NZ 594829 Disclosed is the use of (+)-1,4-dihydro-7-[(3S,4S)-3-methoxy-4-(methylamino)-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid in the manufacture of a composition for treating cancer in a subject having a BRCA2 mutation that impairs BRCA2 activity, wherein the composition is for administration of a dose of about 10-100 mg/m2 of (+)-1,4-dihydro-7-[(3S,4S)-3-methoxy-4-(methylamino)-1-pyrrolidinyl]-4-oxo-1-(2-thiazolyl)-1,8-naphthyridine-3-carboxylic acid.