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. 2016 Sep-Oct;6(5):e149-e154.
doi: 10.1016/j.prro.2016.01.004. Epub 2016 Jan 12.

Posttreatment FDG-PET-CT response is predictive of tumor progression and survival in anal carcinoma

Kelly E Goldman  1 , Evan C White  2 , Aroor R Rao  3 , John S Kaptein  4 , Winston W Lien  3
Affiliations

Posttreatment FDG-PET-CT response is predictive of tumor progression and survival in anal carcinoma

Kelly E Goldman et al. Pract Radiat Oncol. 2016 Sep-Oct.

Abstract

Purpose: We hypothesize that posttreatment F-18 fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) metabolic response predicts clinical outcomes in patients with anal cancer treated with chemoradiation.

Methods and materials: This was a single-institution retrospective review of 148 patients treated definitively for anal squamous cell carcinoma between 2005 and 2012. All patients were followed with posttreatment PET-CT scans and clinical examinations. Progression-free survival (PFS), cause-specific survival, and overall survival (OS) estimates were calculated using the Kaplan-Meier method.

Results: The median follow-up was 34 months (range, 5-89 months). Pretreatment PET was successful in detecting the primary tumor in 140 cases (95%). Computed tomography (CT) alone was able to detect primary tumors in 78 of 122 patients who had pretreatment CT scans (64%). Inguinal or pelvic lymph nodes were FDG avid in 68 patients, with only 41 of these patients having enlarged lymph nodes by CT criteria (60.3%). Initial posttreatment PET-CT was obtained on average 12.7 ± 4.3 weeks after the last day of radiation (range, 5-25 weeks). Overall complete metabolic response (CR) on initial PET-CT was found in 82 patients (58%). Partial metabolic response was noted in 52 (36.9%) and progression in 7 patients (5%). Only 12/82 patients (14.6%) with a FDG-PET CR eventually recurred. The negative predictive value of a PET-CT scan performed between 13 and 25 weeks posttreatment was 92.9%. The 2-year PFS for patients with CR versus non-CR was 89.8% and 69.2%, respectively (P = .004). The 2-year OS for CR versus non-CR patients was 94.8% and 79.3% (P = .036).

Conclusions: Complete metabolic response on posttreatment FDG PET-CT is highly predictive of increased PFS and OS in patients treated with chemoradiation for anal carcinoma. In addition to close clinical surveillance, we recommend obtaining posttreatment PET-CT scans >12 weeks following definitive treatment for anal cancer.

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