Rash characteristics
Table 3 summarizes the patient demographics, associated ICIs, rash
characteristics, and other irAEs according to the rash type.
Maculopapular rash was the most common inflammatory eruption in each ICI
class (anti–PD-1 antibody, 21/29; anti–PD-L1 antibody, 5/6;
anti–CTLA-4 antibody, 2/2; and combined anti–PD-1 and anti–CTLA-4
therapy, 5/5). However, no obvious correlation was found between ICI
classes and rash types.
Maculopapular rash was the most common type in patients with lung cancer
and melanoma (n = 14 and n = 10, respectively). Overall, no specific
trends were observed between tumor types and rash types.
The duration from the start of ICI treatment to cutaneous reaction
varied according by rash type. Maculopapular rash, erythema multiforme,
and SJS had a short median latency, ranging 11.0–94.5 days. Conversely,
lichenoid reaction, psoriasiform reaction, bullous pemphigoid, and
scleroderma-like eruption had a longer median latency, ranging
140.0–231.0 days. The longest latency of 509 days (32 cycles of
nivolumab completed) was noted in a patient with maculopapular rash. The
shortest latency of 0 days (6 h after administering pembrolizumab) was
also noted in a patient with maculopapular rash. Pruritus was observed
in 24 patients (57.1%), and there were one case of maculopapular rash
and one case of lichenoid reaction with mucosal lesions other than SJS.
The mean blood eosinophil count was elevated (range, 4.5–19.8%) in
patients with maculopapular rash, erythema multiforme, lichenoid
reaction, psoriasiform reaction, and SJS. By contrast, the mean blood
eosinophil count was not significantly elevated (range, 0.9–3.8%) in
patients with bullous pemphigoid and scleroderma-like eruption.
Other irAEs, including adrenalitis, colitis, hepatitis, cholangitis,
diabetes mellitus, hypophysitis, pneumonitis, thyroiditis, and
parotitis, were found in patients with maculopapular rash (n = 8) and
lichenoid reaction (n = 2).