Technical aspects of radiation therapy for anal cancer

Volumetric Modulated Arc Therapy Improves Outcomes in Definitive Radiochemotherapy for Anal Cancer Whilst Reducing Acute Toxicities and Increasing Treatment Compliance

Simple Summary

Intensity-modulated radiotherapy (IMRT) is the standard of care in definitive chemoradiotherapy (CRT) for anal cancer. Only a limited number of studies have analyzed the clinical results with VMAT (volumetric modulated arc therapy, the advanced form of IMRT). We conducted a retrospective study on patients treated at our institution. We compared the outcomes of VMAT-treated and 3DCRT (3D conformal radiotherapy)-treated patients. VMAT reduced acute toxicities (i.e., primarily dermatitis and enteritis) to a great extent. Additionally, VMAT relevantly improved treatment compliance (i.e., less CRT interruptions/delays, shorter overall treatment time, and higher absolute 5-fluorouracil dose applied). Finally, we found improved cancer-specific survival and distant control in VMAT-treated patients. The present study underlines the great progress that has been achieved with IMRT/VMAT in the CRT of anal cancer. Our study is the first to demonstrate an improvement in treatment compliance and outcomes with VMAT. Future studies could address whether VMAT is advantageous when compared to conventional IMRT.

Abstract

Background: Intensity-modulated radiotherapy (IMRT) is the standard of care in chemoradiotherapy (CRT) for anal cancer. Until now, only a limited number of studies have analyzed the results with VMAT (volumetric modulated arc therapy). We conducted a retrospective study on patients treated at our institution. Patients and Methods: We included patients who received curative CRT for anal cancer. We compared VMAT-treated and 3DCRT (3D conformal radiotherapy)-treated patients. We analyzed toxicities (acute: CTCAE criteria; late: LENT/SOMA criteria), treatment compliance, overall survival, cancer-specific survival (CSS), distant control (DC), and locoregional control. Results: A total of 149 patients (3DCRT: n = 87, VMAT: n = 62) were included. The median follow-up was longer in 3DCRT-treated patients (3DCRT: 61.3 months; VMAT: 39.1 months; p < 0.05). VMAT-treated patients had more G3 tumors (3DCRT: 12/87 (13.8%); VMAT: 18/62 (29.0%), p < 0.001). VMAT reduced acute toxicities ≥grade 3 (3DCRT: n = 48/87 (55.2%); VMAT: n = 11/62 (17.7%), p < 0.001). VMAT improved treatment compliance (less interruptions/delays) (3DCRT: 37/87, 42.5%; VMAT: 4/62, 6.5%; p < 0.001), provided a shorter median overall treatment time (3DCRT: 41 days; VMAT: 38 days; p = 0.02), and gave a higher median absolute 5-fluorouracil dose (3DCRT: 13,700 mg; VMAT: 14,400 mg; p = 0.001). Finally, we found improved CSS (p = 0.02; 3DCRT: 81.9% at 3 years; VMAT: 94.1% at 3 years) and DC (p = 0.01; 3DCRT: 89.4% at 3 years; VMAT: 100.0% at 3 years) with VMAT. Summary: Our study is the first to demonstrate improved treatment compliance and outcomes with VMAT for anal cancer. Previous studies have indicated that organs at risk sparing might be more improved with the use of VMAT vs. with conventional IMRT. Future studies should address whether these advantages lead to a further reduction in CRT-associated morbidity.

Intravenous contrast media in radiation therapy planning computed tomography scans - Current practice in Ireland

Introduction

While Computerised Tomography (CT) remains the gold standard in radiation therapy (RT) planning, inferior soft tissue definition remains a challenge. Intravenous contrast (IVC) use during CT planning can enhance soft tissue contrast optimising Target Volume (TV) and Organ at Risk visualisation and delineation. Despite this known benefit, there are no guidelines for when and how to use IVC in RT planning scans in Ireland.

Aim

The study aims to examine the patterns of practice in relation to the use of IVC in RT planning scans in Ireland and to determine the level of compliance with international guidelines. Radiation Therapists (RTT) IVC training will also be investigated.

Materials and methods

An anonymised online survey was designed based on previously-reported literature. This was distributed to all RT departments in Ireland. The survey contained open, closed and Likert scale questions that investigated IVC practices in each department.

Results

75% (n = 9/12) of Irish departments responded. All responding departments reported using IVC. RTTs cannulated patients in 67% (n = 6/9) of the departments and administration contrast in all departments. Variations from recommended guidelines were found in disease sites where IVC was routinely used and in the assessment of renal functioning prior to contrast administration. IVC training varied in duration and number of supervised procedures required to fulfill competencies.

Conclusion

IVC is used extensively in Irish RT departments. There are variations in IVC practice between departments and with international recommended guidelines.

Unforeseen Computed Tomography Resimulation for Initial Radiation Planning: Associated Factors and Clinical Impact

Purpose

Repeat computed tomography (CT) simulation is problematic because of additional expense of clinic resources, patient inconvenience, additional radiation exposure, and treatment delay. We investigated the factors and clinical impact of unplanned CT resimulations in our network.

Methods and Materials

We used the billing records of 18,170 patients treated at 5 clinics. A total of 213 patients were resimulated before their first treatment. The disease site, location, use of 4-dimensional CT (4DCT), contrast, image fusion, and cause for resimulation were recorded. Odds ratios determined statistical significance.

Results

Our total rate of resimulation was 1.2%. Anal/colorectal (P < .001) and head and neck (P < .001) disease sites had higher rates of resimulation. Brain (P = .001) and lung/thorax (P = .008) had lower rates of resimulation. The most common causes for resimulation were setup change (11.7%), change in patient anatomy (9.8%), and rectal filling (8.5%). The resimulation rate for 4DCTs was 3.03% compared with 1.0% for non-4DCTs (P < .001). Median time between simulations was 7 days.

Conclusions

The most common sites for resimulation were anal/colorectal and head and neck, largely because of change in setup or changes in anatomy. The 4DCT technique correlated with higher resimulation rates. The resimulation rate was 1.2%, and median treatment delay was 7 days. Further studies are warranted to limit the rate of resimulation.

Comparative accuracy of qualitative and quantitative 18F-FDG PET/CT analysis in detection of lymph node metastasis from anal cancer

PURPOSE

To compare the diagnostic performance of qualitative and quantitative 18F-FDG PET/CT in detection of regional and distant lymph node metastasis in patients with anal cancer.

METHODS

Between 2004 and 2017, 28 patients with anal cancer who had staging PET/CT and pathological assessment of suspicious lymph nodes were included. For qualitative analysis, positive lymph nodes were defined as uptake visually higher than the liver reference uptake. For quantitative study, lymph nodes were contoured to determine maximum standard uptake value (SUV_max) and metabolic tumor volume (MTV). Receiver operating characteristic (ROC) curves were plotted to extract the optimal cut-offs and area under the curve (AUC) of SUV_max, lesion to background (L/B) ratio, short axis diameter (SAD), and MTV of lymph nodes. Histopathologic analysis was a reference standard.

RESULTS

A total of 28 lymph nodes (24 inguinal, 2 external iliac, 1 internal iliac, and 1 paraaortic nodes) in 28 patients on PET/CT were included. With the qualitative visual analysis, 19 patients were categorized as positive for nodal metastasis with sensitivity, specificity, and accuracy of 85%, 75%, and 82%. The optimal SUV_max and L/B ratio cut-offs were 2.6 and 1.0 with both sensitivity and specificity of 95% and 75% (AUC of SUV_max = 0.893, AUC of L/B ratio = 0.912). Using the best cut-off of 1.6 cm for SAD and 3.65 cm³ for MTV, both sensitivity and specificity were 80% and 100% (AUC of SAD = 0.950, AUC of MTV = 0.931).

CONCLUSIONS

SUV_max optimization may be helpful in enhancing the diagnostic accuracy of 18F-FDG PET/CT in nodal staging patients with anal cancer.

Dosimetric comparison of different radiation techniques (IMRT vs. 3-dimensional) of the "true" (deep) ano-inguinal lymphatic drainage of anal cancer patients

Introduction

The ano-inguinal lymphatic drainage (AILD) is located in the subcutaneous adipose tissue of the proximal medial thigh. Currently, there are no recommendations for an inclusion of the ‘true’ AILD in the clinical target volume (CTV) of definitive chemoradiation for anal cancer patients. To estimate the relevance of inguinal recurrence, we compared the incidental dose to the AILD in anal cancer (AC) patients who were treated either with Volumetric Arc Therapy – Intensity Modulated Radiation Therapy (VMAT-IMRT) or conventional 3D-radiation technique.

Methods

One VMAT-IMRT-plans and one 3D-plans were calculated on the same target volumes and identical dose prescription in ten patients. We defined the volume of the AILD on the planning CT-scans based on the information of new fluorescence methods. Furthermore, we defined several anatomical subvolumes of interest inside the AILD. We examined and compared absolute and relative dosimetric parameters of the AILD and different anatomical subunits.

Results

The Dmean of the AILD was 40 Gy in the 3D-group and 38 Gy in the IMRT-group. Dmean and Dmedian as well as the V30Gy of the AILD and all subvolumes of the caudal AILD were significant higher using 3D-RT compared to IMRT. Even though the absolute differences were small, in the caudal aspect of the ano-inguinal lymphatic drainage the V30Gy could be more than 10% less with VMAT-IMRT.

Conclusions

3D-RT was slightly superior to IMRT in terms of dose coverage of the AILD. However, the absolute differences were very small. Some relevant caudal parts of the AILD received an insufficient dose for treating potential micrometastases. Particularly in high-risk situations, this may lead to inguinal recurrence and therefore the true deep AILD should be included into the target volume in high risk patients.

Quality Control of Radiation Delivery for Lower Gastrointestinal Cancers

OPINION STATEMENT

Assessing the quality of health care delivered is a priority across medical specialties, but it is particularly critical for radiation oncology, a field with rapid introduction of new technologies and treatment paradigms. Deviation from acceptable standards can lead to delivery of inferior therapies and medical errors that can directly compromise patient clinical outcome, thus leading to disparities in quality of care. Professional oncologic specialty societies often take ownership of standardizing best practices by issuing evidence-based disease-specific consensus guidelines. They also inform quality indicators that are set as requirements for accreditation, maintenance of certification, and reimbursement. Cooperative groups also create benchmarks for quality radiation therapy through design of clinical protocols that set standard-of-care treatment practices. Pelvic radiotherapy for colorectal and anal cancers has undergone a significant transformation in radiation planning and delivery including increased complexity in contour segmentation with a transition from three-dimensional to intensity-modulated radiation therapy (IMRT). Compliance with quality metrics proposed in national consensus guidelines and participation in clinical trials help keep practicing radiation oncologists up-to-date with advances in our field and well-trained to provide safe and effective high-value care.

Anal Carcinoma: A Series of Cases with a Literature Review

The aim of this study was to analyze the cases of five patients with squamous cell carcinoma (SCC) and to draw attention to the dilemma in the treatment of incontinence on admission of these patients and to present, through a literature review, locations of the surgical treatment.

The anal carcinoma is a rare disease which involves different histopathological (HP) types of cancer. They account for about 2.5% of all digestive cancers. The treatment of the disease is multimodal. There are dilemmas about screening of precancerous lesions and treatment of diagnosed incontinence. There is a high similarity between HPV infection and SCC. Our methods and results were compared with the data from the literature.

In the period of three years (from 2013 to 2015), five cases of the anal carcinoma were diagnosed and treated in the regional hospital. In all of our cases, the disease was histopathologically confirmed as SCC of the anal and perianal areas. It excluded the cases of anal adenocarcinoma (AAC).

Nearly half of the patients (40%) were incontinent and the rectum excision was one of the possible solutions. Distinction in histopathological structure created the confusion in the treatment of these patients. The dilemma we had was whether to do an amputation of the rectum in patients with incontinence before the standardized Chemoradiation therapy (CRT). The review of the literature sums up certain conclusions.

The diagnosis of SCC includes the perianal "ulcer" that does not heal, as well as atypical anoperianal growths. Surgical treatment of SCC is indicated when the diameter of lesion is small (2 cm), or the disease is persistent or recurrent. In the case of anal incontinence because of the tumor changes, the abdominoperineal resection of the rectum (APR) is an alternative to performing bipolar colostomy and CRT. The review of the literature using MEDLINE/PubMed databases did not find the case with restoring anal continence after this treatment. Testing a larger number of patients with incontinence on admission would provide a more clear answer to the question of the treatment of these patients.

Genital invasion or perigenital spread may pose a risk of marginal misses for Intensity Modulated Radiotherapy (IMRT) in anal cancer

BACKGROUND

While intensity modulated radiotherapy (IMRT) in anal cancer is feasible and improves high-dose conformality, the current RTOG/AGITG contouring atlas and planning guidelines lack specific instructions on how to proceed with external genitalia. Meanwhile, the RTOG-Protocol 0529 explicitly recommends genital sparing on the basis of specific genital dose constraints. Recent pattern-of-relapse studies based on conventional techniques suggest that marginal miss might be a potential consequence of genital sparing. Our goal is to outline the potential scope and increase the awareness for this clinical issue.

METHODS

We present and discuss four patients with perigenital spread in anal cancer in both early and advanced stages (three at time of first diagnosis and one in form of relapse). Genital/perigenital spread was observed once as direct genital infiltration and thrice in form of perigenital lymphatic spread.

RESULTS

We review the available data regarding the potential consequences of genital sparing in anal cancer. Pattern-of-relapse studies in anal cancer after conventional radiotherapy and the current use of IMRT in anal cancer are equivocal but suggest that genital sparing may occasionally result in marginal miss. An obvious hypothesis suggested by our report is that perigenital lymphovascular invasion might be associated with manifest inguinal N+ disease.

CONCLUSIONS

Local failure has low salvage rates in recent anal cancer treatment series. Perigenital spread may pose a risk of marginal misses in IMRT in anal cancer. To prevent marginal misses, meticulous pattern-of-relapse analyses of controlled IMRT-series are warranted. Until their publication, genital sparing should be applied with caution, PET/CT should be used when possible and meeting genital dose constraints should not be prioritized over CTV coverage, especially (but not only) in stage T3/4 and N+ disease.