Application Value Study Of Interstitial Brachytherapy Technique Based On CT For Cervical Cancer

Objective:1.To present a new technique of 3-dimensional computed tomography-guided interstitial brachytherapy for locally advanced cervical cancer,offering a more advantageous clinical treatment approach.2.To evaluate the dosimetric advantage on the current technique of computed tomography-guided interstitial brachytherapy compared with the conventional intracavitary brachytherapy for locally advanced cervical cancer.3.Locally recurring cervical cancer after surgery and adjuvant radiotherapy remains a major therapeutic challenge,we introduce a new therapeutic technique for such patients: interstitial brachytherapy guided by 3-dimensional computed tomography.Materials and methods:1.The current interstitial brachytherapy technique was performed using a‘‘hybrid'' applicator combining uterine tandem and several interstitial metal needles;metal needles were inserted freehand under 3-dimensional computed tomography guidance.Fifty-two locally advanced cervical cancer patients with poor tumor response to external beam radiotherapy,and a residual tumor > 5 cm after external beam radiotherapy were included.The high-risk clinical target volume(HR-CTV),intermediate-risk clinical target volume(IR-CTV),and organs at risk were contoured.The total dose the patients received,including external beam radiotherapy(45 Gy in25 fractions)and high dose rate interstitial brachytherapy(30 Gy in 5 fractions),was biologically normalized to conventional 2 Gy fractions(EQD2).D90 and D100 for HR-CTV and IR-CTV and D2 cc for the bladder,rectum,and sigmoid were analyzed.Treatment related complications during uterine tandem and interstitial metal needles implantation were investigated.2.Twenty-eight locally advanced cervical cancer patients with bulky tumors and/or parametrial extension(tumor size > 5 cm)after external beam radiotherapy received 3-dimensional computed tomography-guided interstitial brachytherapy(the same method described above).Dosimetric outcomes of the current study,including the total dose(external beam radiotherapy + high dose rate brachytherapy)D90 for the HR-CTV and D2 cc for the bladder,rectum,and sigmoid were compared with a former patient group consisting of 30 individuals who received the conventional intracavitary brachytherapy(uterine tandem + ovoid pairs).3.We present a new technique of interstitial brachytherapy for locally recurring cervical cancer.The main character of the technique is that several interstitial metal needles are inserted recurring tumor under 3-dimensional computed tomography guidance.Sixteen patients with recurrent cervical cancer after radical surgery and adjuvant external beam radiotherapy were included in this study.Six Gy in 6 fractions were prescribed for the HR-CTV of every patient.D90 and D100 for HR-CTV of the current interstitial brachytherapy,and the cumulative D2 cc for the bladder,rectum,and sigmoid,including previous external beam radiotherapy and present brachytherapy were analyzed.Treatment related complications during metal needles implantation were investigated.Results:1.The mean D90 and D100 value for HR-CTV was 88.4 ± 3.5 Gy and 68.3 ±4.4 Gy,respectively.The mean D90 and D100 value for IR-CTV was 68.7 ± 4.8 Gy and 55.8 ± 6.3 Gy,respectively.For all the patients,D90 for HR-CTV reached 85 Gy;88.5% of the patients received D90 for HR-CTV of 87 Gy or greater.The mean D2 cc for the bladder,rectum,and sigmoid were 81.1 ± 5.6 Gy,65.7 ± 5.1 Gy and63.1±5.4 Gy,respectively.86.0% of the metal needles were placed in the lateral 2-5and 7-10 o'clock positions in the uterine canal.93.5% of all the implanted needles were useful for ultimate brachytherapy.The mean number of metal needles was 6.9 ±1.3 for each brachytherapy;the mean implantation depth of the needle was 3.0 ± 0.9cm.During metal needles implantation,five patients showed intestine perforation.there was no bladder perforation or obvious infection complications,no case of severe bleeding,requiring transfusion or hospitalization for prolonged periods,was observed.2.In total,150 conventional intracavitary brachytherapy plans and 140 interstitial brachytherapy plans were performed.The mean D90 values for HR-CTV in the interstitial brachytherapy group was 88.1 ± 3.3 Gy,which was significantly higher than 76.9 ± 5.7 Gy in the intracavitary brachytherapy group(P < 0.01).85.7%of the patients received D90 for HR-CTV of 87 Gy or greater in the interstitial brachytherapy group,and only 6.7% of the patients received D90 for HR CTV of87 Gy or greater in the intracavitary brachytherapy group.The D2 cc for the bladder,rectum,and sigmoid were 84.7 ± 6.8 Gy,69.2 ± 4.2 Gy,67.8 ± 4.5 Gy in the intracavitary brachytherapy group and 81.8 ± 6.5 Gy,66.8 ± 4.0 Gy,64.8 ± 4.1 Gy in the interstitial brachytherapy group.3.The mean D90 and D100 value for HR-CTV was 52.5 ± 3.3 Gy and 27.7 ±3.1 Gy,respectively.93.4% of the patients received D90 for HR-CTV of 50 Gy or greater.The cumulative D2 cc for the bladder,rectum,and sigmoid were 85.6 ± 5.8 Gy,71.6 ± 6.4 Gy,and 69.6 ± 5.9 Gy,respectively.95.9% of all the implanted needles were useful for ultimate brachytherapy.The mean number of metal needles was 6.1 ±1.5 for each brachytherapy;the mean implantation depth of the needle was 3.5 ± 0.9cm.During metal needles implantation,one patient with bladder involvement had a bladder perforation,and two patients had perforation of the intestine.No case of obvious infection and severe bleeding complication.Conclusion:1.3-dimensional computed tomography-guided interstitial brachytherapy using the ‘‘hybrid'' applicator combining uterine tandem and metal needles results in good dose-volume histogram parameters and minor treatment related complications for the locally advanced cervical cancer patients with a residual tumor > 5 cm after external beam radiotherapy and is,thereby,clinically possible feasible.However,the long term curative effect and possible toxicity need further clinical observation in the future study.2.The new interstitial brachytherapy technique guided by 3-dimensional computed tomography provides a significant dosimetric advantage for the locally advanced cervical cancer patients with poor tumor response to external beam radiotherapy and a residual tumor > 5 cm,compared with the conventional intracavitary brachytherapy,offering basic theoretic support for clinical application.3.3-dimensional computed tomography-guided interstitial brachytherapy using the free medal implantation technique for locally recurring cervical cancer after surgery and adjuvant radiotherapy results in good dose-volume histogram parameters and acceptable treatment related complications.The current technique may be clinically feasible.However,long term clinical outcomes should be further investigated.