Australasian Gastrointestinal Trials Group (AGITG) Contouring Atlas and Planning Guidelines for Intensity-Modulated Radiotherapy in Anal Cancer

Reduction of elective lymph node volume in radiotherapy of early anal squamous cell cancer: a comparative study between two Swedish university hospitals

BACKGROUND

Anal squamous cell cancer (ASCC) in early stages (T1-2N0M0) is treated with chemoradiotherapy with a 3-year overall survival (OS) exceeding 90%. In Swedish guidelines, it has been optional to include the external iliac and presacral lymph node (LN) stations in radiotherapy (RT) treatment fields in early ASCC. Two Swedish hospitals treating ASCC (SU: Sahlgrenska University Hospital; UU: Uppsala University Hospital) have chosen different approaches since 2010.

MATERIAL AND METHODS

This study included consecutive patients with early ASCC (T1-2N0M0) treated between 2010 and 2017 at both sites (SU n = 70; UU n = 46). Data were retrieved from medical records and RT charts.

RESULTS

At SU, the external iliac and presacral LN stations were included in elective LN irradiation in 96.8% (n = 60) and 95.2% (n = 59) patients compared to 2.4% (n = 1) and 29.3% (n = 12) at UU. The mean elective LN volume was 2,313 cc (interquartile range [IQR] 1,951-2,627) in the SU cohort compared to 1,317 cc (IQR 1,192-1,528) in the UU cohort, p < 0.0001. No case of regional LN recurrence was seen in either cohort. Disease specific survival (DSS) at 5 years was 95.7% (confidence interval [CI] 90.1-100.0) in the SU cohort and 97.8% (CI 93.2-100.0) in the UU cohort (p 0.55). OS at 5 years was 84.5% (CI 76.1-93.0) in the SU cohort and 82.6% (CI 69.6-89.1) in the UU cohort (p 0.8).

INTERPRETATION

We found no differences in regional recurrence, DSS or OS between the cohorts treated with different elective LN volumes. In this population-based study, reduction of RT volume in early ASCC did not lead to inferior outcome.

MRI morphological characteristics of lymph nodes in anal squamous cell carcinoma

OBJECTIVES

Pre-treatment staging of anal squamous cell carcinoma (ASCC) includes pelvic MRI and [18F]-fluorodeoxyglucose positron emission tomography with computed tomography (PET-CT). MRI criteria to define lymph node metastases (LNMs) in ASCC are currently lacking. The aim of this study was to describe the morphological characteristics of lymph nodes (LNs) on MRI in ASCC patients with PET-CT-positive LNs.

METHODS

ASCC patients treated at Skåne University Hospital between 2009 and 2017 were eligible for inclusion if at least one positive LN according to PET-CT and a pre-treatment MRI were present. All PET-CT-positive LNs and PET-CT-negative LNs were retrospectively identified on baseline MRI. Each LN was independently classified according to pre-determined morphological characteristics by two radiologists blinded to clinical patient information.

RESULTS

Sixty-seven ASCC patients were included, with a total of 181 PET-CT-positive LNs identified on baseline MRI with a median short-axis diameter of 9.0 mm (range 7.5-12 mm). MRI morphological characteristics of PET-CT-positive LNs included regular contour (87%), round shape (89%), and homogeneous signal intensity on T2-weighed images (67%). An additional 78 PET-CT-negative LNs were identified on MRI. These 78 LNs had a median size of 6.8 mm (range 5.5-8.0 mm). The majority of PET-CT-negative LNs had a regular contour, round shape, and a homogeneous signal that was congruent to the primary tumor.

CONCLUSIONS

There are MRI-specific morphological characteristics for pelvic LNs in ASCC. PET-CT-positive and negative LNs share similar morphological features apart from size, with PET-CT-positive LNs being significantly larger. Further studies are needed to determine discrimination criteria for LNM in ASCC.

Long-term outcomes of definitive radiation with volumetric modulated arc therapy and concurrent chemotherapy for squamous cell carcinoma of the anus in a regional Australian cancer centre

INTRODUCTION

Concurrent chemoradiotherapy is the standard of care in the curative intent treatment of squamous cell carcinoma (SCC) of the anus. Volumetric arc therapy (VMAT) is a highly conformal radiation therapy technique that has been implemented to reduce toxicity for these patients. However, there are few reports evaluating the long-term outcomes of VMAT. Thus, we evaluated the survival and toxicity outcomes of anal cancer patients treated in our regional cancer centre undergoing curative intent chemoradiotherapy using VMAT and following the Australian EviQ guidelines.

METHODS

All consecutive patients treated with the VMAT technique for curative-intent definitive chemoradiotherapy for anal SCC at our institution from 2013 until 2022 were retrospectively reviewed for survival and toxicity outcomes. Kaplan-Meier estimates of locoregional control, distant metastasis-free survival, disease-free survival, anal cancer-specific survival and overall survival were obtained.

RESULTS

In total, 44 patients were analysed. The median follow-up was 48.9 months (Range 7.8-107). 97.7% of patients completed the prescribed radiation therapy and 88.6% chemotherapy. Five patients (11.4%) recurred. Four (9.1%) had isolated local failures, and one (2.3%) had an isolated distant failure. There were no regional nodal failures. The Kaplan-Meier estimates for locoregional control, distant metastasis-free survival, disease-free survival, anal cancer-specific survival and overall survival were 90.3%, 97.7%, 88.1%, 97.1% and 87% at 3 years, and 90.3%, 97.7%, 88.1%, 93.0% and 72.3% at 5 years, respectively. Acute grade 3 genitourinary (GU), gastrointestinal (GI) and skin toxicities occurred in 2.2%, 6.8% and 13.6% of patients, respectively. There were no acute grade 4 toxicities. Late grade 2 GU and GI toxicities occurred in 6.8% and 11.3% of patients, respectively. There were no late grade 3 or 4 toxicities or treatment-related deaths. The 5 -year colostomy-free survival rate was 86.4%.

CONCLUSION

Outcomes for anal SCC after definitive chemoradiotherapy using VMAT in our regional cancer centre results in low rates of grade 3/4 toxicity, high rates of organ preservation and excellent survival outcomes.

Capecitabine/cisplatin combined with concurrent intensity-modulated radiation therapy: a feasible therapeutic strategy for anal squamous cell carcinoma

PURPOSE

To evaluate the efficacy and safety of capecitabine/cisplatin (XP) combined with intensity-modulated radiation therapy (IMRT) in patients with non-metastatic anal squamous cell carcinoma (ASCC).

METHOD AND MATERIALS

All patients with ASCC who received radical concurrent chemoradiotherapy in the past 8 years were screened. Patients who received XP or mitomycin/5-fluorouracil (MF) were selected and analyzed retrospectively.

RESULTS

ASCC is an uncommon cancer, there were 36 patients were included in our study. The XP group and MF group included 18 patients each. The clinical complete response (cCR) rates in the XP group and the MF group were 94.4% and 88.9%, respectively (P = 1). The 2-year local control (LC), disease-free survival (DFS), and colostomy-free survival (CFS) rates were higher in the XP group than in the MF group (100% vs 93.3%, P = 0.32). Hematologic toxicities, especially grade ≥ 3 leukopenia (11.1% vs 44.4%, P = 0.06) and neutropenia (5.6% vs 61.1%, P = 0.001), were lower in the XP group than MF group. As a result of fewer side effects, fewer patients in the XP group demanded the dose reduction of chemotherapy (11.1% vs 50%, P = 0.03) and radiation interruption (55.6% vs 77.8%, P = 0.289). Delayed radiotherapy was shorter in the XP group (2.5 vs 6.5 days, P = 0.042) than in the MF group.

CONCLUSION

The XP regimen was as effective as the MF regimen in non-metastatic ASCC. Compared with the standard MF regimen, XP combined with IMRT showed higher treatment completion and lower toxicities. It could be considered a feasible alternative for patients with non-metastatic ASCC.

Gender-Affirming Surgery and Cancer: Considerations for Radiation Oncologists for Pelvic Radiation in Transfeminine Patients

Access to gender-affirming surgery is increasing for many transgender and nonbinary people in the United States, and radiation oncologists must be equipped to care for patients who have undergone such surgery in the region of their planned radiation treatment field. There are no guidelines for radiation treatment planning after gender-affirming surgery, and most oncologists do not receive training in the unique needs of transgender people with cancer. We review common gender-affirming genitopelvic surgeries for transfeminine people, including vaginoplasty, labiaplasty, and orchiectomy, and summarize the existing literature on the treatment of cancers of the neovagina, anus, rectum, prostate, and bladder in these patients. We also describe our systematic treatment approach and rationale for pelvic radiation treatment planning.

Stability of metabolic tumor volume may enable radiotherapy dose painting in anal cancer

PURPOSE

To evaluate the variability of the 18F-FDG-PET/CT-based metabolic tumor volume (MTV) in anal cancers during fractionated chemoradiotherapy (CRT), and assess the impact of this variability on dosimetric accuracy in MTV-targeted dose painting.

METHODS

Eleven patients with anal squamous cell carcinoma who received fractionated chemoradiotherapy with curative intent were included. 18F-FDG PET/CT images were acquired at pre- and mid-treatment. Target volumes and organs at risk (OARs) were contoured manually on both image series. The MTV was generated from the PET images by thresholding. Treatment plans were retrospectively optimized for both image series using volumetric modulated arc therapy (VMAT). Standard plans prescribed 48.6 Gy, 54 Gy and 57.5 Gy in 27 fractions to elective regions, lymph node metastases and primary tumor, respectively. Dose painting plans included an extra dose level of 65 Gy to the MTV. Pre-treatment plans were transferred and re-calculated at mid-treatment basis.

RESULTS

MTV decreased from pre- to mid-treatment in 10 of the 11 patients. On average, 71 % of MTVmid overlapped with MTVpre. The median and mean doses to the MTV were robust against anatomical changes, but the transferred dose painting plans had lower D98% values than the original and re-optimized plans. No major differences were found between standard and dose painting plans for OARs.

CONCLUSIONS

Despite volumetric changes in the MTV, adequate dose coverage was observed in most dose painting plans. The findings indicate little or no need for adaptive dose painting at mid-treatment. Dose painting appears to be a safe treatment alternative with similar dose sparing of OARs.

Nordic anal cancer (NOAC) group consensus guidelines for risk-adapted delineation of the elective clinical target volume in anal cancer

Background: To date, anal cancer patients are treated with radiotherapy to similar volumes despite a marked difference in risk profile based on tumor location and stage. A more individualized approach to delineation of the elective clinical target volume (CTVe) could potentially provide better oncological outcomes as well as improved quality of life. The aim of the present work was to establish Nordic Anal Cancer (NOAC) group guidelines for delineation of the CTVe in anal cancer.Methods: First, 12 radiation oncologists reviewed the literature in one of the following four areas: (1) previous delineation guidelines; (2) patterns of recurrence; (3) anatomical studies; (4) common iliac and para-aortic recurrences and delineation guidelines. Second, areas of controversy were identified and discussed with the aim of reaching consensus.Results: We present consensus-based recommendations for CTVe delineation in anal cancer regarding (a) which regions to include, and (b) how the regions should be delineated. Some of our recommendations deviate from current international guidelines. For instance, the posterolateral part of the inguinal region is excluded, decreasing the volume of irradiated normal tissue. For the external iliac region and the cranial border of the CTVe, we agreed on specifying two different recommendations, both considered acceptable. One of these recommendations is novel and risk-adapted; the external iliac region is omitted for low-risk patients, and several different cranial borders are used depending on the individual level of risk.Conclusion: We present NOAC consensus guidelines for delineation of the CTVe in anal cancer, including a risk-adapted strategy.

Impact of dose escalation on colostomy-free survival and treatment outcome in squamous cell anal carcinoma

PURPOSE

Primary radiochemotherapy (RCT) constitutes the standard of care for early- and advanced-stage anal carcinoma. This retrospective study investigates the impact of dose escalation on colostomy-free survival (CFS), overall survival (OS), locoregional control (LRC), progression-free survival (PFS), and acute and late toxicities in patients with squamous cell anal cancer.

METHODS

Considered were the outcomes of 87 patients with anal cancer treated with radiation/RCT between May 2004 and January 2020 at our institution. Toxicities were evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE version 5.0).

RESULTS

The 87 patients received treatment with a median boost of 63 Gy to the primary tumor. With a median follow-up of 32 months, the 3‑year CFS, OS, LRC, and PFS were 79.5%, 71.4%, 83.9%, and 78.5%, respectively. Tumor relapse occurred in 13 patients (14.9%). Dose escalation to > 63 Gy (maximum 66.6 Gy) to the primary tumor in 38/87 patients revealed a nonsignificant trend for improved 3‑year CFS (82.4% vs. 97%, P = 0.092), a significantly improved CFS for T2/T3 tumors (72.6% vs. 100%, P = 0.008), and a significantly improved 3‑year PFS for T1/T2 tumors (76.7% vs. 100%, P = 0.035). While acute toxicities did not differ, dose escalation > 63 Gy led to a higher rate of chronic skin toxicities (43.8% vs. 69%, P = 0.042). Treatment with intensity-modulated radiotherapy (IMRT) showed a significant improvement in 3‑year OS (75.4% vs. 53.8%, P = 0.048). In multivariate analysis, significant improvements for T1/T2 tumors (CFS, OS, LRC, PFS), G1/2 tumors (PFS), and IMRT (OS) were shown. The nonsignificant trend for CFS improvement with dose escalation > 63 Gy was also apparent in multivariate analysis (P = 0.067).

CONCLUSION

Dose escalation > 63 Gy (maximum 66.6 Gy) may improve CFS and PFS for certain subgroups, with a concomitant increase in chronic skin toxicities. Modern IMRT seems to be associated with an improvement in OS.

A planning-based feasibility study of MR-Linac treatment for anal cancer radiation therapy

The hybrid magnetic resonance image (MRI) scanner and radiation therapy linear accelerator (MR-Linac) has the potential to enhance clinical outcomes for anal cancer (AC) patients with improved soft tissue visualization and daily plan adaption but has planning and delivery limitations due to the incorporation of MRI. We aimed to identify if Elekta Unity MR-Linac-based radiation therapy is feasible for anal cancer. Ten prospectively enrolled AC patients treated with radical chemoradiotherapy were replanned for MR-Linac treatment using departmental planning criteria. For comparison, and to reduce interobserver variability, volumetric modulated arc radiation therapy (VMAT) plans were also created for each patient by the same single senior radiation therapist. Plans were compared using departmental dosimetric plan criteria, as well as conformity and homogeneity indices, monitor units (MUs) and measured plan delivery (beam-on) time. Results were deemed clinically acceptable. Target and organ at risk (OAR) doses were comparable between MR-Linac plans and VMAT plans, although PTV45Gy D98% coverage was compromised in 3 of 10 MR-Linac plans due to caudocranial length exceeding the limits of the MR-Linac. MR-Linac plans had lower MUs, median of 689.1 vs 849.65 (p = 0.002), but took over twice as long to deliver, 529.5s vs 224s (p = <0.0001) as VMAT plans. MR-Linac planning and treatment of AC is feasible for a subset of patients. The current physical limitations of the Elekta Unity system mean patients with large caudocranial elective PTV45Gy target volumes may not be covered dosimetrically to the required clinical standard. Longer image verification and treatment delivery times of the MR-Linac also mean patient selection and intrafractional IGRT are likely to be integral to ensuring high quality clinical outcomes in this rare cancer.

Feasibility Trial of Intensity Modulated Proton Therapy to Reduce Toxicity in Anal Cancer Patients

PURPOSE

The purpose of this trial was to assess the patient and physician-reported toxicity in anal cancer patients undergoing definitive chemoradiation with intensity-modulated proton therapy (IMPT).

METHODS

Patients with stage II and III anal cancer were treated with IMPT. All patients received 2 cycles of 5-fluorouracil and mitomycin concurrently with radiation. Toxicity was assessed at baseline, weekly during chemoradiation, and in follow-up using physician-graded common terminology criteria for adverse events (CTCAE) v 4.0 and PRO-CTCAE. The primary endpoint was to define point estimates and 95% CI for acute ≥ grade 2/3 gastrointestinal (GI), genitourinary (GU), dermatologic, and hematologic toxicity. The proportion of PRO-CTCAE questions scored ≥3 for each domain was compared with the baselinse. The proportion of ≥ grade 2 and ≥ grade 3 toxicities were compared with historic intensity-modulated radiotherapy patients treated on RTOG 0529.

RESULTS

Fourteen patients were enrolled from 2017 to 2020. Rates of physician-reported GI, GU, dermatologic, and hematologic toxicity were not significantly different between patients treated with IMPT compared with patients treated with intensity-modulated radiotherapy. Rates of patient-reported dermatologic and GU toxicity were low at baseline with a peak at week 6 (91% and 58% PRO-CTCAE items ≥ grade 3, respectively) and normalization to baseline 3 months after IMPT. In contrast, the proportion of high-grade PRO-CTCAE GI scores was 40% at baseline, which persisted through 1-year posttreatment.

CONCLUSIONS

Clinician-reported toxicity was not improved with IMPT in the context of this underpowered trial. High-grade GI symptoms persisted for 12 months and were similar to baseline. Additional measures are needed to minimize acute and chronic toxicity related to chemoradiation.

The Role of MRI and PET/CT in Radiotherapy Target Volume Determination in Gastrointestinal Cancers-Review of the Literature

Positron emission tomography with computed tomography (PET/CT) and magnetic resonance imaging (MRI) could improve accuracy in target volume determination for gastrointestinal cancers. A systematic search of the PubMed database was performed, focusing on studies published within the last 20 years. Articles were considered eligible for the review if they included patients with anal canal, esophageal, rectal or pancreatic cancer, as well as PET/CT or MRI for radiotherapy treatment planning, and if they reported interobserver variability or changes in treatment planning volume due to different imaging modalities or correlation between the imaging modality and histopathologic specimen. The search of the literature retrieved 1396 articles. We retrieved six articles from an additional search of the reference lists of related articles. Forty-one studies were included in the final review. PET/CT seems indispensable for target volume determination of pathological lymph nodes in esophageal and anal canal cancer. MRI seems appropriate for the delineation of primary tumors in the pelvis as rectal and anal canal cancer. Delineation of the target volumes for radiotherapy of pancreatic cancer remains challenging, and additional studies are needed.

Clinical target volume and organs at risk segmentation for rectal cancer radiotherapy using the Flex U-Net network

Purpose/Objectives

The aim of this study was to improve the accuracy of the clinical target volume (CTV) and organs at risk (OARs) segmentation for rectal cancer preoperative radiotherapy.

Materials/Methods

Computed tomography (CT) scans from 265 rectal cancer patients treated at our institution were collected to train and validate automatic contouring models. The regions of CTV and OARs were delineated by experienced radiologists as the ground truth. We improved the conventional U-Net and proposed Flex U-Net, which used a register model to correct the noise caused by manual annotation, thus refining the performance of the automatic segmentation model. Then, we compared its performance with that of U-Net and V-Net. The Dice similarity coefficient (DSC), Hausdorff distance (HD), and average symmetric surface distance (ASSD) were calculated for quantitative evaluation purposes. With a Wilcoxon signed-rank test, we found that the differences between our method and the baseline were statistically significant (P< 0.05).

Results

Our proposed framework achieved DSC values of 0.817 ± 0.071, 0.930 ± 0.076, 0.927 ± 0.03, and 0.925 ± 0.03 for CTV, the bladder, Femur head-L and Femur head-R, respectively. Conversely, the baseline results were 0.803 ± 0.082, 0.917 ± 0.105, 0.923 ± 0.03 and 0.917 ± 0.03, respectively.

Conclusion

In conclusion, our proposed Flex U-Net can enable satisfactory CTV and OAR segmentation for rectal cancer and yield superior performance compared to conventional methods. This method provides an automatic, fast and consistent solution for CTV and OAR segmentation and exhibits potential to be widely applied for radiation therapy planning for a variety of cancers.

Comparative analysis of toxicity in patients with anal cancer undergoing definitive simultaneous integrated boost (SIB) or sequential integrated boost (SeqB) radiotherapy

PURPOSE

To compare toxicity of radiotherapy (RT) with concomitant chemotherapy (CHT) in patients (pts) with anal cancer treated with simultaneous integrated boost (SIB) versus sequential boost (SeqB).

METHODS

Sixty-six patients were treated from 2007 to 2021. Thirty patients underwent to SeqB concurrent to CHT and 37 to SIB-group. Toxicity assessment has been considered in acute and in late toxicities for gastrointestinal (GI), genitourinary (GU), cutaneous (CU) districts, according to Common Terminology Criteria for Adverse Events (CTCAE), Version 5.0. The Wexner scale among summary scoring systems has been used as a tool to measure fecal incontinence. The chi-square test for ordinal variables were used to evaluate the association between patient and treatment characteristics and acute or late severe toxicity. Univariable logistic regression models were fit to evaluate predictive factors associated with fecal incontinence.

RESULTS

Median follow-up was 61.5 months (IQR, 27.1-121.7 months) for all patients. Severe acute toxicity (≥ G2) was observed in 49 patients (74.2%). Late toxicity (≥ G2) occurred in 13 cases (19.6%). In assessment of cutaneous toxicity, there was also a significant reduction in ≥ G1 in SIB group with 29 patients (80.5%) vs SeqB group with 29 patients (96.6%) (p-value = 0.046). Of both groups 11 patients (16.6%) developed fecal incontinence, 8 (22%) in the SIB group and 3 (10%) in the SeqB.

CONCLUSION

SIB for anal cancer treatment results in reduced acute and late cutaneous toxicity compared to SeqB. According to our results the rate of other acute and late toxicities are low and comparable between the two groups.

Inguinal nodal clinical target volume delineation based on analysis of anatomical locations of normal and metastatic lymph nodes in pelvic malignant tumors

PURPOSE

To optimize inguinal nodal clinical target volume (CTV) delineation based on analysis of the anatomical locations and embryonic development of normal and metastatic inguinal lymph nodes (ILNs) in patients with pelvic malignant tumors, including cervical, vaginal, vulvar, and anal tumors.

MATERIALS AND METHODS

One hundred and eighty-one patients with pelvic malignancies and 415 involved ILNs treated with intensity-modulated radiation therapy were selected. First, the inguinal nodal CTV was divided into three fields as follows: I, horizontal superficial inguinal field; II, vertical superficial inguinal field; and III, deep inguinal field. Initial CTV delineation of each field was based on analysis of the anatomical locations and embryonic development of normal ILNs. Subsequently, the positions of metastatic ILNs relative to the proper anatomical landmarks or vessels were determined to optimally delineate the final ILN CTV contours. Eighty percent of the data acquired (n = 145) were used as test data for optimization and analysis, the remaining 20% (n = 36) were used for delineation validation.

RESULTS

In total, 252 positive ILNs in 103 cervical cancer patients, 94 positive ILNs in 41 vulvar cancer patients, 8 positive ILNs in 3 vaginal cancer patients, and 61 positive ILNs in 34 anal cancer patients were enrolled. Detailed target volume contouring guidelines for the three divisions were determined on images. All positive ILNs from the remaining 20% patients were located in the CTV boundaries delineated based on analysis of 80% of the data acquired. Importantly, the final inguinal nodal CTV field determined using our method was substantially smaller than defined by existing atlases, and the femoral vessels were excluded in the delineation.

CONCLUSIONS

This study provided anatomical, embryonic, surgical, and statistical evidence to facilitate ILN CTV delineation in radiotherapy planning for patients with pelvic malignancies.

Doublecortin-like kinase 1 is a therapeutic target in squamous cell carcinoma

Doublecortin like kinase 1 (DCLK1) plays a crucial role in several cancers including colon and pancreatic adenocarcinomas. However, its role in squamous cell carcinoma (SCC) remains unknown. To this end, we examined DCLK1 expression in head and neck SCC (HNSCC) and anal SCC (ASCC). We found that DCLK1 is elevated in patient SCC tissue, which correlated with cancer progression and poorer overall survival. Furthermore, DCLK1 expression is significantly elevated in human papilloma virus negative HNSCC, which are typically aggressive with poor responses to therapy. To understand the role of DCLK1 in tumorigenesis, we used specific shRNA to suppress DCLK1 expression. This significantly reduced tumor growth, spheroid formation, and migration of HNSCC cancer cells. To further the translational relevance of our studies, we sought to identify a selective DCLK1 inhibitor. Current attempts to target DCLK1 using pharmacologic approaches have relied on nonspecific suppression of DCLK1 kinase activity. Here, we demonstrate that DiFiD (3,5-bis [2,4-difluorobenzylidene]-4-piperidone) binds to DCLK1 with high selectivity. Moreover, DiFiD mediated suppression of DCLK1 led to G2/M arrest and apoptosis and significantly suppressed tumor growth of HNSCC xenografts and ASCC patient derived xenografts, supporting that DCLK1 is critical for SCC growth.

Mesorectal motion evaluation in rectal cancer MR-guided radiotherapy: an exploratory study to quantify treatment margins

BACKGROUND

Mesorectal motion (MM) is a source of uncertainty during neoadjuvant chemoradiotherapy (nCRT) delivery for locally advanced rectal cancer (LARC). Previously published experiences using cone-beam computed tomography imaging have already described significant movement. Aim of this analysis is to assess inter-fraction MM using the higher tissue contrast provided by hybrid magnetic resonance imaging (MRI) in LARC patients (pts) treated with MRI guided radiation therapy (MRgRT).

METHODS

The total mesorectum, its superior (Msup), middle (Mmid) and lower (Mlow) regions were contoured on the positioning MRIs acquired on simulation day and on each treatment day. Six PTVs were obtained adding 0.5, 0.7, 1, 1.3, 1.5 and 2 cm margin to the whole mesorectum, starting from the simulation MRI. Margins including 95% of the mesorectal structures during whole treatment in 95% of patients (pts) were considered adequate.

RESULTS

A total number of 312 fractions of 12 consecutive pts was retrospectively analyzed. The different mesorectum regions show specific motion variability. In particular, Msup shows larger variability in left, right and anterior directions, while the Mlow in caudal and posterior ones. The anterior margin is significantly larger in the Msup than in the other regions.

CONCLUSION

Different mesorectal regions move differently throughout the radiotherapy treatment, with the largest MM in the Msup anterior direction. Asymmetrical margins are recommended.

Deep learning empowered volume delineation of whole-body organs-at-risk for accelerated radiotherapy

In radiotherapy for cancer patients, an indispensable process is to delineate organs-at-risk (OARs) and tumors. However, it is the most time-consuming step as manual delineation is always required from radiation oncologists. Herein, we propose a lightweight deep learning framework for radiotherapy treatment planning (RTP), named RTP-Net, to promote an automatic, rapid, and precise initialization of whole-body OARs and tumors. Briefly, the framework implements a cascade coarse-to-fine segmentation, with adaptive module for both small and large organs, and attention mechanisms for organs and boundaries. Our experiments show three merits: 1) Extensively evaluates on 67 delineation tasks on a large-scale dataset of 28,581 cases; 2) Demonstrates comparable or superior accuracy with an average Dice of 0.95; 3) Achieves near real-time delineation in most tasks with <2 s. This framework could be utilized to accelerate the contouring process in the All-in-One radiotherapy scheme, and thus greatly shorten the turnaround time of patients.

Anal squamous cell carcinoma: Impact of radiochemotherapy evolution over years and an explorative analysis of MRI prediction of tumor response in a mono-institutional series of 131 patients

Introduction

Radiochemotherapy (RCHT) for the treatment of anal squamous cell carcinoma (ASCC) has evolved dramatically, also thanks to intensity-modulated RT (IMRT) and 3D image guidance (3D IGRT). Despite most patients presenting fair outcomes, unmet needs still exist. Predictors of poor tumor response are lacking; acute toxicity remains challenging; and local relapse remains the main pattern of failure.

Patients and methods

Between 2010 and 2020, ASCC stages I–III treated with 3D conformal radiotherapy or IMRT and CDDP-5FU or Mytomicine-5FU CHT were identified. Image guidance accepted included 2D IGRT or 3D IGRT. The study endpoints included freedom from locoregional recurrence (FFLR), colostomy free survival (CFS), freedom from distant metastasis (FFDM), overall survival (OS), and acute and late toxicity as measured by common terminology criteria for adverse events (CTCAE) version 5.0. An exploratory analysis was performed to identify possible radiomic predictors of tumor response. Feature extraction and data analysis were performed in Python™, while other statistics were performed using SPSS^® v.26.0 software (IBM^®).

Results

A total of 131 patients were identified. After a median FU of 52 months, 83 patients (63.4%) were alive. A total of 35 patients (26.7%) experienced locoregional failure, while 31 patients (23.7%) relapsed with distant metastasis. Five year FFLR, CFS, DMFS and PS resulted 72.3%, 80.1%, 74.5% and 64.6%. In multivariate analysis, 2D IGRT was associated with poorer FFLR, OS, and CFS (HR 4.5, 4.1, and 5.6, respectively); 3DcRT was associated with poorer OS and CFS (HR 3.1 and 6.6, respectively). IMRT reduced severe acute gastro-intestinal (GI) and severe skin acute toxicity in comparison with 3DcRT. In the exploratory analysis, the risk of relapse depended on a combination of three parameters: Total Energy, Gray Level Size Zone Matrix’s Large Area High Gray Level Emphasis (GLSZM’s LAHGLE), and GTV volume.

Conclusions

Advances in radiotherapy have independently improved the prognosis of ASCC patients over years while decreasing acute GI and skin toxicity. IMRT and daily 3D image guidance may be considered standard of care in the management of ASCC. A combination of three pre-treatment MRI parameters such as low signal intensity (SI), high GLSZM’s LAHGLE, and GTV volume could be integrated in risk stratification to identify candidates for RT dose-escalation to be enrolled in clinical trials.

Dose-Volume Constraints fOr oRganS At risk In Radiotherapy (CORSAIR): An "All-in-One" Multicenter-Multidisciplinary Practical Summary

BACKGROUND

The safe use of radiotherapy (RT) requires compliance with dose/volume constraints (DVCs) for organs at risk (OaRs). However, the available recommendations are sometimes conflicting and scattered across a number of different documents. Therefore, the aim of this work is to provide, in a single document, practical indications on DVCs for OaRs in external beam RT available in the literature.

MATERIAL AND METHODS

A multidisciplinary team collected bibliographic information on the anatomical definition of OaRs, on the imaging methods needed for their definition, and on DVCs in general and in specific settings (curative RT of Hodgkin's lymphomas, postoperative RT of breast tumors, curative RT of pediatric cancers, stereotactic ablative RT of ventricular arrythmia). The information provided in terms of DVCs was graded based on levels of evidence.

RESULTS

Over 650 papers/documents/websites were examined. The search results, together with the levels of evidence, are presented in tabular form.

CONCLUSIONS

A working tool, based on collected guidelines on DVCs in different settings, is provided to help in daily clinical practice of RT departments. This could be a first step for further optimizations.

ECOG-ACRIN Guideline for Contouring and Treatment of Early Stage Anal Cancer Using IMRT/IGRT

PURPOSE

Previous anal cancer guidelines delineate target volumes similarly for all patients with squamous cell carcinoma of the anal canal and/or perianal skin (SCCA), regardless of disease stage. The purpose of this guideline is to provide customized radiation treatment recommendations for early stage (T1-2 N0 M0) anal cancer treated with intensity modulated and image guided radiation therapy (RT).

METHODS AND MATERIALS

A contouring atlas and radiation treatment recommendations for the ongoing, randomized phase II trial of deintensified chemoradiation for early stage SCCA (EA2182) was created by an expert panel of radiation oncologists. A literature search was conducted to update and expand these recommendations into a guideline for routine clinical use.

RESULTS

For the majority of cases, we recommend treatment in the supine, frog leg position with the use of a customized immobilization device and daily image guided RT to ensure optimal bone and soft tissue alignment. Vaginal dilators can be used daily during RT to maximize genitalia sparing. We recommend use of a 10-mm margin on the gross tumor plus including the anal complex to create the primary clinical target volume. To define the elective lymph node clinical target volume, we recommend starting with a 7-mm expansion on blood vessels, but then further refining these volumes based on the anatomic location. A 5- to 10-mm planning target volume (PTV) margin is suggested based on institutional setup and patient-specific factors. When using a simultaneous integrated boost technique, a dose of 50.4 Gy to primary PTV and 42 Gy to lymph node PTV, both delivered over 28 fractions, with chemotherapy is appropriate for early stage anal cancer.

CONCLUSIONS

This guideline provides anatomic, clinical, and technical instructions to guide radiation oncologists in the planning and delivery of intensity modulated and image guided RT for early stage SCCA.

Acute toxicity and patient-reported outcomes in anal canal cancer: results of a pilot study

INTRODUCTION

Anal canal cancer (ACC) is uncommon. The gold standard of care is chemoradiotherapy treatment. However, this treatment is associated with considerable acute and late side effects. The aim of this pilot study was to evaluate acute toxicity and patient-reported outcomes (PRO) in these patients from planning to 3 months after treatment.

METHODS

Sixteen patients were recruited to this prospective observational study from March 2015 to December 2017. All patients received volumetric modulated arc therapy (VMAT) in 30#. Toxicity data were graded by a Radiation Oncologist using the Common Terminology Criteria for Adverse Effects (CTCAE) version 4 at planning, weekly during treatment, 6-week and 3-month post-treatment. PRO data were collected using the EORTC QLQ C30 and CR29 questionnaires completed by patients at planning, mid and end treatment and 3-month post-treatment.

RESULTS

The majority of toxicity and PRO items peaked in severity at the end of treatment (week 6). Skin was the only item where >50% of patients had ≥ grade 2 toxicity at any point with 75% having ≥ grade 2 at week 6. Patient-reported embarrassment significantly increased over time (P < 0.001). No meaningful relationships were found between PRO and CTCAE results.

CONCLUSION

After reaching their maximum severity at the end of treatment, the majority of toxicity and PRO items approached baseline levels by 3-month post-treatment. The results of this study suggest that PROs are an important complementary tool to CTCAE and provide greater understanding of patients' perception of treatment side effects.

Overview of Radiation Treatment Volume Variations in Anal Cancer Contouring Guidelines

Recently, the XXX guideline was published to describe recommended treatment volumes in patients with diagnosis of early-stage anal cancer. There are notable differences in descriptions for the both the primary target and elective nodal volumes when comparing this guideline with established guidelines from the United Kingdom National Cancer Research Institute, Australasian Gastrointestinal Trials Group and Radiation Therapy Oncology Group. Support for these volume differences is based on retrospective data, but ultimately, prospective data from ongoing clinical trials are needed to validate these approaches.

Hematologic Toxicity Comparison of Intensity Modulated Proton Therapy and Intensity Modulated Radiation Therapy in Anal Cancer Patients

PURPOSE

We hypothesize that hematologic toxicity will be lower in anal cancer patients treated definitively with intensity modulated proton therapy (IMPT) compared with patients treated with intensity modulated radiation therapy (IMRT).

METHODS

Patients enrolled on a prospective feasibility trial assessing the use of IMPT for anal cancer were compared with contemporaneous patients treated with IMRT. Blood counts were collected during chemoradiation. Hematologic events were graded according to CTCAE version 5.0. Pelvic bone marrow (PBM) and positron emission tomography-defined active bone marrow (ABM) were defined and contoured for each patient. Toxicity rates, PBM and ABM dose metrics were compared between groups.

RESULTS

Forty-one patients treated with definitive chemoradiation for anal cancer between 2015 and 2021 were included in this analysis. Of the evaluable patients, 14 patients were treated with IMPT and 27 were treated with IMRT. All PBM dose metrics were lower in patients receiving IMPT. Patients treated with IMPT versus IMRT also had a significantly lower ABM mean dose (1996 vs. 3073 Gy, P<0.01). However, there was no statistically significant difference in hematologic toxicity between the groups. Seventy percent of patients treated with IMRT had at least 1 grade ≥3 hematologic event compared with 86% in the IMPT group (P=0.48).

CONCLUSION

Proton treatment reduced bone marrow doses but was not associated with lower hematologic toxicity when compared with IMRT.

Anal Cancer: Emerging Standards in a Rare Rare Disease

The social stigma surrounding an anal cancer diagnosis has traditionally prevented open discussions about this disease. However, as recent treatment options and an increasing rate of diagnoses are made worldwide, awareness is growing. In the United States alone, 9,090 individuals were expected to be diagnosed with anal cancer in 2021. The US annual incidence of squamous cell carcinoma of the anus continues to increase by 2.7% yearly, whereas the mortality rate increases by 3.1%. The main risk factor for anal cancer is a human papillomavirus infection; those with chronic immunosuppression are also at risk. Patients with HIV are 19 times more likely to develop anal cancer compared with the general population. In this review, we have provided an overview of the carcinoma of the anal canal, the role of screening, advancements in radiation therapy, and current trials investigating acute and chronic treatment-related toxicities. This article is a comprehensive approach to presenting the existing data in an effort to encourage continuous international interest in anal cancer.

Current treatment and future directions in the management of anal cancer

Although rare, the rate of squamous cell carcinoma of the anus (SCCA) is rising globally. Most patients present with nonmetastatic disease and are curable with appropriate treatment, which has evolved significantly over the last several decades. Before the 1970s, SCCA was managed with radical surgery, resulting in a permanent colostomy. Researchers found that preoperative treatment with chemotherapy and concurrent radiation could achieve a pathologic complete response. After this observation, definitive therapy shifted from radical surgery to sphincter-preserving chemoradiation. Investigations into the necessity of chemotherapy and the optimal regimen found that chemotherapy with mitomycin-C and 5-fluorouracil is required for cure. Further studies evaluating the addition of induction or maintenance chemotherapy, monoclonal antibody therapy, or higher radiation doses have demonstrated no significant benefit to disease control. Advanced radiation delivery with intensity-modulated radiotherapy techniques is now considered the standard of care because of its prospectively determined, favorable acute toxicity profile compared with 3-dimensional conformal radiation. It is important to note that chemoradiation treatment response may be slow (up to 26 weeks) and should be assessed through serial clinical examinations. Today, surgical management of SCCA is reserved only for the lowest risk, early stage tumors or for recurrent/persistent disease. Current studies are evaluating radiation dose de-escalation in early stage disease and radiation dose escalation and the addition of immune checkpoint inhibitors in locally advanced cancers. In reviewing how and why modern-day treatment of SCCA was established, the objective of this report is to reenforce adherence to current treatment paradigms to assure the best possible outcomes for patients.

Efficient Magnetic Nanocatalyst-Induced Chemo- and Ferroptosis Synergistic Cancer Therapy in Combination with T1-T2 Dual-Mode Magnetic Resonance Imaging Through Doxorubicin Delivery

Excessive iron ions in cancer cells can catalyze H₂O₂ into highly toxic ^•OH and then promote the generation of reactive oxygen species (ROS), inducing cancer ferroptosis. However, the efficacy of the ferroptosis catalyst is still insufficient because of low Fe(II) release, which severely limited its application in clinic. Herein, we developed a novel magnetic nanocatalyst for MRI-guided chemo- and ferroptosis synergistic cancer therapies through iRGD-PEG-ss-PEG-modified gadolinium engineering magnetic iron oxide-loaded Dox (ipGdIO-Dox). The introduction of the gadolinium compound disturbed the structure of ipGdIO-Dox, making the magnetic nanocatalyst be more sensitive to weak acid. When ipGdIO-Dox entered into cancer cells, abundant Fe(II) ions were released and then catalyzed H₂O₂ into highly toxic OH^•, which would elevate cellular oxidative stress to damage mitochondria and cell membranes and induce cancer ferroptosis. In addition, the iRGD-PEG-ss-PEG chain coated onto the nanoplatform was also broken by high expression of GSH, and then, the Dox was released. This process not only effectively inhibited DNA replication but also further activated cellular ROS, making the nanoplatform achieve stronger anticancer ability. Besides, the systemic delivery of ipGdIO-Dox significantly enhanced the T₁- and T₂-weighted MRI signal of the tumor, endowing accurate diagnostic capability for tumor recognition. Therefore, ipGdIO-Dox might be a promising candidate for developing an MRI-guided chemo- and ferroptosis synergistic theranostic system.

Deep learning-based automatic delineation of anal cancer gross tumour volume: a multimodality comparison of CT, PET and MRI

BACKGROUND

Accurate target volume delineation is a prerequisite for high-precision radiotherapy. However, manual delineation is resource-demanding and prone to interobserver variation. An automatic delineation approach could potentially save time and increase delineation consistency. In this study, the applicability of deep learning for fully automatic delineation of the gross tumour volume (GTV) in patients with anal squamous cell carcinoma (ASCC) was evaluated for the first time. An extensive comparison of the effects single modality and multimodality combinations of computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) have on automatic delineation quality was conducted.

MATERIAL AND METHODS

18F-fluorodeoxyglucose PET/CT and contrast-enhanced CT (ceCT) images were collected for 86 patients with ASCC. A subset of 36 patients also underwent a study-specific 3T MRI examination including T2- and diffusion-weighted imaging. The resulting two datasets were analysed separately. A two-dimensional U-Net convolutional neural network (CNN) was trained to delineate the GTV in axial image slices based on single or multimodality image input. Manual GTV delineations constituted the ground truth for CNN model training and evaluation. Models were evaluated using the Dice similarity coefficient (Dice) and surface distance metrics computed from five-fold cross-validation.

RESULTS

CNN-generated automatic delineations demonstrated good agreement with the ground truth, resulting in mean Dice scores of 0.65-0.76 and 0.74-0.83 for the 86 and 36-patient datasets, respectively. For both datasets, the highest mean Dice scores were obtained using a multimodal combination of PET and ceCT (0.76-0.83). However, models based on single modality ceCT performed comparably well (0.74-0.81). T2W-only models performed acceptably but were somewhat inferior to the PET/ceCT and ceCT-based models.

CONCLUSION

CNNs provided high-quality automatic GTV delineations for both single and multimodality image input, indicating that deep learning may prove a versatile tool for target volume delineation in future patients with ASCC.

Radiotherapy of anal canal cancer

We present the update of the recommendations of the French society for radiation oncology on external radiotherapy and brachytherapy of anal canal carcinoma. The following guidelines are presented: indications, treatment procedure, as well as dose and dose-constraints objectives, immediate postoperative management, post-treatment evaluation, and long-term follow-up.

A Pattern of Care Report on the Management of Patients with Squamous Cell Carcinoma of the Anus—A Study by the Italian Association of Radiotherapy and Clinical Oncology (AIRO) Gastrointestinal Tumors Study Group

Background and objectives: The diagnosis and therapy of squamous cell carcinoma of the anus may vary significantly in daily clinical practice, even if international guidelines are available. Materials and Methods: We conducted a pattern of care survey to assess the management of patients with anal cancer in Italy (38 questions). We analyzed 58 questionnaires. Results: Most of the respondents work in public and/or university hospitals (75.8%) in northern Italy (65.5%). The majority (88.0%) treat less than 20 patients/year. Common examinations for diagnosis and staging are anorectal endoscopy (84.5%), computed tomography scan (86.2%) and pelvic magnetic resonance imaging (MRI) (96.5%). The most frequently prescribed dose to primary tumor is 50–54 Gy (46.5–58.6%) for early stage disease and 54–59.4 Gy (62.1–32.8%) for locally advanced cases. Elective volumes are prescribed around 45 Gy (94.8%). Most participants use volumetric intensity modulated radiotherapy (89.7%) and a simultaneous integrated boost (84.5%). Concurrent radiotherapy, 5-fluorouracil and mitomycin is considered the standard of care (70.6%). Capecitabine is less frequently used (34.4%). Induction chemotherapy is an option for extensive localized disease (65.5%). Consolidation chemotherapy is rarely used (18.9%). A response evaluation is conducted at 26–30 weeks (63.9%) with a pelvic MRI (91.4%). Follow-up is generally run by the multidisciplinary tumor board (62.1%). Conclusions: Differences were observed for radiotherapy dose prescription, calling for a consensus to harmonize treatment strategies.

A blind randomized validated convolutional neural network for auto-segmentation of clinical target volume in rectal cancer patients receiving neoadjuvant radiotherapy

Background

Delineation of clinical target volume (CTV) for radiotherapy is a time‐consuming and labor‐intensive work. This study aims to propose a novel convolutional neural network (CNN)‐based model for fast auto‐segmentation of CTV. To evaluate its performance and clinical utility, a blind randomized validation method was used.

Methods

Our proposed model was based on the generally accepted U‐Net architecture using computed tomography slices with CTV contours delineated by experienced radiation clinicians from 135 rectal patients receiving neoadjuvant radiotherapy. The Dice similarity coefficient (DSC) and 95th percentile Hausdorff distance (95HD) were used to measure segmentation performance. The validated dataset of additional 20 patients for clinical evaluation by 10 experienced oncology clinicians from 7 centers was randomly and blindly divided into two groups for clinicians' scoring and Turing test, respectively. Second evaluation was performed with different randomization after 2 weeks.

Results

The mean DSC and 95HD values of the proposed model were 0.90 ± 0.02 and 8.11 ± 1.93 mm for CTV of rectal cancer patients, respectively. The average time for automatic segmentation in the validation groups was 15 s per patient. By clinicians' scoring, the AI model performed better than manually delineating, though the differences were not significant (Week 0: 2.59 vs. 2.52, p = 0.086; Week 2: 2.55 vs. 2.47, p = 0.115). Additionally, the mean positive rates in the Turing test were 40.5% in Week 0 and 45.2% in Week 2, which demonstrated the great intelligence of our model.

Conclusions

Our proposed model can be used clinically for assisting contouring of CTVs in rectal cancer patients receiving neoadjuvant radiotherapy, which improves the efficiency and consistency of radiation clinicians' work.

Long-term Patterns of Failure and the Value of Blood Prognostic Markers in Anal Cancers Treated With Intensity-Modulated Radiation Therapy

BACKGROUND

To analyze the long-term outcomes and prognostic value of hematological parameters in anal cancer patients receiving intensity-modulated radiation therapy (IMRT).

MATERIALS

Hospital records of consecutive patients with anal squamous cell carcinoma who received curative-intent IMRT according to a standardized contouring protocol between 2010 and 2020 were reviewed. Locoregional failure-free survival (LRFS), distant metastasis-free survival (DMFS), progression-free survival (PFS), and overall survival (OS) were estimated using the Kaplan-Meier method. Coverage of locoregional recurrences by the initial IMRT volumes were assessed. The prognostic value of pretreatment blood counts for PFS and OS were determined using Cox regression analysis.

RESULTS

A total of 166 patients were analyzed with a median follow-up of 3.3 years. Forty-six percent and 54% of patients had Stage I-II and IIIA-B cancers, respectively. The 5-year LRFS, DMFS, PFS and OS were 81%, 89%, 65% and 76% respectively. Grade ≥ 3 toxicity occurred in 5% of patients. Of all patients who relapsed, 70% had only locoregional recurrence as first site of failure. Ninety percent of locoregional recurrences were in-field. Hemoglobin, neutrophil and platelet counts were associated with PFS on univariable analysis, but only cancer stage and p16 status remained prognostic on multivariable analysis. Patients with more advanced cancer stages also had higher baseline neutrophil counts. Performance status and neutrophil counts were prognostic for OS on multivariable analysis.

CONCLUSION

This study affirms the long-term efficacy and safety of IMRT. Treatment resistance, rather than radiation geographic miss, is a major issue underpinning locoregional recurrences. Pretreatment blood counts were not validated to be independently prognostic for disease recurrence.

Treatment of Squamous Cell Carcinoma of the Anus, Unresolved Areas and Future Perspectives for Research: Perspectives of Research Needs in Anal Cancer

Anal cancer is a relatively rare, mostly HPV-related cancer. The curative treatment consists of concurrent chemoradiation delivered with modern radiotherapy techniques. The prognosis for most patients with early localized disease is very favourable; however patients with locally advanced disease and/or HPV negative tumours are at higher risk of locoregional and distant treatment failure. Tailored approaches are presently being investigated to determine the most suitable regimen in terms of radiotherapy dose prescription, target volume selection, normal tissue avoidance, and combination therapy. Metastatic anal cancer is treated with chemotherapy aiming at prolonged survival. The role of immune therapy in the clinical setting is being investigated. There is little knowledge on the biology of anal cancer, and an urgent need for more clinical and translational research dedicated to this disease. In this article, the evidence-base for the current treatment is briefly reviewed, and perspectives on future research needs are high-lighted.

Delineation of organs at risk

The delineation of organs at risk is the basis of radiotherapy oncologists' work. Indeed, the knowledge of this delineation enables to better identify the target volumes and to optimize dose distribution, involving the prognosis of the patients but also their future. The learning of this delineation must continue throughout the clinician's career. Some contour changes have appeared with better imaging, some volumes are now required due to development of knowledge of side effects. In addition, the increasing survival time of patients requires to be more systematic and precise in the delineations, both to avoid complications until now exceptional but also because re-irradiations are becoming more and more frequent. We present the update of the recommendations of the French Society for Radiation Oncology (SFRO) on new findings or adaptations to volumes at risk.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

FDG-PET/CT in the Radiotherapy Treatment Planning of Locally Advanced Anal Cancer: A Monoinstitutional Experience

Aims

Radiotherapy with concurrent 5-fluorouracil/mitomycin-C based chemotherapy has been established as definitive standard therapy approach for anal cancer. Intensity Modulated Radiotherapy (IMRT) leads to a precise treatment of the tumor, allowing dose escalation on Gross Tumor Volume (GTV), with a surrounding healthy tissues sparing. Our study assessed the impact of 18-Fluorodeoxyglucose positron emission tomography (18FDG-PET/CT) on the radiotherapy contouring process and its contribution to lymphatic spread detection, resulting to a personalization of Clinical Target Volume (CTV) and dose prescription.

Methods

Thirty-seven patients, with histologically proven squamous cell carcinoma of the anal canal (SCCAC) were analyzed. All patients were evaluated with history and physical examination, trans-anal endoscopic ultrasound, pelvis magnetic resonance imaging (MRI), computed tomography (CT) scans of the chest, abdomen and pelvis and planning 18FDG-PET/CT. The GTV and CTV were drawn on CT, MRI and 18FDG-PET/CT fused images.

Results

Thirty-four (91%) out of 37 patients presented lymph nodes involvement, in one or more areas, detected on 18FDG-PET/CT and/or MRI. The 18FDG-PET/CT showed positive lymph nodes not detected on MRI imaging (PET+, MRI−) in 14/37 patients (38%). In 14 cases, 18FDG-PET/CT allowed to a dose escalation in the involved nodes. The 18FDG-PET/CT fused images led to change the stage in 5/37(14%) cases: four cases from N0 to N1 (inguinal lymph nodes) and in one case from M0 to M1 (common iliac lymph nodes).

Conclusions

The 18FDG-PET/CT has a potentially relevant impact in staging and target volume delineation/definition in patients affected by anal cancer. In our experience, clinical stage variation occurred in 14% of cases. More investigations are needed to define the role of 18FDG-PET/CT in the target volume delineation of anal cancer.

Treatment outcomes and prognostic factors after chemoradiotherapy for anal cancer

BACKGROUND

Squamous cell carcinoma of the anus (SCCA) is a rare malignancy with rising incidence, associated with human papilloma virus (HPV). Chemoradiotherapy (CRT) is the preferred treatment. The purpose was to investigate treatment failure, survival and prognostic factors after CRT.

MATERIAL AND METHODS

In this prospective observational study from a large regional centre, 141 patients were included from 2013 to 2017, and 132 were eligible for analysis. The main inclusion criteria were SCCA, planned radiotherapy, and performance status (ECOG) ≤2. Patient characteristics, disease stage, treatment, and treatment response were prospectively registered. Disease-free survival (DFS), overall survival (OS), and locoregional treatment failure after CRT were analysed. Hazard ratios (HRs) were estimated with Cox`s proportional hazards model.

RESULTS

Median follow-up was 54 (range 6-71) months. Eighteen patients (14%) had treatment failures after CRT; of these 10 (8%) had residual tumour, and 8 (6%) relapse as first failure. The first treatment failure was locoregional (11 patients), distant (5 patients), and both (2 patients). Salvage abdomino-perineal resection was performed in 10 patients, 2 had resections of metastases, and 3 both. DFS was 85% at 3 years and 78% at 5 years. OS was 93% at 3 years and 86% at 5 years. In analyses adjusted for age and gender, HPV negative tumours (HR 2.5, p = 0.024), N3 disease (HR 2.6, p = 0.024), and tumour size ≥4 cm (HR 2.4, p = 0.038) were negative prognostic factors for DFS.

CONCLUSION

State-of-the-art chemoradiotherapy for SCCA resulted in excellent outcomes, and improved survival compared with previous national data, with <15% treatment failures and a 3-year DFS of >80%.

Optimal Radiotherapy Dose in Anal Cancer: Trends in Prescription Dose and Association with Survival

PURPOSE

Definitive chemoradiotherapy represents a standard of care treatment for localized anal cancer. National Comprehensive Cancer Network guidelines recommend radiotherapy (RT) doses of ≥ 45 Gy and escalation to 50.4-59 Gy for advanced disease. Per RTOG 0529, 50.4 Gy was prescribed for early-stage disease (cT1-2N0), and 54 Gy for locally advanced cancers (cT3-T4 and/or node positive). We assessed patterns of care and overall survival (OS) with respect to the RT dose.

METHODS

The National Cancer Database identified patients with non-metastatic anal squamous cell carcinoma from 2004 to 2015 treated with chemoradiotherapy. Patients were stratified by RT dose: 40-< 45, 45-< 50, 50-54, and > 54-60 Gy. Crude and adjusted hazard ratios (HR) were computed using Cox regression modeling.

RESULTS

A total of 10,524 patients were identified with a median follow-up of 40.7 months. The most commonly prescribed RT dose was 54 Gy. On multivariate analysis, RT doses of 40-< 45 Gy were associated with worse OS vs. 50-54 Gy (HR 1.68 [1.40-2.03], P < 0.0001). There was no significant difference in OS for patients who received 45-< 50 or > 54-60 Gy compared with 50-54 Gy. For early-stage disease, there was no significant association between RT dose and OS. For locally advanced disease, 45-< 54 Gy was associated with worse survival vs. 54 Gy (HR 1.18 [1.04-1.34], P = 0.009), but no significant difference was detected comparing > 54-60 Gy vs. 54 Gy (HR 1.08 [0.97-1.22], P = 0.166).

CONCLUSIONS

For patients with localized anal cancer, RT doses of ≥ 45 Gy were associated with improved OS. For locally advanced disease, 54 Gy but not > 54 Gy was associated with improved OS.

What is the optimal treatment for T1N0 anal squamous cell carcinoma? Analysis of current practices in the prospective French FFCD ANABASE cohort

INTRODUCTION

for localized T1N0 squamous cell carcinoma of the anus (SCCA) standard radiotherapy (RT) may result in overtreatment and alternative strategies are debated.

METHODS

T1N0M0 SCCA treated between 2015 and 2020 by local excision (LE) or RT were analyzed from the French prospective FFCD ANABASE cohort. Treatment strategies, recurrence-free and colostomy-free survivals (RFS, CFS) and prognostic factors were reported.

RESULTS

among 1135 SCCA patients, 99 T1N0M0 were treated by LE(n = 17,17.2%), or RT (n = 82,82.8%) including RT alone (n = 65,79.2%) or chemo-RT (n = 17, 20.7%). Median follow-up was 27.2 months [0.03-54.44]. Median tumor size were 11.4 mm [0.9-20] and 15.3 mm [2-20] in the LE and RT groups respectively. Mean RT tumor dose was 59.4 Gy [18-69.4 Gy]. One patient in LE group and 9 in RT group had a pelvic recurrence, either local (60%), nodal (10%) or both (30%). RFS and CFS at 24 months were 92.2%[95%CI,83.4-96.4] and 94.6%[95%CI,86.1-98.0], at 36 months 88.1%[95%CI,77.1-94.2] and 88.5%[95%CI,77.0-94.5], in LE and RT group respectively, without any significative difference (HR = 0.57;[95%CI,0.07-4.45];p = 0.60). By univariate analysis, male gender was the only prognostic factor(HR = 5.57;95%CI, 1.76-17.63; p = 0.004).

CONCLUSION

this cohort confirms the heterogeneity of T1N0M0 SCCA management, questioning the place of RT alone, reduced dose or RT volume, and the safety of LE.

Concurrent Chemoradiation in Anal Cancer Patients Delivered with Bone Marrow-Sparing IMRT: Final Results of a Prospective Phase II Trial

We investigated the role of the selective avoidance of haematopoietically active pelvic bone marrow (BM), with a targeted intensity-modulated radiotherapy (IMRT) approach, to reduce acute hematologic toxicity (HT) in anal cancer patients undergoing concurrent chemo-radiation. We designed a one-armed two-stage Simon’s design study to test the hypothesis that BM-sparing IMRT would improve by 20% the rate of G0–G2 (vs. G3–G4) HT, from 42% of RTOG 0529 historical data to 62% (α = 0.05; β = 0.20). A minimum of 21/39 (54%) with G0–G2 toxicity represented the threshold for the fulfilment of the criteria to define this approach as ‘promising’. We employed ¹⁸FDG-PET to identify active BM within the pelvis. Acute HT was assessed via weekly blood counts and scored as per the Common Toxicity Criteria for Adverse Effects version 4.0. From December 2017 to October 2020, we enrolled 39 patients. Maximum observed acute HT comprised 20% rate of ≥G3 leukopenia and 11% rate of ≥G3 thrombocytopenia. Overall, 11 out of 39 treated patients (28%) experienced ≥G3 acute HT. Conversely, in 28 patients (72%) G0–G2 HT events were observed, above the threshold set. Hence, ¹⁸FDG-PET-guided BM-sparing IMRT was able to reduce acute HT in this clinical setting.

Patterns of pathologic lymph nodes in anal cancer: a PET-CT-based analysis with implications for radiotherapy treatment volumes

Background

This study investigates the patterns of PET-positive lymph nodes (LNs) in anal cancer. The aim was to provide information that could inform future anal cancer radiotherapy contouring guidelines.

Methods

The baseline [18F]-FDG PET-CTs of 190 consecutive anal cancer patients were retrospectively assessed. LNs with a Deauville score (DS) of ≥3 were defined as PET-positive. Each PET-positive LN was allocated to a LN region and a LN sub-region; they were then mapped on a standard anatomy reference CT. The association between primary tumor localization and PET-positive LNs in different regions were analyzed.

Results

PET-positive LNs (n = 412) were identified in 103 of 190 patients (54%). Compared to anal canal tumors with extension into the rectum, anal canal tumors with perianal extension more often had inguinal (P < 0.001) and less often perirectal (P < 0.001) and internal iliac (P < 0.001) PET-positive LNs. Forty-two patients had PET-positive LNs confined to a solitary region, corresponding to first echelon nodes. The most common solitary LN region was inguinal (25 of 42; 60%) followed by perirectal (26%), internal iliac (10%), and external iliac (2%). No PET-positive LNs were identified in the ischiorectal fossa or in the inguinal area located posterolateral to deep vessels. Skip metastases above the bottom of the sacroiliac joint were quite rare. Most external iliac PET-positive LNs were located posterior to the external iliac vein; only one was located in the lateral external iliac sub-region.

Conclusions

The results support some specific modifications to the elective clinical target volume (CTV) in anal cancer. These changes would lead to reduced volumes of normal tissue being irradiated, which could contribute to a reduction in radiation side-effects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08187-8.

Radiotherapy with Intensity-Modulated (IMRT) Techniques in the Treatment of Anal Carcinoma (RAINSTORM): A Multicenter Study on Behalf of AIRO (Italian Association of Radiotherapy and Clinical Oncology) Gastrointestinal Study Group

Simple Summary

Concurrent chemo-radiotherapy is the standard treatment in anal cancer. Intensity-modulated radiotherapy (IMRT) was proved to reduce severe, acute and late toxicities. Moreover, IMRT techniques allow for the planning and delivery of a simultaneous integrated boost (SIB), with a differential dose per fraction given to selected sub-regions during the same treatment session. This boost modality provides the chance to employ a dose-painted approach with a reduction in overall treatment time that could result in a potential clinical advantage. Since a large variability in dose prescription to the primary tumor and elective or involved lymph nodes can be found in available guidelines and clinical practice, a multicenter analysis was conducted to evaluate the pattern of care and the impact of radiotherapy parameters on clinical outcomes for anal cancer patients treated with IMRT techniques within a national cohort.

Abstract

A multi-institutional retrospective study was conducted to evaluate the pattern of care and clinical outcomes of anal cancer patients treated with intensity-modulated radiotherapy (IMRT) techniques. In a cohort of 987 patients, the clinical complete response (CR) rate (beyond 6 months) was 90.6%. The 3-year local control (LC) rate was 85.8% (95% CI: 84.4–87.2), and the 3-year colostomy-free survival (CFS) rate was 77.9% (95% CI: 76.1–79.8). Three-year progression-free survival (PFS) and overall survival (OS) rates were 80.2% and 88.1% (95% CI: 78.8–89.4) (95% CI: 78.5–81.9), respectively. Histological grade 3 and nodal involvement were associated with lower CR (p = 0.030 and p = 0.004, respectively). A statistically significant association was found between advanced stage and nodal involvement, and LC, CFS, PFS, OS and event-free survival (EFS). Overall treatment time (OTT) ≥45 days showed a trend for a lower PFS (p = 0.050) and was significantly associated with lower EFS (p = 0.030) and histological grade 3 with a lower LC (p = 0.025). No statistically significant association was found between total dose, dose/fraction and/or boost modality and clinical outcomes. This analysis reports excellent clinical results and a mild toxicity profile, confirming IMRT techniques as standard of care for the curative treatment of anal cancer patients. Lymph node involvement and histological grade have been confirmed as the most important negative prognostic factors.

Cisplatin/capecitabine with intensity-modulated radiation therapy in anal squamous cell carcinoma: a preliminary study

OBJECTIVE

Mitomycin (MMC)/5-fluoroural (5-FU) with concurrent radiation is the standard treatment of anal squamous cell carcinoma (ASCC). The aim of this study is to evaluate the efficacy and safety of cisplatin/capecitabine (XP) as an alternative with intensity-modulated radiation therapy (IMRT) in ASCC setting.

METHODS

We retrospectively screened all patients with stage I-IV ASCC from January 2010 to June 2019. The records of patients who received definitive chemoradiation with cisplatin/capecitabine (XP) and IMRT were collected and analyzed.

RESULTS

The first patient was treated with XP in 2017, so totally 11 patients were included in our study from January 2017 to June 2019. All patients have experienced clinical complete response (cCR). After a median follow-up of 30 months (range, 18-39 months), no patient had local recurrence or distant metastasis. Two-year colostomy-free survival (CFS) and two-year disease-free survival (DFS) were both 100%. The median overall survival (OS) has not reached. Grade 3 acute toxicities included leukopenia (1, 9.1%), neutropenia (2, 18.2%) and thrombocytopenia (2, 18.2%). No grade 4 acute adverse events occurred.

CONCLUSION

In our study, cisplatin/capecitabine combined with IMRT was safe in ASCC patients, with favorable efficacy as an alternative, and is expected to be explored in study with larger sample.

Evolution of the Role of Radiotherapy for Anal Cancer

Prior to the 1980s, the primary management of localized anal cancer was surgical resection. Dr. Norman Nigro and colleagues introduced neoadjuvant chemoradiotherapy prior to abdominoperineal resection. Chemoradiotherapy 5-fluorouracil and mitomycin C afforded patients complete pathologic response and obviated the need for upfront surgery. More recent studies have attempted to alter or exclude chemotherapy used in the Nigro regimen to mitigate toxicity, often with worse outcomes. Reductions in acute adverse effects have been associated with marked advancements in radiotherapy delivery using intensity-modulated radiation therapy (IMRT) and image-guidance radiation delivery, resulting in increased tolerance to greater radiation doses. Ongoing trials are attempting to improve IMRT-based treatment of locally advanced disease with efforts to increase personalized treatment. Studies are also examining the role of newer treatment modalities such as proton therapy in treating anal cancer. Here we review the evolution of radiotherapy for anal cancer and describe recent advances. We also elaborate on radiotherapy's role in locally persistent or recurrent anal cancer.

Intensity modulated radiotherapy for anal canal squamous cell carcinoma: A 16-year single institution experience

Introduction

To report long-term efficacy and adverse events (AEs) associated with intensity modulated radiotherapy (IMRT) for patients with anal canal squamous cell carcinoma (ASCC).

Materials and methods

This was a retrospective review of patients with ASCC who received curative-intent IMRT and concurrent chemotherapy (98%) between 2003 and 2019. Overall survival (OS), colostomy-free survival (CFS), and progression-free survival (PFS) were estimated using the Kaplan-Meier method. The cumulative incidence of local recurrence (LR), locoregional recurrence (LRR), and distant metastasis (DM) were reported. Acute and late AEs were recorded per National Cancer Institute Common Terminology Criteria for AEs.

Results

127 patients were included. The median patient age was 63 years (interquartile range [IQR] 55-69) and 79% of patients were female. 33% of patients had T3-4 disease and 68% had clinically involved pelvic or inguinal lymph nodes (LNs).The median patient follow-up was 47 months (IQR: 28-89 months). The estimated 4-year OS, CFS, and PFS were 81% (95% confidence interval [CI]: 73%-89%), 77% (95% CI: 68%-86%), and 78% (95% CI: 70%-86%), respectively. The 4-year cumulative incidences of LR, LRR, and DM were 3% (95% CI: 1%-9%), 9% (95% CI: 5%-17%), and 10% (95% CI: 6%-18%), respectively. Overall treatment duration greater than 39 days was associated with an increased risk of LRR (Hazard Ratio [HR]: 5.2, 95% CI: 1.4-19.5, p = 0.015). The most common grade 3+ acute AEs included hematologic (31%), gastrointestinal (GI) (17%), dermatologic (16%), and pain (15%). Grade 3+ late AEs included: GI (3%), genitourinary (GU) (2%), and pain (1%). Current smokers were more likely to experience grade 3+ acute dermatologic toxicity compared to former or never smokers (34% vs. 7%, p < 0.001).

Conclusions

IMRT was associated with favorable toxicity rates and long-term efficacy. These data support the continued utilization of IMRT as the preferred treatment technique for patients with ASCC.

Interobserver variability in clinical target volume delineation in anal squamous cell carcinoma

We evaluated the inter-physician variability in the target contouring of the radiotherapy for anal squamous cell carcinoma (ASCC). Clinical target volume (CTV) of three patients diagnosed with ASCC was delineated by seven experienced radiation oncologists from multi-institution. These patients were staged as pT1N1a, cT2N0, and cT4N1a, respectively, according to 8^th edition of the American Joint Committee on Cancer staging system. Expert agreement was quantified using an expectation maximization algorithm for Simultaneous Truth and Performance Level Estimation (STAPLE). The maximum distance from the boundaries of the STAPLE generated volume with confidence level of 80% to those of the contour of each CTV in 6 directions was compared. CTV of pelvis which includes primary tumor, perirectal tissue and internal/external iliac lymph node (LN) area (CTV-pelvis) and CTV of inguinal area (CTV-inguinal) were obtained from the seven radiation oncologists. One radiation oncologist did not contain inguinal LN area in the treatment target volume of patient 2 (cT2N0 stage). CTV-inguinal displayed moderate agreement for each patient (overall kappa 0.58, 0.54 and 0.6, respectively), whereas CTV-pelvis showed substantial agreement (overall kappa 0.66, 0.68 and 0.64, respectively). Largest variation among each contour was shown in the inferior margin of the CTV-inguinal. For CTV-pelvis, anterior and superior margin showed the biggest variation. Overall, moderate to substantial agreement was shown for CTV delineation. However, large variations in the anterior and cranial boarder of the CTV-pelvis and the caudal margin of the CTV-inguinal suggest that further studies are needed to establish a clearer target volume delineation guideline.

Bone Marrow-Sparing IMRT in Anal Cancer Patients Undergoing Concurrent Chemo-Radiation: Results of the First Phase of a Prospective Phase II Trial

Simple Summary

Hematological toxicity may be a consistent issue in anal cancer patients undergoing concurrent chemo-radiation, with a potentially detrimental effect on clinical outcomes and patient compliance to treatment. Chemotherapy is the most important trigger, since it induces myelosuppression, but radiation dose delivered to the hematopoietically active bone marrow (BM) also plays an important role. Active bone marrow can be identified using functional imaging with 18-Fluoro-2-deoxy-glucose positron emission tomography (¹⁸FDG-PET) and selectively spared during radiation delivery via intensity-modulated radiotherapy (IMRT). We investigated, within a prospective phase II trial, the potential effectiveness of targeted avoidance of active BM comprised within pelvic bones in reducing the acute hematologic toxicity profile of anal cancer patients undergoing concomitant chemo-radiation for squamous cell carcinoma of the anus. The results of the first step of the study fulfilled the criteria to define BM-sparing IMRT as “promising” and to continue with the second step of the phase II trial.

Abstract

Purpose: to investigate the role of selective avoidance of hematopoietically active BM within the pelvis, as defined with ¹⁸FDG-PET, employing a targeted IMRT approach, to reduce acute hematologic toxicity (HT) profile in anal cancer patients undergoing concurrent chemo-radiation. Methods: a one-armed two-stage Simon’s design was selected to test the hypothesis that BM-sparing approach would improve by 20% the rate of G0–G2 (vs. G3–G4) HT, from 42% of RTOG 0529 historical data to 62% (α = 0.05 and the β = 0.20). At the first stage, among 21 enrolled patients, at least 9 should report G0–G2 acute HT to further proceed with the trial. We employed ¹⁸FDG-PET to identify active BM within the pelvis. Acute HT was assessed via weekly blood counts and scored as per the Common Toxicity Criteria for Adverse Effects version 4.0. Results: from December 2017 to October 2019, 21 patients were enrolled. Maximum observed acute HT comprised 9% rate of ≥G3 leukopenia and 5% rate of ≥G3 neutropenia and anemia. Overall, only 4 out of 21 treated patients (19%) experienced ≥G3 acute HT. Conversely, 17 patients (81%) experienced G0–G2 events, way above the threshold set by the trial design. Conclusion: ¹⁸FDG-PET-guided BM-sparing IMRT was able to reduce acute HT in anal cancer patients treated with concomitant chemo-radiation. These results prompted us to conclude the second part of this prospective phase II trial.

Auto-segmentations by convolutional neural network in cervical and anorectal cancer with clinical structure sets as the ground truth

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The network provided auto-segmentations with high overlap with ground truth volumes.

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Evaluation of femoral heads/bladder auto-segmentations showed highest overlap.

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Annotated structure sets from daily clinical practice is feasible as ground truth.

Background

It is time-consuming for oncologists to delineate volumes for radiotherapy treatment in computer tomography (CT) images. Automatic delineation based on image processing exists, but with varied accuracy and moderate time savings. Using convolutional neural network (CNN), delineations of volumes are faster and more accurate. We have used CTs with the annotated structure sets to train and evaluate a CNN.

Material and methods

The CNN is a standard segmentation network modified to minimize memory usage. We used CTs and structure sets from 75 cervical cancers and 191 anorectal cancers receiving radiation therapy at Skåne University Hospital 2014-2018. Five structures were investigated: left/right femoral heads, bladder, bowel bag, and clinical target volume of lymph nodes (CTVNs). Dice score and mean surface distance (MSD) (mm) evaluated accuracy, and one oncologist qualitatively evaluated auto-segmentations.

Results

Median Dice/MSD scores for anorectal cancer: 0.91–0.92/1.93–1.86 femoral heads, 0.94/2.07 bladder, and 0.83/6.80 bowel bag. Median Dice scores for cervical cancer were 0.93–0.94/1.42–1.49 femoral heads, 0.84/3.51 bladder, 0.88/5.80 bowel bag, and 0.82/3.89 CTVNs. With qualitative evaluation, performance on femoral heads and bladder auto-segmentations was mostly excellent, but CTVN auto-segmentations were not acceptable to a larger extent.

Discussion

It is possible to train a CNN with high overlap using structure sets as ground truth. Manually delineated pelvic volumes from structure sets do not always strictly follow volume boundaries and are sometimes inaccurately defined, which leads to similar inaccuracies in the CNN output. More data that is consistently annotated is needed to achieve higher CNN accuracy and to enable future clinical implementation.