Historically, endometrial cancer has been classified as type I or type II. Type I endometrial cancers are typically estrogen driven, low grade, with endometrioid histology, and have a more favorable prognosis. In contrast, type II endometrial cancers are typically high grade, have more aggressive histologies (eg, serous or clear cell), and have a poorer prognosis.1
While this system provides a helpful schema for understanding endometrial cancers, it fails to represent the immense variation of biologic behavior and outcomes in endometrial cancers and oversimplifies what has come to be understood as a complex and molecularly diverse disease.
UNC Chapel Hill
Dr. Jennifer Haag
In 2013, The Cancer Genome Atlas (TCGA) performed genomic, transcriptomic, and proteomic characterization of 373 endometrial carcinomas. They identified four categories with distinct genetic profiles corresponding to clinical outcomes: 1) DNA polymerase epsilon (POLE) mutated; 2) mismatch repair deficient; 3) copy number high/p53 abnormal; and 4) copy number low/no specific molecular profile.2 By providing both predictive and prognostic information, these molecular features may be incorporated into treatment planning decisions in the future.
Dr. Katherine Tucker
The POLE-mutated subtype are endometrial cancers with recurrent mutations in the POLE gene, which is involved in DNA replication and repair. POLE mutations occur in about 5%-10% of endometrial cancers. Despite some more aggressive histopathologic findings (eg, higher grade, deeper myometrial invasion, positive lymphovascular space invasion), recurrences rarely occur, and patients with POLE mutations have the best prognosis of the four molecular subtypes, with a 5-year recurrence-free survival of 92%-100%.3
The mismatch repair–deficient (MMRd) subtype are endometrial cancers with abnormalities in any of the mismatch repair proteins (MLH1, PMS2, MSH2, MSH6). These alterations may result from hereditary or somatic mutations in any of the MMR genes or epigenetic changes in the MLH1 promoter. Germ-line mutations are associated with Lynch syndrome; thus, patients found to have a germ-line mutation in any of the MMR genes necessitate a genetics referral. The MMRd subtype accounts for about 20%-30% of endometrial cancers, and patients with MMRd tumors have an intermediate prognosis, with a 5-year recurrence-free survival of about 70%.3. These tumors are more responsive to the use of immunotherapy checkpoint inhibitors. Two recent landmark trials showed improved outcomes in patients with advanced MMRd endometrial cancer treated with immune checkpoint inhibitors in addition to standard chemotherapy.4,5
The worst prognosis belongs to the copy number high subgroup, which accounts for approximately 10% of endometrial cancers. Five-year recurrence-free survival is ~50%.3 These tumors often contain TP53 mutations and are composed of aggressive histologies, such as serous, clear cell, high-grade endometrioid, and carcinosarcomas. Recent data suggests that human epidermal growth factor receptor 2 (HER2) amplification may also be prevalent in this subgroup.6
Endometrial cancers that lack any of the above alterations fall into the no specific molecular profile (NSMP) or copy number low subgroup. Mutations in other genes, such as PTEN, PIK3CA, CTNNB1, KRAS, and ARID1A, are often present in these tumors. As the most common subtype, this heterogeneous group accounts for about 50% of all endometrial cancers. These tumors frequently comprise endometrioid histology with estrogen and progesterone receptor positivity, high rates of response to hormonal therapy, and an overall intermediate to favorable prognosis, with a 5-year recurrence-free survival of ~75%.3
The use of whole-genome sequencing in TCGA limits the clinical applicability of testing because of the cost and complex methodologies involved. Multiple algorithms have been developed in the interim that approximate TCGA subtypes using relatively less expensive and more widely available testing methods, such as immunohistochemistry and next-generation sequencing. In the ProMisE algorithm, immunohistochemistry for p53 and MMR proteins is used as a surrogate for copy number high and MMRd tumors, respectively, and targeted sequencing is used to identify POLE mutations.7
Full molecular classification of endometrial tumors provides important prognostic information and allows for incorporation into treatment planning. To this end, the new 2023 International Federation of Gynecology and Obstetrics (FIGO) endometrial cancer staging incorporates an option for the addition of molecular subtype, with the stance that it allows for better prognostic prediction.8 While complete molecular classification is not required, it is encouraged. Furthermore, several clinical trials are currently investigating different treatment regimens based on these distinct molecular profiles.
Dr. Haag is a gynecologic oncology fellow in the Department of Obstetrics and Gynecology, University of North Carolina Hospitals, Chapel Hill. Dr. Tucker is assistant professor of gynecologic oncology at the University of North Carolina at Chapel Hill. They have no conflicts of interest.
References
1. Bokhman JV. Two pathogenetic types of endometrial carcinoma. Gynecologic Oncology. 1983;15(1):10-17.
2. Kandoth C et al. Integrated genomic characterization of endometrial carcinoma. Nature. 2013;497(7447):67-73.
3. León-Castillo A et al. Molecular classification of the PORTEC-3 trial for high-risk endometrial cancer: Impact on prognosis and benefit from adjuvant therapy. J Clin Oncology. 2020;38(29):3388-3397.
4. Mirza MR et al. Dostarlimab for primary advanced or recurrent endometrial cancer. N Engl J Med. 2023;388(23):2145-2158.
5. Eskander RN et al. Pembrolizumab plus chemotherapy in advanced endometrial cancer. N Engl J Med. 2023;388(23):2159-2170.
6. Talia KL et al. The role of HER2 as a therapeutic biomarker in gynaecological malignancy: Potential for use beyond uterine serous carcinoma. Pathology. 2023;55(1):8-18.
7. Kommoss S et al. Final validation of the ProMisE molecular classifier for endometrial carcinoma in a large population-based case series. Annals Oncology. 2018;29(5):1180-1188.
8. Berek JS et al. FIGO staging of endometrial cancer: 2023. Int J Gynaecol Obstet. 2023;162(2):383-394.