High Precision RT For Soft-Tissue Sarcoma

This research study aims at defining 1) how retroperitoneal sarcomas change over the course of radiotherapy and 2) how radiotherapy affects your well-being. While the investigators know that radiotherapy before surgery is safe and effective, the amount of tumor motion and size change during radiotherapy is unknown. There is also very little information that describes the side-effects of radiotherapy in the treatment of this disease.

Soft-tissue sarcomas (STS) that arise from the retroperitoneum are rare malignancies that are anatomical located deep within the abdominal area and thus pose challenges to surgical and radiotherapeutic management of the patient. As a result, the local control and overall survival for patients with retroperitoneal sarcomas (RPS) are worse than STS from the extremities. Current treatment strategy involves pre-operative radiotherapy followed by surgery. Use of intensity-modulated radiotherapy (IMRT) in RPS had allowed for more conformal treatments with the aim of sparing normal tissues from high doses of irradiation. Yet the accuracy and coverage of IMRT depend highly on target motion, and little is known about the motion of RPS during the course of radiotherapy. As well, RPS are commonly in close proximity to sensitive organs for which the long-term toxicity and effect on quality of life secondary to radiation is unknown. The current study seeks to evaluate the extent of tumor motion during radiotherapy and the impact of radiotherapy to patient toxicity and quality of life. At the conclusion of this study, our results will hopefully identify the optimum PTV, the importance of different normal tissues and their dose-volume constraints, the role of image guidance, and the potential for dose escalation in the treatment of RPS.

Data from these patients will be added to retrospectively gathered data from the PMH radiotherapy data bank (approximately 50 patients). The data collected will be analyzed using descriptive statistics.

Radiotherapy for the treatment of retroperitoneal sarcoma. IMRT will be 50.4 Gy given in 28 fractions.

Images and information from the daily CT will be used for the repositioning of the patient prior to their treatments as per standard procedures.

To determine the extent of inter-fractional and intra-fractional movement of the GTV during radiotherapy treatments.

To quantify and describe the movement of the tumor during and between radiotherapy treatments using imagings acquired during the course of radiotherapy planning and treatments.

To assess the acute and long-term toxicity of pre-operative radiotherapy as a function of the dose given to normal tissues and its impact on patient quality of life.

To describe the effect of radiotherapy to the patient by measuring the acute and long-term side-effects of radiation therapy.

Describe variations in the volume and shape of the GTV over the course of the treatment and need for adaptive therapy.

Correlate the pattern of local recurrence with the dose of radiation delivered accounting for motions and volume changes of target structures.

To determine whether there is a pattern of local relapse with the actual dose of radiation delivered to the tumor environment when tumor volumetric and positional changes are taken into account.

Inclusion Criteria: Pathologically (histologically or cytologically) proven diagnosis of sarcoma (except for GIST, Ewing's sarcoma and rhabdomyosarcoma) within the retroperitoneum. These include patients with locally recurrent disease Planned to receive pre-operative radiotherapy Will undergo a planning CT Karnofsky Performance Status of ≥ 70 within 28 days prior to study entry No systemic chemotherapy given prior to pre-operative radiotherapy Able to provide written, informed consent Women of childbearing potential and men who are sexually active must practice adequate contraception. Exclusion Criteria: Tumor pathology of GIST, Ewing's sarcoma or rhabdomyosarcoma Metastatic disease to the retroperitoneum from a primary sarcoma not originating from the retroperitoneum Systemic chemotherapy given prior to pre-operative radiotherapy. Intent on giving chemotherapy ≤ 12 months from the completion of radiotherapy Inability to undergo a 4D-CT simulation KPS < 70 Unable to provide informed consent Pregnant women