925P - Treatment discontinuation of immune checkpoint blockade in patients with head and neck squamous cell carcinoma experiencing complete or nearly complete remission

Background

PD-1 antibodies have become standard of care in the treatment of recurrent/metastatic head and neck squamous cell carcinoma (HNSCC) in first or second-line palliative treatment. After 4 years of follow up, 17% of the initial Keynote-48 study population is alive. In clinical routine, it remains an unresolved question how to deal with the situation of complete remission concerning treatment continuation.

Methods

In a retrospective case analysis we collected patients with HNSCC who experienced complete or very good partial remission under PD-1 inhibition. A very good partial remission was defined as a residual tumor substrate without contrast enhancement on CT and no change in residual tumor mass within the last 6 months.

Results

53 patients derived from 6 centers in Germany were identified. PD-L1 CPS was 0 in 2 pts, 1-20 in 13 pts. >20 in 13 pts and missing in 25. Nivolumab was given in 28 pts. (52%), pembrolizumab in 18 pts (34%), pembrolizumab/chemotherapy in 3 and other immunotherapies in 4 pts. At the first staging after therapy initiation, 28 pts (52%) had a partial remission (PR) and 6 (11%) a complete remission (CR). The median time to very good partial or CR was 7 months. Of the 53 patients, 17 remain on treatment to date of data collection. 36 patients discontinued treatment, 11 because of toxicity. Of the 36 patients, 9 experienced disease progression of whom 7 patients were treated again with PD-1 inhibitor. First course of ICI had a median duration of 25 months. The majority of patients (75%) remained in remission after treatment discontinuation with a median follow up of 7 months. Of the 7 patients who were re-challenged 4 had a PR, 1 SD, 1 PD and 1 missing.

Conclusions

To our knowledge, this is the first case collection of patients with complete or very good partial remission of head and neck SCC patients receiving PD-1 inhibitors for whom treatment discontinuation may be considered. After treatment discontinuation, the majority of patients remain in remission and 71% of patients experience disease control when re-exposed to PD-1 inhibitors. Extension of this case collection and long-term follow-up is needed to guide patient counseling in regard to the question of safe treatment discontinuation.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

K. Klinghammer: Financial Interests, Personal, Advisory Board: BMS, MSD; Financial Interests, Personal, Invited Speaker: Merck Sanofi, onkowissen, Biontech; Non-Financial Interests, Principal Investigator: AstraZeneca, gsk, Kura Oncol., MSD, Biontech; Non-Financial Interests, Advisory Board: DGHO, DKG, AIO. S. Ochsenreither: Financial Interests, Personal, Advisory Board: MSD, BMS, Janssen, Ipsen, Immunocore, Genemab, Pfizer; Financial Interests, Personal, Invited Speaker: MSD, Merck, Immunocore, Janssen; Financial Interests, Personal, Other, Support for travel / meeting: Janssen, Pfizer; Financial Interests, Personal, Advisory Board, Patent of T-cell therapy target: Fred Hutchinson cancer Research Center. All other authors have declared no conflicts of interest.