We performed an analysis inserting one or two heyman capsules into the uterus in addition to a tandem-ring applicator when conducting an intracavitary brachytherapy in patients with cervical cancer. We observed a mean improvement of 0.42 Gy per fraction leading to a calculated mean EQD2 of 80.72 Gy compared to 77.84 Gy for D90 HR-CTV and 92.53 Gy compared to 88.66 Gy for D98 GTVres. In 3 of the 7 analyzed patients the benefit from the addition of heyman capsules seemed to be greater compared to the others, whereas in 3 patients no improvement was observed. At the same time, the insertion of additional Heyman capsules did not require additional training.
Multiple studies have demonstrated the necessity to perform brachytherapy in patients treated by primary radio-chemotherapy for cervical cancer [1, 2]. The relationship between the applied dose and local control as well as patient survival are well understood [15, 16]. Particularly in patients with large primary tumors, doses exceeding 85 Gy for HR-CTV are essential.
In our cohort, the estimated overall benefit in local control according to Tanderup et al. would be around 2% for FIGO stage II patients but rises to approximately 5–8% for FIGO stages III and IV . Taking into account only patients that benefitted from the additional applicators the estimated improvement in local control is 5–10% for stages II-IV. In other patients no benefit through additional applicators was achieved. Compared to combined intracavitary/interstitial brachytherapy with reported cumulative EQD2 D90 HR-CTV of approximately 87–90 Gy and increases of 5–10 Gy our approach is showing a considerably smaller improvement [8, 11, 17, 18]. The implementation, however, is easier and viable in any department that regularly performs intracavitary brachytherapy with a tandem-ring applicator. The Method utilized in our institution is an adapted version of the heyman packing method which demonstrated excellent results in patient populations treated by primary radiotherapy for endometrial cancer due to comorbidities [19, 20]. In comparison to the technique applied for endometrial cancer, we used only two capsules in addition to the traditional tandem-ring applicator as only the cervix and the initial tumor extension need to be covered by an adequate dose [19, 20].
The characteristics of patients that potentially benefit from this concept are yet to define. Since the benefit was relatively consistent over fractions, certain primary tumor and their spatial situations to the organs at risk are likely to be predictors for an advantage from this concept. In fractions with only one heyman capsule, no profit was observed. Therefore, we recommend the usage of two heyman capsules. The planning time and the time needed to place the applicators, on the other hand, increases when additional applicators are used. Furthermore, the exact position of the heyman capsules is difficult to control beforehand as the tube of the heyman capsules that are positioned into the cervix is flexible. Therefore, potential advantages in dose coverage should be weighed against the increased expenditure. Since patients that did not benefit from the procedure in the first fraction did not seem to benefit in further fractions, it seems reasonable to test the addition of applicators in the first fraction and decide whether to continue thereafter. Subsequent slipping of the Heyman capsules is unlikely as they are fixed together with the tandem-ring applicator by using a tamponade.
The limitations of this study are the small patient and fraction numbers. These impede conclusions on the characteristics of patients that potentially benefit from this procedure.