Study Confirms Predictive Value of Ki-67 in Rare Melanoma Subtype

High Ki-67 expression is associated with more aggressive disease and predictive of worse survival outcomes in patients with acral melanoma, according to a retrospective study from Chinese researchers published in Scientific Reports.¹

Although Ki-67 is considered a key predictor of tumor cell proliferation across cancer types, there is a lack of definitive research regarding its prognostic value in patients with acral melanoma, according to corresponding study author Di Wu, MD, Department of Oncology, Cancer Center, The First Hospital of Jilin University, Changchun, China, and coauthors. Acral melanoma is a subtype of cutaneous melanoma that is rare and racially specific. It rarely occurs in Caucasian patients but is a common melanoma subtype in Chinese patients.²

In their study, Wu et al found that at a median follow-up of 70.9 months, there was a significant difference in disease-free survival (DFS) between patients with low Ki-67 expression (<30%) and high Ki-67 expression (≥30%), with a median DFS of 74.1 months vs 26.8 months, respectively (HR, 1.42; 95% CI 1.04-1.92, P = .025). The 1-, 3-, and 5-year DFS rates all favored the low-expression group at 77.3% vs 68.2%, 53.1% vs 45.9%, and 47.0% vs 41.2% respectively.¹

Similarly, there was also a significant difference in overall survival (OS), with a median OS that was not reached in the low-expression group compared with 52.1 months in the high-expression group (HR, 2.91; 95% CI, 2.04-4.16; P <.001). The 1-, 3-, and 5-year OS rates all favored the low-expression group at 97.8% vs 93.7%, 87.6% vs 64.6%, and 78.5% vs 44.9%, respectively.

Univariate analysis confirmed that high Ki-67 expression was associated with worse DFS (HR, 1.42; 95% CI, 1.04-1.92; P = .026) and OS (HR, 2.83; 95% CI, 2.04-4.16; P <.001) were associated with poorer OS. On multivariate analysis, high expression was associated with worse OS (HR 2.11; 95% CI, 1.46-3.06; P <.001); however, high expression was not associated with poorer DFS.

“In our study, the high Ki-67 expression group exhibited significantly shorter median DFS and OS compared to the low-expression group, consistent with two other Chinese studies, where high Ki-67 expression was associated with poor prognosis,” Wu et al wrote.

Study Background and Patient Characteristics

The study used demographic and clinical data from 324 patients diagnosed with acral melanoma between February 2011 and May 2023 at 5 melanoma treatment centers in China. Patients were required to have histologically or cytologically confirmed acral melanoma with a single primary lesion and evaluable Ki-67 data. Patients who did not receive resection or who had other malignant tumors were excluded from enrollment. The researchers conducted their retrospective analysis of the data in December 2024.

Of the total population, 55.8% (181 patients) had Ki-67 expression below 30% and 44.2% (143 patients) had expression above 30%. The study population comprised 154 men (47.5%) and 170 women (52.5%). The median patient age at diagnosis was 60 years (range, 22-86).

The researchers noted no significant differences between the 2 cohorts regarding sex, tumor site (hand vs foot), left/right orientation, association with a nevus, trauma history, mitotic rate, gene mutation profile, or prior adjuvant therapy.

Patients with Ki-67 expression levels ≥30% had several clinical and pathological characteristics linked to more aggressive disease including being older (aged ≥60 years, 62.2% vs 44.2% in the low–Ki-67 group), stage III disease (31.5% vs 16.0%, respectively), ulceration (65.7% vs 54.1%), thicker tumors (Breslow thickness T4: 45.5% vs 24.3%), elevated LDH levels (≥250 U/L: 14.0% vs 6.6%), and positive sentinel lymph node biopsy (28.0% vs 11.1%).

Study Conclusion

“Our study is consistent with previous studies, suggesting that Ki-67 serves as a significant independent factor influencing the prognosis of some melanoma subtypes, and emphasizing high Ki-67 expression in clinical practice could more accurately predict acral melanoma patient prognosis,” Wu and coauthors wrote in their concluding remarks.

REFERENCES:

1. Teng Y, Wu J, Zhang W, et al. Association between Ki-67 and clinical outcomes in 324 Chinese patients with resectable acral melanoma. Sci Rep. 2025;15(1):30130. doi: 10.1038/s41598-025-15751-w

2. Huang K, Xu Y, Gabriel EM, et al. Comparative analysis of acral melanoma in Chinese and Caucasian patient. J Skin Cancer. 2020:5169051. doi: 10.1155/2020/5169051