The investigators conduct this study to evaluate the efficacy and adverse effect of salvage concurrent chemo-proton therapy (CCPT) with or without surgical resection in previously irradiated recurrent rectal cancer.

The obtaining of local control in previously irradiated recurrent rectal cancer is crucial for survival prolongation as well as quality of life of patients. But, it is not easy to get with surgery and/or conventional radiotherapy (RT) because of the limitation of RT dose. Proton therapy has unique advantage showing superior dose distribution focusing tumor escaping surrounding normal tissues using "Bragg-peak".

Inclusion Criteria:

• previously diagnosed as rectal cancer and received curative intent treatment
• diagnosed as recurrent rectal cancer either pathology or radiologic exam
• discussed at tumor board and recommend proton therapy
• previous history of pelvic area radiotherapy
• Eastern Cooperative Oncology Group performance status of 0 to 2
• informed consent to present study
• consent to contraception for 6 months during and after study participation
• maintained bone marrow function ( absolute neutrophil count ≥ 1,2 * 109/L, platelet count ≥ 100 * 109/L)
• maintained renal, hepatic function creatinine clearance ≥ 50 mL/minute total bilirubin ≥ 2.2 mg/dl alkaline phosphatase ≥ 192 U/L

Exclusion Criteria:

• Pregnant and/or breastfeeding woman
• Less than 12 weeks of expected survival
• Uncontrolled active co-morbidity