目的：評估蟹足腫患者罹患癌症的風險以及此族群接受放射治療後的致癌風險。 材料與方法：使用健保資料庫蒐集 1997 年至 2011 年之間新診斷之蟹足腫病患，病患必須為 二十歲以上且過去無癌症診斷。以標準化發生率比（standardized incidence ratio, SIR），評估蟹 足腫病患罹患癌症之風險，同時也評估使用放射線治療蟹足腫是否增加罹癌風險。 結果：本研究總共蒐集了 18,646 位蟹足腫病患，追蹤期中位數為 5.6 年，共有 338位病人罹患 癌症。蟹足腫病患之全癌症標準化發生率比稍高於一般族群（SIR 1.12, 95% 信賴區間 1.00–1.24, p= 0.049），特別是在女性（SIR 1.22, 95% 信賴區間 1.06–1.40, p= 0.006）。針對單一癌症，蟹足 腫病患罹患骨骼及軟組織癌症之風險顯著提升（SIR 3.84, 95% 信賴區間 1.99–6.71, p< 0.001）。 在所有蟹足腫病患中，只有 22 位接受放射治療，因樣本數過少而無法準確的評估其罹癌風險。 結論：蟹足腫病患相較於一般族群有較高的罹癌風險，特別是骨骼及軟組織癌症。蟹足腫病患 接受放射線治療的人數很少，因此無法進一步評估放射治療引起的癌症風險，但也表示目前在 台灣，放射治療於蟹足腫治療的使用率仍偏低。

Background : To evaluate the cancer risk in keloid patients and the risk of radiationassociated malignancy in keloid patients who received radiotherapyy (RT) in a population-based study. Materials and Methods : Patients with newly diagnosed keloid who were aged 20 years or above and had no antecedent cancers between 1997 and 2011 were recruited from Taiwan National Health Insurance Research Database. We used standardized incidence ratios (SIRs) to calculate the cancer incidence for keloid patients and also for the subgroup of patients who received RT for keloid. Results : A total of 18,646 keloid patients were enrolled. During a median follow-up time of 5.6 years, 338 patients developed cancers. The overall risk of cancer was slightly increased in keloid cohort (SIR 1.12, 95% confidence interval [CI] 1.00–1.24, p= 0.049), especially in women (SIR 1.22, 95% CI 1.06–1.40, p= 0.006). For specific cancer type, the risk of bone and soft tissue sarcoma was significantly elevated (SIR 3.84, 95% CI 1.99–6.71, p< 0.001). In the keloid cohort, only 22 (0.12%) patients received RT for keloid treatment. The cancer risk in this subgroup (SIR 2.34, 95% CI 0.28–8.46) cannot be estimated precisely as a consequence of lack of power. Conclusion : Keloids may be associated with an elevated cancer risk, especially for bone and soft tissue sarcoma. The risk of radiation-induced cancers cannot be estimated because the number of keloid patients who received RT is scarce; however, it implies that RT might be underused for treatment of keloids in Taiwan.