10 General Aspects of Head and Neck Brachytherapy

General Aspects of Head and Neck Brachytherapy

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 30/01/2019

1. SUMMARY

Brachytherapy alone or combined with other treatment modalities is a highly selective treatment option in the management of squamous cell tumors head and neck region. The physical properties of the radioactive sources provide an advantageous conformation of the clinical target volume (Treated Volume) compared to other radiation techniques due to the rapid dose fall-off into the surrounding normal tissues. PDR and HDR brachytherapy with stepping sources and CT-based planning have replaced LDR brachytherapy as the new standard of care although the implantation and planning rules generated during the LDR era must be used as a reference. Brachytherapy alone yields local control rates above 90% in a) T1 and small T2 tumours with low risk of node involvement arising in areas of functional or cosmetic importance as well as in b) selected advanced lip tumors. Brachytherapy alone should also be considered under c) medical contraindication for radical surgery or in cases of d) small lesions arising in previously irradiated areas. Combined EBRT and brachytherapy yields local control rates in excess of 80% in patients e) unfit for surgery with cT1-2N0 tumors that require node irradiation or in f) advanced T3-4 and/or N + tumors that would require resections with functional or cosmetic impact or in g) patients who may require high radiation doses that are precluded by the proximity to dose-sensitive structures. Adjuvant brachytherapy can also be used after surgery in h) accesible lesions if the surgical pathology reveals that the neck is negative and that there is an indication for postoperative irradiation of the primary tumor bed. Similarly, adjuvant brachytherapy can be used in combination with external chemoirradiation for i) dose escalation in well-defined areas of the surgical bed such as those with positive margins or extracapsular spread.

2. GENERALITIES

(ACR), initiated practice guidelines aimed to normalize clinical indications and treatment parameters.The gradual implementation of these recommendations into routine clinical practice will probably allow in the near future the integration of standardized brachytherapy treatments intomultidisciplinary clinical trials. [1,2]

Scope Head and Neck Cancer Brachytherapy (HN BT) refers to the use of radioactive implants, alone or combined with other treatment modalities, in the management of squamous cell tumors and their variants arising in lip, oral cavity, oropharynx, nasopharynx, larynx and hypopharynx as well as cervical lymph nodes metastases of cutaneous or unknown origin. Proof of Concept Brachytherapy remains an important treatment option in the armamentarium of the radiation oncologist treating head and neck cancer. The physical properties of the radioactive sources provide an unparalleled conformation of the clinical target volume (TreatedVolume) due to the rapid dose fall-off into the surrounding normal tissues (Figure 1). Unlike other anatomical areas, HN BT is extremely demanding due to the number and importance of the normal tissue structures that constrain accessibility and dose delivery. Evidence Practice guidelines usually categorize the recommendations for HN BT as NCCN 2A (there is uniform consensus based on low levels of evidence including clinical experience, that the recommendation is appropriate) or NCCN 2B (there is no uniform consensus -even though no important disagreement- about the appropriateness of the recommendation). The scientific evidence that supports HNBT is limited because the majority of the published data has been produced at single expert institutions. This carries the disadvantage of limited sample size and reproducibility and makes difficult a cross-comparison of results between centers as well as the implementation of standards of treatment. During the 1990s, several scientific societies like the American Brachytherapy Society (ABS), the Groupe Européen de Curiethérapie of the European Society for Radiotherapy and Oncology (GEC-ESTRO) and the American College of Radiology

3. HEAD AND NECK BRACHYTHERAPY TODAY: AN HISTORICAL PERSPECTIVE

HNBT emerged as a formidable oncological solution in the middle part of the XXth century. In an era of non-functional head and neck surgery and rudimentary external beam irradiation (EBRT), HN BT soon became a main player in the HN arena. HN BT proved effective andmuch less traumatic than other treatment options. In addition, patients unsuitable for radical surgery could still benefit from HN BT due to a shorter anesthetic time, a less problematic post-procedure status and a faster recovery after treatment. The implementation of technical developments such as 192 Ir hairpins and afterloading catheters facilitated the implementation of HNBT that was incorporated into the armamentarium of both radiation oncology and surgical teams. In addition, the design of systems that directed the source geometry placement and dose calculation such as the Paris [3] andManchester systems notably strengthened the quality of the treatment in an era without computer aids. In the last quarter of the XXth century, the developments in anesthesia, surgical resection with immediate reconstruction and postoperative care began to widen the indications for functional surgery and increased the number of patients considered to be good surgical candidates. As a result, surgery and HN BT started to compete for the same case load. The complete pathological information derived from a comprehensive surgical procedure was rapidly acknowledged as the main source of information in an era of otherwise limited medical imaging. Hence, HN BT was progressively relegated as a treatment of frail patients and poor surgical candidates. On the other hand, the development in EBRT with the implementation of 3D treatment planning