are predictive of chemoradiotherapy outcome in anal cancer, although HPV negativity and N3 stage are the strongest single predictors. Predictions can be improved by combining HPV with PET parameters such as MTV, TLG or ZMP. PET 2 weeks into treatment does not provide added predictive value.

ADVANCES IN KNOWLEDGE

Pre-treatment PET parameters of anal cancer showed a predictive role independent of clinicopathological factors. Although the PET parameters show substantial reduction from pre- to mid-treatment, the changes were not predictive of chemoradiotherapy outcome.

Prognostic Significance of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography in Anal Squamous Cell Carcinoma: A Systematic Review and a Meta-Analysis

Purpose

Prognostic significance of fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) in anal squamous cell carcinoma (SCC) has been evaluated in several studies; however, the results seem to be controversial and no consensus exists about its predictive capability. The current meta-analysis was carried out to comprehensively investigate the prognostic significance of ¹⁸F-FDG-PET parameters in patients with anal SCC.

Methods

A comprehensive literature search of PubMed/MEDLINE and Scopus databases was performed to retrieve pertinent articles published until August 5th 2018, concerning the prognostic significance of ¹⁸F-FDG-PET in patients with anal SCC. No language restriction was used. Several prognostic factors were reported for progression-free survival (PFS) and overall survival (OS) including pretreatment maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), inguinal nodal uptake, and metabolic response to therapy.

Results

Eleven studies (741 patients) were included. The pooled hazard ratio (HR) for the probability of PFS was 5.36 (95% confidence interval (95% CI): 3.12–9.21, p < 0.001) for metabolic response to therapy and 1.98 (95% CI: 1.26–3.12, p=0.003) for SUVmax. The pooled HR for the probability of OS was 5.87 (3.02–11.39, p < 0.0001) for metabolic response to therapy. On the other hand, the study revealed that the pooled HRs of MTV and inguinal nodal uptake for PFS were 1.56 (95% CI: 0.96–2.53, p=0.072) and 1.79 (95% CI: 1–3.21, p=0.051), respectively.

Conclusions

Our findings propose that some ¹⁸F-FDG-PET parameters could serve as prognostic indicators in anal SCC, but further larger studies are needed in this setting.