Article in the Telegraph
"A review of research studies involving more than 380,000 women concluded there was no evidence that self-examination had any effect on deaths from breast cancer.
It may even be doing more harm than good as women who thought they found lumps underwent biopsies that turned out to be unnecessary.
Self examination led to twice as many biopsies that turned out to be negative for cancer than women who did not check their breasts."
You can reduce your risk of developing breast cancer and most other cancers by eating less salt/sodium and eating plenty of fruit and (unsalted) vegetables.