Is anti-PD-1 immunotherapy a means for post-irradiation tumor clearance in head and neck cancer?

Chemo-radiotherapy is the standard treatment for locally advanced head-neck cancer (LA-HNC). However, about 30% of tumors do not respond or even progress shortly after the completion of radiotherapy. We investigated whether anti-PD1 immunotherapy can eradicate the irradiated tumor and reverse the ominous prognosis of these patients. We retrospectively analyzed a small series of 9 patients with LA-HNC who did not respond (6/9) or showed local disease progression (3/9) during chemo-radiotherapy and were treated with nivolumab anti-PD1 immunotherapy. Immunotherapy started 1.5 months after the end of radiotherapy. Out of 9 patients, 3 (33.3%) had a complete response and 3 (33.3%) partial response at 6 months after the onset of immunotherapy. Two patients are alive with no evidence of disease at 36 months. One more patient with partial response and without disease progression survived 16 months after therapy when he died from intercurrent disease. Immunotherapy showed an excellent tolerance profile. One patient developed an extensive skin rash on the 16th cycle. Anti-PD-1 immunotherapy after radiotherapy can lead to clearance of the remnant tumor and ameliorate the prognosis of patients. Randomized trials are necessary to establish post-irradiation immunotherapy as a standard of care in this ill-fated subgroup of HNC patients.