Over the last decades, biomarkers have become an extremely important tool in the care of patients with ovarian cancer. Biomarkers are capable of differentiating benign versus malignant masses, detecting the disease at an earlier stage, and monitoring the cancer’s response to treatment and its recurrence1.
Patients with epithelial ovarian cancer (EOC) have a 5-year survival rate for all stages estimated at 45.6%2, but when effective early stage detection is possible (in roughly 20% of cases), the survival rate reaches 70%3. It is worth noting that roughly three-quarters of ovarian cancers are diagnosed when the disease has progressed to advanced-stages (stage III or IV), and has spread to peritoneal surfaces, or other organs4. This trend explains the high mortality rate of advanced stage disease at initial diagnosis5. Importantly, as the disease progresses, treating and managing patients becomes more challenging3.
For example, when the disease is detected at stage I (where the cancer is limited to the ovaries), 90% of patients can be cured with surgery, chemotherapy and radiotherapy. Similarly, when the cancer has spread to the pelvis in stage II, 70% of the patients can still be cured. In more advanced stages where the cancer has spread throughout the abdomen or beyond, the percentage of curable patients drops to 20%1. These differences in survival rates may also reflect the fact that currently available treatment strategies are much more successful in early stages, when the cancer has not yet spread7.
Ovarian Cancer Treatment Strategies
As previously mentioned, current treatment strategies combine debulking surgeries, drug treatment and radiation therapy. Depending on the type of ovarian cancer, treatment options may include: chemotherapy, hormone therapy, and targeted therapy.
Chemotherapy: Administered intravenously (IV), intraperitonially (IP), or by a combination of IV/IP, chemotherapeutic agents are selected based on the stage of OC. The most frequently used are platinum-based drugs (cis-platin and the less toxic carboplatin), and drugs in the Taxane family (Paclitaxel and Docetaxel)3. Specifically, one common IV chemotherapy regimen is the combination of Carboplatin (AUC 6-7) with Paclitaxel (175mg/ m2) for three to six cycles8.
Hormone Therapy: Including hormones or hormone-blocking drugs, this systemic therapy is most often used to treat ovarian stromal cancers, but rarely used for EOC9. Therapy includes luteinizing-hormone-releasing hormone (LHRH) agonists that lower estrogen levels in premenopausal women, tamoxifen (often used to treat breast cancer and in ovarian stromal cancer but rarely used in advanced EOC), which also has anti-estrogen activity, and aromatase inhibitors that help reduce estrogen levels by inhibiting the enzyme aromatase that turns other hormones into estrogen in post-menopausal women9.
Targeted Therapy: Drugs that identify and attack cancer cells specifically while doing little damage to normal cells. Targeted therapies change how cancer cells grow, divide, repair themselves, or interact with other cells10. For example, angiogenesis (the physiological process through which new blood vessels form from pre-existing vessels) plays a key role in the initiation and progression of ovarian carcinogenesis11. Bevacizumab (Avastin), an angiogenesis inhibitor, acts by interfering with a protein called VEGF (that signals and promotes the formation of new blood vessels) and slows or stops cancer growth. Bevacizumab has been shown to increase the overall survival of high risk patients in a phase 3 randomized study12. Another group of targeted therapy drugs include (poly (ADP)-ribose polymerase) inhibitors (PARPi), that may help prevent cancer cells from repairing their damaged DNA, thus causing them to die. Specifically, the use of PARP inhibitors for the treatment of cancers with defects in the BRCA1 (BReast CAncer gene 1) or BRCA2 tumor suppressor proteins (which are also involved in the repair of DNA damage), appears to be a promising approach. PARPis are specifically lethal for cancer cells with homologous recombination (HR) deficiency, which characterize 50% of HGSCs13,14. However, multiple resistance mechanisms to PARPi have also been identified11,15.
Despite targeted therapy’s (including Bevacizumab and PARP inhibitors) strong impact on ovarian cancer, there is no cure for advanced stages of ovarian cancer. Specifically, there is an urgent need to identify therapies that provide longer-lasting relief for patients with normal BRCA genes, and for patients with platinum-resistant cancers.
Over the past few years, clinical trials have revealed promising treatment options, including Immunotherapy, vaccines and cell cycle checkpoint inhibitors.
- Active immunotherapy aims to stimulate an anti-tumor response from the patient’s own immune system, and thus induce immunological memory
- Passive immunotherapy includes the administration of immune components that promote the anti-tumor response
- Immunomodulation includes all approaches that enhance immune responsiveness16.
Vaccines: Cancer vaccines are immunotherapeutics proposed to “educate” and activate the immune system to generate specific effector T-cells capable of detecting and killing tumor cells. The ideal tumor-associated antigens should not be present in normal tissue, while being overexpressed in tumor cells. These tumor-associated antigens should also be easily recognized by the immune cells and therefore trigger the immune response also at low doses (strong immunogenicity)16. Some of the common cancer vaccines are developed and tested using different methods such as epigenetics and genetics, and can be administered alone, or in combination with cytokines or other accelerating factors3.
Cell cycle checkpoints: A few cell cycle checkpoint inhibitors are already in clinical testing or under development. Following DNA damage, cells initiate multiple responses to protect the genome and ensure survival17. One of these mechanisms includes the activation of specific cell cycle checkpoints that block the cell cycle, allowing the cell to repair its DNA. HGSOC, for example, is characterized by a mutant or null p53 which leads to the dysfunction of the p53-dependent G1/S phase checkpoint. Consequently, HGSOC relies on G2 checkpoint arrest to facilitate DNA damage repair18 . This emphasizes the importance of therapeutics that specifically target the G2/M phase checkpoint.
With multiple treatment options available for patients, prognostic biomarkers that correlate to disease progression are critical. As previously mentioned, the main factor responsible for OC’s high mortality is the high rate of advanced stage disease at initial diagnosis5. Specifically, as the disease progresses, treating and managing patients becomes more challenging3. It is therefore critical to identify predictive prognostic biomarkers for patient response to treatment in order to establish effective treatment strategies and increase overall survival. Currently, commonly used biomarkers to monitor recurrence and predict prognosis are Cancer Antigen 125 (CA125) and Human Epididymis Protein 4 (HE4)3.
CA125: Expression of CA125 is elevated in 85% of serous, 65% of endometrioid, 40% of clear-cell, 36% of undifferentiated and only 12% of mucinous ovarian cancers19. For the past three decades, CA125 has become the most widely used tumor marker in ovarian cancer, although its limitations in sensitivity and specificity negatively affect its performance19. Furthermore, CA125 is known to be elevated in only 50% of early stage OC patients, and in about 80% of advance stage OC patients20
Given the aforementioned limitations of CA125, many efforts have been made to identify additional or complementary biomarkers for OC.
HE4 (human epididymis protein 4) is present in the epithelium of fallopian tubes, endometrium, endocervical glands, but not in ovarian surface epithelium. Elevated expression levels of HE4 have been observed in 93-100% of serous, 80-100% of endometrioid and 50-83% of clear-cell carcinomas of the ovary, while HE4 is absent in mucinous ovarian cancer 21,22
It has been demonstrated that HE4 mRNA levels are higher in ovarian cancer tissue compared to benign22,23. Specifically, Moore and colleagues showed that HE4 is indeed a useful single marker in differentiating benign versus ovarian cancer patients24. Furthermore, HE4 is also highly expressed in epithelial ovarian cancer, which accounts for 85-90% of ovarian cancer among the various pathological types25. In recent years, HE4 has also become an interesting marker to monitor disease progression, and predict prognosis23. Studies have confirmed the effectiveness of HE4 in the preoperative assessment of patients with ovarian cancer26. Yang and colleagues provided evidence that preoperative serous HE4 may be regarded as an index to estimate the likelihood of successful cytoreductive surgery in women with ovarian cancer. Specifically, by using a demarcation criterion of 600 pmol/l (values greater than 600 pmol/l indicate lower possibility of optimal debulking by cytoreductive surgery), HE4 predicted incomplete cytoreductive surgery with a sensitivity of 77% and a specificity of 32% 23. These results suggested that higher levels of HE4 in OC patients are linked to worse prognosis.
In the past few decades, CE CT has played an important role in both pre-operative staging and follow-up, due to the cost-effectiveness and the availability of this technique27. In preoperative staging, CE CT is capable of determining the presence of a malignant adnexal mass, as well as the extent of the disease, two very crucial aspects for treatment planning. CE CT is also an effective tool to assess treatment response, and disease recurrence28.
In 2013, Manganaro and colleagues were able to correlate CE CT results with HE4 levels. Specifically, they found that HE4 serum levels, combined with CE CT imaging, could improve the monitoring management of women affected by EOC28. This represents an important finding, since CE CT imaging is known to cause considerable side effects due to ionizing radiation and contrast medium injections28. Therefore, the use of biomarkers such as HE4 for follow-up as an alternative to imaging, might significantly benefit the patient.
HE4 might also be a promising additional tool for the evaluation of advanced high-grade serous carcinoma (HGSC) patient’s response to neoadjuvant chemotherapy (NACT)29. HGSC is the most common and deadliest type of ovarian cancer, with more than two-thirds of HGSCs diagnosed at an advanced stage30.
The primary standard treatment for EOC, as previously mentioned, is cytoreductive surgery followed by chemotherapy. An alternative approach includes the use of NACT, followed by interval debulking surgery (IDS). In 2014, Vallius and colleagues showed that an 80% variation of HE4 levels during NACT was associated with poor prognosis, thus suggesting that HE4 change during NACT correlates with overall survival (OS). Pre-IDS HE4 and CA125 values predicted IDS outcome in primarily inoperable patients29. Taken together, these results suggest that HE4 may be a helpful tool when deciding whether to proceed to IDS or to second-line chemotherapy29.
A recent longitudinal study by Salminen and colleagues also confirmed the possibility of using HE4 (as a complement to CA125) in HGSC treatment monitoring and in the prognostic stratification of patients31 . Specifically, in this prospective clinical study HE4 was indeed an effective tool in the evaluation of cytoreductibility and the prognostic stratification of patients at disease progression. The investigators found that the measurement of HE4 levels could aid clinicians in detecting platinum resistant disease, while offering support for the determination of individual targeted therapies. HE4 performed equally well to, if not better than, CA125 in all of the time-points evaluated: at baseline, nadir and in 1st relapse31.
Furthermore, a prospective study by Angioli looked into changes in serum CA125 and HE4 levels at the beginning, and during, first-line chemotherapy, in order to find correlations of these biomarkers with platinum-based chemotherapy response. They found that, contrary to CA125, HE4 profile was significantly associated with platinum-based chemotherapy response. Additionally, the time required for HE4 normalization during initial chemotherapy, was a valid indicator for the identification of patients who are not responding to treatment, after the third cycle of chemotherapy. Specifically, HE4 levels were >70 pmol/L after primary surgery and three cycles of chemotherapy32.
Similarly, an interesting study by Potenza and colleagues looked into the correlation of serum CA125 and HE4 levels prior to each chemotherapy cycle together with their response curve to the clinical response to treatment, platinum-sensitivity, and progression-free survival (PFS). They found that HE4 decreases more rapidly during chemotherapy than CA125. CA125 had a delay of 21 days. Furthermore, HE4 was redetected faster than CA125 in patients who experienced a poor chemotherapy response26.
Finally, other studies have also suggested that the regular measurement of HE4 levels during the firstline treatment of ovarian cancer may be of prognostic significance. Specifically, the normalization of HE4 levels at end of treatment, and the 50% reduction of HE4 concentrations before interval cytoreductive surgery, are both important and strong predictive factors of time to progression and overall survival time33 .
Taken together, these results suggest that HE4 is a promising and effective tool for monitoring the response to chemotherapy in ovarian cancer patients.
Despite the continued efforts and steady improvements in ovarian cancer treatment, this disease still remains the deadliest malignancy in women. Specifically, the poor clinical outcome is due to the deficiency of effective tools for detecting the disease at an early stage, chemotherapy resistance and increased heterogeneity of the disease3. Thus, identifying biomarkers that help monitor response to treatment and predict prognosis, can indeed represent an effective tool for the improvement of EOC survival.
1. Wei-Lei Yang and Robert C. Bast Jr. ZL. The role of Biomarkers in the Management of Epithelial Ovarian Cancer. Expert Rev Mol Diagn. 2017;17(6):577-591. doi:10.1016/j.physbeh.2017.03.040
2. Oronsky B, Ray CM, Spira AI, Trepel JB, Carter CA, Cottrill HM. A brief review of the management of platinum-resistant–platinum-refractory ovarian cancer. Med Oncol. 2017;34(6). doi:10.1007/s12032-017-0960-z
3. Chandra A, Pius C, Nabeel M, et al. Ovarian cancer: Current status and strategies for improving therapeutic outcomes. Cancer Med. 2019;8(16):7018-7031. doi:10.1002/cam4.2560 4. Kobayashi E, Ueda Y, Matsuzaki S, et al. Biomarkers for screening, diagnosis, and monitoring of ovarian cancer. Cancer Epidemiol Biomarkers Prev. 2012;21(11):1902-1912. doi:10.1158/1055- 9965.EPI-12-0646
5. Rauh-Hain JA, Krivak TC, Del Carmen MG, Olawaiye AB. Ovarian cancer screening and early detection in the general population. Rev Obstet Gynecol. 2011;4(1):15-21. doi:10.3909/riog0143
6. U.S. Department of Health and Human Services C for DC and P and NCI. U.S. Cancer Statistics Working Group. U.S. Cancer Statistics Data Visualizations Tool, based on 2019 submission data (1999-2017). www.cdc.gov/cancer/dataviz
7. stopcancerfund.org. Ovarian Cancer: What Are the Treatment Options? Accessed January 12, 2020. https://stopcancerfund.org/t-ovarian-cancer/ovarian-cancer-what-are-the…
8. Benedet JL, Bender H, Jones H, Ngan HY, Pecorelli S. FIGO staging classifications and clinical practice guidelines in the management of gynecologic cancers. FIGO Committee on Gynecologic Oncology. Int J Gynaecol Obstet. 2000;70(2):209-262. doi:10.1016/S0020-7292(00)90001-8
9. American Cancer Society. Hormone Therapy for Ovarian Cancer. Accessed April 11, 2020. https://www.cancer.org/cancer/ovarian-cancer/treating/hormone-therapy.h…
10. American Cancer Society. Targeted Therapy for Ovarian Cancer. Accessed May 11, 2020. https://www.cancer.org/cancer/ovarian-cancer/treating/targeted-therapy…
11. Kim JY, Cho CH, Song HS. Targeted therapy of ovarian cancer including immune check point inhibitor. Korean J Intern Med. 2017;32(5):798-804. doi:10.3904/kjim.2017.008
12. Oza AM, Cook AD, Pfisterer J, et al. Standard chemotherapy with or without bevacizumab for women with newly diagnosed ovarian cancer (ICON7): Overall survival results of a phase 3 randomised trial. Lancet Oncol. 2015;16(8):928-936. doi:10.1016/S1470-2045(15)00086-8
13. Kossaï M, Scoazec J. Ovarian Cancer : A Heterogeneous Disease. Published online 2018:41-49. doi:10.1159/000479006
14. Konstantinopoulos PA, Ceccaldi R, Shapiro GI and DA. Homologous Recombination Deficiency: Exploiting the Fundamental Vulnerability of Ovarian Cancer Panagiotis. Vol 5.; 2015. doi:10.1158/2159-8290.CD-15-0714.
15. Lord CJ, Ashworth A. Mechanisms of resistance to therapies targeting BRCA-mutant cancers. Nat Med. 2013;19(11):1381-1388. doi:10.1038/nm.3369
16. Palaia I, Tomao F, Sassu CM, Musacchio L, Panici PB. Immunotherapy for ovarian cancer: Recent advances and combination therapeutic approaches. Onco Targets Ther. 2020;13:6109-6129. doi:10.2147/OTT.S205950
17. Lee JM, Minasian L, Kohn EC. New strategies in ovarian cancer treatment. Cancer. 2019;125(S24):4623-4629. doi:10.1002/cncr.32544
18. Haynes B, Murai J, Lee J, Branch M, Branch T. Restored replication fork stabilization, a mechanism of PARP inhibitor resistance, can be overcome by cell cycle checkpoint inhibition. 2018;71:1-7. doi:10.1016/j.ctrv.2018.09.003.Restored
19. Nowak M, Janas Ł, Stachowiak G, Stetkiewicz T, Wilczyński JR. Review paper Current clinical application of serum biomarkers to detect ovarian cancer. 2015;14(4):254-259. doi:10.5114/pm.2015.55887
20. Prorok PC, Andriole GL, Bresalier RS, et al. Design of the Prostate , Lung , Colorectal and Ovarian ( PLCO ) Cancer Screening Trial. 2000;2456:273-309.
21. Drapkin R, Von Horsten HH, Lin Y, et al. Human epididymis protein 4 (HE4) is a secreted glycoprotein that is overexpressed by serous and endometrioid ovarian carcinomas. Cancer Res. 2005;65(6):2162-2169. doi:10.1158/0008-5472.CAN-04-3924
22. Galgano MT, Hampton GM, Frierson HF. Comprehensive analysis of HE4 expression in normal and malignant human tissues. Mod Pathol. 2006;19(6):847-853. doi:10.1038/modpathol.3800612
23. Yang Z, Luo Z, Zhao B, et al. Diagnosis and preoperative predictive value of serum HE4 concentrations for optimal debulking in epithelial ovarian cancer. Oncol Lett. 2013;6(1):28-34. doi:10.3892/ol.2013.1339
24. Moore RG, Brown AK, Miller MC, et al. The use of multiple novel tumor biomarkers for the detection of ovarian carcinoma in patients with a pelvic mass. Gynecol Oncol. 2008;108(2):402- 408. doi:10.1016/j.ygyno.2007.10.017
25. Köbel M, Kalloger SE, Boyd N, et al. Ovarian carcinoma subtypes are different diseases: Implications for biomarker studies. PLoS Med. 2008;5(12):1749-1760. doi:10.1371/journal.pmed.0050232
26. Potenza E, Parpinel G, Laudani ME, Macchi C, Fuso L, Zola P. Prognostic and predictive value of combined HE-4 and CA-125 biomarkers during chemotherapy in patients with epithelial ovarian cancer. Int J Biol Markers. Published online 2020:172460082095519. doi:10.1177/1724600820955195
27. Forstner R, Sala E, Kinkel K, Spencer JA. ESUR guidelines: Ovarian cancer staging and follow-up. Eur Radiol. 2010;20(12):2773-2780. doi:10.1007/s00330-010-1886-4
28. Manganaro L, Michienzi S, Vinci V, et al. Serum HE4 levels combined with CE CT imaging improve the management of monitoring women affected by epithelial ovarian cancer. Oncol Rep. 2013;30(5):2481-2487. doi:10.3892/or.2013.2682
29. Vallius T, Hynninen J, Auranen A, et al. Serum HE4 and CA125 as predictors of response and outcome during neoadjuvant chemotherapy of advanced high-grade serous ovarian cancer. Tumor Biol. 2014;35(12):12389-12395. doi:10.1007/s13277-014-2553-1
30. Kim J, Park EY, Kim O, et al. Cell origins of high-grade serous ovarian cancer. Cancers (Basel). 2018;10(11):1-28. doi:10.3390/cancers10110433
31. Salminen L, Gidwani K, Grènman S, et al. HE4 in the evaluation of tumor load and prognostic stratification of high grade serous ovarian carcinoma. Acta Oncol (Madr). 2020;0(0):1-8. doi:10.1080/0284186X.2020.1827157
32. Angioli R, Capriglione S, Aloisi A, et al. Can HE4 predict platinum response during first-line chemotherapy in ovarian cancer? Tumor Biol. 2014;35(7):7009-7015. doi:10.1007/s13277-014- 1836-x
33. Chudecka-Głaz A, Cymbaluk-Płoska A, Wȩaowska M, Menkiszak J. Could HE4 level measurements during firstline chemotherapy predict response to treatment among ovarian cancer patients? PLoS One. 2018;13(3):1-16. doi:10.1371/journal.pone.0194270