SESSION TITLE: Student/Resident Lung Cancer SESSION TYPE: Student/Resident Case Report Slide PRESENTED ON: Sunday, October 29, 2017 at 04:30 PM - 05:30 PM INTRODUCTION: Cancer regression in the absence of treatment is extremely rare, especially in primary lung malignancies. Historically, treatment options include chemotherapy, surgery, or radiation, depending on stage, however, newer therapies that modulate cellular immunity demonstrate prolonged disease-free survival compared to standard treatment. Non-Small Cell Lung Cancer is a leading cause of lung cancer mortality with 60 month survival rates of 6 to 82 percent, depending on 7th edition TNM classification. We report a case of a man found to have adenocarcinoma on biopsy that resolved without treatment. CASE PRESENTATION: A 64 year old man with a 60 pack-year smoking history and chronic obstructive pulmonary disease, was found to have a PET-avid 1.1 cm pulmonary nodule without evidence of lymphadenopathy or metastatic disease. Six months after discovery he underwent percutaneous biopsy of the nodule. Pathologic examination revealed adenocarcinoma with lymphocytic infiltrates. Immunohistochemical stains were positive for CK-7, but negative for CK-20 and TTF-1. When he presented five months later to establish care after relocation, follow up imaging demonstrated resolution of the nodule. The patient denied any form of interval treatment. For five years he was followed with surveillance imaging without recurrence. DISCUSSION: The concept of immunologic mechanisms mediating tumor regression is not new. In his 1917 case series of spontaneous regressions of malignancy, G.L. Rohdenburg attributed several “causes of absorption” to acute infection1. Clinical applications have stemmed from this idea, such as Coley’s toxin and intracystic Bacillus Calmette-Guérin. Immune modulation of the PD-1 pathway in NSCLC has shown improved tumor response. Recently, Menon and Eaton described an AIDS patient with resolution of biopsy-proven metastatic disease with reconstitution of the immune system2. Without any extrinsic therapy to explain his nodules’ regression, one hypothesis to explain our patient's spontaneous regression is an immunologic mechanism. CONCLUSIONS: Spontaneous regression of solid tumors is an uncommon phenomenon, most frequently reported in melanoma, renal cell carcinoma, embryonal tumors, and sarcoma. It is rarely described in primary thoracic tumors. In a review of all spontaneously regressing thoracic malignancies from 1951-2008, only five cases represented primary thoracic malignancies, including two mesotheliomas3. Thus, true spontaneous regression of primary thoracic malignancy is exceedingly rare. Reference #1: Rohdenburg, G.L. Fluctuations in the Growth Energy of Malignant Tumors in Man, with Especial Reference to Spontaneous Recession. The Journal of Cancer Research April 1 1918,193-225 Reference #2: Menon, MP. et al. Spontaneous Regression of Non-Small-Cell Lung Cancer in AIDS After Immune Reconstitution. Journal of Thoracic Oncology, Vol.10, Issue 1 Reference #3: Kumar, T. et al. Spontaneous regression of thoracic malignancies. Respiratory Medicine, 2010 vol.104,1543-1550 DISCLOSURE: The following authors have nothing to disclose: Taylor Myers, Timothy Vossler, Bart Moulton No Product/Research Disclosure Information