Overview                                                                   

The lungs are paired organs located within the chest responsible for oxygenating the blood and for dispelling carbon dioxide, a waste product of the body.  Each lung is divided into separate lobes: 3 on the right and 2 of the left.  The left lung is smaller than the right due to the presence of the heart in the chest cavity.

The bronchial tree includes the trachea (windpipe) which brings air into the lungs.  The trachea divides into tubes known as bronchi which in turn further divide into small branches known as bronchioles.  At the end of each bronchiole are air sacs known as alveoli.

Nearly 200,000 lung cancers are diagnosed each year in the United States.  Lung cancer is second only to skin cancer in incidence in this country.  Cancers may arise from any part of the lung.  However, most arise from the bronchi. 

Lung cancers are divided into 2 main types: Small Cell and Non-Small Cell Lung Cancer (NSCLC).  NSCLC is considerably more common, comprising nearly 85% of all newly diagnosed lung cancer cases per year.  NSCLC consists of several subtypes, including adenocarcinoma, squamous cell, large cell and bronchioalveolar carcinoma. 

Lung cancer patients most commonly present with a cough, typically tinged with blood.  Other symptoms and signs may include shortness of breath (particularly on exertion) and weight loss.

Interested in learning more about lung cancer? Check out the American Cancer Society website.

Role of Radiation Therapy                                     

Radiation therapy occupies an important role in the treatment of all types of lung cancer.  In NSCLC patients, RT is commonly delivered in conjunction with surgery, particularly in patients undergoing surgery found to have disease involvement in regional lymph nodes (view paper).  Often such patients are treated with concomitant chemoradiotherapy (view paper).

Radiotherapy may be used alone in patients with early stage lung cancer patients in place of surgery (view paper) or in combination with chemotherapy in patients with locally advanced tumors not amenable to surgery (view paper).

Small cell lung cancers are most commonly treated with a combination of systemic chemotherapy and consolidative chest irradiation (view paper).  In select patients, treatment may also include prophylactic cranial irradiation (PCI) in order to reduce the incidence of disease spread to the brain and improve survival (view paper).

Radiation Therapy Techniques                              

The current standard radiotherapy approach in lung cancer patients is 3D conformal radiation therapy (3DCRT).  Treatment typically includes the lung tumor and regional lymphatics.  A typical treatment course involves parallel opposed treatment beams followed by a boost consisting of oblique (angled) beams.  Oblique beams are used to minimize the dose to the spinal cord.

Example initial opposed field treatment plan in a patient with inoperable NSCLC

4D Computed Tomography/Respiratory Gating              

A concern with the irradiation of lung cancers is that many of these tumors move with respiration.  Motion poses a number of special problems, including problems with accurate target definition (moving targets may appear blurred on CT and larger in size) and increased irradiation of normal tissues (larger fields are often used to ensure that the tumor is not missed).

To improve the visualization of moving tumors, a variety of techniques have been proposed.  One of the simplest is voluntary breath hold, in which the patient holds his or her breath during imaging.  This is often problematic, however, in many lung cancer patients due to poor lung function.

At UCSD, a more sophisticated approach has been implemented known as 4D computed tomography (4DCT) imaging and respiratory gating.  A 4D CT scan is comprised a large number of individual CT scans obtained at various phases of the respiratory cycle. This approach allows the radiation oncologist to watch the movement of the tumor with respiration.  Interestingly, some tumors have considerable movement, others have only minimal movement.  Unfortunately, it is not possible to predict in advance which tumors move and which do not.  Thus, a 4DCT is used to evaluate all patients.

Healthy Volunteer Undergoing a 4DCT Scan.  Note small box on the abdomen with infrared markers and the infrared detector at the bottom of the treatment couch.  Respiration is monitored by the movement of the box and the images are sorted according to the phase of the breathing cycle.

Together with the Medical Physicist, the Radiation Oncologist uses the 4DCT data to decide whether it is best to deliver treatment only at specific phases of breathing (“gated therapy”) or with the patient freely breathing. 

If gated therapy is selected, the physician and physicist must select the proper respiratory phase to deliver treatment.  During treatment the patient’s respiration is monitored and the beam is turned on and off during the phases when tumor movement is minimal.  Using this approach, significant reductions in the volume of normal lung tissue is achieved, potentially reducing the risk of radiation toxicity.

Monitor at Treatment Console in a patient treated with respiratory gating.  The beam is turned on and off automatically based on the breathing cycle of the patient.

At UCSD, respiratory gating is performed using the Varian real-time position management (RPM) system. At simulation, a small “box” is placed on the patient’s chest/upper abdomen.  Specialized cameras as used to monitor the motion of this box during respiration.  This information is used to correlate the position of the lung tumor with specific phases of the respiratory cycle.  At treatment, motion of the box allows the treatment beam to be turned on and off (gating) during specific phases of the breathing cycle.

Hypofractionated Stereotactic Radiosurgery

While traditionally delivered in small daily fractions over multiple weeks, increasing intererest exists today using few large fractions (hypofractionation) in the treatment of early stage lung cancers (see stereotactic body radiosurgery).

The hypofractionated approach has been used successfully in Japan for many years and has only recently been popularized in the United States.  It is an exciting approach given that treatment may be delivered with as few as 3-4 fractions, significantly reducing the need for multiple weeks of radiotherapy.

Stereotactic Radiosurgery plan of a patient with an inoperable stage IA lung cancer.  The prescription dose was 48 Gy delivered with 4 fractions with respiratory gating.

Ask your radiation oncologist whether hypofractionated stereotactic lung radiosurgery is right for you.

UCSD Lung Cancer Team                                                 

The UCSD Lung Cancer Team is comprised of dedicated professional with considerable experience in the treatment of patients with lung cancers. 

Ajay Sandhu M.D. is the Chief of the Lung Cancer Service in the UCSD Department of Radiation Oncology.

Ajay Sandhu, M.D. Chief, Lung Cancer Cancer Service Department of Radiation Oncology

Dr. Sandhu has considerable experience in the treatment of lung cancer patients with the latest radiotherapy techniques including 4D Computerized Tomography (4DCT), respiratory gating and hypofractionated stereotactic body radiosurgery.  

Working with Dr. Sandhu in the Department of Radiation Oncology is Radiation Nurse, Polly Nobiensky, R.N.

Polly Nobiensky, R.N., B.S.N. Radiation Nurse Department of Radiation Oncology

The treatment of lung cancer patients is a team approach. Dr. Sandhu works together with Medical Oncologist, Lyudmila Bazhenova M.D., and Cardiothoracic surgeons, Anthony Perricone, M.D. and Patricia Thistlethwaite, M.D.

Anthony Perricone, MD Cardiothoracic Surgeon

Patricia Thistlethwaite, MD PhD Cardiothoracic Surgeon

Lung Cancer Publications by UCSD Radiation Oncology Faculty         

Listed below are Lung Cancer Articles published by members of the UCSD Department of Radiation Oncology.  For a full list of published articles by UCSD Radiation Oncology faculty see Research section

Mell LK, Malik R, Komaki R, Movsas B, Swann RS, Langer C, Antonadou D, Koukourakis M, Mundt AJ. Effect of amifosine on response rates in locally advanced non-small cell lung cancer patients treated on randomized controlled trails: a meta-analysis. Int J Radiat Oncol Biol Phys 2007;68:111-8

Cui Y, Dy JG, Sharp GC, Alexander B, Jiang SB. Robust fluoroscopic respiratory gating for lung cancer radiotherapy without implanted fiducial markers. Phys Med Biol 2007;52:741

Berbeco RI, Pope CJ, Jiang SB. Measurement of the interplay effect in lung IMRT treatment using EDR2 films. J Appl Clin Med Phys 2006;28:33-42

Berbeco R, Nishioka S, Shirato H, Jiang SB. Residual motion of lung tumors in end-of-inhale repiratory gated radiotherapy based on external surrogates. Med Phys 2006;33:4149

Flampouri S, Jiang SB et al. Estimation of the delivered patient dose in lung IMRT treatment based on deformable registration of 4DCT data and Monte Carlo simulations. Phys Med Biol 2006;51:2763

Jiang SB. Technical aspects of image-guided respiration-gated radiation therapy. Med Dosim 2006;31:141

Neicu T, Berbeco R, Wolfgang J, Jiang SB. Synchronized moving aperture radiation therapy (SMART) improvement of breathing pattern reproducibility using respiratory coaching. Phys Med Biol 2006;51:617

Berbeco RL, Mostafavi H, Sharp GC, Jiang SB. Towards fluoroscopic respiratory gating for lung tumours without radiopaque markers. Phys Med Biol 2005;50:4481

Berbeco RL, Nishioka S, Shirato H, Chen GT, Jiang SB. Residual motion of lung tumours in gated radiotherapy with external respiratory surrogates. Phys Med Biol 2005;50:3655

Shih HA, Jiang SB et al. Internal target volume determined with expansion margins beyond composite gross tumor volume in 3DCRT for lung cancer. Int J Radiat Oncol Biol Phys 2004;60:613

Jiang SB, et al. An experimental investigation on intra-fractonal organ motion effects in lung IMRT treatments. Phys Med Biol 2003;48:1773

Neicu T, Shirato H, Seppenwoolde Y, Jiang SB. Synchronized moving aperture radiation therapy (SMART) average tumour trajectory for lung patients. Phys Med Biol 2003;48:587

Saw CB, Korb LJ, Pawlicki T. Dose volume assessment of high dose rate 192Ir endobronchial implants. Int J Radiat Oncol Biol Phys 1996;34:917

Sibley G, Mundt AJ, et al. Treatment of Stage III Non-Small Cell Lung Cancer Using High Dose Conformal Radiotherapy.  Int  J Radiat  Oncol  Biol  Phys 1995;33:1001