April 18, 2013

Today, we will be discussing the aspects of lung cancer.

• Lung cancer

1.      It is the most common invasive malignancy in the USA.

2.      What are the structures of respiration from large to very small?  Trachea, primary bronchi, secondary and tertiary bronchi, bronchioles, terminal bronchioles, and alveolar sacs.

3.      Squamous cell (epidermoid) carcinoma is usually associated with tobacco, and occurs most frequently in men, and often located centrally in proximal bronchi.

4.      There has been a recent rise in adenocarcinoma, occurs most often in women, and more peripherally located, arising in bronchioles or alveoli.

5.      Small cell occurs more centrally.

6.      Large cell more peripherally.

7.      Many patients with lung cancer will have other disease processes within the lung at the same time (i.e. emphysema, COPD, asthma, bronchitis, TB, etc.).

8.      Incidence rates of lung cancer in men has been dropping over the past decade while incidence rates for women have risen over the past decade.

9.      The greatest risk for lung cancer is smoking a lot of cigarettes 2 or more packs per day.

• Types of lung cancer

1.      Small cell lung cancer (oat cell) is aptly named for its physiological property – these are much smaller cells.

2.      About 85-90% of lung cancers are non-small cell lung cancer (NSCLC).

3.      Three main subtypes of NSCLC are adenocarcinoma, squamous cell carcinoma, and large cell carcinoma.

• Treatment considerations

1.      Surgery – only 20% of all patients with lung cancer may be considered candidates for surgery; of those up to 90% may be respectable.

2.      Combination radiation and chemo represents the standard of care for patients with local residual disease postoperatively or for unresectable disease.

3.      Current standard therapy would include concurrent, sequential, or alternating chemo and radiation, using radiation tumor doses between 4500-5400cGy at 180-200cGy per fraction, one fraction per day and five fractions per week.

• Palliative considerations

1.      Palliative radiation is common for bone and brain metastases.

2.      Skeletal pain can be relieved for extended periods of time in up to 90% of patients treated.

3.      Doses between 3000-4000cGy in 200-300cGy daily dose fractions are enough for pain relief and bone healing.

4.      Radiation doses of 3000-4000cGy in 10-15 fractions produce symptomatic relief in 35-75% of patients with brain metastases.

5.      Which type of lung cancer commonly metastasizes to the brain?  Small cell metastasizes to the brain frequently.  A prophylactic dose of radiation is given to the brain immediately upon diagnosis of oat cell lung cancer.

• Treatment planning:  critical structures

1.      What are the critical structures?  The healthy lung, heart, and spinal cord.

2.      Remaining under the spinal cord dose tolerance is especially important when large treatment fields are used and multiple vertebral segments are exposed.

3.      When 60% or more of the heart is treated with 4500-5500 cGy, pericarditis and pancarditis may result and long-term complications can follow

4.      What is pericarditis? Pancarditis?  Pericarditis is the inflammation of the sac surrounding the heart, the pericardium.  Pancarditis is the inflammation of the whole heart, the epicardium, myocardium and the endocardium.

• Side effects (complications are not the same as side effects; complications usually result from doses that exceed organ tolerance).

1.      Acute

a.       Dermatitis, erythemaa, & esophagitis.

b.      Dyshagia (at approximately 3000cGy).

2.      Chronic

a.       Dry, nonproductive cough.

b.      Fibrosis of lungs.

c.       Subcutaneous fibrosis of skin.

• Complications

1.      Major complications from exceeding dose limits to normal lung are radiation pneumonitis and fibrosis.

a.       Pneumonitis occurs from 1-3 months after radiation.

b.      Pneumonitis is a general inflammation of the lung.

c.       Fibrosis occurs 2-4 months after radiation.

d.      Fibrosis of the lung is scarred lung tissue.

·        Treatment planning:  fields

1.      Parallel opposed fields

2.      AP/PA fields are designed to include the primary tumor volume or clinical target volume with a 2.0-2.5cm margin of apparently normal tissue (planning target volume).

3.      Definition of tumor volume should be obtained before chemotherapy is initiated.

4.      Boost fields are generally to the GTV only.

5.      What is the GTV?  It is the palpable tumor mass, gross tumor volume.

·        Treatment planning:  special considerations

1.      Because patients with bronchogenic cancers typically have compromised pulmonary function before radiation therapy begins, the use of progressively reduced field sizes becomes even more necessary with these patients.

2.      Accurate patient positioning is most essential.

3.      Of critical importance is arm position with off-cord boosts because the probability of the patient rolling to one side or the other increases if the arms are raised above the head.

4.      Orthogonal images are taken to determine cord depth (anterior and lateral films of thorax taken at right angles).

5.      Spinal depth varies along the cord, and dose varies with depth, creating a complex dosimetric issue.

6.      Also patients with scoliosis (excessive curvature of the spine) require special attention to beam customization and field shape.

7.      When parallel opposed beams are weighted anteriorly to reduce the spinal cord dose, the dose to which structure should also be measured so tolerance isn’t exceeded?  The heart should be monitored to keep it safe.

8.      Chemo drugs such as doxorubicin (Adriamycin) have cardiac toxicity that has a synergistic effect when the drug is used in combination with radiation.

9.      Large volumes of lung are projected to have at least a 50% complication rate at 3000cGy.

• Doses

1.      Doses to control or cure localized small cell lung cancer range from 4500-5400cGy at 180-200cGy per fraction.

2.      Doses to control or cure localized non small cell lung cancer range from 6000-7500cGy at 180-200cGy per fraction.

3.      Doses may be reduced when chemo is happening at the same time.

4.      Total dose varies depending on the intent of therapy. 

5.      Intended curative treatments are typically higher doses and more complex field arrangements.

6.      Intended palliative treatments generally have the option of lower total doses, shorter courses, and simpler field arrangements.

7.      Doses to control or cure bronchogenic carcinomas range from 6000-7500cGy.

8.      Initial fields are generally dosed to 4000-4500cGy with boost fields following in various combinations.

9.      Dose to relieve airway obstruction ranges from 4000-5000cGy.

• Dose calculations

1.      How do you calculate the course of a treatment plan when you have the total dose and daily fractionation? 

2.      If the dose has a range, take the lowest total dose, divided by the highest possible fractionation, divided by 5 (days/tx per week) – this gives the fastest time frame. 

3.      Then take the highest total dose, divided by the smallest possible fractionation, divided by 5 – this gives the longest possible time frame. 

4.      Ex. Small cell has total dose of 4500-5400 cGy with 180-200 per fraction at 5 days a week. This dose has a possible treatment course of 4.5 to 6 weeks.

http://www.cccnevada.com/medical-services/cyberknife-radiosurgery/
I'm not sure if I should put this with lung cancer or breast cancer, but because the cyberknife treated the cancer in the lung and not in the breast I am inclined to post it here.
This a link to a video of a woman who had a triple negative breast cancer (there are no receptors on the cancer to do hormone therapy) that went into remission and then popped up in her lung as a 1cm tumor.  The cyberknife was able to target the tumor very precisely with 137 different angles.  The cyberknife was able to destroy the metastasized tumor; she had been cancer free for seven months.  If she makes it to the five year mark, she will be the first triple negative breast cancer patient to live that long.