13 Head and Neck - Oropharynx

Head and Neck - Oropharynx

3

THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 15/02/2021

13 Head and Neck - Oropharynx

Ashwini Budrukkar, Gyoergy Kovacs, Rafael Martinez-Monge, Christine Haie-Meder, Erik Van Limbergen, Vratislav Strnad

1. Summary 2. Introduction

3 3 4 4 4 5 6 7

9. Treatment planning

15 16 17 17 21 22 23

10. Dose, dose rate and fractionation 11. Monitoring and posttreatment care

3. Anatomical topography 4. Pathology and staging

12. Results

5. Work up

13. Adverse side effects 14. Key messages

6. Indications, contra-indications 7. Tumour and target volumes

15. References

8. Techniques

1. SUMMARY

Radiation therapy with or without chemotherapy is the standard of care for oropharyngeal cancers. With excellent control rates and reduction in the toxicity with modern external beam radiotherapy, the use of brachytherapy in oropharyngeal cancers has become less common. Brachytherapy, however, has a potential to deliver high doses to the centre of the tumour which is also the most common site of relapse. Various brachytherapy series have shown excellent tumour control rates and reduction in normal tissue toxicity compared to external beam radiotherapy. It may therefore be advantageous to combine the two modalities and optimize the outcomes further in this modern era.

2. INTRODUCTION

Interstitial brachytherapy for oropharynx is challenging. While interstitial brachytherapy has been in use since many decades; with the advent of intensity modulated radiation therapy (IMRT) there has been a debate regarding use of IMRT or BT [15]. While BT has advantages of being a time-tested technique with excellent local control rates and acceptable toxicity, IMRT is promoted for its non-invasive nature. As both modalities result in very good outcomes combining the two modalities could result in further improvements in control rates and reduction in toxicities. Combined IMRT and BT has resulted in excellent local control rates [16]. Brachytherapy due to its rapid fall off of the dose has greater ability to reduce doses to the critical structures than IMRT. Important among these are reductions in the dose to parotids and to constrictor muscles [17,18]. Combined IMRT and BT has resulted in reduction in xerostomia and improved quality of life [16]. Brachytherapy has also resulted in decreased doses to the dysphagia aspiration related structures (DARS) and improved quality of life [19]. Brachytherapy has evolved from the era of preloaded applicators to low dose rate BT and now to pulse dose rate (PDR) and high dose rate (HDR) BT [20]. The planning has evolved from X ray based planning to three dimensional computerized tomography (CT) based planning with various optimization techniques [20]. This has resulted in the ability to reduce doses to critical structures close to the implant such as mandible thereby minimising the long term sequelae of BT [21].

There has been an increase in the incidence of oropharyngeal cancer in the last decade in the western world which has been attributed to the presence of human papilloma virus (HPV) [1]. Significantly improved clinical outcomes have been observed with radiotherapy for oropharyngeal cancers in HPV positive patients [2,3] compared to HPV negative cancers. This has resulted in the different staging system for HPV positive and negative cancers in the 8th UICC TNM staging [4]. A similar increase in the incidence has however not been observed in the Asian countries [5]. Management of oropharyngeal tumours is challenging due the important role of the oropharynx in speech and swallowing. Early stage disease is managed with single modality treatment either in the form of surgery or radiation and for advanced stage disease multimodality treatment in the form of chemoradiation is considered. Surgery for oropharyngeal tumours involves extensive resection which has an impact on speech and swallowing [6]. This results in increased treatment-related morbidity and impaired quality of life [6]. More recently there has been a resurgence in the surgical management especially in HPV positive tumours using robotic surgery [7]. Radiation therapy either external beam alone or combined with brachytherapy (BT) has resulted in excellent outcomes for oropharyngeal cancers [8–13]. Combined external beam radiation therapy (EBRT) and brachytherapy has resulted in improved local control rates as compared to either modality alone [14].