162 Outcomes following ablative therapy of pulmonary oligometastases in patients with HPV-positive head and neck cancer

Local ablation of oligometastases has been shown to improve patient survival (1). Oligometastases are more frequent in viral-related head and neck squamous cell carcinomas (HNSCC) compared to non-viral HNSCC, with lung as the most common site (2). We reviewed patients with HPV-positive (+) HNSCCs who developed lung metastases, and report outcomes for all patients, focusing on those receiving definitive intent local ablation. We reviewed all HPV(+) HNSCCs patients who developed distant metastases (DM) to lung ± other organs after definitive radiotherapy or chemoradiotherapy at our institution from January 2003 to December 2021. DM in lung were further classified as oligometastases (≤5 lesions) vs polymetastases. Among those patients classified as oligometastases, we pragmatically sub-staged according to the American Joint Commission on Cancer 8th edition for primary non-small cell lung cancer (NSCLC) (3) (oligometastasis mimicking the behavior of NSCLC) to assess differences in outcome after local ablative therapy. Oligometastases in lung were confirmed by p16(+) staining to rule out lung primary when possible. Definitive intent local ablation (LA) was defined as either surgical resection or definitive-intent [EQD2 ≥40 Gy; alpha/beta=10 Gy] (chemo)radiation. Overall survival (OS) and progression free survival (PFS) after lung metastases were estimated by Kaplan Meier curves, with log rank test for outcome comparison. Of 1908 consecutive patients treated during the study period, 170 (9%) developed DM to lung and other sites. Lung was the only DM site in 79 patients (4%), of whom, 20 (1%) had oligometastases and underwent LA: 15 underwent surgery (1 lobectomy, 2 segmentectomies, 12 wedge resections), 1 surgery + radiation, 3 radiation alone and 1 chemoradiation. Median follow-up was 2.0 years (range 0-13.5). For OM patients receiving LA, OS at 3 and 5 years after detection of metastasis was 69% and 57%; PFS was 40% at 3 years and 34% at 5 years. When patients who developed isolated lung metastases were staged as per the TNM 8th edition for lung cancer, most patients were N0 (n=16) and early stage. Some patients with N+ disease (n=4) or very advanced T category disease (T4, n=1) were treated with definitive intent as well. OS of oligometastatic lung DM treated with local ablative treatment according to lung cancer N stage showed 75% at 3 years and 75% at 5 years for N+ disease, and 67% at 3 years and 50% at 5 years for N0 disease (p = 0.587). PFS of oligometastatic lung DM treated with ablative treatment according to lung cancer N stage was not statistically different with 25% at 3 years and 25% at 5 years for N+ disease, and 44% at 3 years and 36% at 5 years for N0 disease (p = 0.678). For comparison, across all 170 patients with DM to lung and other sites, OS at 3 and 5 years after detection was 22% and 16%. For the 150 patients who did not receive LA, these rates were 15% and 10% respectively. For the 79 with lung-only DM who did not receive LA, these rates were 21% and 16% respectively. These were statistically different compared to OS at 3 and 5 years for OM patients receiving LA (p < 0.001). Patients with oligometastatic HPV(+) HNSCC to lung treated with local ablation with definitive intent have significantly longer OS compared to those with polymetastatic disease who had palliative treatment or best supportive care treatment. Isolated lung lesions, large lung lesions, and lung lesions with nodal involvement treated with definitive intent all showed substantially longer OS compared with patients who did not receive ablative therapy. Isolated pulmonary DM in patients with HPV(+) HNSCC should be considered for local ablation with definitive intent.

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