Treatment Options For Adenoid Cystic Carcinoma

Introduction to adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is a salivary gland cancer in the head and neck region. It is considered a rare type of secretory gland cancer that accounts for 10 % of all salivary gland cancers. However, that does not mean it is limited to the salivary glands, as it can also affect other sites (distant metastases) like the breast, lacrimal glands in the eyes, or trachea. Although ACC is a slow-growing cancer with a high survival rate (five years), it often returns after several years. Survival rates decline at the ten-year mark.¹

Symptoms of ACC vary depending on the location of the tumour (usually in the head and neck region). When occurring in the salivary glands, the most common symptoms include the presence of a painless lump or swelling, facial numbness, difficulty swallowing, and changes in speech. However, it is important to note that these symptoms can also be caused by other non-cancerous conditions.

Early detection and treatment are key to a good prognosis.² ACC was named as such due to how it appears under the microscope. The main feature it exhibits is a cyst-like structure that is usually surrounded by glandular cells (cells that form the actual gland). 

ACC differs from other types of salivary gland cancer in terms of growth rate. Despite being an aggressive form of tumour, it progresses slowly over a long period, making it harder to diagnose in its early stages. 

Aggressive salivary gland cancers like ACC tend to invade surrounding tissues, like the blood vessels and nerves around the tumour. Accordingly, this particular kind of salivary gland cancer can be challenging to remove without damaging vital structures around it. In addition, ACC is also more likely to reoccur or manifest as distant metastasis, usually in the bones or lungs, due to its uncanny ability to infiltrate tissue.³   

How does adenoid cystic carcinoma happen?

Well, the specific reason for this particular salivary gland cancer to manifest is still unknown. But like any other salivary gland cancer, there are risk factors that contribute to the development of ACC, such as radiation and chemical exposure. It is also important to note that this type of salivary gland cancer is not a result of lifestyle or personal choice of action.⁴

ACC is a rare form of salivary gland cancer; thus, it can be difficult to diagnose. Some of the challenges faced during diagnosis include misdiagnosis due to its similarity to other types of cancer that are benign (slow-growing, non-aggressive) or malignant (aggressive with the potential to metastasise). 

Misdiagnosis can lead to delayed and/or inappropriate treatment selection, which worsens the patient’s prognosis. Therefore,  healthcare providers should always keep ACC as a potential cause when evaluating patients with relevant symptoms and related imaging test results.

Diagnosis

The diagnosis of salivary gland cancers like ACC can be difficult due to the nature of the disease and the symptoms overlapping with other conditions. Thus, it requires a comprehensive evaluation that includes many factors such as physical examination, medical history and other diagnostic protocols.⁵

Initially, the healthcare professional will ask you about your medical history, especially about exposure to any relevant radiation or chemicals. During the physical examination, the doctor will examine the affected area thoroughly and note down any lumps and abnormalities. Next comes imaging, which is a vital aspect of diagnosing ACC. 

Scans

Depending on the location, the doctor may request one or more of the following scans: 

• Ultrasound
• Magnetic Resonance Imaging (MRI)
• Computed Tomography (CT)

These imaging techniques provide the necessary information to visualise and determine the accurate size, specific location and severity of the infiltration into the surrounding tissue.

Biopsy

While imaging tests can provide valuable information, a definitive diagnosis of ACC requires a tissue biopsy. During a biopsy, a small tissue sample is collected from the suspected tumour site for laboratory examination. 

Depending on the location and accessibility of the tumour, different biopsy techniques could be implemented: 

• Fine-needle aspiration 
• Core needle biopsy
• Surgical excisional biopsy⁶ 

Then, the sample is sent to the laboratory, where a pathologist analyses it to look for the characteristic features that may indicate that the sample is an ACC tumour. These characteristics may include the presence of cyst-like structures surrounded by glandular cells and the invasive growth pattern of the tumour.

Immunohistochemistry (using the antibodies to detect the antigens in a tissue sample) can be performed in addition to genetic testing to identify changes in genes that cause the specific behaviour observed in cancer.

Treatment options

Surgical intervention

Surgical intervention plays an important role in the treatment of ACC. The surgery and its protocol depend on multiple factors, such as the size, location and extent of infiltration in the surrounding area of the tumour.

In cases where the tumour is limited to a specific area, surgical removal is simpler and can involve the excision of the tumour along with a margin of healthy tissue. 

In advanced cases of ACC, extensive surgery might be required, which may or may not involve removing nearby lymph nodes or even parts of affected organs the ACC is present on.⁷ 

Reconstruction techniques, such as bone structures, may be used to restore the function and appearance of the affected area whenever feasible.

Radiation therapy

Radiation therapy is commonly used in the treatment of ACC. Radiation therapy uses high-energy X-rays or other forms of radiation to target and destroy cancer cells. It may be administered before surgery (neoadjuvant radiation therapy) to shrink the tumour or after surgery (adjuvant radiation therapy) to eliminate any remaining cancer cells for good measure. 

Radiation therapy can also be used as the primary treatment modality in cases where surgery is not feasible. This can be the case if the tumour is located in an area not suitable for surgical removal, or has infiltrated the surrounding vital organs thus making it not possible to remove without causing damage to those organs.⁸

Systemic therapy

Systemic therapy, which includes chemotherapy, targeted therapy, and immunotherapy may be considered in some cases of ACC. 

Chemotherapy

Chemotherapy involves the use of medications (powerful chemicals) that circulate throughout the body to kill cancer cells (usually cancers with distant metastases). Although ACC has traditionally shown limited response to standard chemotherapy drugs, new treatment options are emerging, and ongoing research aims to identify more effective agents to improve patient prognosis despite distant metastases.⁹

Targeted therapy

Targeted therapy focuses on specific molecular or genetic abnormalities present in the tumour cells and uses those to mark the cells for killing, which is very beneficial in cases with distant metastases. This approach aims to disrupt the signalling pathways that promote the growth and survival of cancer cells. 

Immunotherapy

Immunotherapy aims to produce immune cells that target and eliminate cancer cells based on the specific molecules and markers on the cancer cells. 

While targeted therapies are not yet widely established for ACC, ongoing clinical trials and advancements in precision medicine hold promise for the future.^{10, 11}

Other treatment modalities

Supportive care is an essential aspect of an ACC treatment plan. This includes addressing symptoms, managing the side effects of treatment, and providing emotional and psychological support. Palliative care may also be integrated to improve the quality of life for individuals with advanced or distant metastatic ACC, as well as provide support for their family members.

Multidisciplinary treatment approach 

The management of ACC often involves a multidisciplinary approach tailored to the tumour characteristics and your overall health. The primary goal of treatment is to achieve complete removal of the tumour while minimising the risk of recurrence and preserving organ function.

It is essential to consult with a multidisciplinary team of healthcare professionals, including oncologists (doctors who treat cancer) and surgeons experienced in treating ACC. They will assess the extent of the disease and develop an individualised treatment plan based on the specific characteristics of your tumour.³

Prognosis and long-term management

The prognosis for ACC varies depending on several factors: 

• The location and stage of the tumour (If it has metastasised or not) 
• The growth patterns 
• The presence of genetic alterations 

While ACC is generally known for its slow-growing nature, it can exhibit aggressive behaviour and local recurrence and distant metastasis tendency, particularly to the lungs and bones.

ACC is often considered a chronic disease requiring long-term management. The approach to managing ACC involves regular monitoring and follow-up with healthcare professionals to assess the tumour's response to treatment and detect any signs of recurrence or metastasis. These appointments may include physical examinations, imaging tests, and laboratory investigations.¹²

If ACC is completely removed by surgery, regular follow-up is crucial to monitor any signs of local tumour recurrence or distant spread. Early detection of recurrence allows timely intervention and appropriate treatment adjustments. The frequency of follow-up visits may vary depending on several factors, but these visits usually occur every few months initially and may become less frequent over time.

On the other hand, if ACC is not completely removable or has already spread, a palliative care approach may be adopted. Long-term management of ACC also involves adopting a comprehensive approach, which encompasses maintaining a healthy lifestyle like regular exercise, a balanced diet, and avoidance of tobacco and excessive alcohol consumption. Engaging in activities that reduce stress and promote mental well-being, such as relaxation techniques and support groups, can also contribute to a better overall quality of life.¹¹

Summary

Adenoid cystic carcinoma (ACC) is a rare cancer that primarily affects the salivary glands but can also occur in other areas. Symptoms include painless lumps, facial numbness, swallowing difficulties, and speech changes. Diagnosis involves medical history evaluation, physical examination, imaging tests, and a biopsy.

ACC management requires a multidisciplinary approach. Treatment options include surgery, radiation therapy, and sometimes chemotherapy, targeted therapy and immunotherapy. Prognosis varies based on tumour characteristics and stage of cancer. Long-term management involves regular monitoring and follow-up to detect recurrence or metastasis. Palliative care can enhance the quality of life in advanced (distant metastases) cases.

A healthy lifestyle, stress reduction, and support from healthcare professionals and networks are vital for managing ACC.