Proceedings of the 49th Annual ASTRO Meeting S755

whether the patients received surgery or surgery and radiotherapy. Head neck primary, localized or regional disease, tumor size #5cm predicted better CSS. Estimated 2-, 5-, and 10-year rates of OS and CSS for the entire group of patients were 88%, 61%, and42%, respectively; and 91%, 68%, and 47%, respectively (Fig.).

Conclusions: ASPS SEER database revealed that ASPS mostly occurred in young individuals. Better OS and CSS were associatedwith head primary, localized, small tumor size. Patients with regional or contiguous disease also demonstrated better survival ratescompared with those who had other sites of metastatic disease.

Author Disclosure: Y.J. Hitchcock, None; K. Macdonald, None; S. Lessnick, None; L. Chen, None; J. Chen, None; L. Randall,None.

2985 Surveillance, Epidemiology, and End Results (SEER) Database Analysis of Microcystic Adnexal

Carcinoma (Sclerosing Sweat Duct Carcinoma) of the Skin

S. C. Patel1, J. B. Yu2, R. H. Decker2, R. C. Blitzblau2, D. M. Housman3, L. D. Wilson2

1Howard University College of Medicine, Washington, DC, 2Yale University School of Medicine, New Haven, CT, 3MemorialSloan-Kettering Cancer Center, New York, NY

Purpose/Objective(s): Microcystic Adnexal Carcinoma (MAC), also known as sclerosing sweat duct carcinoma, malignantsyringoma, syringoid carcinoma, and trichofolliculoma with perineural invasion, is a very rare cancer of the skin. It has beendescribed previously in small case reports and retrospective series, and is thought to be a slow growing, locally aggressive andrecurrent cancer. Prior reports have also noted a predilection for the head and neck. In addition, prior radiotherapy is thought tobe a risk factor for MAC. This is the largest report of MAC in the literature.

Methods/Materials: The National Cancer Institute (NCI) SEER 1973-2003 database was investigated, and patients with scleros-ing sweat duct carcinoma of the skin were detected. A descriptive analysis was performed, investigating age, gender, site of disease,use of radiation, extent of surgery, and reason for death. Overall survival was calculated by using the Kaplan-Meier method. Rel-ative survival was calculated in SEER*Stat 5, using age-, race-, gender- and year of diagnosis-matched U.S. mortality data.

Results: MAC of the skin was recorded in 164 patients. Ten patients received radiation. Ninety-two percent of patients receivedsurgery. Sixty percent of subjects were female. Median age at diagnosis was 67.5 years old. The median recorded tumor size was 15mm (range 1 mm–150 mm), though tumor size was not recorded for 102 patients. Race distribution was 91% white, 4% black orasian/pacific islander, and 5% unknown/other. As expected, the site of disease predominated in the head and neck (74%). The re-maining reported sites included trunk 10%, upper limb/shoulder 9%, and lower limb/shoulder 6%. Seventy-six percent of diseasewas confined to the dermis or localized but not otherwise specified. Seven percent had invaded through the entire dermis, and 7%had invaded locally to underlying soft tissue and bone. Disease invasion was unknown in 9%. There was no recorded metastaticdisease though these were possibly coded as non-skin sites and not captured in our analysis. Lymph nodes were removed in only 6cases. The 5-year overall survival was 90% ([95% CI: 80%–95%]). The 5 and 10-year relative survival 99.6% (SE: 3.1% and 3.9%,respectively). All 8 deaths occurred before 3 years (Fig.).

Conclusions: This SEER database analysis confirms previously published characteristics. MAC tends to occur in the skin of thehead and neck (74%), in whites (91%), and in females (60%). It is locally invasive and rarely metastasizes to lymph nodes. Overalland relative survival is excellent. Radiation is rarely used for treatment.

S756 I. J. Radiation Oncology d Biology d Physics Volume 69, Number 3, Supplement, 2007

Author Disclosure: S.C. Patel, None; J.B. Yu, None; R.H. Decker, None; R.C. Blitzblau, None; D.M. Housman, None;L.D. Wilson, None.