Lung cancer arises from lung squamous cells which, due to genetic changes (mutations), have stopped to function properly and are no longer controlled by the organism. A large group of such mutated cells form a cancerous tumour. There are several forms of lung cancer which differ in the course of disease and way of treatment. Approximately 95% of all LC cases are accounted for by four histological types: adenocarcinoma (approx. 40% — the most common type), squamous cell carcinoma (approx. 30%), small cell carcinoma (approx. 15%) and large cell carcinoma (approx. 10%). Small cell lung carcinoma (SCLC) differs from the other types in many biological and clinical features (fast growth, strong tendency to produce metastases to other organs, sensitivity to chemotherapy and radiotherapy). Those distinctive characteristics form the basis for the commonly used division into small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC).
The lungs can also be the site where metastases of other cancers are likely to settle. Less common primary lung cancers are mesotheliomas and carcinoid tumours.
The information we provide here only refer to the two most prevalent lung cancer types: small-cell lung carcinoma and non-small-cell lung carcinoma. Metastatic tumours and the above mentioned rare malignancies are not discussed.
Lung cancer is the most common malignancy in Poland. In recent years, approx. 16,000 men and approx. 6,000 women have been diagnosed with LC annually. It is also the cause of the largest number of cancer-related deaths in males and females. In 2010, 22,512 deaths were registered, including 16,716 in men and 6,177 in women.
The risk of developing lung cancer depends mostly on an active or passive exposure to carcinogenic components of tobacco smoke (approx. 90% of all cancer cases), and – to a much smaller degree – on certain physical and chemical environmental factors (radioactive metals and gaseous products of their decomposition, nickel, chromium, arsenic, asbestos, hydrocarbon compounds) and genetic factors.
Early stage lung cancer has no symptoms. After growing to a large size, it may cause local respiratory problems, such as:
- Cough (especially if the nature of cough changes in smokers)
- Shortness of breath,
- Pain in the chest
- Recurrent or persistent pneumonia
- Hoarse voice,
- Swallowing disorders,
- Pain the the shoulder
Or non-specific general symptoms, such as:
- Joints ache
- General weakness
- Loss of body weight
- Increased body temperature
- Superficial sensibility disorders
- Symptoms of venous thrombosis
The above symptoms are non-specific, meaning they can occur for completely different reasons. The most common symptom of LC is coughing. As this symptom also occurs in addicted smokers, who are particularly exposed to this disease, any change in the nature or intensity of cough should be examined by a doctor.
If LC is suspected, some additional tests should be taken, such as chest X-ray, CT, phlegm examination. Should cancer be detected in imaging or cancerous cells found in the phlegm, some other tests may be ordered, such as PET or MRI to find other cancer foci.
The decisive diagnostic procedure is histopathology that consists in collecting a small sample tissue from the suspected focus and analysing under microscope. Sample collection (biopsy) is usually performed during bronchoscopy [a procedure of inserting a thin tube-like instrument into the airways) or during surgery. Histopathological examination allows to determine the type of cancer (small-cell vs. non-small-cell carcinoma) and plan further diagnostic and therapeutic actions.
In non-small cell lung cancer, staging is based on the so-called TNM classification which takes into account the location and size of the tumour (T factor), presence of cancer cells in the lymph nodes (N factor) and presence of cancer cells (metastases) in other parts of the body (M factor).
Based on the TNM classification, clinical stage is then assessed as latent carcinoma of stage 0 (in situ cancer) – when the neoplastic process is in its initial latent period, or as stage I (small, confined tumour) up to stage IV (generalised disease with metastases).
A similar assessment system may be applied for small-cell carcinoma, but a simplified division is used into LD, limited disease, and ED, extensive disease.
Treatment method depends on the histopathological type and stage.
Low stage cancer (I, II or some IIIA cases): the treatment of choice is surgery involving a complete removal of pulmonary parenchyma. Apart from surgery, most patients also receive chemotherapy which may be administered before surgery (preoperative chemotherapy also known as neoadjuvant chemotherapy) or after surgery (adjuvant chemotherapy). In some cases, surgery may also be followed by radiotherapy.
Patients who do not qualify for surgery may be treated with radiation therapy typically combined with chemotherapy delivered before or during radiotherapy.
Locally advanced cancer – stage IIIA and some IIIB cases
Treatment at this stage consists of chemotherapy administered before or during radiotherapy. Some patients qualify for surgery typically combined with radiotherapy and chemotherapy.
Advanced cancer – stage IIIB and IV
Treatment at this stage is of palliative nature only, meaning that its only purpose it to reduce the suffering associated with the disease. Depending on the clinical situation, treatment involves chemotherapy, palliative radiotherapy or just symptomatic treatment.
Patients with SCLC are mainly treated with chemotherapy.
While surgical procedure is a basic approach in most cancer types, the role of that method in SCLC remains controversial – it may only be considered for patients with a very low stage cancer, which applies to less than 5% of all SCLC cases.
Standard chemotherapy involves the administration of 4-6 courses at 21-day intervals:
Patients with a limited disease, good performance status and unaffected by other factors increasing the risk of complications may be treated with combined chemotherapy i radiotherapy. That treatment modality may be applied sequentially, i.e. chemotherapy followed by radiotherapy, or concurrently. Concurrent radiochemotherapy, as compared to sequential use of both methods, increases the chance for recovery or long-term remission with longer survival, however; at the expanse of relatively high share of radiation toxicity.
SCLC very often spreads to the brain; therefore, patients who show response to therapy should be treated with preventive brain irradiation. Radiotherapy is started within 2–5 weeks of chemotherapy completion to continue for two weeks.
Treatment of relapsed disease
Treatment of relapsed disease after prior chemotherapy or radiochemotherapy depends on the effectiveness of the first-line procedure and patient’s performance status. If recurrence has occurred no sooner than three months after prior chemotherapy, which brought an objective response, an attempt is made to repeat the primary regimen. Unfortunately, for patients in whom no response was achieved to primary treatment or the response was shorter than three months, the chance to obtain a response in a second line treatment is small.
Adverse effects associated with radiotherapy of the chest region – lung cancer
During and immediately after (up to 3 months) radiotherapy:
- redness and exfoliation of the skin at the irradiated site,
- feeling of dry skin, itching sensation
- loss of hair at the irradiated site,
- coughing (dry, tiring, sometime with bloodstained sputum)
- pain in the chest
- pain when swallowing, sometimes requiring a change of diet
- dryness in the throat and oesophagus
- hoarse voice
- general weakness
- shortness of breath
- problems with swallowing that require a stomach tube for feeding
Long after radiotherapy (more than three months):
- discolouring of the skin at the irradiated site
- dry cough
- worse tolerance for physical effort
- persisting problems with swallowing
- pulmonary fibrosis
- changes in electrocardiogram
- cardiac contractility disorders
- increased risk of heart attack
Follow-up exams are recommended after the completion of therapy. Those exams enable early detection of recurrence, possible complications or independent primary cancer. Within the first two years following treatment, follow-up visits are held every three months and include alternate chest X-ray and CT. Over the next three years follow-up is carried out every six months and then, every twelve months.