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Paper text:
cancer of the uterine cervix is the commonest malignancy affecting women in developing countries , including india and its incidence is second to the breast cancer globally accounting for 15% of all new female cancers .
mortality related to the cervical cancer has shown a decline worldwide due to its early detection and treatment of early stage ( localized ) disease .
radical hysterectomy ( rh ) and pelvic lymphadenectomy is widely used curative surgery for early stage ( stage i to iia ) cervical cancer as well as for stage iib disease in some asian and european countries .
cervical cancer is staged clinically as per the international federation of gynecology and obstetrics figo staging system .
figo system is widely used and acceptable clinical staging in spite of its inherent limitation of underestimation of disease and inability to assess the metastatic involvement of pelvic and para - aortic nodes .
the frequency of pelvic and para - aortic node metastases increases incrementally with figo stage .
lymph node metastases are seen in 12 - 22% in stage ib , 10 - 27% in stage iia and 34 - 43% in stage ii b of cervical cancer . as per historic series based on surgicopathological examination ,
pelvic and para - aortic nodes may be involved in 12 - 62% of patients with early stage cervical cancer and regarded as the single most important prognostic determinant .
patients with pelvic and para - aortic nodes metastases have high rate of disease recurrence and poor progression free survival
. therefore , assessment of nodal metastases in the cervical cancer becomes clinically relevant , even if it is not part of routine figo staging .
lymph nodal assessment can be done noninvasively with morphological imaging modalities like contrast - enhanced computed tomography ( cect ) and magnetic resonance imaging ( mri ) .
mri is preferred over cect for initial staging workup as it accurately evaluates local disease ( t stage ) , involvement of neighboring structures and nodes ( n stage ) .
both cect and mri rely on size criteria and have shown modest sensitivity in predicting nodal metastases in the cervical cancer .
a node to be regarded / interpreted as pathological / metastatic on ct / mri , should have dimension of > 1 cm in short - axis .
therefore , sub - centimeter to centimeter sized visualized nodes on ct / mri are not considered metastatic in accordance with size criteria ; even though they may or later pathologically proven to harbor micro - metastases ( disease per se ) . in this situation ,
fluorodeoxyglucose ( fdg ) pet scan is advantageous , as it relies on metabolic criteria rather than the size of a node .
proliferating malignant cells within the metastatic node demonstrate high glycolytic activity and therefore , show focally increased uptake of 18-fluorine labeled glucose analogue ( fdg ) on pet scan .
pet scan is highly sensitive modality in detecting hypermetabolic foci ( positive nodes ) in pelvic and para - aortic regions without providing their exact anatomical details .
there are many studies published describing fdg pet as an effective imaging technique for nodal staging in the cervical cancer . for diagnosis of para - aortic metastases , sensitivities and specificities of fdg pet
have been reported to be between 75 - 86% and 92 - 97% , respectively . for diagnosis of pelvic nodal metastases , sensitivity ranges from 80% to 100% and specificity from 92% to 100% .
havrilesky et al . , in their meta - analysis incorporating 15 studies on cervical cancer have reported higher pooled sensitivity of pet scan ( 79% ) in comparison to mri ( 72% ) and ct ( 47% ) in detecting pelvic nodes . however , there are apparent inconsistencies in these studies inform of patient selection criteria .
majority of these studies have used pet scanners ( not pet  ct ) and included either patients with locally advanced cervical cancer ( stage ii to iva ) or heterogeneous patient population incorporating both endometrial and cervical cancers and both recurrent and newly diagnosed cervical cancer .
results of these studies can not be extrapolated in practice in patients with early stage cervical cancer .
there are only few studies published , which have focused on potential clinical utility of fdg pet - ct in early and operable cervical cancer .
advent of dedicated hybrid pet - ct scanners have taken care of the above mentioned limitations of both morphological imaging ( size criteria ) and metabolic imaging ( lack of anatomical information ) .
we have done a meta - analysis of published studies in literature with the objective ( 1 ) to evaluate the diagnostic accuracy and explore the current role of fdg pet / ct in detection of nodal metastases in early stage or operable cervical cancer ( 2 ) whether fdg pet / ct as pre - operative imaging can obviate or safely replace surgical nodal staging ? .
advent of dedicated hybrid pet - ct scanners have taken care of the above mentioned limitations of both morphological imaging ( size criteria ) and metabolic imaging ( lack of anatomical information ) .
we have done a meta - analysis of published studies in literature with the objective ( 1 ) to evaluate the diagnostic accuracy and explore the current role of fdg pet / ct in detection of nodal metastases in early stage or operable cervical cancer ( 2 ) whether fdg pet / ct as pre - operative imaging can obviate or safely replace surgical nodal staging ? .
we screened medline ( pubmed ) database in december 2011 using keywords relevant to the cervical cancer like fdg pet / ct , nodal staging , pre - operative evaluation , early stage cervical cancer .
we selected only those published studies from peer reviewed literature , which fulfilled preset strict inclusion criteria of our study ( 1 ) early stage or operable cervical cancer ( below stage iib , few european countries consider even stage iib as operable ) .
studies where only pet scanner used ( not integrated pet / ct ) were excluded .
( 4 ) histopathological confirmation of nodal involvement was available , which fulfilled preset strict inclusion criteria of our study .
there were only six published studies , which could fulfill the criteria for analysis [ table 1 ] .
sironi et al . , performed fdg pet / ct in consecutive 47 patients with figo stage ia or ib before rh and pelvic lymph node dissection .
these authors analyzed patient based sensitivity , specificity , negative predictive value ( npv ) and accuracy of fdg pet / ct to be 73% , 97% , 89% , and 89% , respectively .
chung et al . , also found similar sensitivity ( 36% ) of fdg pet / ct in their series of 34 patients with stage ia2 to iib .
jacob et al . , performed fdg pet / ct pre - operatively in 80 patients with operable cervical cancer ( early stage ) and diagnosed nodal metastases in 14 of 24 histopathologically proven cases ( sensitivity 58% ) .
they could optimally select their patients for surgery based on fdg pet / ct finding and could significantly reduce significant proportion of patients for multimodality treatment ( from 30% to 12.5% , p < 0.01 ) associated with its morbidity .
bentivegna et al . , missed pelvic and para - aortic nodes in 4 of 16 patients ( 25% ) with cervical cancer stage ib1 evaluated with fdg pet / ct .
sensitivity in this group could not be calculated technically as fdg pet scan was not positive in any of the patients .
performed para - aortic lymphadenectomy in their 38 patients with negative pre - operative mri and fdg pet / ct .
fdg pet / ct found to be false negative in 3 of 38 patients ( 8% ) in histopathologically proven para - aortic node metastases ( npv 92% ) .
pelvic and para - aortic lymph node dissection followed by histopathology is the gold standard for diagnoses of regional nodal metastases in cervical cancer . as we know that surgical nodal dissection is associated with its immediate and delayed complications
therefore , objective of any imaging modality should be the pre - operative accurate diagnosis of pelvic and para - aortic nodal metastases in early stage cervical cancer so that need for surgical nodal staging can be avoided or obviated .
analysis of published six studies [ table 1 ] incorporating a total 374 patients , have shown low to moderate sensitivity ( 32 - 73% ) of fdg pet / ct for detection of nodal metastases in early stage cervical cancer.[1015 ] it means that pre - operative imaging with fdg pet / ct similar to mri and ct scan ; can not replace the surgical staging in early cervical cancer due to its moderate and variable sensitivity . although , these studies have reported a high npv of fdg pet / ct scan in the range of 83 - 92% in predicting locoregional nodes .
but these figures of npv are not high enough and not within clinically acceptable limits to allow use fdg pet / ct scan as a screening modality to exclude pelvic and para - aortic nodal involvement noninvasively in early stage cervical cancer .
sironi et al . , have shown that fdg pet / ct fails to detect diseased nodes having size < 5 mm .
therefore , sub - centimeter sized nodes with micro - metastases ( microscopic disease ) is still a concern and remain elusive from fdg pet / ct similar to other imaging modalities .
therefore , role of fdg pet / ct in nodal staging in an early and operable cervical cancer is questionable .
however , fdg pet / ct has shown promising results in patients with a locally advanced cervical cancer ( stage iib to iva ) .
fdg pet / ct performed in pre - treatment setting is advantageous for many other reasons .
if pre - treatment fdg pet / ct scan shows positive nodes in the para - aortic region then this information is vital for deciding therapeutic strategy and radiation field can be extended to include para - aortic region in such cases .
magnitude of uptake in primary lesion has prognostic significance and is useful for evaluation of treatment response if baseline study is available .
fdg pet / ct is suboptimal in nodal staging for early stage cervical cancer contrary to its impressive performance in locally advanced disease .
introduction : nodal metastases in cervical cancer have prognostic implications . 
 imaging is used as an adjunct to clinical staging for evaluation of nodal metastases . 
 fluorodeoxyglucose ( fdg ) positron emission tomography / computed tomography ( pet / ct ) has an advantage of superior resolution of its ct component and detecting nodal disease based on increased glycolytic activity rather than node size . 
 but there are limited studies describing its limitations in early stage cervical cancers.objective:we have done meta - analysis with an objective to evaluate the efficacy of fdg pet / ct and its current clinical role in early stage and operable cervical cancer.materials and methods : studies in which fdg pet / ct was performed before surgery in patients with early stage cervical cancers were included for analysis . 
 pet findings were confirmed with histopathological diagnosis rather than clinical follow - up . 
 fdg pet / ct showed lower sensitivity and clinically unacceptable negative predictive value in detecting nodal metastases in early stage cervical cancer and therefore , can not replace surgicopathological staging . 
 false negative results in presence of microscopic disease and sub - centimeter diseased nodes are still the area of concern for metabolic imaging . however , these studies are single institutional and performed in a small group of patients . 
 there is enough available evidence of clinical utility of fdg pet / ct in locally advanced cervical cancer . but 
 these results can not be extrapolated for early stage disease.conclusion:the current data suggest that fdg pet / ct is suboptimal in nodal staging in early stage cervical cancer .