Osteogenic Sarcoma

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What is Osteogenic Sarcoma?

The condition known as osteogenic sarcoma affects the bone of the body. Although a majority of those affected are adolescents and children, this may occur to those who are older than 60 and those who received radiation treatment ^{[1, 2, 3, 4]}.

Figure 1- Osteosarcoma growth in the femur

Osteogenic sarcoma or osteosarcoma is the most frequently occurring type of bone malignancies. It commonly occurs in rapidly growing bones such as the bones of the upper arms, legs, thighs, and the shin. Although its exact cause is unknown, the absence of a tumor-suppressing gene is associated with a higher risk for the development of osteosarcoma. The prognosis for this condition is high especially if the tumor is still confined to its original bone. About 3 out of 4 individuals can be cured if the malignant cells have not spread elsewhere ^{[1, 2, 3, 4]}.

There are 2 major types of bone cells: the osteoblasts and the osteoclasts. The osteoblasts are responsible for the development of the bone matrix which is responsible for bone strength. On the other hand, the primary role of osteoclasts is to break down bone matrix to prevent its build up and maintain the shape of the bone.

The cancer cells of osteogenic sarcoma function the same as osteoblasts. These cells form the bone matrix which is not as strong as the ones formed by normal osteoblasts ^[1]. The sarcoma usually develops in areas where there is rapid bone growth such as the near the ends of the distal femur, proximal tibia, and proximal humerus. It also develops in the pelvis, jaw, and shoulders. Figure 1 shows an osteosarcoma growth in the femur ^{[1, 2, 3, 4]}.

Risk Factors

The presence of risk factors in an individual may increase the likelihood of an individual in developing osteosarcoma. The risk factors are different for different types of malignancies. Lifestyle-related risk factors have not been associated with osteosarcoma ^[1].

Age

Individuals who are between 10 and 30 have the biggest risk for developing osteosarcoma. This is probably due to the fact that this is a period of rapid bone growth. The risk decreases after this period but increases again after the age of 60. Development of osteosarcoma at this age is more related to the presence of another bone condition ^[1].

Gender

The condition is more common in males than in females. The female patient develops this at an earlier age because the growth spurt occurs earlier ^[1].

Radiation to bones

Patients who received radiation therapy for another condition have an increased likelihood of developing osteosarcoma. Undergoing radiation therapy at an early age and receiving a high dose of radiation further increases the risk of this malignancy ^[1].

Bone diseases

Having specific non-cancerous bone conditions may increase the possibility of having osteosarcoma at a later age. In the medical condition known as Paget disease of the bone, abnormal bone formations develop in one or more bones. The one who most commonly develops this is those who are more than 50 years of age. Osteosarcoma develops in about 1% of individuals who have Paget disease of the bone ^[1].

Subtypes

There 3 subtypes of osteogenic sarcoma and are classified depending on their appearance on x-rays and how a tissue sample appear under a microscope. Knowing the type of osteosarcoma will be helpful in identifying the stage of the malignancy and the treatment it requires ^[1].

High-grade

This is the fastest growing variety and most sarcomas found in children and adolescents are of this type. When a sample of high-grade osteosarcoma is viewed under a microscope, the cells are barely recognizable from normal bone cells. A number of cells are seen to be in the process of dividing into new cells ^[1].

Intermediate

An intermediate-grade osteosarcoma contains both the characteristics of high-grade and low-grade sarcoma. This is an uncommon type of sarcoma and is treated as a low-grade when identified on a patient ^[1].

Low-grade

An osteosarcoma of this type grows the slowest compared to the other 2. When viewed under a microscope, its cells look more similar to normal bone cells and only a few cells are dividing when it is viewed under a microscope ^[1].

TNM Classification

The TNM classification assesses the primary tumor (T), regional lymph nodes (N), and distant metastasis (M) of a tumor growth. This will become the basis for the staging and treatment protocol of the malignancy ^{[1, 5]}.

Primary Tumor

TX	The primary tumor cannot be assessed
T0	There is no evidence of the primary tumor
T1	The tumor is less than 8cm at its widest
T2	The tumor is more than 8cm at its widest
T3	There are discontinuous tumor in the primary bone site

Regional lymph nodes

NX	The regional lymph nodes cannot be assessed
N0	There are no metastasis in the regional lymph nodes
N1	Metastasis is present in the regional lymph nodes

Distant Metastasis

MX	The presence of distant metastasis cannot be assessed
M0	There are no distant metastasis present
M1a	Metastasis is present in the lungs
M1b	Other distant sites of metastasis are present

Histologic grade

GX	The histologic grade cannot be assessed
G1	The cells are well differentiated – low grade
G2	The cells moderately differentiated – low grade
G3	The cells are poorly differentiated
G4	The cells are undifferentiated

Staging

Stage	T	N	M	Grade
I-A	T1	N0	M0	G1,2 low grade, GX
I-B	T2	N0	M0	G1,2 low grade, GX
	T3	N0	M0	G1,2 low grade, GX
II-A	T1	N0	M0	G3,4 high grade
II-B	T2	N0	M0	G3,4 high grade
III	T3	N0	M0	G3
IV-A	Any T	N0	M1a	Any G
IV-B	Any T	N1	Any M	Any G
IV-B	Any T	Any N	M1b	Any G

Signs & Symptoms

Because of the nature of this condition, the presence of the malignancy is initially discovered because of the signs and symptoms that it causes ^{[1, 2, 3, 4]}.

Pain

The most common symptom reported by patients with osteosarcoma is the presence of pain in the affected bone. The pain that felt may be constant throughout the day but it can worsen at night. It may also increase the performance of activity. The patient may also limp if one of the leg bones is affected ^{[1, 2, 3, 4]}.

Swelling

After several weeks of feeling pain, there will be swelling in the affected area. If the bones of the arm or legs are involved, it may be possible to feel the lump or mass. Upon inspection, the muscles of the cancerous arm or leg may appear to be smaller than the opposite extremity ^{[1, 2, 3, 4]}.

Other symptoms

The patient may also report a reduction in the range of motion because of the presence of the bone growth. Bone fractures may occur to a rare type of osteosarcoma.

A telangiectatic osteosarcoma weakens the bone that is affected and makes it more prone to fractures. Individuals who have a fracture may report the limb to be swelling for several weeks and have become very painful after the fracture ^{[1, 2, 3, 4]}.

Diagnosis

Medical history and physical examination

The most common reason for a consultation is the presence of pain in the affected bone. Because pain is a general symptom, it can also be a cause of a delay in diagnosing osteogenic sarcoma.

The physician will get more information about the pain such as the date it started, any factors that may aggravate the pain, and what can provide relief to the pain. The presence of risk factors may be identified as well to help in establishing the diagnosis ^{[1, 2, 4]}.

After eliciting the history, the physician will perform a physical examination. The affected area may be palpated to attempt to feel for the mass. Other parts of the body will also be checked to identify any other symptoms that may be present ^{[1, 2, 4]}.

An x-ray is the first test that the physician will order if an osteogenic sarcoma is suspected. The x-ray will be able to pick-up any abnormal bone growth in the affected bone ^{[1, 2, 4]}.

Figure 2 – osteosarcoma x ray hand

Although the results of the x-ray will be able to show the osteosarcoma, the physician may order a Magnetic Resonance Imaging (MRI) scan to have a more detailed view of the tumor. It will be able to show the full extent of the condition by showing the condition of the marrow inside the affected bone and the condition the soft tissues surrounding the tumor. The MRI will also provide information if the tumor has metastasized to other parts of the body ^{[1, 2, 4]}.

A bone scan may also be performed to patients who have osteosarcoma. This imaging test will be able to provide a visualization of the whole skeleton at once and will be able to tell if the sarcoma has spread to other bones in the body ^{[1, 2, 4]}.

Figure 3 – Osteosarcoma sunburst appearance

Biopsy

Performing a biopsy is considered the gold standard in establishing the diagnosis of osteogenic sarcoma because it will be able to differentiate this condition to other types of cancer of the bones. There are 2 types of biopsies that can be performed: the needle biopsy and an open biopsy ^{[1, 2, 4]}.

In a needle biopsy, a hollow needle is used to obtain a small sample of the tumor. Because there is no incision that will be made, this procedure may be done under local anesthesia. If an open biopsy is done, the surgeon will have to make an incision to expose the tumor before a sample of the tumor is taken. The patient may have to be under general or regional anesthesia for this procedure ^{[1, 2, 4]}.

The tumor samples will then be sent to a pathologist for examination. The result of the biopsy will indicate the grade and the stage of the tumor ^{[1, 2, 4]}.

Treatment

The treatment that the patient will receive will depend on the stage, size, location, and position of the tumor. In most cases, chemotherapy and surgery are effective to cure the patient of osteogenic sarcoma. Radiation is rarely used but may be needed if the tumor can’t be removed by surgery ^{[1, 2, 3, 5, 6]}

Chemotherapy

Chemotherapy utilizes antineoplastic medications to help in shrinking and killing the cancer cells. This is usually done before performing a surgical procedure to reduce the size of the tumor. The duration of the treatment would depend if cancer has spread to other parts of the body. Once the chemotherapy is finished, a surgical may be performed to remove the remaining tumor in the body ^{[1, 2, 3, 5, 6]}.

Surgery

The type of surgical procedure that will be performed depends on the size and position of the tumor. The surgery may entail removal of a portion of the bone and be replaced with a prosthesis if required^{[2, 3]}. This type of surgical procedure is known as limb-sparing surgery.

If the malignancy has affected the surrounding nerves and blood vessels, there may be a need to perform an amputation or removal of the affected limb. The patient will then be fitted with a prosthetic in order to be able to perform activities of daily living ^[3]. A chemotherapy may be prescribed after the surgical procedure to remove microscopic cancer cells that may be left behind ^{[1, 2, 3, 5, 6]}.

Recurrence

Osteogenic sarcoma may recur even after the completion of the treatment protocol. There is a need for follow-ups with the physician to identify the development of new tumors ^{[2, 3]}.

References

American Cancer Society. (2014, April 18). About Osteosarcoma. https://www.cancer.org/cancer/osteosarcoma/about/what-is-osteosarcoma.html
Higuera, V. (2016, January 4). Osteosarcoma. http://www.healthline.com/health/osteosarcoma#Overview1
The Sidney Kimmel Comprehensive Cancer Center. (2016). Retrieved from Johns Hopkins Medicine.
Picci, P. (2007). Osteosarcoma (Osteogenic sarcoma). Orphanet Journal of Rare Diseases.
Choy, E. (2015, December 31). Osteogenic Sarcoma Staging. Retrieved from Medscape: http://emedicine.medscape.com/article/2007306-overview
Choy, E. (2016, February 10). Osteogenic Sarcoma Treatment Protocols. Retrieved from Medscape: http://emedicine.medscape.com/article/2006667

Osteogenic Sarcoma

What is Osteogenic Sarcoma?

Risk Factors