Cancer Committee Chairman: Suresh Katakkar, M.D.
Tumor Board: Suresh Katakkar, M.D.
Clinical Lecturer, Medicine
MB/BS
Radiation therapy can also cause spontaneous pneumothorax,
mesothelioma, and lung cancer. In the mediastinum, radiation
therapy may cause thymic cysts, calcified lymph nodes, and esophageal
injuries.
Cardiovascular complications of radiation therapy are often
delayed and insidious. Premature coronary artery stenosis
occurs after radiation therapy to the mediastinum. Radiation
therapy may also give rise to calcifications of the ascending
aorta, pericardial disease, valvular injuries, and conduction
abnormalities. Women who undergo thoracic irradiation before
the age of 30 years have a high risk of developing a second
breast cancer. Radiation-induced sarcomas are an infrequent
but well-recognized complication of radiation therapy. Other
chest wall injuries due to radiation therapy are osteochondroma
and rib or clavicle fractures. Knowledge of the imaging features
of injuries caused by radiation therapy can prevent
misinterpretation as recurrent tumor and may facilitate
further treatment.
Vascular Injuries
Radiation-induced vasculopathy usually occurs after a lapse
of about 10 years (
39).
Radiation injuries within the vascular
tree most often affect
the capillaries, sinusoids, small arteries,
veins, and large
arteries (
8).
When major damage (eg, thrombosis
or rupture) is sustained by
an elastic artery, the damage tends
to be clinically
significant (
40,
41).
The only differentiating
feature from radiation arteritis is
that radiation-induced vasculopathy
is limited to the
radiation field. Stenoses and occlusions are
more frequently
reported than are perforations and pseudoaneurysms
(
42).
Arterial bleeding from a radiation ulcer is potentially
more
life threatening (
43).
Mediastinal fibrosis produces obliteration
of normal fat
planes and anatomic landmarks, which is responsible
for
distortion and stricture of normal vessels (
Figs
5,
6).
Lung fibrosis: Lung fibrosis and difficulty breathing are
significant late complications following radiation treatment for
Hodgkin?s disease and other cancers requiring radiation to the lungs. In
one clinical study of 36 patients with stage I-IIA Hodgkin?s lymphoma
treated with radiation therapy, a decrease in lung function was noted in
all patients. However, this decrease in lung function appeared to
improve over time and was thought to be reversible.
Heart disease is also a late complication of radiation to the
mediastinum. In one group of 157 patients receiving primary treatment
with radiation to the mediastinum, 8.3% died of heart disease, which was
5 times what would have been expected for this age group. The risk of
heart disease is associated with higher radiation doses and larger field
sizes.
Breast Cancer.—Tangential beam radiation
portals are frequently
used to treat patients with breast
cancer. Typically, a 1.5–3-cm
strip of underlying
peripheral lung is included in the irradiated
volume.
Radiation pneumonitis or fibrosis occurs at the peripheral
lung anterolaterally, has a characteristic shape, and is better
visualized at CT than at chest radiography (
13,
21)
(
Fig
10).
The supraclavicular portal is generally positioned
with the
inferior border at the first or second intercostal
space. When
supraclavicular portals are used,
radiation-induced change occurs
in the apex of the lung; the
resulting lesions are similar to
those seen in pulmonary
tuberculosis (
Fig
10). Internal mammary
lymph nodes are irradiated with an
anteroposterior or oblique
beam angle to match the medial
tangential beam portal, resulting
in paramediastinal lung
changes (
13)
(
Fig
11).
.