14 Nasopharynx Cancer

Nasopharynx Cancer

3

THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 10/09/2019

14 Nasopharynx Cancer

Warren Bacorro, Michael Mejia, Erik Van Limbergen, Joseph T.S. Wee, Melvin L.K. Chua

1. Summary 2. Introduction

3 3 4 4 4 4 6 6

9. Treatment planning

12 13 16 16 18 19 19

10. Dose, Dose Rate, Fractionation

3. Anatomical topography

11. Monitoring

4. Pathology 5. Work up

12. Results

13. Adverse side effects 14. Key messages

6. Indications, contra-indications 7. Tumour and Target Volume

15. References

8. Technique

1. SUMMARY

The excellent outcomes achieved with the current management of nasopharyngeal cancer, which incorporates modern external beam radiotherapy techniques, and concurrent chemotherapy for locally-advanced disease, have resulted in the relegation of brachytherapy as a tool for salvage treatment for recurrent or persistent disease and possibly, for dose-escalation in primary locally- advanced cases where chemotherapy is contraindicated. Brachytherapy allows for delivery of higher doses to the nasopharynx and moderate doses to the proximal parapharyngeal spaces, clivus, inferior sphenoid, posterior maxillary sinuses, and posterior nasal cavity while sparing largely the pterygoid muscles, visual pathway, spinal cord, brainstem and pituitary gland. This dosimetry profile makes brachytherapy a useful tool in salvage re-irradiation where organ-at-risk tolerances could be significantly restrictive. Image-guidance and three-dimensional planning, together with the use of modern fractionation schemes, could improve further control and toxicity outcomes. Endoscopy-guidance and incorporation of interstitial techniques are currently under exploration.

2. INTRODUCTION

in Table 1), radiotherapy (RT) alone is the primary treatment modality. This is because the nasopharynx presents a challenging anatomical site for wide-field surgical resection. Moreover, compared to other squamous cell carcinomas of the head and neck, NPC is exquisitely radiosensitive [Chua, 2016]. It is therefore appreciable that factors relating to RT dosimetry and accuracy are crucial to achieving long-term tumour control [Ng, 2014]. On this note, the transition from two-dimensional (2D) external beamRT (EBRT) to contemporary RT techniques like intensity-modulated RT (IMRT) and image-guided RT (IGRT) have been pivotal in driving the improved survival, including reducing late RT-induced toxicities and better quality of life scores reported in NPC patients, even for those with advanced T3-4 and N2-3 disease [Lee, 2015; Peng, 2012; Au, 2017]. In patients with locoregionally advanced disease (Stage II to IV), radiotherapy with concurrent high dose cisplatin given every 3 weeks with or without adjuvant/neoadjuvant chemotherapy is the standard of care. In this regard, CCRT is an effective measure for targeting occult systemic metastases and for its radiosensitising effect. Altogether, these have resulted in superior local tumour control, with the majority of cases being now sufficiently treated with EBRT alone, with the shift in disease relapse patterns being currently dominated by distant metastasis [Chua, 2017].

Nasopharynx cancer (NPC) is a unique disease, with specific demographical and epidemiological patterns: men are more commonly affected thanwomen, with SouthernChinese and certain Southeast Asian populations being themost susceptible racial group. Overall global incidences are low, but there is preponderance for extremely high rates (age-standardised rates, ASR, of 10-30 cases per 100,000 person-years) in specific parts of the world, including Southern and Eastern China, Southeast Asia, and Northern and Eastern Africa [Wee, 2015; Chua, 2016]. Broadly, these regions can be grouped according to their reported ASRs. Southern and Eastern China, including Guangdong, Guangzhou, Guangxi, Fujian and Hainan report 15-30 cases per 100,000 person-years for males. This is followed by parts of Southeast Asia (Singapore, Malaysia, Indonesia, Vietnam and Philippines) and Northern/ Eastern Africa (Algeria, Kenya and Tunisia) that report 3-10 cases per 100,000 person-years for males. In these regions where NPC is endemic, this disease is invariably associated with exposure to the Epstein-Barr virus (EBV). ASRs for NPC in other parts of the world are typically less than 1 per 100,000 person-years.

In patients with localised or Stage I NPC (staging summarized