- What Are Sarcomas?
The term sarcoma comes from the Greek ‘sarx’ meaning “flesh”. It is a general term describing group of devastating malignant neoplasms, or cancers, that arises from transformed connective tissue cells such as bone, cartilage, and fat cells, which originate from the embryonic mesenchymal cells.
Because these tissues are found everywhere on the body, sarcomas can arise anywhere and are frequently hidden deep in the limbs (which is where majority of the body’s connective tissue is), with the tendency to present late due to vague symptoms. Sarcomas account for 15-20% of childhood cancer diagnoses and about 1% of adult cancer diagnoses.
They can also occur in places where cancers of epithelial origin (carcinomas) are more common, and hence present as an occasional surprise to pathologists. They can present as breast sarcomas, ovarian sarcomas, uterine sarcomas, lung sarcomas and stomach sarcomas.
Although relatively rare, Sarcomas contribute disproportionately to cancer burden in our community, as they mostly affect the young. They are also the most aggressive primary cancers with an overall 50 per cent mortality or survival rate at five years.
Sarcoma are rare by the prolific standards of the most common cancers including breast and prostate and hence have trouble attracting research funding from governments to find a cure with such small patient numbers.
- How Do Patients Get Followed Up?
There are no published data to indicate the optimal routine follow up policy of surgically treated patients with localized disease.
The malignancy grade affects the likelyhood and speed at which relapses takes place. The risk assessment based on tumour grade, size and tumour site therefore helps in choosing a routine follow-up policy. Tumours less than 5cm have a much better prognosis, and hence the importance of EARLY diagnosis and intervention.
High risk patients generally relapse within 2-3 years, while low risk patients may relapse later, although it is less likely. Relapses most often occur in the lungs for soft tissue sarcomas, and not necessarily at the primary site.
Early detection of local or metastatic recurrence to the lungs may have prognostic implications, since lung metastases are generally asymptomatic at a stage in which they are suitable for surgery. Routine follow up therefore focus on these sites. MRI is generally use to follow up local relapse and CT scan for lung metastases.
A practical approach in several institutions is as follows: The surgically treated intermediate/ -high grade patient may be followed up every 3-4 months in the 2-3 years, then twice a year up to the fifth year and once a year thereafter. Low -grade sarcoma patients may be followed for local relapse every 4-6 months, with chest X-rays or CT scan at more relaxed intervals in the first 3-5 years, then yearly.
- What Are The Classfication Of Sarcomas?
There are many different types of Sarcomas, which are classified according to the primary affected tissue. These include soft tissue sarcomas and bone sarcomas (cartilage sarcomas although not strictly bone are classified with the bone sarcomas).
Although the list is not exhaustive, bone sarcomas include; osteosarcoma (bone), chondrosarcoma (cartilage) and Ewings sarcoms (immature nerve tissue, usually in bone marrow)
Soft tissue sarcomas include; liposarcoma (fat), fibrosarcoma (connective tissue), angiosarcoma (blood vessels), leiomyosarcoma (smooth muscle), rhabdomyosarcoma (skeletal muscle), lymphangiosarcoma (lymph vessles), neurofibrosarcoma (peripheral nerves) synovial sarcoma (synovial tissue). Kaposi sarcoma which is common in immunospressed patients is not a true sarcoma in that it is of epithelial origin.
In addition to being named based on the tissue of origin, sarcomas are also assigned a grade (low, intermediate, or high) based on defined pathological characteristics Low grade sarcomas are usually treated surgically, although sometimes radiation therapy or chemotherapy are used. Intermediate and high grade sarcomas are more frequently treated with a combination of surgery, chemotherapy and/or radiation therapy Since higher grade tumors are more likely to undergo metastasis (invasion and spread to regional and distant sites), they are treated more aggressively. The recognition that some sarcomas are sensitive to chemotherapy improved the survival of some patients. For example, in the era before chemotherapy, long term survival for patients with localized osteosarcoma was only approximately 20%, but now has risen to 60-70%.
- What Are The Risk Factors?
Scientists do not fully understand why some people develop sarcomas while the vast majority do not. However, by identifying common characteristics in groups with unusually high occurrence rates, researchers have been able to single out some factors that may play a role in causing sarcomas.
Osteosarcoms, being the most frequent primary cancer of bone, has its highest incidence in adolescents, where it accounts for 10% of all solid cancers. Risk factors associated with the occurrence of osteosarcomas include, previous radiation therapy, Paget’s disease of the bone and inherited germ line abnormalities such as the Li-Fraumeni syndrome, Werner syndrome, Rothmund-Thomson syndrome, Bloom syndrome and hereditary retinoblastoma.
Ewings sarcoma (ES) is the second most common primary malignant bone cancer, which occurs most frequently in children and adolescents, with a median age at diagnosis being 15 years.
Chondrosarcomas being the most frequently occurring bone sarcomas of adulthood can occur in multiple lesions in patients with osteochondromas and enchondromatosis.
- How Are Sarcomas Diagnosed?
The definitive diagnosis is done through a surgical biopsy for a suspicious looking lump, which has been imaged via X -Rays or MRI (magnetic resonance imaging). The biopsied the tissue is then analysed by a pathologist.
Since sarcomas are ubiquitous in their site of origin, and are treated with a multimodality treatment (involving multiple teams of doctors), a multidisciplinary approach in the establishment of the accurate diagnosis is therefore mandatory. This includes pathologists, radiologists, surgeons, radiation oncologists, medical oncologists and paediatric oncologists (when applicable).
Ideally, his should be carried out in reference centres for sarcoma and or within reference networks sharing multidisciplinary expertise and treating high number of patients annually. These centres are involved in ongoing clinical trial, in which sarcoma patients enrolment is highly encouraged.This cetralised referral should be pursued from the time of the clinical diagnosis of a suspected sarcoma. In practice, referral of patients with a lesion likely to be a sarcoma would be recommended. This would mean referring all patients with an unexplained deep mass of soft tissue or bone.
For patients in Australia the reference centres can be found at the Australasian Sarcoma Study Group (ASSG) “Find a sarcoma specialist link” www.australiansarcomagroup.org
In soft tissue sarcomas, MRI is the main imaging modality, although X Rays should be the first step to rule out bone sarcomas.
- Why Research Sarcomas?
Treatment of Sarcoma is costly, prolonged often ineffective, with extremely high morbidity and mortality. Surgery is generally the treatment of choice. Depending on the type of Sarcoma being treated, a combination of surgery, radiotherapy and sometimes chemotherapy though a multidisciplinary medical team approach has been used, which has improved survival of some Sarcomas considerably from 20 per cent to 50 per cent. However, this has not progressed over more than the last decade due to a lack of high level research. Sarcomas are not only forgotten cancers, but still not well understood.
Since they are not well understood, they tend to be misdiagnosed and therefore present late as they are uncommon in general practice. There are many benign diseases that may have similar symptoms.
Research into any sarcoma will benefit all sarcoma patients as there are significant similarities between all types of sarcomas.