FDG-PET/CT in the evaluation of anal carcinoma

doi:10.1016/j.ijrobp.2006.01.009

International Journal of Radiation OncologyBiologyPhysics

Volume 65, Issue 3, 1 July 2006, Pages 720-725

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https://doi.org/10.1016/j.ijrobp.2006.01.009 Get rights and content

Purpose: Surgical staging and treatment of anal carcinoma has been replaced by noninvasive staging studies and combined modality therapy. In this study, we compare computed tomography (CT) and physical examination to [¹⁸F]-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) in the staging of carcinoma of the anal canal, with special emphasis on determination of spread to inguinal lymph nodes.

Methods and Materials: Between July 2003 and July 2005, 41 consecutive patients with biopsy-proved anal carcinoma underwent a complete staging evaluation including physical examination, CT, and 2-FDG-PET/CT. Patients ranged in age from 30 to 89 years. Nine men were HIV-positive. Treatment was with standard Nigro regimen.

Results: [¹⁸F]-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) detected 91% of nonexcised primary tumors, whereas CT visualized 59%. FDG-PET/CT detected abnormal uptake in pelvic nodes of 5 patients with normal pelvic CT scans. FDG-PET/CT detected abnormal nodes in 20% of groins that were normal by CT, and in 23% without abnormality on physical examination. Furthermore, 17% of groins negative by both CT and physical examination showed abnormal uptake on FDG-PET/CT. HIV-positive patients had an increased frequency of PET-positive lymph nodes.

Conclusion: [¹⁸F]-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography detects the primary tumor more often than CT. FDG-PET/CT detects substantially more abnormal inguinal lymph nodes than are identified by standard clinical staging with CT and physical examination.

Introduction

Carcinoma of the anal canal accounts for approximately 1.6% of all digestive tract cancers in the United States, with approximately 4000 new cases expected in 2005 (1). Over the last 30 years, the annual incidence of anal carcinoma has increased substantially in both men (160%) and women (78%) (2). Both HIV and human papilloma virus infections are associated with an increased risk of anal carcinoma (3, 4).

Primary tumor size and lymph node metastasis are the key prognostic factors determining both overall and disease-free survival (5, 6). The likelihood of nodal involvement is directly related to the size of the primary tumor, but nodal status does have prognostic value independent of tumor size (7).

Historically, both staging and treatment of anal cancer were surgical, and consisted of abdominoperineal resection with or without an inguinal lymph node dissection. For the past two decades, therapy for epidermoid carcinoma of the anal canal has consisted of combined chemotherapy and radiation therapy to the sites of primary disease and lymphatic spread, usually with prophylactic irradiation of clinically negative groins (8, 9). Surgery has been reserved for salvage therapy in patients with persistent or recurrent disease. This strategy has significantly reduced locoregional recurrence and has lead to markedly improved control of gross nodal disease (6, 8, 10). The rate of inguinal node recurrence specifically has decreased to <5% (5, 6). Present staging consists of physical examination and biopsy of the primary tumor, palpation of the groin, and computed tomography (CT) of the abdomen and pelvis. The presence of inguinal node metastasis calls for a radiation boost to the affected groin (9, 10).

Positron emission tomography with the glucose analog 2-[¹⁸F]-fluoro-2-deoxy-D-glucose (FDG-PET) has been increasingly used in the staging and evaluation of pelvic malignancies, including rectal, cervical, ovarian, endometrial, and vaginal carcinoma (11). Previous reports from this institution have shown FDG-PET to have an increased sensitivity for detection of abnormal lymph nodes compared with CT in both cervical and vaginal carcinoma (12, 13). Since 2003, we have obtained pretreatment whole-body FDG-PET/CT on all patients with anal carcinoma. The goal of this study was to evaluate the utility of FDG-PET/CT as a further nonsurgical option in the staging of carcinoma of the anus, with specific attention to the role of PET in identification of inguinal lymph node metastases.

Section snippets

Patients

The study population consisted of 41 consecutive patients with biopsy-proved carcinoma of the anus referred to the Mallinckrodt Institute of Radiology for radiotherapy between July 2003 and July 2005. The Washington University Human Studies Committee approved this retrospective outcomes review.

All patients underwent a complete staging workup including history and physical examination, anal biopsy, diagnostic abdominal and pelvic CT scans, and whole-body FDG-PET/CT. Fine needle aspiration (FNA)

Visualization of primary tumor

Seven tumors were excised before imaging studies were undertaken. Of the remaining tumors, PET identified 18 of 21 T2 tumors (86%) and each of 13 T3-4 tumors (100%), for a cumulative total of 31 of 34 (91%). CT positively identified 10 of 21 T2 tumors (48%) and 10 of 13 T3-T4 tumors (83%), for a total of 20 of 34 (59%).

Pelvic lymph nodes

Nine of 41 patients (22%) had PET-positive pelvic lymph nodes, whereas 8 of 41 patients (20%) had abnormal pelvic lymph nodes read on CT. Of the 8 patients with abnormal CT

Discussion

Staging and treatment of anal cancer are no longer performed surgically (14). As such, greater emphasis has been placed on noninvasive imaging techniques to define the extent of disease. Determination of nodal status is critically important to disease prognosis and to the tailoring of effective radiation therapy, which consists of radiation to both the primary disease site and the inguinal groin. Importantly, presence of inguinal node metastasis calls for an increased radiation dose to the

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Clinical investigationAnusFDG-PET/CT in the evaluation of anal carcinoma

Introduction

Section snippets

Patients

Visualization of primary tumor

Pelvic lymph nodes

Discussion

Lancet

Radiother Oncol

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Gynecol Oncol

Am J Surg

Gynecol Oncol

Int J Radiat Oncol Biol Phys

Lancet

Cancer statistics, 2005

CA Cancer J Clin

Anal cancer incidence and survivalThe surveillance, epidemiology, and end results experience, 1973–2000

Cancer

Human papillomavirus, smoking, and sexual practices in the etiology of anal cancer

Cancer

Epidermoid carcinoma of the anal canal. Results of curative-intent radiation therapy in a series of 270 patients

Cancer

Epidermoid cancer of the anorectum

Cancer

Clinical investigation
Anus
FDG-PET/CT in the evaluation of anal carcinoma