The new doctor referred her to a surgeon, who diagnosed advanced bowel cancer.
Commissioner Anthony Hill's report said Dr B missed several opportunities to investigate the symptoms further, and failed to arrange adequate follow-up.
He noted that the patient did not present frequently, was at low-risk of bowel cancer, and that the medication prescribed did appear to work for a time.
However the doctor did not act with appropriate care and skill, and was found to be in breach of the Health and Disability Services Consumers' Rights Code.
It was recommended the doctor undertake an audit of patient records to identify any who needed follow-up. She had already provided a written apology to the patient.