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1 All authors: Department of Radiology, Emory University Hospital, 1364 Clifton Rd. NE, Rm. D125A, Atlanta, GA 30322.
Received April 25, 2008;
accepted after revision April 25, 2008.
Address correspondence to S. M. Sabourin
(ssabour{at}emory.edu).
Abstract
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Keywords: head and neck imaging • postirradiation • oncology • osteosarcoma
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| QUESTION 1 All of the following are TRUE regarding postirradiation
sarcoma EXCEPT:
QUESTION 2 Familial retinoblastoma is associated with all of the following second malignant neoplasms EXCEPT:
QUESTION 3 Clinical syndromes and preexisting bone lesions associated with the development of osteosarcoma include all of the following EXCEPT:
QUESTION 4 The most typical radiographic finding of postirradiation osteosarcoma is:
QUESTION 5 Which of the following is TRUE regarding secondary osteosarcomas?
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Solution to Question 1
Lower doses at the periphery of the irradiation portal can result in damage
to the reparative mechanisms without cell death, putting these regions at
highest risk for malignant transformation
[1,
2]. Option A, which is true, is
not the best response. To some degree, improved health care has likely
contributed to patients who receive radiation therapy living long enough to
experience the oncogenic effects of irradiation, and the relative risk of this
type of complication increases with time
[1,
2]. Approximately 80–90%
of postirradiation sarcoma arises in the bone
[1,
2]. Option C, which is true, is
not the best response. Radiologic imaging features alone cannot distinguish
between primary and secondary osteosarcoma. The need for an appropriate
clinical and radiation therapy history is thus a necessity
[1,
2]. Option D, which is true, is
not the best response. Threshold doses have been reported below which
postirradiation sarcoma is said to be negligible—that is, less than 10
Gy of radiation [1,
2]. Option E, which is true, is
not the best response. Two published case review series of postirradiation
sarcomas found a mean latency period of 14.5–15.5 years, a range of
3–65 years after treatment
[1,
2]. Option B, which is not
true, is the best response.
Solution to Question 2
Familial retinoblastoma is associated with multiple second malignant
neoplasms, the most common of which is osteosarcoma. For survivors of
bilateral retinoblastoma, it has been suggested that the cumulative lifetime
risk of developing a second malignant neoplasm is 32%
[3]. Abramson et al.
[3] found that in children who
had received radiation therapy for bilateral or familial unilateral
retinoblastoma, 30% of second malignant neoplasms occurred outside the field
of radiation. Other second malignant neoplasms include melanoma,
rhabdomyosarcoma, malignant fibrous histiocytoma, Ewing's sarcoma, and brain
tumors
[4–7].
Renal cell carcinoma is not regarded as an associated second malignant
neoplasm. Option D is the best response.
Solution to Question 3
Many preexisting benign bone lesions and clinical syndromes have been
associated with an increased risk for developing osteosarcoma. By far, the
most common preexisting lesion is Paget's disease
[8]. Other less common
preexisting bone lesions include fibrous dysplasia, chronic osteomyelitis,
metallic implants, and bone infarction
[8]. Options B and E, which are
associated, are not the correct responses. The association of familial
retinoblastoma with osteosarcoma is well documented
[4–10].
Other less common syndromes include Li-Fraumeni syndrome, Rothmund-Thomson
syndrome, and Werner's syndrome
[11–13].
Options A and D, which are associated, are not the correct responses.
Rothmund-Thomson syndrome and Werner's syndrome are a result of faulty
helicase proteins that predispose cells to faulty DNA replication
[11]. Familial retinoblastoma
and Li-Fraumeni syndrome predispose patients to osteosarcoma by way of faulty
tumor suppression genes—the retinoblastoma gene on chromosome 13q and
p53 on chromosome 17p, respectively
[12,
14,
15]. Achondroplasia is not
associated with osteosarcoma. Option C, which is not associated, is the
best response.
Solution to Question 4
The most typical radiographic finding of secondary osteosarcoma is a
soft-tissue extension of the tumor
[1,
8,
9]. A study by Lee et al.
[9] evaluated the
characteristics of 46 de novo and secondary craniofacial osteosarcomas and
found that all cases had soft-tissue extension of tumor. Option C is the
best response.Their findings also showed tumor matrix mineralization
occurs in 75% of cases, with osteoid matrix calcification occurring most
frequently [9]. Option A is not
the best response. Periosteal reaction is not typically seen; the lesions
usually show a long zone of transition
[9]. Options B and E are not
the best responses. Most postirradiation craniofacial osteosarcomas are
osteolytic with the exception of those occurring in the mandible, which can be
osteoblastic in approximately 50% of the cases
[9]. Option D is not the best
response.
Solution to Question 5
Radical surgical excision is usually the only hope for long-term survival
[2,
4]. Option B is not the best
response. Osteosarcomas are typically composed of high-grade malignant cells
and have a poor 5- to 10-year survival rate
[8]. Options C and D are not
the best responses. Radiographically, an underlying condition in combination
with osteosarcoma may be discernable, suggesting sarcomatous malignant
transformation [1,
2,
8]. Option E is not the best
response. Secondary osteosarcoma transformation has been shown to occur with
increased frequency in the setting of underlying pagetoid bone, with a much
higher incidence of occurrence in patients with the severe polyostotic form of
the disease [8,
16,
17]. Option A is the best
response.
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