What is Bone Cancer (Tumor)?
The skeletal system provides the framework to our body, which is made up of bones and associated cartilages, ligaments, and tendons. The bones are composed of various tissues such as osseous tissue, cartilage, dense connective tissue, epithelium, adipose tissue, and nervous tissue. The osseous (bone) tissue is composed of dense extracellular matrix embedded with widely separated cells. Depending upon density bones tissue is of two types – the compact bone tissue (present on the outer side of bones) and spongy bone tissue (forms the inner part).
Periosteum is a double layer of dense connective tissue that covers the outer surface of bones. Most bones are hollow and the inner hollow cavity of bones is called as the medullary cavity that contains less dense spongy bone tissue and bone marrow. Endosteum is a single layer of connective tissue lining the medullary cavity.
Bone is a common site of metastasis (secondary cancer spread to bone from other primary cancer) for certain cancers like breast cancer, prostate cancer, and lung cancer. Primary bone tumors (that starts in bone tissue and spread to other tissues) are less common than secondary bone cancers. In contrast to other cancer types, it is more common at a younger age with highest incidences observed in individuals aged less than 20 years.
Treatment of Bone Tumors based on Tumor Type
The bone cancer treatment options depend on many factors including but not limited to the type of bone cancer, stage of the disease, location of the cancer, performance status of the patient, patient’s preference, along with other factors.
It mostly starts in osseous tissue, and it is the most common (about 35% of all cases) primary bone cancer, which mostly affects individuals aged between 10 and 30 years. It is more common in men than women.
It has mainly 3 histological subtypes: intramedullary (most common subtype), surface, and extra-skeletal. Long bones of legs and arms are the most common site for these types of cancers.
In patients with localized osteosarcoma, surgery involving wide excision (either limb-sparing or amputation) is considered as the preferred treatment. Chemotherapy is recommended before and after surgery. For patients with metastatic osteosarcoma, chemotherapy is the mainstay of treatment. Rarely, surgical resection of primary and metastatic site may be done if the metastatic disease is completely resectable, as assessed by the surgeon.
It starts in cartilage tissue, and it is the second most common (about 30% of all cases) primary bone cancer, which mostly affects individuals aged above 20 years.
It has mainly following 5 subtypes: conventional (most common subtype), clear cell, dedifferentiated, myxoid, and mesenchymal. The pelvis and proximal femur are the most common site affected by these types of bone cancers.
In patients with resectable chondrosarcoma, surgery involving wide excision (either limb-sparing or amputation) or intralesional excision is considered the preferred treatment approach. Chemotherapy may be added before and/or after surgery. For patients with unresectable chondrosarcoma at an unfavorable location such as the base of the skull or in the spine, radiotherapy is employed as the preferred treatment approach.
The actual tissue of origin for Ewing sarcoma is unknown. It is the third most common (about 16% of all cases) primary bone cancer, which mostly affects youngsters and teenagers. Ewing sarcoma is more common in white people compared to African Americans and Asian Americans. The characteristic feature of Ewing sarcoma includes fusion of EWS gene on chromosome 22q12 with ETS family genes and expression of CD99 surface glycoproteins. Long bones of legs, pelvis bones, and bones of the chest wall are the most common site for Ewing sarcoma.
Patients with localized Ewing sarcoma are usually treated with chemotherapy as first-line treatment. This is followed by local control therapy including surgery or radiotherapy depending upon the resectability and site of cancer. This is usually followed by chemotherapy. For patients with metastatic Ewing’s sarcoma, chemotherapy is the mainstay of treatment. Rarely, surgical resection of primary and surgery/radiotherapy of metastatic site may be done if possible, as assessed by the oncologist.
It starts in osseous tissue and may involve cartilage tissue, and it mostly affects individuals aged above 30 years. It has mainly following 3 subtypes: conventional (most common subtype), chondroid, and dedifferentiated. The base of skull, spine, and sacrum are the most common sites affected by these types of bone cancers. They tend to grow slowly and usually recur after treatment.
In patients with resectable chordoma, surgery involving wide excision with/without radiotherapy is considered the preferred treatment approach. For patients with unresectable chordoma, radiotherapy or targeted therapy is employed as the first-line treatment approach.
Undifferentiated pleomorphic sarcoma (UPS)
It is also known as malignant fibrous histiocytoma (MFH). It usually starts in soft tissues associated with bones (connective tissues such as ligaments, tendons, fat, and muscle). It mostly affects middle-aged and elderly individuals. Long bones of legs and arms are the most common site affected by this type of bone cancer. It may be present as a low-grade or as a high-grade variant.
In patients with localized UPS, surgery involving wide excision (either limb-sparing or amputation) is considered as the preferred treatment. Chemotherapy is recommended before and after surgery. For patients with metastatic UPS, chemotherapy is the mainstay of treatment. Rarely, surgical resection of primary and metastatic site may be done if the metastatic disease is completely resectable, as assessed by the surgeon.
Giant cell tumor of bone
It may be present as a benign or malignant form with benign subtype being more common. It mostly affects middle-aged (20 to 40 years) individuals. Long bones in legs (usually near the knee) are the most common site affected by this type of bone cancer. They generally recur multiple times after treatment with increases aggressiveness after each recurrence.
In patients with localized GCTBs, surgery involving wide excision, intralesional excision, or curettage with/without bone cement is considered the preferred treatment approach. For patients with unresectable GCTBs, radiotherapy or targeted therapy may be employed as the first-line treatment approach.
Types of Surgery for Bone Tumors
Surgery is considered the treatment of choice for almost all bone cancer. Surgery may also be employed to collect biopsy sample. The main goal of surgery is to remove all cancerous tissue. Thus, cancerous tissue along with some nearby normal tissue is usually removed to obtain margin negative for cancer cells. This is known as wide-excision.
Surgery may also be employed in some cases of metastatic disease where complete removal of metastatic cancer tissue is possible. Following are some common surgical procedures carried out for bone cancer treatment:
In this surgery, all the tissue containing cancer and some of the nearby tissue is removed leaving the working limb (an arm or a leg) in place. This is generally possible in case of early-stage disease where the tumor is limited to a part of bone (not affecting nearby nerves and blood vessels) and the part can be replaced with an endo-prosthetic device (prosthetic device that joins two ends of the same bone or of different bones) or the bone ends can be joined together without the requirement of a prosthesis.
In this surgical procedure, the entire limb or a part of a limb is removed leaving behind a shorter limb without or with very little function. This is generally performed when limb-sparing surgery is not possible, for example, in case of a tumor that has invaded nearby nerves, or blood vessels, which required these tissues to be removed during the surgery. A prosthesis may be attached to the amputated limb which may impart some function (depending upon the extent of amputation) with proper rehabilitation.
In this surgical procedure, a limb is partially reconstructed to restore/maintain functionality even when a part of a limb is required to be removed. For example, if the bones from the mid-thigh including the knee joint are required to be removed, the lower leg and foot can be rotated and attached to the thigh bone in a way that the ankle joint work as a new knee joint. This procedure is known as rotationplasty.
In this surgical procedure, the cancerous bone tissue is removed by scraping and leaving behind the normal bone of the original size. However, a cavity or a hole is created in the treated bone. The cavity/hole can be filled with a bone cement (a chemical substance – polymethylmethyacrylate that hardens to fill the cavity in a bone). This procedure also helps in killing any remaining cancer cells because the bone cement releases a lot of heat while hardening.