Radiotherapy remains a major player in the treatment of patients suffering from lung cancer. Half of patients will receive radiotherapy at some point in their disease history, either for cure or palliation.
Radiotherapy for Lung Cancer
Radiotherapy remains a major player in the treatment of patients suffering from lung cancer. Half of patients will receive radiotherapy at some point in their disease history, either for cure or palliation. While surgery remains the treatment of choice for early-stage disease, the new radiotherapeutic techniques are becoming more than a simple alternative. It can also be used as Primary treatment when surgery is not possible.
While surgery remains the treatment of choice for early-stage lung cancer even in elderly patients, many of them are unsuitable for such an approach due to comorbidities or patient/relatives’ refusal. In these cases, radiotherapy especially stereotactic body radiation therapy (SBRT) is a good option
Mechanism of action
At a cellular level the radiation beam causes the formation of free radicals that interact with DNA causing damage. If the cell is able to repair the damage, then it will be resistant to radiotherapy and survive. Cells that succumb to lethal radiation damage die by the process apoptosis and are removed by the body’s normal mechanisms.
Types of lung cancer
- Non-small cell lung cancer (NSCLC)
(adenocarcinoma, squamous cell carcinoma, large cell carcinoma and bronchoalveolar carcinoma)
- Small cell lung cancer (SCLC)
(It has two categories. Limited disease: Disease confined to one side only. Extensive disease: Disease with extensive spread)
Radiotherapy for non-small cell lung carcinoma (NSCLC)
There are two types of radiotherapy for NSCLC
- Radical radiotherapy
- Palliative radiotherapy
What is Radical radiotherapy?
Radical radiotherapy aims to cure the cancer. It has following techniques / types:
- SBRT or stereotactic ablative radiation (SAR or SABR)
- Classical external beam radiation
- Brachytherapy
- Proton beam therapy
Radical radiotherapy is given in two groups of patients.
- The first includes patients who have a tumor that can undergo surgical removal but surgery is deemed too risky because of other lung or heart diseases that patient might be suffering from.
- The second group includes patients that are generally fit for surgery but that have advanced disease that is unresectable.
Recommended for patients with stages I–III
Work-up prior radical radiotherapy
Ideally all patients should have
- A combined positron emission tomography and computed tomography (PET-CT) scan .
- Lung function test.
- SABR/stereotactic body radiation therapy (SBRT)
SABRT allows the delivery of very high radiation doses to small early-stage lung cancers. SBRT is commonly used to treat early-stage lung cancer (stage I/II) in surgically unfit patients or those who refuse surgery. The treatment course is shorter than conventional radiotherapy and is usually associated with an acceptable toxicity profile. Only 1 – 8 sessions required over 1.5 – 2 weeks.
- Classical external beam radiation (EBRT)
It is used when SABR not possible. Various regimes are used (e.g. 20 sessions over 4 weeks or 30–33 sessions over 6.5 weeks). It has low dose and longer duration as compared to SABR in which dose is high but duration is less.
- Endobronchial Brachytherapy (EBBT)
Endobronchial Brachytherapy refers to the placement of source of radiation within or in close proximity to the tumor in order to provide high doses of radiation directly to tumor only. Compared with external beam radiation therapy (EBRT), brachytherapy is given only to the tumor with the intent of sparing the healthy normal tissues in the pathway of radiation beam. It is given with the help of bronchoscope (a tube with camera that enters through the mouth or nose and reaches the lungs).
It is not a first line, curative, or sole therapy for lung cancer. It may be indicated for the treatment of large tumors that are obstructing airway (usually non-small cell lung cancer [NSCLC]) that are not amenable to surgical resection and/or external beam radiation). Thus, patients with acute life-threatening symptoms of airway obstruction that need immediate relief can be treated with EBBT but only after external beam radiation (EBRT) have been employed to shrink tumor size. EBRT is immediate in effect. In contrast, the effect of EBBT is usually delayed by two to three weeks and the initial response may cause edema and inflammation which can temporarily worsen airway compromise.
- Proton beam therapy
It is used as an alternative to standard radiation. Radiation with protons is associated with superior outcome as compared to standard radiation with photon.
Proton therapy is progressively being introduced in stage III non-small cell lung cancer (NSCLC) treatment but can be given in early stages as well. Protons have many potential advantages over photon therapy, owing to their physical characteristics. Protons precisely deliver powerful radiation dosage to the target tumor matching its shape, volume or depth thus sparing heart, esophagus (food pipe), spine and other structure resulting in higher survival rates and improved quality of life.
It is usually given five days a week. Stage I lung cancer is treated over two weeks with five to 12 sessions. For stage II and III lung cancer, treatment duration is six to seven weeks with 30-35 sessions.
What is Palliative radiotherapy?
Radiotherapy may be used to relieve other symptoms that patient experiences because of spread of cancer to other body parts such as bone pain, blood in sputum, difficulty in breathing and difficulty in swallowing. The aim of palliative radiotherapy is to give maximum relief to cancer patients with minimum side effects in the quickest possible time.
In patients with poor performance status (who are too weak to bear excess of radiation), one or two sessions of radiotherapy give as good result and provide relief to their bothersome symptoms. It is given as a two-week treatment schedule.
In patients of good performance status, but who have disease that is too large for radical radiotherapy, 12–13 treatments of radiotherapy on daily basis give a survival benefit.
Palliative radiotherapy is administered using a simple technique that usually allows the treatment to be delivered on the same day.
Radiotherapy side-effects
Radiation-induced toxicity is related to the volume of normal tissues irradiated. The organs at risk during chest radiation are the spinal cord, lung, esophagus and heart.
Common acute side-effects seen during radiotherapy for lung cancer include:
- Esophagitis (irritation of esophagus)
- Skin irritation (dermatitis)
- Cough
- Fatigue
- Nausea/vomiting
Most are resolved 2–4 weeks after radiotherapy.
Acute pneumonitis can occur 1–6 months after radiation. Most patients have only Xray changes without any clinical symptoms. Clinical symptoms are cough, breathlessness, low blood oxygen and fever. Symptomatic radiation pneumonitis can be treated with corticosteroids after excluding an infection.
Delayed complications include:
- pulmonary fibrosis (shrinkage of lung)
- pericarditis (inflammation of layer around heart)
- pericardial effusion (collection of fluid around heart)
- Heart disease
- esophageal stenosis (narrowing)
- rib fracture
Pulmonary fibrosis usually evolves 6 months to several years after treatment.
Esophageal toxicity is the most common acute toxicity during chest irradiation. While esophagitis can be severe, it is rarely a reason to stop treatment if managed adequately.
Esophageal stenosis is a rare complication.
There are chances of early occurrence of cardiac problems in patients undergoing radiation.
Spinal cord radiation injury is a very rare but serious complication of radiotherapy.
Vertebral and rib fractures may also occur, especially in cases of osteoporosis or long-term steroid treatment.
- Radiotherapy for small cell lung cancer (SCLC)
Small cell lung cancer is basically sensitive to chemotherapy so radiotherapy is either not required or given along with or after chemotherapy.
Patients with limited stage disease (disease confined to one side) are given radiotherapy to the chest disease, with the first or second cycle of chemotherapy. If unfit for combination treatment, chemotherapy is given first followed by radiotherapy.
Patients with extensive disease, including brain involvement, or poorer functional status, chemotherapy is given first. If there is a good response, palliative radiotherapy may be given for relief of other bothersome symptoms just like in non-small cell lung cancer.
Prophylactic cranial irradiation (PCI)
The brain is a common site for spread (metastases) from SCLC, even in patients who have had a good response to chemotherapy. This is because the brain is relatively protected from chemotherapy by the blood-brain barrier. Prophylactic cranial irradiation (PCI), that is basically radiation to brain only, has been proposed as a means to prevent brain metastases in patients who have responded well to chemotherapy. Recent clinical trials have shown that PCI is effective in patients with both limited and extensive-stage SCLC. It substantially reduces the risk of developing brain metastases (spread) and improve survival for patients with SCLC. Prophylactic cranial radiotherapy is advised at completion of chemotherapy. It has no significant role in NSCLC.
PCI is given in 10 sessions over 2 weeks.
Dr. Komal Arshad, Pulmonologist
Dr. Komal Arshad, a graduate of Wah Medical College, is a pulmonologist with 8 years of clinical experience, including 5 years pre-specialization and 3 years post-specialization from Shifa International Hospital Islamabad and Military Hospital Rawalpindi. She is currently practicing at Watim General Hospital, Rawalpindi Pakistan as a classified pulmonologist.
