primary urethral cancer ( puc ) is a very rare disease with an annual age - standardized ratio of 1.5 per million women . the most common histological type is transitional cell carcinoma ( 55% ) , squamous cell carcinoma ( 22% ) , and adenocarcinoma ( 16% ) . these include papillary / micropapillary adenocarcinoma , clear cell adenocarcinoma , adenocarcinoma with intestinal differentiation , and unspecified adenocarcinoma [ 1 , 2 ] . primary urethral cancer presents with symptoms such as dysuria and later hematuria or regular bleeding . due to the female anatomy , the surgical approach depends on tumor stage and anatomic location and often results in major surgery with a pelvic exenteration . radiotherapy is an alternative to surgery and include external beam radiotherapy ( ebrt ) , brachytherapy alone , or a combination of the two modalities [ 4 , 6 , 7 ] . this case report describes a case of puc treated with ebrt followed by image guided adaptive interstitial bt ( igabt ) using the gec - estro ( groupe europen de curiethrapie [ gec ] and european society for radiotherapy & oncology [ estro ] ) adaptive target concept originally designed for locally advanced cervical cancer ( lacc ) [ 8 , 9 ] . previous , a supravaginal hysterectomy was performed due to a fibroma , but apart from that , she was without comorbidity . a gynecological examination in general anesthesia , showed an exophytic tumor in the area of the orificium externum urethra ( figure 1 ) . the tumor was infiltrating into the anterior vaginal wall , but mobile in relation to the pubic bones . the tumor dimensions were 2 cm in height and 4.5 cm in width and thickness . a ) clinical examination showed an exophytic tumor infiltrating the anterior wall of the vagina . b ) fdg pet - ct was with metabolic activity in the vulvar region in relationship to the urethra . c , d ) t2 weighted mri showed a hyper intense tumor with expansive growth pattern invading the distal part of the vagina biopsy showed an adenocarcinoma , with an immune profile that was positive for cdk20 + , cdx2 + , cea+ , suggesting a primary origin from the large bowel . a subsequent cystoscopy and computed tomography ( pet - ct ) showed intense metabolic activity in the vulvar region in relation to the urethra , but no lymph node or distant metastasis . magnetic resonance imaging ( mri ) showed a solid tumor at the urethral meatus measuring 4.5 x 1.4 x 2.5 cm with an expansive growth pattern . the tumor was adhered to the urogenital diaphragm and involved the vagina ( figure 1 ) . due to the clinical and radiological findings , it was concluded that the tumor was originating from the skene glands and classified as a puc . the tumor was considered operable with a complete cystectomy followed by construction of an ileal conduit . apart from surgery , chemotherapy during or after radiotherapy was not considered because of lack of evidence in this rare disease . the patient was presented for the different treatment options and agreed to go for an organ sparing strategy with radiotherapy . the elective target for ebrt ( clinical target volume [ ctv]-e ) included pelvic and inguinal lymph nodes and ctv - t , i.e. the gross tumor volume at diagnosis ( gtv - td ) with a margin of 1 cm respecting natural anatomical borders . during contouring , it was ensured that the whole urethra and vagina was included in the ctv - e . this volume included the gtv - td with a 1 cm isotropic margin respecting the ctv - e . external beam radiotherapy was delivered with volumetric modulated arc therapy ( vmat ) . during optimization , it was aimed to cover the target with 95 - 107% of prescribed dose and keep doses to organ at risk ( oar ) as low as possible without compromising the target coverage . homogeneous-45 was used for optimization to achieve a uniform dose of 45 gy in the area where bt would be delivered . after completion of ebrt , a gynecological examination in general anesthesia was made with insertion of an mri compatible dummy  mupit ( martinez universal perineal interstitial template , varian medical systems , inc . , palo alto , ca , usa ) into the vagina . t2 weighted mri ( 3 tesla ) in para - transversal , -coronal and -sagittal planes were performed ( figure 2 ) for preplanning of the implant . during the preplanning procedure , the gec - estro targets ( gtvbt , ctvhr , ctvir ) and oar ( whole urethra , bladder , rectum , and sigmoid ) were defined . . then gtvbt was contoured on the basis of areas with high signal intensity on the mri within the tumor volume . the ctvhr included the gtvbt , and surrounding grey zones in the vagina and para - vaginal space , respecting the clinical findings at the gynecological examination . the ctvir included the initial tumor volume , and was generated based on information from mri and clinical examination at time of diagnosis [ 8 , 9 ] . finally , the pubic bones were contoured to avoid interference between needles and bone during implantation . pre - implant treatment planning was performed on brachyvision ( varian medical systems , inc . a , b ) t2 weighted mri with a dummy mupit in situ was done for virtual preplanning of the implantation . the gtvbt , ctvhr , ctvir , and organs at risk ( oar ) were contoured and preplanning of the subsequent application was conducted . c , d ) a post - implant ct - scan was conducted and based on clinical information and imaging the ctvhr and ctvir as well as organs at risk was contoured for brachytherapy planning . during manual dose optimization , it is aimed to deliver a physical dose of at least 30 gy to the ctvhr and avoid double dose volumes between the needles as well as respect the constraints for each oar after bowel preparation , the actual implantation was performed under general anesthesia . on the day of implantation the implantation was carried out according to the pre - implant treatment plan using the varian mupit template and sharp end steel needles . the target volumes ( ctvhr and ctvir ) were redefined using the information from clinical examination , pre - planning mri , and post - implant ct . organs at risk ( bladder , urethra , rectum , and sigmoid ) were again outlined as they appeared on the post - implant ct ( figure 2 ) . planning aim of pdr - bt was to deliver a physical dose of 30 gy in 50 hourly pulses to ctvhr . the cumulative dose of ebrt and bt was calculated into equivalent dose in 2 gy fractions ( eqd2 ) using  = 10 gy for tumor , and  = 3 gy for normal tissues , and a repair half - time of 1.5 h. treatment planning was based on manual dose optimization with the aim of reaching a total ebrt and bt dose of d90 > 80 gy in the ctvhr and d90 > 60 gy in the ctvir . for oar , the dose to d2cc and the d0.1cc were recorded . the oar constraints used were 70 gy for d2cc rectum and sigmoid , 80 gy for d2cc bladder , and 98 gy for d0.1cc urethra . basal dose was evaluated in the central plane of the ctvhr as the average dose across all basal dose points in the central plane . it was aimed to avoid double dose (  60 gy ) volumes between the needles ( figure 2 ) . radiotherapy was well tolerated with only mild side effects including erythema in the vulvar and inguinal regions . first follow - up was conducted 3 months after the treatment with a clinical examination and imaging . during the gynecological examination , no late effects were diagnosed and the patient had not experienced any changes in urination . primary urethral cancer is a rare disease without any common guideline for the treatment . in this case report , the patient was selected for an organ sparing approach with radiotherapy that included vmat and igabt . development in ebrt with imrt - technique gives an opportunity to treat a relatively large volume and at the same time , decrease the dose to oar , thus reducing acute side effects during treatment as well as the risk for late morbidity . for brachytherapy other developments have taken place . the gec - estro guidelines were designed for lacc using intracavitary or combined intracavitary / interstitial implants [ 8 , 9 ] . studies have shown improvement in local control and limited morbidity after introduction of the gec - estro adaptive target concept . these findings have resulted in attempts to adapt the guidelines into the treatment of other tumors . one study reported outcome of image and laparoscopic guided interstitial brachytherapy for locally advanced primary or recurrent gynecological cancer using the adaptive gec - estro target concept . this study found an encouraging lc - rate of 92% at 3 years and only limited morbidity in 28 patients . in the present case report , it was possible to adapt the gec - estro target concept and define different target volumes at time of bt , which corresponds to gtvbt , ctvhr , and ctvir . furthermore , it was possible to fulfil the planning aims for the target volumes with a d90 of 79.1 gy and 64.8 gy for ctvhr ( volume 6.1 cm ) and ctvir ( volume 17.3 cm ) , respectively . evaluation of doses to oar showed that we were able to respect the dose constraints that were defined with a d2cc of 45.7 gy , and 44.9 gy , for bladder and rectum , respectively . the d0.1cc for urethra was 85.6 gy . these findings indicate that the gec - estro adaptive target concept can be used in the treatment of puc and result in good clinical results . the literature on urethral cancer is limited , but recently a series of 10 women treated with high dose rate interstitial brachytherapy for urethral cancer ( 5 primary and 5 recurrent ) was published . in most patients , the treatment strategy employed ebrt and image guided ( ct ) interstitial bt . all 5 patients with primary tumors were squamous cell histology and treatment results were acceptable with one local and one nodal recurrence , and acceptable morbidity during follow - up . the case report highlights the use of ebrt and igabt in the treatment of urethral cancer and illustrate that modern radiotherapy is a feasible option with a curative potential and limited morbidity , and should be considered in patients with puc . however , more experience is warranted in more patients with longer follow - up to confirm the satisfying results . the present case report shows that ebrt with an image guided adaptive interstitial brachytherapy boost is an attractive treatment of puc with a possibility to provide local control , and at the same time , organ preservation with limited morbidity .
primary urethral cancer ( puc ) is a very rare disease . 
 this case report illustrates a successful treatment approach of a 67-year - old woman with a urethral adenocarcinoma selected for an organ preserving treatment with external beam radiotherapy ( ebrt ) and interstitial brachytherapy ( bt ) boost , using the gec - estro target concept originally designed for locally advanced cervical cancer ( lacc ) . 
 treatment included ebrt with 45 gy in 25 fractions followed by image guided adaptive interstitial bt ( igabt ) with a pulsed - dose - rate ( pdr ) bt boost with 30 gy in 50 hourly pulses . 
 the d90 for ctvhr was 79.1 gy in eqd23 . at 24 months 
 follow - up , the patient was recurrence free and without treatment related side effects .