Soft Tissue Sarcomas - paragraph 4

4 STAGING

4.1 Stage classification

4.1.1
In the UICC/AJCC 1992 tumor stage classification (4.I, 4.II), soft tissue sarcomas constitute one of the three neoplastic diseases in which the malignancy grade is incorporated within the stage. So, grade 1 soft tissue sarcomas are stage 1, grade 2 are stage 2, and grade 3 are stage 3 tumors, provided lymph node or distant metastases are absent. In soft tissue sarcomas, regional lymph node metastases are rare (generally <10%): if present, they give rise to a stage IVA disease. Distant metastases give a stage IVB disease. Within the three stages of localized disease, lesions are further divided into A or B, according to the tumor diameter (A if the maximal tumor diameter is <5 cm; B if it is>5 cm). So, the stage classification takes into account the most important prognostic factors in soft tissue sarcomas. Malignancy grade might also display a predictive value with regard to responsiveness to chemotherapy. Unfortunately, we lack a separate stage classification for local relapses, but TNM annotations can be used to describe local relapses as well.

4.1.2 TNM classification (UICC/AJCC, 1992)

TX: Primary tumor cannot be assessed
T0: No evidence of primary tumor
T1: Tumor 5.0 cm or less in greatest dimension
T2: Tumor more than 5.0 cm in greatest dimension
NX: Regional lymph nodes cannot be assessed
N0: No regional lymph node metastasis
N1: Regional lymph node metastasis
MX: Presence of distant metastasis cannot be assessed
M0: No distant metastasis
M1: Distant metastasis

4.1.3 Stage classification (UICC/AJCC, 1992)

Stage IA = G1, T1, N0, M0
Stage IB = G1, T2, N0, M0
Stage IIA = G2, T1, N0, M0
Stage IIB = G2, T2, N0, M0
Stage IIIA = G3-4, T1, N0, M0
Stage IIIB = G3-4, T2, N0, M0
Stage IVA = any G, any T, N1, M0
Stage IVB = any G, any T, any N, M1

4.1.4
Since the malignancy grade and the tumor diameter are the main prognostic factors for the localized disease, and the presence of distant metastases entails an overall dismal prognosis, the UICC/AJCC stage classification correlates well with prognosis. However, one should pay attention to two complicating factors. Firstly, some tumors are heterogenous and areas with different malignancy grades may coexist: in particular a biopsy may underestimate the tumor grade, since it may miss the highest grade areas, which obviously dictate the clinical aggressiveness of the tumor. Secondly, tumor diameter is mainly important for limb sarcomas. Sarcomas arising in the trunk, particularly in the retroperitoneum, tend to be large tumors which are unlikely to allow adequate surgical excisions and, even if small, may be located so as to prevent adequate surgery. So, the prognosis of trunk sarcomas is generally poorer by comparison with their limb counterparts, somewhat independent of the tumor diameter. In this regard the staging system does not differentiate among different sites of disease nor between operable and inoperable lesions, while surgery is always the prerequisite of any chance of cure in soft tissue sarcomas. It would be difficult for a stage classification to separate operable from inoperable lesions in a ubiquitous disease like soft tissue sarcomas; in addition, operability criteria may differ from an institution to another and evolve depending on the evolution of demolitive and reconstructive surgery techniques.

4.1.5
Overall, radically excised stage 1 tumors have a good cure rate, which may be >80-90%. They tend to recur locally if inadequately excised and give rise to distant metastases only late in their natural history, often after a process of dedifferentiation.

4.1.6
Stage 3 sarcomas are very aggressive diseases, both locally and at distant sites. Their cure rate, if adequately treated, may average 40-50%, but may be less for largest deep lesions. Relapses tend to occur early in their natural history, often within the first two years from surgery.

4.1.7
Stage 2 sarcomas resemble grade 3 sarcomas in their systemic potential, but they tend to give metastases relatively later, i.e. within 5 years. Possibly their cure rate is intermediate between grade 1 and grade 3 sarcomas (>50%).

4.1.8
Stage classification may be less meaningful for treatment planning than for prognosis. In fact, from the surgeon's standpoint, it is the tumor localization, and the infiltration of critical anatomic structures, which dictate the kind of intervention necessary and thereby the potential of local control, and eventually of cure. In any case, grade (stage) 1 lesions tend not to extend outside the reactive zone, while grade (stage) 2-3 sarcomas may give rise to skip lesions outside the reactive zone. This influences surgical conduct.

4.1.9
Stage IVA disease (regional lymph node present) is rare, but its prognosis seems closer to overtly metastatic disease.

4.1.10
Stage IVB (metastatic disease) should be divided into two categories. The first group is made up of patients with isolated lung metastases (i.e. without extrapulmonary concurrent sites of disease) that accounts for as high as 80of patients at their first distant relapse. Complete surgical excision (metastasectomy) is feasible in <80of these patients and results in a>20probability of cure. The second group comprises patients with unresectable lung metastases accounting for approximately >20of relapsing patients. These patients have an overall 5 year survival below 5%.

4.2 Staging procedures

4.2.1
The extent of the primary tumor should be assessed by the best radiological resources available depending on the site of disease. It is recommended that either computerized tomography scan or magnetic resonance be employed. Magnetic resonance can give coronal and sagittal views in addition to transaxial ones, and may better contrast muscles and vessels. If considering surgery, angiography or other special evaluations may prove necessary preoperatively. Bone scan may be useful to show bone infiltration. Given the high frequency of lung metastases and the potential of treatment through surgery of resectable lung metastases, chest X-ray and possibly lung computerized tomography are recommended in all patients. Computerized tomography adds to the sensitivity of chest X-ray, bringing it from >60to >80%, while specificity, which is as high as 95for chest X-rays, somewhat decreases. The prior probability of synchronous distant metastases in the sarcoma patient at first diagnosis is 20%, and lung lesions are present in most metastatic patients. In the absence of lung lesions, bone and liver lesions are relatively rare (<20%). Bone scan and liver ultrasonography, or liver computerized tomography scan, are therefore optional in the preoperative staging of the sarcoma patient, but may add somewhat to the probability of detecting distant metastases.

References

4.I
Soft tissues. In: American Joint Committee on Cancer: Manual for Staging of Cancer. Philadelphia: JB Lippincott Company, 4th ed., 1992, pp 131-135.

4.II
Soft tissues. In: UICC, TNM Classification of Malignant Tumors. P. Hermanek, LH Sobin (eds), New York London Paris Tokyo, Springer, Berlin Heidelberg, 5th ed, 1992.

4.III
Chang AE, Matory YL, Dwyer AJ, Hill SC, Girton ME, Steinberg SM et al. Magnetic resonance imaging versus computed tomography in the evaluation of soft tissue tumors of the extremities. Ann Surg 1987; 205: 340-348.

4.IV
Gaynor JJ, Tan CC, Casper ES, Collin CF, Friedrich C et al. Refinement of clinicopathologic staging for localized soft tissue sarcoma of the extremity: a study on 423 adults. J Clin Oncol 1992; 10: 1317-1329.

4.V
Lawrence W, Donegan WL, Natarajan N, Mettlin C, Beart R, Winchester D. Adult soft tissue sarcomas. A pattern of care survey of the American College of Surgeons. Ann Surg 1987; 205: 349-359.

4.VI
Pass HI, Dwyer A, Makuch R, Roth JA. Detection of pulmonary metastases in patients with osteogenic and soft-tissue sarcomas: the superiority of CT scan compared with conventional linear tomograms using dynamic analysis. J Clin Oncol 1985; 3: 1261-1265.

4.VII
Ruka W, Emrich LJ, Driscoll DL, Karakousis CP. Prognostic significance of lymph node metastasis and bone, major vessel, or nerve involvement in adults with high-grade soft tissue sarcomas. Cancer 1988; 62: 999-1006.

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