As Dr. William Newsom closed the doors to Grass Valley Hematology-Oncology Friday afternoon, he officially retired from a career that spanned  35 years, touched the lives of thousands and created a lasting legacy in the community — a comprehensive cancer center in Grass Valley that focused on the treatment of the whole patient, not just the disease. Friday was a stark contrast to his first day of work here 31 years ago. Newsom and his wife, Dr. Christine Newsom, an internist, moved to Nevada County from San Francisco to open a practice together. With their 6-month-old son, they arrived in …