Introduction: Increased tumor burden is associated with inferior outcomes in different lymphoma subtypes. Surrogates of tumor burden, such as the maximum tumor dimension of the “bulkiest” lesion on computed tomography (CT) have been used as a prognostic index for many years. Recently, the total metabolic tumor volume (MTV), tumor lesion glycolysis (TLG) and SUV max in basal PET-CT have emerged as promising and robust biomarkers of outcomes in patients with Hodgkin's Lymphoma (HL). Interim PET-CT is also a well-established prognostic factor for PFS in HL. We aim to identify quantitive parameters from basal PET-CT to predict early response in interim PET (iPET) as a surrogate of PFS. Methods: We performed a retrospective analysis of the database of 562 patients with HL who were enrolled between November 2008 and March 2020 in the GATLA-LH-05 trial. We searched for patients who underwent a basal PET-CT at the same PET center; MTV was computed using 41% maximum standardize uptake value method: TLG and SUVmax were derived. After 3 cycles of ABVD all patients underwent an iPET. In this published trial patients with a negative iPET had a PFS of 90% vs 65% in patients with iPET positive. Mann Whitney test was performed to analyze difference of MTV, TLG and SUV max, between PET positive and PET negative cohorts. Results: Of the total population, 64 patients had complete information for this analysis, 40 (62.5%) patients had iPET negative, and 24 (37.5 %) iPET positive. According to positive vs negative interim PET we identified the following difference in basal PET. (Table 1): In this retrospective analysis, difference between the distribution of the baseline values of MTV and TLG variables, was statistically significant between the group of patients that achieved an IPET negative vs those who had IPET positive (p = 0.001 and p = 0.005 respectively). Finally, SUV max at baseline PET did not show significant differences between patients who did or did not achieve an iPET negative (p = 0.1). Conclusions: In this explorative study, a high total MTV and TLG at baseline PET are robust parameters to predict early response in the interim PET. In this analysis we demonstrate the association of high basal MTV and TLG as a predictor of early metabolic response, a surrogate of PFS. This contributes to the growing evidence of the importance of these values to predict outcome. SUV max did not show correlation with early metabolic response. A prospective clinical trial to reevaluate these important findings in a larger group of patients, with an attempt to determine a reliable cut-off value in MTV and TLG is being planned. Keywords: Hodgkin lymphoma No conflicts of interest pertinent to the abstract.

Introduction: Surgery is the standard treatment of rectal cancer after neoadjuvant therapy. Some authors advocate a nonoperative management (NOM) after complete clinical response (cCR) following chemoradiotherapy (CRT). We compare our results with NOM to standard resection in a retrospective analysis. Methods: A retrospective review of locally advanced rectal cancer patients following preoperative treatment was assessed in order to identify those patients who achieved clinical complete response (cCR) selected for a non operative management (NOM) and those patients who obtained pathological complete response (pCR) after total mesorectal excision. From February 2008 to December 2015 were analyzed from our database both groups of patients after reviewing all Non metastatic rectal adenocarcinoma selected for preoperative treatment. All operated patients who demonstrated a pCR in the specimen after neoadjuvant CRT were selected from our database to form the control group. The NOM group consists of all rectal cancer patients who appeared to have a complete clinical response after neoadjuvant treatment based on digital examination, endoscopy and magnetic resonance (MRI) who were not submitted to surgery. cCR was defined between digital exam, endoscopic criteria, MRI and CEA. Follow-up for NOM approach was performed during the first two years with MRI and EUS three-monthly and CT six-monthly. Patients in both groups were assessed for age, gender, tumor localization, pre-treatment cea levels, initial clinical staging (cT cN, EMVI, CRM), preoperative CRT and adjuvant chemotherapy. The aim was to compare long term outcomes between both groups regarding disease free survival (local and distance recurrence) and overall survival. Results: The operative group consisted of 42 patients submitted to CRT and resection that had pCR at the surgical specimen. The mean time interval from end of CRT to surgery was 12w(8-16), and the surgical procedure was LAR in 34 (81%) patients and APR in the remaining 8 (19%). In the NOM group, 35 patients were included. There were not found predictors of relapse after comparison clinical variables between the two groups. (p:NS for: age, gender, median distance to anal verge, CEA levels, initial clinical staging, preoperative treatment and adjuvant treatment). Three (8,5%) recurrences in NOM group and six (14%) in the surgical group occurred after a follow-up of 38 months (8-62m) and 42 months (6-86m) months respectively. In the NOM group, there were 3 local recurrences and were surgically salvaged. In the surgical group there were 6 recurrences. There were 2 isolated pelvis recurrences not amenable for surgery, 2 patients had distant lung metastases and 2 patients had both local and distant relapse. No differences were observed in DFS between NOM and surgical group (89% vs 86%, p:0,55). Regarding OS there was here was a higher OS favoring NOM group (100% vs 86%: p: 0,008). Conclusion: The NOM achieved a DFS comparable to the standard surgical treatment. A NOM with a close fup was a feasible approach, had optimal outcome avoiding unnecessary morbidity and functional consequences associated with radical surgery.

291 Background: Positron emission tomography (PET) is an imaging technique whose principle is the detection of metabolic activity of tumor cells but in urology its use had been restricted due to urinary excretion of the radiotracer and overlap with urological structures, the use of hybrid PET (PET-CT) would allow its use for monitoring patients with urothelial tumors. Methods: Between 2007 and 2010 we performed PET-TC images in consecutive patients with suspected recurrences in CT scan or MRI. All patients had renal, bladder and uretral cancer and were treated with urothelial cancer diagnosis. We evaluate the usefulness of FDG PET-CT and its impact on behavior therapy in suspected recurrence in patients with urothelial carcinoma, compared with conventional studies. Results: 17 patients were studied for suspected recurrence. All patients had positive images previously on CT scan and MRI; positive PET-TC was observed in 14 and 3 studies were negative. The positive PET-CT showed more number of lesions and change the medical and surgical strategy. Of the three studies negative on PET- CT none had recurrence and remain disease free. PET/CT is in a great benefit to the detection recurrence in the follow up of patients with urothelial cancer diagnosis. These results showed an increased sensitivity and specificity over previous work with conventional PET technology. In the series studied, the implementation of PET-CT (FDG) in the follow up of patients with urothelial tumors were an useful tool. Conclusions: PET/CT is in a great benefit to the detection recurrence in the follow up of patients with urothelial cancer diagnosis. These results showed an increased sensitivity and specificity over previous work with conventional PET technology. In the series studied, the implementation of PET-CT (FDG) in the follow up of patients with urothelial tumors were an useful tool. However, multicenter studies and more patients are required to define its role. No significant financial relationships to disclose.

INTRODUCTION:Imatinib is the standard first-line therapy for advanced gastrointestinal stromal tumor. (18)F-fluorodeoxyglucose PET computed tomography (FDG PET/CT) shows a faster response than computed tomography in nonpretreated patients.PATIENTS & METHODS:After disease progression on imatinib 400 mg, 16 patients were exposed to 800 mg. Tumor response was evaluated by FDG PET/CT on days 7 and 37. Primary objective was to correlate early metabolic response (EMR) with progression-free survival (PFS).RESULTS:EMR by FDG PET/CT scan was not predictive of PFS. Median PFS in these patients was 3 months. Overall survival was influenced by gastric primary site (p = 0.05).CONCLUSION:The assessment of EMR by FDG PET/CT in patients with advanced gastrointestinal stromal tumor exposed to imatinib 800 mg was not predictive of PFS or overall survival.