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ypT0 cases, the overall survival was 91.1%, not significantly different (P ¼ .25) compared with the remaining group (87.2%). Among ypT0 cases, the relapse-free survival was 94.5%, which was significantly different (P ¼ .03) compared with the remaining group (78.2%). There were no treatment-associated fatalities. Thirty-two patients (10.96%) experienced Grade III/IV toxicities (proctitis, epithelitis, and neutropenia). Conclusion: Tumor localization was identified as a predictive factor for pCR in LARC treated with preoperative chemoradiation. Upper rectal tumors are more likely to develop complete responses. Delay in surgery was identified as a favorable predictive factor for TRG1-3. The relapse-free survival in pCR group was higher compared with non-pCR.

2536 Background: Clinical response is determined after 2 or 3 cycles of chemotherapy by changes in tumor size as assessed by conventional imaging procedures such as computed tomography (CT). The aim of this study was to evaluate the use of sequential F-18 FDG PET to predict response to standardized chemotherapy for metastatic colorectal cancer (mCRC). Methods: Clinical response, as assessed by RECIST criteria, served as the reference. Investigators were free to choose chemotherapy regimen. F-18 FDG PET images after every second cycles of chemotherapy were analyzed semiquantitatively for each metastatic lesion using standardized uptake values (SUVs) normalized to patients’ blood glucose levels. PET responses were prospectively assessed as either complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), or progressive metabolic disease (PMD). In addition, sum of SUV of all metastatic lesions (sSUV) and a maximal SUV (mSUV) were recorded each PET-CT scan. Results: Twenty-four patients underwent 73 PET-CT scans since March 2005. The response to chemotherapy included CR in 1 (4.2%), PR in 10 (42%) by RECIST criteria. Median duration of follow- up was 8.3 months (range, 1.7 - 16.2) and median progression free survival (PFS) time was 6.4 months. At the baseline evaluation, PET-CT was the more sensitive test to find metastatic lesion than conventional assessment in 12 (50.0%). Baseline sSUV and mSUV was not significantly different between clinical responders and non-responders. After 2 cycles of chemotherapy, sSUV and mSUV was more decreased in clinical responder with significance (P=.023 and .020, respectively). In the 22 evaluable patients, PET responses were as followed: CMR in 1 (4.5%), PMR in 11 (50.0%), SMD in 7 (31.8%) and PMD in 3 (12.0%). Estimated median PFS was significantly prolonged in metabolic responders: PMR 8.3 months, SMD 4.7 months and PMD 2.3 months (P=.040). Patient with CMR had no evidence of progression for 14.7 month follow-up. Conclusions: In patients with mCRC, sequential FDG-PET predicted PFS and was more accurate than clinical response criteria. FDG- PET appears to be a promising tool for early prediction of response to chemotherapy. No significant financial relationships to disclose.

Background: Adjuvant chemotherapy results in early menopause in the majority of premenopausal patients due to premature ovarian failure and consequent skeletal morbidity. Zoledronic acid (ZA) is known to prevent bone loss in postmenopausal women. The purpose of this study was to determine whether ZA can prevent bone loss in premenopausal women undergoing adjuvant chemotherapy for breast cancer.Methods: This study is a randomized, open-label, phase III multicenter trial. Premenopausal women older than age 40 were randomly assigned to ZA group (two infusions of 4 mg IV, every 6 months) or observation group after surgery. All patients were treated with the same adjuvant chemotherapy regimen (AC-->T; 4 cycles of AC followed by 4 cycles of paclitaxel or docetaxel). The first infusion of ZA was given on day 1 of the first chemotherapy. All patients received supplementations with oral calcium 600 mg/d and vitamin D 400 IU/d. The bone mineral density (BMD) was measured at the baseline, 6th and 12th months. Bone turnover markers were measured before chemotherapy and in 3, 6, 12 months.Results: Between March 2007 and May 2008, a total of 110 premenopausal women were enrolled in this study and the majority of women (91.8%) developed amenorrhea at 1 year post chemotherapy. The mean percent change of BMD in lumbar spine was +0.5% in the ZA group versus -3.6% in the observation group at 6 months (p<0.01) and, -1.0% versus -7.5%, at 12 months (p<0.01). Differences in percent change of BMD from baseline between two groups were 6.5% (95% CI, 5.2 to 7.9%) for the lumbar spine, and 3.6% (95% CI, 2.2% to 5.1%) for the femoral neck (p<0.01). Type I collagen metabolite PINP levels at 12 months were significantly higher in the observation group than in the ZA group; 72.7 mg/l (range 21.8∼250 mg/l) versus 30.8 mg/l (range 14.7∼62.7 mg/l) (p=0.0001). Changes of other bone turnover markers including urinary N-telopeptide, bone alkaline phosphatase, and serum C-telopeptide were also significantly different between two groups (p<0.01). ZA was generally well tolerated, and adverse event profile was similar between two groups.Conclusion: Adjuvant chemotherapy with AC-->T induced amenorrhea in the majority of patients over 40 years in this study. Treatment with two infusions of ZA 4 mg every 6 months effectively prevented bone loss within the first year of adjuvant chemotherapy for early breast cancer in premenopausal women. Regular BMD measurements and early bisphosphonate therapy should be considered for this population. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2104.

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