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SC16 - Superior Sulcus Tumors (ID 340)
- Event: WCLC 2016
- Type: Science Session
- Track: Radiology/Staging/Screening
- Presentations: 1
SC16.03 - Radiotherapy for Sulcus Superior Tumors (ID 6665)
14:30 - 15:45 | Author(s): M. Werner-Wasik
Superior sulcus tumors (SST) are unique among lung cancer in that they have a tendency for the invasion into the chest wall and a spread superiorly outside the lungs, namely into the brachial plexus and the sympathetic chain, therefore causing a well-defined constellation of symptoms and signs, such as chest wall/arm/shoulder pain, Horner’s syndrome, spinal cord compression, upper extremity edema etc. A primary surgical resection is rarely performed, and bi- or trimodality therapies are most often implemented, depending on tumor stage. A comprehensive evaluation of the tumor extent is mandatory before any intervention is undertaken. Following tumor biopsy to establish a diagnosis of non-small cell lung cancer, standard lung cancer staging studies need to be obtained, such as the chest and upper abdomen computerized tomography (CT) scan with intravenous contrast, a PET CT scan and contrast-enhanced brain imaging (CT or MRI). Routine blood work and pulmonary function testing are standard as well. However, there are two additional radiographic studies which are necessary for each superior sulcus tumors: (1) MRI scan of the brachial plexus; (2) MRI scan of the cervical and thoracic spine. The rationale for imaging of the brachial plexus is not to confirm that the plexus is invaded (which is evident based on the presenting symptoms and a physical examination), but rather to assess the degree of its vertical involvement, since only the lowest trunks of the brachial plexus can be safely resected without fear of causing paralysis of the upper extremity. The MRI of the vertebral column serves a double purpose: (1) to assess the degree (if any) of vertebral involvement and resulting resectability; (2) to image the proximity of the tumor to the spinal cord, which is crucial for radiation planning. SSTs can cause thecal sac or spinal cord compression by extending into the spinal canal through neural foramina, without apparent spine invasion, hence the need for the MRI, which provides a superior image quality than a chest CT scan. The overall treatment strategy depends on the nodal status (“N” stage). For those patients without nodal involvement (“N0”) or with involvement only of the ipsilateral hilar lymph nodes (“N1”), a common approach is to use concurrent induction chemo-radiotherapy, followed by the surgical resection. If obvious mediastinal nodal involvement is seen (“N2 or N3”), the recommendation is for definitive concurrent chemo-radiotherapy without subsequent surgery. Therefore, invasive staging of the mediastinum, either with mediastinoscopy or with EBUS, is mandatory, since it may result in avoiding surgery as part of management. General thoracic radiation therapy (RT) principles apply to the SSTs, such as: (1) use of the CT simulation for tumor and normal tissue imaging; (2) use of 6-10 MV photon energies (unless protons are applied); (3) careful definition of the GTV, Gross Tumor Volume, to include the visible tumor on lung windows and the abnormal lymph nodes on soft tissue windows; (4) adequate margins for the CTV, Clinical Target Volume, and the PTV, Planning Target Volume. In particular, a tendency to have very tight margins around the tumor which is in close proximity to the spinal cord should be avoided at all cost, since this may result in a marginal tumor failure. In comparison to lung cancers in other locations, local tumor progression of a SST can have devastating clinical consequences, resulting in unmanageable pain, limb paralysis and a low quality of life. The commonly used total RT doses are: 45-60 Gy in trimodality therapy (chemo-RT, then surgery) or 60-70 Gy in bimodality therapy (chemo-RT) in 2 Gy daily fractions. The dose-limiting normal structures are usually the spinal cord and brachial plexus. The maximum allowed dose to the spinal cord may need to be higher (54-55 Gy) in SSTs than in other lung cancers (50 Gy) in order not to compromise the minimum dose prescribed to the PTV by attempting to “spare” spinal cord. In patients presenting with severe pain, a simple field arrangement (such as anterior and posterior opposed fields) treating the tumor with wide margins is a good initial option allowing for a quick start, followed by a more advanced planning technique, such as 3-dimensional RT, intensity modulated RT (IMRT) or VMAT. The tolerance of brachial plexus was classically described as a maximum dose of 65 Gy, with recent publications suggesting that higher doses, up to 78 Gy result in 12% risk of Grade>3 radiation-related brachial plexopathy, and that brachial plexopathy is more common as a result of tumor progression than radiation damage. The most quoted prospective clinical trial reporting on treatment outcomes of SSTs is a landmark Phase II SWOG 9416 study, in which 95/110 enrolled patients without disease progression (86%) received thoracic RT to 45 Gy in 1.8 Gy fractions with concurrent cisplatin and etoposide chemotherapy, followed by surgery and further adjuvant chemotherapy. Eligible patients were those with T3-T4 primary tumors and N0 or N1 nodal status. The resection rate was 80% and 75% achieved a complete (R0) resection. The pathologic response rate (no tumor in the specimen or microscopic residual) was 56%; the overall 5 yr survival rate was 44% for all patients and 54% for those with a complete tumor resection. Since then, recognition in the surgical community that operating after RT doses higher than 45 Gy is safe, led to a more common use of the full RT dose, i.e. 60 Gy. If the patient initially planned for trimodality therapy is no longer a surgical candidate or refuses surgery, thoracic RT should continue to definitive dose without interruption. Therefore, it is crucial to perform re-imaging for response assessment in the last week of chemo-RT (if doses of <60 Gy are used) rather than schedule those several weeks later. References: Rusch, V.W., Giroux, D.J., Kraut et al. Induction chemoradiation and surgical resection for non-small cell lung carcinomas of the superior sulcus (initial results of Southwest Oncology Group trial 9416 (Intergroup trial 0160)) . J Thorac Cardiovasc Surg 121: 472–483, 2001. Kwong KF, Edelman MJ, Suntharalingam M et al. High-dose radiotherapy in trimodality treatment of Pancoast tumors results in high pathologic complete response rates and excellent long-term survival. J Thoracic Cardiovasc Surg, 129:1250-57, 2005. Eblan MJ, Corradetti MN, Lukens JN et al. Brachial plexopathy in apical non-small cell lung cancer treated with definitive radiation: dosimetric analysis and clinical implications. Int J Radiat Oncol Biol Phys.85:175-81, 2013.
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