This study assesses whether balloon kyphoplasty (BKP) can safely restore height and correct deformity for cancer-related vertebral compression fractures (VCFs) involving the posterior vertebral body wall (PVBW), which is normally considered a relative contraindication. Retrospective cohort study of 158 patients (99M:59F; mean age 63 years) with 228 cancer-related VCFs, who underwent BKP. 112 had VCFs with PVBW defects, and 46 had VCFs with no PVBW defect. Data was assessed preoperatively and at 3 months. In the PVBW defect group, mean pain score decreased from 7.5 to 3.6 (p<0.001). There was a significant decrease in kyphotic angle (p<0.01), anterior vertebral body height (AVBH) (p<0.01) and mid-vertebral body height (MVBH) (p<0.05). In the PVBW intact group, mean pain score decreased from 7.3 to 3.3 (p<0.001). There was a significant improvement in AVBH and MVBH (p<0.001). When comparing groups, kyphotic angle, AVBH and MVBH were significantly worse in the PVBW defect group (P<0.05). More cement leaks occurred in the PVBW defect group. BKP can alleviate pain but does not restore height or correct kyphosis in patients with cancer-related VCFs and PVBW defects. There is no appreciable increase in surgical risk.