 - Women of childbearing potential WOCBP and men must agree to use adequate contraception hormonal or barrier method of birth control; abstinence prior to study entry and for the duration of study participation; WOCBP should use an adequate method to avoid pregnancy for 32 weeks after the last dose of investigational drug; women of childbearing potential must have a negative serum or urine pregnancy test minimum sensitivity 25 IUL or equivalent units of HCG within 24 hours prior to the start of nivolumab; women must not be breastfeeding; men who are sexually active with WOCBP must use any contraceptive method with a failure rate of less than 1 per year; men receiving nivolumab and who are sexually active with WOCBP will be instructed to adhere to contraception for a period of 31 weeks after the last dose of investigational product; women who are not of childbearing potential i.e., who are postmenopausal or surgically sterile as well as azoospermic men do not require contraception; women of childbearing potential WOCBP is defined as any female who has experienced menarche and who has not undergone surgical sterilization hysterectomy or bilateral oophorectomy or who is not postmenopausal; menopause is defined clinically as 12 months of amenorrhea in a woman over 45 in the absence of other biological or physiological causes; in addition, women under the age of 55 must have a documented serum follicle stimulating hormone FSH level less than 40 mIUmL; should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she or the participating partner should inform the treating physician immediately 