Antibodies against human papillomaviruses as diagnostic and prognostic biomarker in patients with neck squamous cell carcinoma from unknown primary tumor

Treatment of patients with neck lymph node metastasis of squamous cell carcinoma (SCC) from unknown primary tumor (NSCCUP) is challenging due to the risk of missing occult tumors or inducing toxicity to unaffected sites. Human papillomavirus (HPV) is a promising biomarker given its causal link to oropharyngeal SCC and superior survival of patients with HPV‐driven oropharyngeal SCC and NSCCUP. Identification of HPV‐driven NSCCUP could focus diagnostic work‐up and treatment on the oropharynx. For the first time, we assessed HPV antibodies and their prognostic value in NSCCUP patients. Antibodies against E6 and E7 (HPV16/18/31/33/35), E1 and E2 (HPV16/18) were assessed in 46 NSCCUP patients in sera collected at diagnosis, and in follow‐up sera from five patients. In 28 patients, HPV tumor status was determined using molecular markers (HPV DNA, mRNA and cellular p16^INK4a). Thirteen (28%) NSCCUP patients were HPV‐seropositive for HPV16, 18, 31, or 33. Of eleven patients with HPV‐driven NSCCUP, ten were HPV‐seropositive, while all 17 patients with non‐HPV‐driven NSCCUP were HPV‐seronegative, resulting in 91% sensitivity (95% CI: 59–100%) and 100% specificity (95% CI: 80–100%). HPV antibody levels decreased after curative treatment. Recurrence was associated with increasing levels in an individual case. HPV‐seropositive patients had a better overall and progression‐free survival with hazard ratios of 0.09 (95% CI: 0.01–0.42) and 0.03 (95% CI: 0.002–0.18), respectively. For the first time, seropositivity to HPV proteins is described in NSCCUP patients, and high sensitivity and specificity for HPV‐driven NSCCUP are demonstrated. HPV seropositivity appears to be a reliable diagnostic and prognostic biomarker for patients with HPV‐driven NSCCUP.