Anti-PD1 immunotherapy and hypofractionated RT for locally advanced squamous cell skin cancer
PO-1550
Abstract
Anti-PD1 immunotherapy and hypofractionated RT for locally advanced squamous cell skin cancer
Authors: Ioannis Koukourakis1, Panagiotis Mamalis2, Axiotis Giaktzidis3, Anna Zygogianni1, Michael Koukourakis4
1Aretaieion University Hospital, Radiation Oncology Unit, 1st Department of Radiology, Medical School, National and Kapodistrian University of Athens, Athens, Greece; 2University Hospital of Alexandroupolis, Department of Radiotherapy / Oncology, Democritus University of Thrace, Alexandroupolis, Greece; 3University Hospital of Alexandroupolis, Department of Radiotherapy / Oncology, Medical School, Democritus University of Thrace, Alexandroupolis, Greece; 4University Hospital of Alexandroupolis, Department of Radiotherapy / Oncology, Medical School, Democritus University of Thrace , Alexandroupolis, Greece
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Purpose or Objective
Locally advanced squamous cell skin cancer (LA-SqSC) is a challenging devastating disease, mainly affecting older patients that refuse to seek medical assistance at earlier stages, and patients with recurring tumors after surgery. Radiotherapy (RT) is often difficult to apply due to large tumor volumes, and extensive ulcerations and tissue necrosis.
Material and Methods
Nineteen (19) patients (median age 85) have been treated according to a therapeutic algorithm involving induction immunotherapy with 4 cycles (q3w) of cemiplimab (anti-PD-1 MoAb). Partial responders (PR) continued immunotherapy for another 4 cycles. Complete responders (CR) received cemiplimab for a total of 24 cycles, or until progression or manifestation of immune-related adverse events (irAEs). Patients with progressive disease (PgD) after 4 cycles or incomplete response after 8 cycles, were subjected, when feasible, to local RT (6 daily fractions of 6Gy). Patients unable to undergo RT or patients recurring after RT were treated with further chemotherapy.
Results
Out of 19 patients, 2 died from intercurrent reasons before completion of the 4th cycle, and 2 refused to continue therapy after the 2nd cycle, due to long travel distances and/or social/financial reasons. Of the remaining 15, 2 (13.3%) had CR, 10 (66.7%) PR and 3 (20%) had stable disease (SD), after the completion of the 4th cemiplimab cycle. After the 8th cycle, 9 (60%) reached CR, 3 (20%) PR, 2 (13.3%) SD and 1 (6.7%) PgD. All PRs and one patient with SD underwent RT, which led to CR of the disease. The remaining two patients refused further therapy. The overall CR rate was 86.7% (13/15), reaching 100% (13 /13) for patients receiving full treatment according to the treatment algorithm. Within a median follow-up of 12 months (4-24 months), only 1 patient progressed locally, providing an estimated 2-year survival of 82.9%. irAEs included 2 patients with generalized skin toxicity (enforcing immunotherapy interruption), and 2 patients with hypothyroidism. RT tolerance was excellent without higher than grade 1 early or late toxicity.
Conclusion
LA-SqSC can be effectively treated with induction cemiplimab immunotherapy followed by a short course hypofractionated RT directed to the residual tumor after the 8th cycle of cemiplimab.