FDG-PET/CT in the Radiotherapy Treatment Planning of Locally Advanced Anal Cancer: A Monoinstitutional Experience.

AIMS: Radiotherapy with concurrent 5-fluorouracil/mitomycin-C based chemotherapy has been established as definitive standard therapy approach for anal cancer. Intensity Modulated Radiotherapy (IMRT) leads to a precise treatment of the tumor, allowing dose escalation on Gross Tumor Volume (GTV), with a surrounding healthy tissues sparing. Our study assessed the impact of 18-Fluorodeoxyglucose positron emission tomography (18FDG-PET/CT) on the radiotherapy contouring process and its contribution to lymphatic spread detection, resulting to a personalization of Clinical Target Volume (CTV) and dose prescription. METHODS: Thirty-seven patients, with histologically proven squamous cell carcinoma of the anal canal (SCCAC) were analyzed. All patients were evaluated with history and physical examination, trans-anal endoscopic ultrasound, pelvis magnetic resonance imaging (MRI), computed tomography (CT) scans of the chest, abdomen and pelvis and planning 18FDG-PET/CT. The GTV and CTV were drawn on CT, MRI and 18FDG-PET/CT fused images. RESULTS: Thirty-four (91%) out of 37 patients presented lymph nodes involvement, in one or more areas, detected on 18FDG-PET/CT and/or MRI. The 18FDG-PET/CT showed positive lymph nodes not detected on MRI imaging (PET+, MRI-) in 14/37 patients (38%). In 14 cases, 18FDG-PET/CT allowed to a dose escalation in the involved nodes. The 18FDG-PET/CT fused images led to change the stage in 5/37(14%) cases: four cases from N0 to N1 (inguinal lymph nodes) and in one case from M0 to M1 (common iliac lymph nodes). CONCLUSIONS: The 18FDG-PET/CT has a potentially relevant impact in staging and target volume delineation/definition in patients affected by anal cancer. In our experience, clinical stage variation occurred in 14% of cases. More investigations are needed to define the role of 18FDG-PET/CT in the target volume delineation of anal cancer.

Mucinous rectal adenocarcinoma can be associated to tumor downstaging after preoperative chemoradiotherapy.

PURPOSE: The aim of this study was to evaluate downstaging as primary end point, and progression-free survival and overall survival as secondary end points, in rectal adenocarcinoma patients treated with preoperative chemoradiation. METHODS: One hundred and thirty-six extraperitoneal adenocarcinoma patients (33 low rectum T2, 74 T3, 29 T4 [without sacral invasion], 25 with mucinous subtype) were treated with posterior pelvis preoperative radiotherapy (5040 cGy total dose, 180 cGy/fr, 5 fr/w, 10-15 MV linac X-rays) and concomitant 5-fluorouracil-based chemotherapy. After 6 to 8 weeks patients underwent surgery and prechemoradiation clinical stage was compared with pathologic stage to evaluate downstaging in each patient. Seventy-four patients received adjuvant chemotherapy. Median follow-up was 39 months (4-84). RESULTS: Forty-four patients had macroscopic complete response, 52 patients had partial response, 37 patients showed no change and 3 patients had progression. At multivariate analysis only histotype showed correlation with downstaging (hazard ratio = 0.350 and 0.138 - 0.885 95 percent confidence interval) because of the evidence for poor downstaging in mucinous subtype. There were no significant differences in overall survival and progression-free survival between adenocarcinoma and mucinous subtype. CONCLUSIONS: The main finding is that mucinous histology is associated with poor downstaging after preoperative chemoradiation but this poor response was not associated with worse outcome in this small study. The good outcome for mucinous histology is at odds with other reports in the literature and requires further study.

Down-staging after two different preoperative chemoradiation schedules in rectal cancer.

AIMS: To compare preoperative down-staging, toxicity and sphincter-saving procedures obtained with preoperative radiotherapy and two different concomitant chemotherapy schedules. METHODS: From February 1997 to August 2001, 68 consecutive patients were treated with external radiotherapy (5040 cGy in 28 fractions) and concomitant chemotherapy: group a) 36 patients (10 T2, 19 T3, 7 T4, 25 adenocarcinoma and 11 mucinous histology) were treated with cis-diamminedichloroplatinum bolus + 5-fluorouracil continuous infusion; group b) 32 patients (14 T2, 18 T3, 27 adenocarcinoma and 5 mucinous histology) were treated with 5-fluorouracil bolus +/- mitomycin C. The interval between the end of radiotherapy and surgery ranged from 4 to 9 weeks. RESULTS: Group a) Overall down-staging was 63.9%. Longitudinal shrinkage of the neoplasm allowed conservative surgery in 6 of 11 patients with a pre-chemoradiation tumor location < or = 3 cm from the external anal ring. When patients with adenocarcinoma (25/36) were studied separately from patients with mucinous histology, 7/25 patients (28%) were found to have no microscopic evidence of residual tumor (pT0); 8/25 (32%) were found to have only rare isolated cancer cells (pTmic); only 7/25 patients (28%) were found to have no change. Overall, 72% patients had down-staging. In contrast, only 5/11 (45.5%) of mucinous tumors had partial down-staging and 6/11 (54.5%) no down-staging at all. Group b) Overall down-staging was 46.9%. When patients with adenocarcinoma (27/32) were studied separately, 7/27 (26%) were found to have pT0, 3/27 (11.1%) pTmic, and 13/27 (48.1%) no change. Only 1/5 (20%) of mucinous tumors had down-staging and 4/5 (80%) had no down-staging at all. Overall toxicity was comparable among groups a and b, except for lower hematologic and gastrointestinal G3-4 toxicity observed in group a. CONCLUSIONS: The overall response allowed conservative surgery in 56 (82.3%) of the 68 patients. Continuous infusion of 5-fluorouracil and diamminedichloroplatinum as a radiosensitizer determined better results in group a than group b (63.9% down-staging vs 46.9% even with a higher incidence of mucinous histology). Mucinous histology, for a definitely lower response rate, could benefit from an even more aggressive approach.