Ovarian cancer is the seventh most
common cancer in women worldwide (18 most common cancers overall). The highest incidence of ovarian cancer is seen Europe
and Northern America; and the lowest incidence in Africa and Asia.
The American Cancer Society estimates that in 2016, there
will be 22,280 new cases of ovary cancer and an estimated 14,240 people will
die of this disease. Owing to slow progression, being relatively asymptomatic in early
stages and with no single reliable screening test it is usually diagnosed at a late stages.
Ultrasound has always been
pivotal in diagnosing pelvic masses and can fairly differentiate cystic vs
solid lesions, provide accurate assessment of size, follow changes in
appearance, and assess vascular supply and flow. So Sonography, along with few specific tumor markers and imaging studies have made it possible to have high index of suspicion, but definitive diagnosis is not possible 100% of time.
Over the years, researchers have developed different models
to accurately characterize adnexal masses as benign or malignant
preoperatively. A recent meta-analysis confirmed
that the International Ovarian Tumor Analysis (IOTA) algorithms such as the Simple
Rules are very effective to preoperatively classify adnexal masses as
benign or malignant.
IOTA developed the simple rules and mathematical models based
on logistic regression (LR 1-2), which are very easy to use in clinical
practice to discriminate between benign and malignant tumors. Logistic regression model 2 is a
mathematical risk prediction model which also includes age beside the 5 ultrasound variables (presence of blood flow
in a papillary structure, irregular cyst walls, ascites, acoustic shadows, and
maximum diameter of the largest solid component).
Clinicians have incorporated the Simple Rules in
practice and the Royal College of Obstetricians and Gynecologists in the United
Kingdom has included the Simple Rules in their Green Top
guideline on the assessment and management of ovarian masses in premenopausal
women.
In spite of all the simplicity and ease of use in practice,
the simple rules have the limitations of inconclusive results in many cases and
absence of risk stratification for malignancy preoperatively.
A recent study published in the American Journal of Obstetrics and Gynecology April, 2016 issue aims to develop and validate a model
based on IOTA Simple Rules to estimate the risk of malignancy in adnexal
masses.
It is an international cross sectional study with 22 oncology
centers, referral centers for ultrasonography, and general hospitals. Data
on 5020 patients were recorded in 3 phases from 2002 through 2012. The 5 simple
rules of being benign or malignant was based on presence of ascites, tumor
morphology, and degree of vascularity at ultrasonography.
All patient underwent a standard transvaginal sonography by
an experienced sonologist/gynecologist. Transabdominal Scan was added as and
when required particularly in very large tumors. The reference standard was the
histopathological diagnosis after the surgical removal of the tumor.
The quantifying predictive value of each of the 10 features
of Simple Rules was estimated. In addition, area under the receiver operating
characteristic curve (AUC), sensitivity, specificity, and predictive values, Positive
likelihood ratio (LR+) and negative likelihood ratio (LR–) were also derived by
multivariate logistic regression.
Data on 4848 patients were analyzed by logistic regression.
The observed malignancy rate was 34% overall (43% in oncology centers, and 17% in
other centers). The median age for benign tumor was 42 vs 57 for malignant tumors.
A simple unilocular cyst was most predictive of a benign tumor,
while presence of ascites was most predictive of malignancy and (irregular
multilocular-solid tumor with largest diameter ≥100 mm) was least predictive.
When an ovarian mass is detected on clinical examination,the
risk of malignancy at an oncology center is 48.7% and 27.5% for patients at
other centers. After sonography if more
of M-features than B-features were present the risk of malignancy was 42% and
was at most 0.29% when ≥2 B-features and no M-features were present. Based on
these findings a simple classification of adnexal masses can be used in
clinical practice to determine the risk of malignancy for an individual patient
and her management subsequently.
Over the years’ various mathematical models based on clinical
and pathological markers are being used to aid in clinical decision making. In
2014 a met analysis by Kaijser J et al confirmed the superiority of IOTA simple rules and
5 simple rules to suggest benign tumor (B-rules):
(1) unilocular cyst;
(2) presence of solid
components where the largest solid component is < 7 mm in largest diameter;
(3) acoustic shadows;
(4) smooth
multilocular tumor less than 100 mm in largest diameter; and
(5) no detectable blood flow on Doppler examination.
5 simple rules to predict malignancy (M-rules):
(1) irregular solid
tumor;
(2) ascites;
(3) at least four papillary structures;
(4) irregular
multilocular-solid tumor with a largest diameter of at least 100 mm; and
(5) very high color
content on color Doppler examination.
The cancer antigen-125 is not one of the variable in the Simple
Rules, it is not included in the Simple Rules risk classification
and adding serum levels of CA 125 to the Logistic regression model does not
help us to discriminate between benign and malignant adnexal masses.
In phase 3 the model was validated and it seen that it works
well both in hands of oncologists as well as general gynecology practitioners. In
low risk patients a ‘wait and watch’ policy could be adapted, with close
monitoring and avoiding unnecessary surgeries whereas in high risk patients it
leads to early diagnosis and improved survival.
References:
http://www.ncbi.nlm.nih.gov/pubmed/24327552?dopt=Abstract
http://www.iotagroup.org/
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