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Vulvar Recurrences After Intensity-modulated Radiation Therapy for Squamous Cell Carcinoma of the Anus

Bagshaw, Hilary, P., MD*; Sause, William, T., MD; Gawlick, Ute, MD; Kim, H., Tae, MD; Whisenant, Jonathan, MD§; Cannon, George, M., MD

American Journal of Clinical Oncology: May 2018 - Volume 41 - Issue 5 - p 492–496
doi: 10.1097/COC.0000000000000322
Original Articles: Gastrointestinal

Objectives: The objective is to determine localregional control (LRC), distant metastasis free survival, disease-free survival, overall survival (OS), and toxicity for patients with squamous cell carcinoma of the anus treated with definitive chemotherapy and intensity-modulated radiation therapy (IMRT).

Materials and Methods: We conducted a retrospective review of patients treated using IMRT for squamous cell carcinoma of the anus at our institution since 2005. Patients with local recurrences were identified and reviewed. The Kaplan-Meier curves were used for LRC and OS.

Results: From 2005 to 2014, 52 patients were treated with IMRT-based chemoradiation for squamous cell carcinoma of the anus. Median dose to the primary tumor was 54 Gy. LRC, distant metastasis free survival, OS, and disease-free survival were 92.3%, 88.5%, 86.5%, and 84.6%, respectively, with a median follow-up of 20 months. Two local failures occurred at the anal primary site and 2 in the vulva. Despite subsequent palliative radiotherapy and chemotherapy, neither patient with a vulvar recurrence achieved disease control.

Conclusions: In a cohort of patients treated with IMRT-based chemoradiation, 2 vulvar recurrences were identified within the avoided external genitalia despite limited recurrence rates within the cohort overall. This experience suggests that for patients with a locally advanced primary tumor and bulky bilateral inguinal or pelvic disease, the in-transit vulvar dermal lymphatics may be at risk for subclinical involvement and subsequent recurrence. If substantiated by a similar pattern of recurrence at other institutions, the external genitalia may need to be reclassified from an avoidance structure to a clinical treatment volume in patients with locally advanced anal cancer.

*Stanford University Hospital and Clinics, Stanford, CA

Intermountain Healthcare Radiation Oncology

Intermountain Colon & Rectal Surgery

§Huntsman Cancer Institute, Salt Lake City, UT

Presented at the 57th Annual Meeting of the American Society for Radiation Oncology, October 18 to 21, 2015, San Antonio, TX.

The authors declare no conflicts of interest.

Reprints: Hilary P. Bagshaw, MD, Department of Radiation Oncology—Cancer Center, Stanford University Hospital and Clinics, 875 Blake Wilbur Drive, Stanford, CA 94305. E-mail: hbagshaw@stanford.edu.

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