Intensity-modulated radiation therapy for the treatment of anal cancer

Toxicity and survival of anal cancer patients treated with intensity-modulated radiation therapy

INTRODUCTION

The definitive treatment of anal cancer with chemoradiotherapy spares abdominoperineal resection for salvage treatment but carries a high burden of toxicity. Intensity-modulated radiation therapy has been implemented to reduce toxicity, reduce treatment breaks and improve survival. However, large and long-term studies are lacking. We aimed to investigate the toxicities and long-term survival of anal cancer patients treated with intensity-modulated radiation therapy at James Cook University Hospital, Middlesbrough.

MATERIALS AND METHODS

We conducted a retrospective analysis of all patients with squamous cell anal cancer treated at James Cook University Hospital between July 2010 and April 2017. All patients were uniformly treated with intensity-modulated radiation therapy-based chemoradiation with curative intent. A subset of these patients was followed-up prospectively by an oncologist for acute and late toxicity. We calculated Kaplan-Meier estimates of survival statistics and compared our results with those of previous trials which used conventional radiotherapy.

RESULTS

We studied 132 patients, including a toxicity subset of 64, for a median follow-up time of 43 months (range 3-84 months). Eleven patients (8.3%) underwent salvage abdominoperineal resection. Grade 3+ acute non-haematological, gastrointestinal, genitourinary and dermatological toxicity were found in 56.2%, 12.3%, 0% and 50.7% of the toxicity subset (n = 64). Median treatment duration was 37 days. Overall and colostomy-free survival at five years were 68.3% and 85.3%, respectively. Tumour size (P = 0.006) and age (P = 0.002) predicted shorter overall survival.

CONCLUSIONS

Intensity-modulated radiation therapy probably reduces acute gastrointestinal and genitourinary toxicity compared with conventional radiotherapy, while resulting in similar overall and colostomy-free survival. We suggest that further dose escalation may improve survival in patients with T3/T4 tumours.

Proposed genitalia contouring guidelines in anal cancer intensity-modulated radiotherapy

OBJECTIVE

Intensity-modulated radiotherapy (IMRT) for anal canal carcinoma (ACC) is associated with favourable toxicity outcomes. Side effects include sexual dysfunction, skin desquamation, pain and fibrosis to perineum and genitalia region. The genitalia are situated anterior to the primary ACC between two inguinal regions providing a challenging structure to avoid. Techniques improving outcomes require robust, consistent genitalia contouring to ensure standardization and production of fully optimized IMRT plans. Official recommendations for genitalia contouring are lacking. We describe a potential genitalia contouring atlas for ACC radiotherapy.

METHODS

Following a review of genitalia CT anatomy, a contouring atlas was generated for male and female patients positioned prone and supine. Particular attention was paid to the reproducibility of the genitalia contour in all planes.

RESULTS

Male and female genitalia positioned prone and supine are described and represented visually through a contouring atlas. Contoured areas in males include penis and scrotum, and in females include clitoris, labia majora and minora. The muscles, bone, prostate, vagina, cervix and uterus should be excluded. The genitalia contour extends laterally to inguinal creases and includes areas of fat and skin anterior to the symphysis pubis for both genders.

CONCLUSION

This atlas provides descriptive and visual guidance enabling more consistent genitalia delineation for both genders when prone and supine. The atlas can be used for other sites requiring radiotherapy planning.

ADVANCES IN KNOWLEDGE

This atlas presents visual contouring guidance for genitalia in ACC radiotherapy for the first time. Contouring methods provide reproducible genitalia contours that allow the provision of accurate dose toxicity data in future studies.

IMRT for locally advanced anal cancer: clinical experience of the Montpellier Cancer Center

Purpose

To assess outcomes of patients with carcinoma of the anal canal (CAC) treated with intensity-modulated radiation therapy (IMRT).

Method and materials

From August 2007 to January 2011, seventy-two patients suffering from CAC were treated with IMRT. Concurrent chemotherapy was added in case of locally advanced tumors. Radiation course consisted in delivering an initial plan to the PTV1 defined as the primary tumor and the risk area including pelvic and inguinal nodes. Forty-five Gy in daily 1.8 Gy-daily fractions were delivered five days a week. A second plan of 14.4-20 Gy to the primary tumor (PTV2) was administered in 1.8-2 Gy-daily fractions, 5 days a week. We present here the results of dosimetry, toxicities, and clinical outcome of the first 39 patients with a median follow-up of 24 months.

Results

Thirty-one women and eight men were included in the present analysis. Tumors were classified as stages I, II, III and IV in 2, 7, 27 and 2 patients, respectively. Median age was 59 years (range, 38-85). Radiotherapy alone (RT) or combined with chemotherapy (RCT) were delivered in 6 (15%) and 33 (85%) patients, respectively.

Six patients (15%) required a treatment break ≥ 3 days, and median time for treatment break was 8 days (range, 3-14 days). Acute grade 3 gastrointestinal (GI) and genitourinary (GU) toxicities were seen in 10 and 5% of patients, respectively. Grade 4 toxicity was only hematologic and occurred in 12% patients receiving RCT. With a median follow-up of 24 months, no patient experienced any late grade 4 toxicity. The 2-year overall survival rate was 89%, the 2-year local relapse free survival was 77% and the 2-year colostomy-free survival rate was 85%.

Conclusion

IMRT is well tolerated with acceptable treatment interruption allowing dose escalation.

[Intensity-modulated radiation therapy for anal carcinoma]

Anal canal carcinoma are highly curable by irradiation, combined with chemotherapy in locally advanced disease, with preservation of sphincter function. The clinical target volume for the nodes is extended, often including the inguinal nodes, which is not usual for other pelvic tumours. Acute and late effects are correlated with the volume and dose delivered to organs at risk, i. e. small bowel, bladder and increased by concomitant chemotherapy. Intensity modulated irradiation (IMRT) makes it possible to optimize the dose distribution in this "complex U shaped" volume, while maintaining the dose distribution for the target volumes. The conversion from conformal irradiation to IMRT necessitates good knowledge of the definition and skills to delineate target volumes and organs at risk, including new volumes needed to optimize the dose distribution. Dosimetric and clinical benefits of IMRT are described, based on early descriptions and evidence-based publication. The growing development of IMRT in anal canal radiotherapy must be encouraged, and long-term benefits should be soon published. Radiation oncologists should precisely learn IMRT recommendations before starting the technique, and evaluate its early and late results for adverse effects, but also for long-term tumour control.