**2.1 Anatomy from an oncologist perspective**

In order to understand a disease, one needs to be well versed with the anatomy of the area and since we want to know the way this would influence a radiation oncologist's outlook, the following section will address anatomy from a radiation oncologists' perspective (**Figure 1**).

Oral cavity includes lips, buccal mucosa, gingivobuccal sulcus, superior and inferior alveolar ridges, teeth & mandible, oral tongue, floor of mouth (FOM),

**Figure 1.** *Anatomical aspects of oral cavity.*

*Radiotherapy in Oral Cancers: Current Perspective and Future Directions DOI: http://dx.doi.org/10.5772/intechopen.99557*

**Figure 2.** *Description of various nodal levels in the neck.*

retromolar trigone (RMT) and hard palate [3]. One needs to know a few terminologies like buccal mucosa which means mucosal surface of lips and cheek, whereas gingival mucosa means mucosal lining of teeth, alveolar arches and gums. The area of maximum incidence of squamous cell carcinoma is at the gingivobuccal sulcus which is the junction of buccal mucosa to gingival mucosa. Floor of mouth is the U-shaped sling formed due to joining of two mylohyoid muscles to a fibrous median raphe. Oral tongue also known as Anterior 2/3rd of tongue includes the tip, lateral border and body which consists of intrinsic and extrinsic muscles. It is imperative to know the muscles as their involvement can upstage the disease, which will be discussed later in the chapter. Intrinsic muscles have no bony attachment and are divided into longitudinal, transverse and vertical groups. Extrinsic muscles do have a bony attachment and originate outside the tongue, and are made up of four paired bundles - genioglossus, hyoglossus, styloglossus and palatoglossus. These can be appreciated well on a CT scan and an MRI scans.

The most important feature of neoplasia is the potential for spread and the most common route of spread in oral cavity tumours is the lymphatic spread (**Figure 2**). Since radiotherapy is a branch which tackles locoregional disease it becomes imperative to have a thorough knowledge of the lymphatic drainage. In order to understand this better, we are dividing the lymphatic channels as functional pathways:


**Figure 3.** *Overview of management of Oral cancers.*

#### **2.2 Basic principles of treatment and broad guidelines**

Radiotherapy is loco-regional form of treatment just like surgery. In oral cavity cancers one needs to keep in mind the functionality and cosmesis when deciding on the management, hence it requires a multidisciplinary team to take a call. For management and prognosis reasons, these tumours are divided in to early stage, locally advanced and metastatic tumours. The flow chart provides concise & definitive steps on how to manage oral cavity tumours (**Figure 3**).

For any malignancy there are only three weapons and they are surgery, radiation therapy and systemic therapy. The sequencing and need of each therapy are a point of debate. However, in oral cavity tumours, mostly all modalities are required and sequencing is usually pre-determined and rationale is also established.

#### *2.2.1 Early stage*

As per TNM this group includes cT1 and cT2, which means localised tumours only. This group is usually tackled by surgery or radiation therapy and role of systemic therapy is limited (**Table 1**).


**Table 1.**

*Rationale for application of radiotherapy in early oral cancers.*

*Radiotherapy in Oral Cancers: Current Perspective and Future Directions DOI: http://dx.doi.org/10.5772/intechopen.99557*


#### **Table 2.**

*Rationale for combined modality therapy in advanced oral cancers.*

### *2.2.2 Locally advanced disease*

As per TNM this group will include cT1-4 and N+ disease. Basically, it means that the disease has spread to nodes and or direct extension to surrounding structures. This group has to be addressed by combined modality therapy and there will always be some amount of deliberation to be had about the sequencing of the three modalities (**Table 2**).

Recurrent tumours: a tumour can be suggested to have recurred if there is disease recurrence after a period of documented complete remission and usually it is taken as 2 follow-ups of 6 weeks apart with a period of 6 months post primary therapy. Based on this they can be:


In the following section we are going to address the basis of radiation, how it is delivered and what are the relevant toxicities encountered.

#### **2.3 Basis for radiation**
