Improving ovarian cancer treatment - Part I


 
  • Ovarian cancer is a deadly disease that is challenging to diagnose and manage
  • Although it only accounts for 3% of cancers in women, it is the 5th leading cause of cancer death among women
  • If diagnosed and treated early before it spreads the 5-year survival rate is 92%
  • But only 15% of women with ovarian cancer are diagnosed early
  • The disease is hard to diagnose because it is rare, the symptoms are relatively benign, and there is no effective screening
  • Ovarian cancer is not one disease, but a collection of subtypes each demanding specific treatment pathways
  • Gold standard treatment is surgery followed by chemotherapy
  • A large proportion of patients develop resistance to chemotherapy
 
Improving ovarian cancer treatment

Part I
 
Are things beginning to improve for people living with ovarian cancer? When the British advertising magnate Lord Maurice Saatchi’s wife died of ovarian cancer in 2012 he described her treatment as, “degrading, medieval and ineffective” leading “only to death”. Ovarian cancer patients have long had limited treatment options, which have not changed much in the past two decades, but recently things have begun to change.

 
In this Commentary
 
This is the first of a 2-part Commentary on ovarian cancer, which briefly describes the condition, explains the difficulties of diagnosing it early, and discusses some of the challenges of developing effective screening mechanisms for the cancer in pre-symptomatic women. Part 2, which will follow separately next week, reports new studies, which hold out the prospect of improved treatment options for women living with ovarian cancer. It also suggests that improvements in ovarian cancer care are both organizational and scientific. Experts believe that they now have a number of treatment options available to them. Utilising and sequencing these appropriately can have a significant impact on the overall survival rates of patients. Multidisciplinary teams, which are not universally available to all ovarian cancer patients, bring together all specialisms involved in the therapeutic pathway to consider and suggest optimal treatment steps for individual patients, and make a significant contribution to improved ovarian cancer care. Both Commentaries draw on some of the world’s most eminent ovarian cancer clinicians and scientists.
 
Ovarian cancer: a complex and deadly disease
 
The ovaries are a pair of small organs located low in the stomach that are connected to the womb and store a woman’s supply of eggs. Ovarian cancer is driven by multicellular pathways, and is better understood as a collection of subtypes with changing origins and clinical behaviors, rather than as a single disease. The tumors often have heterogeneous cell populations, which form unique microcellular environments. The prevalence of ovarian cancer among gynecological malignancies is rising, and is one the most deadly and hard to treat malignancies. While the disease only accounts for about 3% of cancers in women, it is one of the most common types of cancer in women, the 5th leading cause of cancer-related death among women, and the deadliest of gynecologic cancers. The risk of ovarian cancer increases with age. It is rare in women younger than 40, most ovarian cancers develop after menopause. 50% of all ovarian cancers are found in women 63 or older. According to the American Cancer Society the five-year survival rate for all ovarian cancers is 45%. Most women are diagnosed with late-stage ovarian disease and, the 5-year survival rates for these patients are roughly 30%. Age adjusted survival rates of ovarian cancer are improving in most developed countries. For instance, between 1970 and 2010, the 10-year survival rates for ovarian cancer in England increased by 16%, and the 5-year survival rates have almost doubled. This is because of the favorable trends in the use of oral contraceptives, which were introduced early in developed countries. Declines in menopausal hormone use may also have had a favorable effect in older women as well as improved diagnosis, management and therapies. According to Public Health England, over the past 20 years the incidence of ovarian cancer in England has remained fairly stable, although it has decreased slightly in the last few years. Between 2008 and 2010 in England, 36% of some 14,000 women diagnosed with ovarian cancer died in the first year, and more than 1,600 died in the first month. There were 7,378 new cases of ovarian cancer in the UK in 2014 and more than 4,000 women died from the disease.
 
Benign symptoms difficult to diagnose

If ovarian cancer is diagnosed and treated early before it spreads from the ovaries to the abdomen, the 5-year relative survival rate is 92%. However, only 15% of all ovarian cancers are found at this early stage.  This is because it is hard to diagnose since the disease is so rare, the symptoms are relatively benign, and there is no effective screening. As a result, the illness tends not to be detected until the latter stages in around 60% of women, when the prognosis is poor. In about 20% of cases the disease is not diagnosed until it is incurable. Feeling bloated most days for three weeks or more is a significant sign of ovarian cancer. Other symptoms include: feeling full quickly, loss of appetite, pelvic or stomach pain, needing to urinate more frequently than normal, changes in bowel habit, feeling very tired, and unexplained weight loss.
 
“Tumors go from the earliest stage 1 directly to stage 3”
In the video below Hani Gabra, Professor of Medical Oncology at Imperial College, London; and Head of AstraZeneca’s Oncology Discovery Unit says, “Ovarian cancer is often diagnosed late because in many cases the disease disseminates into the peritoneal cavity almost simultaneously with the primary declaring itself. Unlike other cancers, the notion that ovarian cancer progresses from stage 1 to stage 2, to stage 3 is possibly mythological. The reality is, these cancer cells often commence in the fallopian tube with a very small primary tumor, which disseminates directly into the peritoneal cavity. In other words, the tumors go from the earliest of stage 1 directly to stage 3."
 
 
Ovarian cancer screening and CA-125

For years scientists have been searching for an effective screening test for ovarian cancer in pre-symptomtic women. The 2 most common are transvaginal ultrasound (TVUS) and the CA-125 blood test. The former uses sound waves to examine the uterus, fallopian tubes, and ovaries by putting an ultrasound wand into the vagina. It can help find a tumor in the ovary, but cannot tell if the tumor is cancerous or benign. Most tumors identified by TVUS are not cancerous. So far, the most promising screening method is CA-125, which measures a protein antigen produced by the tumor.
 
CA-125 studies
To-date, 2 large ovarian cancer screening studies have been completed: one in the US, and another in the UK. Both looked at using the CA-125 blood test along with TVUS to detect ovarian cancer. In these studies, more cancers were found in the women who were screened, and some were at an early stage. But the outcomes of the women who were screened were no better than the women who were not screened: the screened women did not live longer and were not less likely to die from ovarian cancer.

Another study published in 2017 in the Journal of Clinical Oncology screened 4,346 women over 3 years at 42 centers across the UK, undertook follow-up studies 5 years later, and came to similar conclusions as the 2 previous studies. Further, “there are a number of non-ovarian diseases, which can cause elevated CA-125’s. Breast cancer, endometriosis, and irritation of the peritoneal cavity can all cause elevated CA-125,” says Michael Birrer, Director of Medical Gynecologic Oncology at the Massachusetts General Hospital and Professor of Medicine at Harvard University.


Controversial findings
Findings from screening tests using CA-125 can give false positives for ovarian cancer, and this puts pressure on patients to have further, often unnecessary interventions, which sometimes include surgery. Also, the limitations of the CA-125 test mean that many women with early stage ovarian cancer will receive a false negative from testing, and not get further treatment for their condition. Thus, the potential role of CA-125 for the early detection of ovarian cancer is controversial, and therefore it has not been adopted for widespread screening in asymptomatic women.
 
In the video below Birrer explains that, “pre-operatively and during therapy physicians will usually check CA-125 as a measure of the effectiveness of the therapy. At the completion of therapy one would anticipate that the CA-125 would be normal. After that, it is somewhat controversial as to whether follow-up with CA-125 to test for recurring disease is clinically relevant,” says Birrer. Since the discovery of CA-125 in 1981, there has been intense research focus on novel biomarkers for cancer, and significant scientific advances in genomics, proteomic, and epigenomics etc., which have been extensively used in scientific discovery, but as yet no new major cancer biomarkers have been introduced to practicing oncologists. 

 
Limited treatment options

As most ovarian cancer patients are diagnosed late when the disease has already spread, treatment options are limited. The first line treatment is surgery called debulking, (also known as cytoreduction or cytoreductive surgery), which is the reduction of as much of the volume (bulk) of a tumor as possible. 
 
Be prepared for extensive surgery
Whether a patient is a candidate for surgery depends on a number of factors including the type, size, location, grade and stage of the tumor, pre-existing medical conditions, and in the case of a recurrence, when the last cancer treatment was performed, as well as general health factors such as age, physical fitness and other medical comorbidities. People diagnosed with ovarian cancer, “need to be prepared to have extensive surgery because the real extent of the tumor dissemination cannot be detected by conventional imagining pre-operatively,” says Professor Christina Fotopoulou, consultant gynaecological oncologist at Queen Charlotte's & Chelsea Hospital, London: see video below. 
 
 
Platinum resistance

Surgery is usually followed by chemotherapy. There are more than 100 chemotherapy agents used to treat cancer either alone or in combination. Chemotherapy drugs target cells at different phases of the process of forming new cells, called the cell cycle. Understanding how these drugs work helps oncologists predict, which drugs are likely to work well together. Clinicians can also plan how often doses of each drug should be given based on the timing of the cell phases. Chemotherapy drugs can be grouped by their chemical composition, their relationship with other drugs, their utility in treating specific forms of cancer, and their side effects.  
 
You can reduce chemotherapy resistance by using a combination of drugs that target different processes in the cancer so that the probability that the cancer will simultaneously become resistant to both drugs is much lower than if you use one drug at a time, ” says David Bowtell,  Professor and Head of the Cancer Genomics and Genetics Program at Peter MacCallum Cancer Centre, Melbourne, Australia: see video:
 
 
Improving the chemotherapy agent cisplatin
The standard chemotherapy treatment for ovarian cancer is a combination of a platinum compound, such as cisplatin or carboplatin, and a taxane, which represents a class of drug originally identified from plants. Since cisplatin’s discovery in 1965 and its FDA approval in 1978, it has been used continuously in treatments for several types of cancer, and is best known as a cure for testicular cancer. Scientists have searched for ways to improve the anti-tumor efficacy of platinum based drugs, reducing their toxicity, strengthening them against resistance by expanding the class to include several new analogues of cisplatin, and putting these through clinical studies to broaden the different types of cancers against which they can be safely used.
 
Slow progress transitioning research into clinical practice
Despite these endeavors, platinum resistance remains a significant clinical challenge. Between 55 and 75% of women with ovarian cancer develop resistance to platinum based chemotherapy treatments. Significant research efforts have been dedicated to understanding this, but there has been relatively slow progress transitioning the research into effective clinical applications. According to Birrer, “the mechanism of platinum resistance from a molecular standpoint has not been well defined. It is likely to be heterogeneous, which means that each patient’s tumor may be slightly different. The hope is for targeted therapies and personalised medicine to have a chance of overcoming this, in that we could characterize the mechanism of the platinum resistance and apply and target therapy.”
 
2 theories of platinum resistance
In the video below, Birrer posits 2 theories to explain platinum resistance. “One suggests that under the influence of platinum the tumor changes and becomes resistant. Another suggests that there are 2 groups of cells to begin with. The vast majority of the tumor is sensitive, but there are small clusters of resistant cells. Once you kill the sensitive cells you have only the resistant cells left. Although these 2 theories have been around for about 25 years, there are no definitive data to suggest which theory is right. I have a personal scientific bias to think that the resistant cells are present at the time that we start the therapy. Being able to identify and characterize these cells upfront would be a radical breakthrough because then we would be able to target them at a time when they are only a small portion of the tumor,” says Birrer.
 
 
Takeaways

Saatchi is right; for decades ovarian cancer treatment has been wanting, but studies we describe in part-2 of this Commentary suggest that the tide might be turning for people living with ovarian cancer. So don't miss part-2 next week!
 
 

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