Vallow, Laura A.

The role of radiotherapy for local control of marginally resected, unresectable, and recurrent giant cell tumors of bone (GCToB) has not been well defined. The number of patients affected by this rare disease is low. We present a series of 58 patients with biopsy proven GCToB who were treated with radiation therapy. A retrospective review of the role of radiotherapy in the treatment of GCToB was conducted in participating institutions of the Rare Cancer Network. Eligibility criteria consisted of the use of radiotherapy for marginally resected, unresectable, and recurrent GCToB. Fifty-eight patients with biopsy proven GCToB were analyzed from 9 participating North American and European institutions. Forty-five patients had a primary tumor and 13 patients had a recurrent tumor. Median radiation dose was 50 Gy in a median of 25 fractions. Indication for radiation therapy was marginal resection in 33 patients, unresectable tumor in 13 patients, recurrence in 9 patients and palliation in 2 patients. Median tumor size was 7.0 cm. A significant proportion of the tumors involved critical structures. Median follow-up was 8.0 years. Five year local control was 85%. Of the 7 local failures, 3 were treated successfully with salvage surgery. All patients who received palliation achieved symptom relief. Five year overall survival was 94%. None of the patients experienced grade 3 or higher acute toxicity. This study reports a large published experience in the treatment of GCToB with radiotherapy. Radiotherapy can provide excellent local control for incompletely resected, unresectable or recurrent GCToB with acceptable morbidity.

Abstract Abstract #4018 Background: Preoperative breast magnetic resonance imaging (MRI) has been shown to identify occult breast disease in women with newly diagnosed breast cancer. We sought to determine the accuracy of MRI in predicting the actual pathologic tumor size in women with newly diagnosed breast cancer.
 Methods: Preoperative breast MRI was reviewed in 460 women with newly diagnosed breast cancer. The size in terms of maximum tumor dimension, of 476 incident breast cancers on MRI were recorded and correlated with the actual pathologic size upon surgical resection. The correlation of size from MRI to pathology was determined. The size discrepancy was analyzed in relation to tumor size and histology.
 Results: MRI demonstrated 476 breast cancers (460 in the ipsilateral breast and 16 with concurrent contralateral breast cancer). Median age was 62 with a range of 25 to 91. The T stages of the population included T0 in 19% of the women, 60% had T1 lesions, 18% had T2 lesions and 3% were T3 or T4. The histology consisted of DCIS alone in 20%, infiltrating ductal in 74% and infiltrating lobular in 6%. Pre-operative MRI was unable to define an enhancing lesion usually due to hematoma following core needle biopsy in 9.8% (47/476). MRI described the size of the incident lesion in 90% (429/476). The mean difference in size between the preoperative MRI and the actual pathologic size for the entire group was 2.4 mm. MRI underestimated tumor size in only 3% of cases. The mean difference according to T stage and histology between MRI and actual pathologic size is listed in Table 1. The percentage of difference between MRI size and pathologic size for the entire group is presented in Table 2.
 
 
 
 Discussion: The mean difference in tumor size estimated by preoperative MRI in women with newly diagnosed breast cancer was within 5 mm of the actual pathologic size in 68% of patients. MRI was accurate in predicting T stage with no significant difference in relation to histology or T stage. This analysis further clarifies the role of preoperative MRI in surgical and treatment planning. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4018.

To compare the radiation dose to normal cardiac tissue for 3Dimensional (3D) conformal external beam partial breast irradiation (PBI) and standard whole breast irradiation (WBI), and examine the effect of tumor bed location.For 14 patients with left breast tumors randomized on the National Surgical Adjuvant Breast and Bowel Project B‐39 protocol, computer‐generated radiotherapy treatment plans were devised for WBI and PBI. Tumor bed location was designated according to whether more than 50% of the excision cavity was medial or lateral to the nipple line. The volume of heart receiving doses of 2.5, 5, 10, and 20 Gy was calculated for all PBI and WBI plans. Dose to 5% of the heart volume (D5) and mean heart dose were also calculated. The biologically‐equivalent dose (BED) was calculated to account for the different fractionation used in PBI and WBI.Of the 14 patients, 8 had lateral tumor beds, and 6 had medial tumor beds. The volumes of heart receiving 2.5, 5, 10, and 20 Gy were significantly lower for lateral PBI compared with WBI. For medial PBI, significant cardiac sparing was only seen at a dose of 20 Gy. The difference of D5 values was significant for lateral PBI compared with WBI , but not for medial PBI compared with WBI . The mean dose was also significantly lower for lateral PBI compared with WBI , but not for medial PBI . The results from BED calculations did not change this outcome.Both 3D conformal PBI and standard WBI can deliver relatively low doses to the heart. For patients with lateralized tumor beds, PBI offers significant cardiac sparing compared with WBI. Patients with medial lesions have relatively similar heart dosimetry with PBI and WBI. 3D conformal PBI is an emerging treatment modality and continued participation on clinical trials is encouraged. Patients with left‐sided lesions and lateralized tumor beds warrant special consideration for PBI, given the significant cardiac dose sparing.PACS numbers: 87.53.Tf