C3 and neoplasm: Vice versa, if the complement system is activated before the application of RT, the combined effect [29] could elicit a chain of cellular apoptosis and other forms of radiation-induced cell death outcomes [2], which may be due to C3b/iC3b fragments [42] and sub-lytic membrane-attack complex (MAC) [43] deposition on the tumor-cell surface while the plasma membrane was still intact without being destroyed by the ionizing RT.