Californium-252 interstitial implants in carcinoma of the tongue

A Radiobiological Model for the Relative Biological Effectiveness of High-Dose-Rate252Cf Brachytherapy

While there is significant clinical experience using both low- and high-dose-rate 252Cf brachytherapy, there are minimal data regarding values for the neutron relative biological effectiveness (RBE) with both modalities. The aim of this research was to derive a radiobiological model for 252Cf neutron RBE and to compare these results with neutron RBE values used clinically in Russia. The linear-quadratic (LQ) model was used as the basis to characterize cell survival after irradiation, with identical cell killing rates (S(N) = S(gamma)) between 252Cf neutrons and photons used for derivation of RBE. Using this equality, a relationship among neutron dose and LQ radiobiological parameter (i.e., alpha(N), beta(N), alpha(gamma), beta(gamma)) was obtained without the need to specify the photon dose. These results were used to derive the 252Cf neutron RBE, which was then compared with Russian neutron RBE values. The 252Cf neutron RBE was determined after incorporating the LQ radiobiological parameters obtained from cell survival studies with fast neutrons and teletherapy photons. For single-fraction high-dose-rate neutron doses of 0.5, 1.0, 1.5 and 2.0 Gy, the total biologically equivalent doses were 1.8, 3.4, 4.7 and 6.0 RBE Gy with 252Cf neutron RBE values of 3.2, 2.9, 2.7 and 2.5, respectively. Using clinical data for late-responding reactions from 252Cf, Russian investigators created an empirical model that predicted high-dose-rate 252Cf neutron RBE values ranging from 3.6 to 2.9 for similar doses and fractionation schemes and observed that 252Cf neutron RBE increases with the number of treatment fractions. Using these relationships, our results were in general concordance with high-dose-rate 252Cf RBE values obtained from Russian clinical experience.

[Salvage therapy of advanced squamous cell carcinoma of the mouth cavity and oropharynx. Results of interstitial high-dose-rate brachytherapy combined with ablative tumor surgery]

PURPOSE

The clinical effect of high-dose-rate (HDR) interstitial brachytherapy combined with tumor resection was investigated in this retrospective study on patients with recurrent oral and oropharyngeal squamous cell carcinoma.

PATIENTS AND METHODS

Oral and oropharyngeal squamous cell carcinoma in 38 patients were treated over a period of 7 years (1988-1994) by HDR interstitial brachytherapy using Gammamed 12i equipment. Pretreatment of patients in terms of irradiation and surgery differed (33 irradiated with a total dose between 60.0 and 75.6 Gy, including 8 patients with additional surgery; 1 patient with surgery alone, and 4 patients without any pretreatment). Indications for interstitial brachytherapy differed according to individual responses to treatment and medical histories.

RESULTS

Interstitial brachytherapy was successful in the majority of patients, i.e. complete remission: 12, partial remission: 19, no change: 2, progression: 5. Local control and overall survival including patients with surgical treatment was 59% and 81% at 6 months and 47% and 49% after 12 months, respectively.

CONCLUSION

Interstitial HDR brachytherapy with Iridium 192 is recommended in patients with local recurrences or second primary carcinomas after previous external radiotherapy in the head and neck region. Combination of interstitial brachytherapy and surgery is preferable for these patients.

Interstitial high-dose rate brachytherapy with iridium-192 in patients with oral squamous cell carcinoma

Thirty-four patients with recurrent oral and oropharyngeal carcinomas were treated over a period of 4 years, by interstitial high-dose rate (HDR) brachytherapy (BT) using an iridium-192 source (Gammamed 2i and 12i equipment, Sauerwein, Germany) and fractionated application (1 up to 3 times, weekly recovery phases, single maximum dose 10 Gy). Pretreatment characteristics of patients in terms of irradiation (RT) and surgery differed (22 had external RT alone, with a total dose between 60.0 and 75.6 Gy; RT and surgery: 7; surgery alone: 1). The initial TNM-stages (UICC, Hermanek et al., 1987) of patients were: I = 2, II =3, III = 7, IV = 22. In the majority of cases, clinical indications for HDR-BT included tumour recurrence or progression following external RT, and second primary tumours of the oral cavity. Therapy was successful in most cases, i.e. complete remission: 11, partial remission: 16, no change: 2, progression: 5. Local control and overall survival rates, including patients surgically treated after BT, were at 6 months 58% and 62%, and 44% and 53% at 12 months, respectively. This type of treatment is recommended in patients with local recurrence or second primary tumours after previous external RT in the head and neck region. However, the benefit of interstitial HDR-BT remains questionable, particularly in patients with large tumours and lymph node metastases.

Perioperative neutron brachytherapy with californium-252

Between 1973 and 1988, 495 patients were treated with Cf-252 neutron brachytherapy. Cf-252 neutron therapy sources developed in the USSR has been used in the trial. A numerical reconstruction method for localization of Cf-252 cell coordinates by projections on orthogonal radiographs has been designed and used for treatment planning. Eight (1.6%) patients with recurrent and persistent head and neck tumors and ages from 32 to 48 years (mean age 43 years) were treated with Cf-252 perioperative neutron brachytherapy. There were three patients with oral cavity, one with oropharynx, three with parotid gland cancers, and one with a skin tumor. The dose rate ranged fro 3.2 cGy/h to 11.1 cG/h, the minimal peripheral dose ranged from 3 Gy to 8 Gy. Initial local control was achieved in all patients. Local recurrence developed in two cases. Three patients died in first year after therapy. Three patients died during the second year. Two patients are long term cures, one patient more than nine years and one eight years, that is 25% of the treated patients.