STEREOTACTIC RADIOTHERAPY FOR LUNG, LIVER AND BRAIN TUMORS

By Michael D. Sapozink, M.D.,PH.D

Southwest Oncology Centers is pleased to have the first facilities in Arizona to use helical Tomotherapy to offer exciting new treatment for lung and liver tumors, by providing 3-D soft tissue image guided intensity modulated radiotherapy. Lung cancer is the third most common cancer diagnosed in the U.S. and the leading cause of cancer deaths. While most patients can undergo surgery as initial treatment, some individuals have other serious medical conditions which make surgery too risky. Others may have cancers which began in other organs, but have relapsed with one or two tumors in the lungs or liver. Previously these patients might be offered treatment with chemotherapy, conventional radiation therapy, or both. However, many patients with serious medical problems cannot tolerate chemotherapy, and the doses of radiation which can be delivered are limited because of the potential damage to functioning lung or liver tissues. When radiation therapy could be used, 30-35 treatments over 6-8 weeks were often necessary to achieve tumor control rates in the 50% range.

BRAIN TUMORS

Stereotactic Radiosurgery (SRS) and Fractionated Stereotactic Radiotherapy (FSRT) are image guided techniques which have been used to treat primary or metastatic brain tumors for many years. Conventional techniques usually involve neurosurgical attachment of a device to immobilize the skull and geometrically define targets within the head. When Tomotherapy is used for brain tumor stereotactic radiotherapy, a tight fitting rigid plastic facemask is constructed to enable precision delivery of high doses of radiation to small to moderate tumor volumes. Very thinly sliced CT scans are obtained to identify the skull and critical brain structures such as the optic nerves. Identical very thinly sliced MRI scans and sometimes molecular imaging with PET scans are also performed, with the patient in the same position, to locate the brain tumor(s) and other critical healthy structures; and these images are superimposed on the planning CT scans by a computer. The Tomotherapy planning system then computes a series of beam shapes and intensities, which will deliver a uniform high dose to the target volume, while minimizing the dose to the rest of the brain. Before each treatment a CT scan is obtained by the Tomotherapy treatment machine using the highest degree of precision and superimposed on the planning CT scan. The brain and, if possible, the target tumor, are visualized in 3 dimensions. Any observed inter- or intra- treatment positional variations are corrected by transferring any changes required to superimpose the images on the computer too modify the treatment couch position. These techniques require one to ten treatments over one day to two weeks at Southwest Oncology Centers. Results have been excellent. Only 2 of nearly one hundred patients with acoustic and other cranial neuromas have required surgery for tumor growth. Very few patients with brain metastases have required surgery for increased tumor growth or brain swelling.

Applicable for:

Small high grade gliomas

Recurrent low grade gliomas

Small benign tumors – acoustic neuromas, cranial nerve schwannomas, meningiomas

Vascular malformations

Brain metastases ( from other primary tumors)

LUNG AND LIVER TUMORS

Fractionated Stereotactic Body Radiotherapy uses the same concept of delivering high doses of radiation, in 3-5 treatments over 2 weeks, to modest sized tumors in the lungs or liver, which are precisely targeted during treatment planning and actual treatment. Recent reports using Tomotherapy and other techniques indicate control rates approaching 90% for selected patients with medically inoperable tumors. To plan such treatment a custom fitting body cast is made which permits the patient to be placed in a reproducible position for each treatment. Thinly sliced CT scans are obtained to identify and locate the normal structures and the tumor(s) within the region of treatment. Frequently molecular imaging with PET scanning is also performed, with the patient in the same immobilized position, to better define the target cancer; and these images are superimposed on the planning CT scans by a computer. The Tomotherapy planning system again computes a series of beam shapes and intensities, which will deliver a uniform high dose to the target volume, while minimizing the dose to other organs in the region, as the treatment beam follows a spiral path around the patient. Before each treatment a CT scan is obtained by the Tomotherapy treatment machine and superimposed on the planning CT scan. The target tumor is visualized in 3 dimensions and any observed day to day positional variations are corrected by transferring any changes required to superimpose the images to modify the treatment couch position

Fractionated Stereotactic Body Radiotherapy has been fairly well tolerated, particularly considering the degree of debilitation of many of the patients who are considered for this treatment. Published reports of this technique have not indicated that, although the biologically effective doses delivered to such tumors are much higher, there are no greater long term risks of damage to other organs than would be expected with conventional treatment techniques. Comparisons of Tomotherapy dose distributions with those of other conventional IMRT techniques also consistently show better protection of normal tissues from moderate to high doses of radiation

Applicable for:

Small primary small cell or non-small cell lung cancer ( in patients with severe medical problems or advanced age who cannot tolerate surgery and/or chemotherapy)

Small primary liver tumors ( hepatocellular carcinoma )

Solitary or symptomatic Lung metastases ( from other primary tumors)

Solitary or symptomatic Liver metastases ( from other primary tumors)

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