Abstract
To assess the role of sentinel lymph-node biopsy (SLNB) and FDG-PET in staging and radiation treatment (RT) of anal cancer patients. This retrospective study was performed on 80 patients (male: 32, female: 48) with a median age of 60 years (39–89 years) with anal squamous cell carcinoma who were treated from March 2008 to March 2018 at the IRCCS San Raffaele Hospital. Patients without clinical evidence of inguinal LNs metastases and/or with discordance between clinical evidence and imaging features were considered for SLNB. FDG-PET was performed in 69/80 patients. Patients with negative imaging in inguinal region and negative SLNB could avoid RT on groin to spare inguinal toxicity. CTV included GTV (primary tumour and positive LNs) and pelvic ± inguinal LNs. PTV1 and PTV2 corresponded to GTV and CTV, respectively, adding 0.5 cm. RT dose was 50.4 Gy/28 fractions to PTV2 and 64.8 Gy/36 fractions to PTV1, delivered with 3DCRT (n = 24) or IMRT (n = 56), concomitant to Mitomycin-C and 5-FU chemotherapy. FDG-PET showed inguinal uptake in 21/69 patients (30%) and was negative in 48/69 patients (70%). Lymphoscintigraphy was performed in 11/21 positive patients (4 patients SLNB confirmed inguinal metastases, 6 patients false positive and 1 patient SLN not found), and in 29/48 negative patients (5/29 showed metastases, 23/29 true negative and 1 SLN not found). Sensitivity, specificity, positive and negative predictive value of FDG-PET were 62%, 79%, 40% and 82%, respectively. Median follow-up time from diagnosis was 40.3 months (range: 4.6–136.4 months): 69 patients (86%) showed a complete response, 10 patients (13%) a partial response, 1 patient (1%) a stable disease. Patients treated on groin (n = 54) versus not treated (n = 26) showed more inguinal dermatitis (G1–G2: 50% vs. 12%; G3–G4: 17% vs. 0%, p < 0.05). For patients treated on groin, G3–G4 inguinal dermatitis, stomatitis and neutropenia were significantly reduced with IMRT against 3DCRT techniques (13% vs. 36%, p = 0.10; 3% vs. 36%, p = 0.003; 8% vs. 29%, p = 0.02, respectively). SLNB improves the FDG-PET inguinal LNs staging in guiding the decision to treat inguinal nodes. IMRT technique significantly reduced G3-G4 toxicities when patients are treated on groin.
Highlights
To assess the role of sentinel lymph-node biopsy (SLNB) and FDG-PET in staging and radiation treatment (RT) of anal cancer patients
In the present study we reported our experience about the role of SLNB compared to FDG-PET in terms of disease staging and the clinical impact of inguinal irradiation with the use of advanced RT techniques
Lymphoscintigraphy was performed in 11/21 (52%) patients: SLNB confirmed inguinal metastases in 4/10 patients (40%), 6/10 patients (60%) were false positive and SLN was not found in 1 patient
Summary
A retrospective comparison between FDG-PET inguinal LNs evaluation and SLNB results was made. Patients without clinical evidence of inguinal LNs involvement or with discordance between diagnostic imaging and clinical examination were considered for the SLNB protocol. As the inguinal LNs irradiation is the standard treatment in anal cancer, all patients enrolled in this study with positive SLNB were treated on groin. Sensitivity, specificity, area under the curve (AUC), positive and negative predictive values of FDG-PET against SLNB were assessed in the subgroup of patients that performed both examinations. N. patients (%) Gender Male Female Median age (range) Histological subtype Squamous Localization Anal canal Anal canal + rectal Anal canal + margin T1 T2 T3 T4*. Informed consent was obtained from all individual participants included in the study
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