Introduction

Lip cancer is a type of oral cancer which begins in the tissues of the lip, most commonly affecting the lower lip due to its higher chances of exposure to environmental factors. It tends to develop from squamous cells and presents as a persistent lump or ulcer. Risk factors for lip cancer include tobacco use, excessive sun exposure, alcohol and infection with human papillomavirus (HPV).¹ The treatment methods can vary depending on the severity and stage of cancer and can include radiation therapy, chemotherapy or surgery. This discussion will specifically focus on the role of radiation therapy in treating lip cancer.

Basics of radiation therapy

What Is radiation therapy?

Radiation therapy uses high-energy rays to destroy cancer cells and disrupt their growth and division. This treatment damages the DNA within the cancer cells, which prevents them from replicating. Although healthy non-malignant cells may also be affected by radiation, there are methods used to help minimise these effects. Radiation therapy is typically a non-invasive procedure that can be used alongside other treatment methods such as chemotherapy and surgery. Radiation therapy is planned to specifically target the tumour using imaging techniques such as CT and MRI scans. This is to help deliver the maximum dose of radiation to the cancerous tissue and minimise the effect on as much healthy tissue as possible.² A treatment plan is created where radiation therapy is typically given over multiple sessions over a specific period, depending on the severity and location of the tumour.

Types of radiation therapy used in lip cancer

External beam radiation therapy (EBRT)

The most commonly used type of radiation therapy for lip cancer is EBRT, which is a machine that delivers high-energy rays from outside the body. Advanced technologies like 3D conformal radiation therapy and intensity-modulated radiation therapy (IMRT) deliver targeted therapy which shapes the radiation beams depending on the contour and size of the tumour. This is beneficial as it reduces impact on nearby healthy tissues such as the gums, teeth, and salivary glands. EBRT is generally used with deeper and larger tumours or when surgery is not possible.³

Brachytherapy (internal radiation)

Brachytherapy is when radioactive sources are placed directly into the tumour tissue. For lip cancer, this generally involves the implantation of small radiation seeds or wires in the lip under anaesthesia. This process allows for a high dose of radiation to be delivered to the tumour and limits its exposure to the surrounding tissue.³ Brachytherapy is most effective for smaller lip cancers and usually has better cosmetic and functional outcomes. Compared to EBRT, the duration of treatment is generally shorter and is usually used in early stages or potentially used as a boost after EBRT if needed.

Indications for radiation therapy in lip cancer

Radiation therapy can be used to treat lip cancers for multiple key indicators. As a primary treatment, it can be beneficial for localised small tumours or individuals who are not suitable for the option of surgery. When used as adjuvant therapy, this is generally after surgery to kill any remaining cancer cells, which is especially important when there are high-risk features like positive margins or lymph node involvement. Radiation therapy is a non-surgical treatment that can help control the disease when the tumour is inoperable or has recurred after initial treatment.⁴ Furthermore, it can also be used in advanced cases as a palliative use when a cure is not possible but can help relieve symptoms such as pain or difficulty so that a patient's quality of life can be improved.⁵ 

Planning and delivery of radiation therapy

A pre-treatment evaluation is needed before radiation therapy commences. This involves using imaging techniques such as CT or MRI scans to assess the parameters of the tumour, taking a biopsy of the affected area to reach a confirmed diagnosis, and a dental evaluation to address any oral issues that may be affected by radiation. When the evaluation is completed, the planning for radiation therapy starts by using a process called simulation, where the patient is positioned and immobilised while detailed scans are used to map out the exact area to be treated. This plan is then personalised to make sure the radiation dose is precisely delivered in small daily fractions over a certain time period, eventually delivering the total dose.⁶

Effectiveness of radiation therapy

Radiotherapy is a highly effective treatment for early-stage lip cancer. It has high rates of local control and good long-term outcomes, especially when the tumour is small and well-localised. This treatment option is able to preserve lip structure and function, which makes it more favourable compared to surgery in some cases. The size and depth of the tumour, its precise placement on the lip, the stage at diagnosis, and the patient's overall health and immune condition are some of the critical variables that affect the overall effectiveness of treatment. For radiation therapy to be as effective as possible, early detection and thorough patient selection are essential.⁴

Side effects and management

Common side effects

Generally, patients who have radiation therapy for lip cancer will experience similar short-term side effects, such as redness and irritation of the skin surrounding the affected area. It is also common for them to experience dry mouth (xerostomia), mouth sores and changes in taste.⁷ 

Long-term effects

Occasionally, radiation therapy can reveal side effects that are delayed and may appear months to years after the treatment. These effects may include fibrosis (hardening or stiffening of soft tissues), a higher risk of dental decay due to reduced saliva production, and in rare cases, secondary cancers may develop. These side effects, although uncommon, highlight the importance of ongoing monitoring and preventive care.⁷

Supportive care

Side effects must be effectively managed for the patient to remain comfortable and adhere to therapy. Dental hygiene check-ups, the use of mouthwashes or topical medications for sores, sufficient pain management, and nutritional support like soft meals or high-calorie supplements to maintain weight and energy, are examples of supportive measures after radiation therapy. Involving nutritionists and dentists early on can significantly improve patient outcomes both during and after treatment.

Advantages and limitations

Advantages

Radiation therapy as a treatment for lip cancer has multiple important advantages. One of the main advantages is organ preservation, as it allows for the lip to remain in form and maintains its function and appearance that is necessary for eating and speaking. With radiation being a non-invasive treatment, it avoids all the risks that are generally associated with undergoing surgery and is a preferred option for individuals who would like to avoid the undesirable risks. Radiation therapy provides great cosmetic outcomes with minimal scarring.

Limitations

Although there are many benefits, this treatment may not be suitable for every patient. Larger, highly invasive, or recurrent tumours may respond less well to it; in these cases, surgery may provide better management. In addition to this, there is a chance that radiation may cause adverse effects, such as tissue fibrosis, dental problems, and a slight chance of developing additional tumours. When selecting the best course of treatment, these considerations need to be carefully taken into account.⁸

Future directions and research

Radiation therapy for lip cancer is constantly evolving and has promising improvements aimed at increasing results while minimising side effects. By varying the radiation beams' intensity, new methods like intensity-modulated radiation therapy (IMRT) enable more accurate tumour targeting while protecting surrounding healthy tissues. Another new option is proton treatment, which is incredibly useful in sensitive tissues like the lips, as it administers radiation more precisely and causes less damage outside of the tumour, potentially lowering long-term consequences. Along with advancements in technology, there is an increasing trend towards more individualised methods. These involve customising therapy regimens according to molecular profiles, tumour features, or specific genetic markers. Such methods could direct more efficient, individualised treatment for every patient by predicting how a tumour would react to radiation.⁸

Summary

To summarise, for many lip cancer patients, especially those with early-stage tumours or those looking to preserve their organs, radiation therapy is a useful and successful treatment option. Through sophisticated procedures, it can be customised to meet individual demands and gives good cosmetic results and high success rates. To get the best results, cautious patient selection and side effect management are crucial. It is impossible to overestimate the significance of multidisciplinary care; thorough and well-coordinated therapy is ensured by close cooperation between supportive care teams, surgeons, oncologists, and dentists. Lastly, for those with lip cancer, an improved prognosis and preservation of quality of life depend on early diagnosis and prompt care.