Exemestane in Post-Menopausal Women With NSCLC

Inclusion Criteria * Recurrent or progressive advanced stage non-small cell lung cancer (no small cell component) with most recent treatment being an FDA approved immune checkpoint inhibitor (pembrolizumab, atezolizumab, or nivolumab) NOTE: Pathology reports documenting the diagnosis of NSCLC are required to be reviewed to confirm outside diagnosis * Sufficient tumor tissue available from original diagnosis or subsequent biopsy for analysis of estrogen receptor and aromatase - tumor block or a minimum of 5 unstained slides * Failed at least 1 prior FDA approved treatment for advanced NSCLC. Patients with EGFR/ALK/ROS1 rearrangements should have received an FDA-approved TKI prior to enrollment on this trial. * Measureable disease by RECIST version 1.1 * Post-menopausal defined as * Age ≥ 55 years and 1 year or more of amenorrhea * Age \< 55 years and 1 year or more of amenorrhea with an estradiol assay \< 20 pg/mL * Surgical menopause with bilateral oophorectomy * ECOG performance status 0, 1 or 2 \* Life expectancy of 3 months or more in the opinion of the enrolling investigator and documented in the medical record * Adequate organ function within 14 days of study enrollment defined as: * Hematology: \*\* Absolute neutrophil count (ANC) ≥ 1500/mm³, Platelets ≥ 100,000/mm³, Hemoglobin ≥ 8 g/dL * Biochemistry: * Total Bilirubin within normal institutional limits * AST/SGOT and ALT/SGPT ≤ 2.5 x upper limit of normal (ULN), except if there is known hepatic metastasis, wherein transaminases may be ≤ 5 x institutional ULN. * Serum creatinine ≤ 1.5 mg/dl or glomerular filtration rate \> 50 ml/min * Must have recovered to CTCAE v 4 Grade 1 or better from the acute effects of any prior surgery, chemotherapy or radiation therapy. Chronic residual toxicity (i.e. peripheral neuropathy) is permitted. * A minimum time period must elapse between the end of a previous treatment and start of study therapy: * 1 week from the completion of radiation therapy for brain metastases * 4 weeks from the completion of chemotherapy or any experimental therapy * 4 weeks from prior major surgery (such as open biopsy or significant traumatic injury) * Voluntary written consent before any research related procedures or therapy Exclusion Criteria * Known active CNS disease - If patient has history of brain metastases, the brain lesions must have been treated with radiation and/or surgery - patients should be neurologically stable and requiring ≤10mg oral prednisone equivalence of steroids per day * Any toxicity from immune-related toxicity from prior immune therapy that would preclude further treatment with anti-PD-1/PDL-1 inhibitor or ongoing IR toxicity ≥ Grade 2 * Requiring \> 10 mg prednisone equivalence of steroids per day for immune-related toxicity * Inability or unwilling to swallow study drug * Any gastrointestinal condition causing malabsorption or obstruction (eg, celiac sprue, gastric bypass surgery, strictures, adhesions, history of small bowel resection, blind loop syndrome) * Currently using hormone replacement therapy (oral or patch) or/and phytoestrogen supplements (i.e. black cohosh) * Known hypersensitivity to exemestane or its excipients * Any serious underlying medical condition that, in the opinion of the enrolling physician, would impair the ability of the patient to receive protocol treatment * Prior malignancy, with the exception of curatively treated squamous cell or basal carcinoma of the skin or in situ cervical cancer, unless there is a 3-year disease-free interval * Concomitant use of strong CYP3A4 inducers such as rifampicin, phenytoin, carbamazepine, phenobarbital, or St. John's wort as these may significantly reduce the availability of exemestane