Clinical observations of early and late normal tissue injury in patients receiving fast neutron irradiation

Fast neutron therapy for squamous cell carcinoma in the head and neck region: results of a randomized trial

A randomized trial of fast neuron therapy compared with 4MV photons for patients with head and neck cancer is reported. One hundred and sixty-eight patients were recruited between 1977 and 1984. The minimum follow-up is 2 years. Three patients were withdrawn before treatment began. Eighty-five were allocated to neutron therapy and 80 to receive photon therapy. All patients had squamous cell cancers in one of four primary sites: oral cavity, oropharynx, larynx, and hypopharynx. Local tumor control was similar in both groups: 44.7% after neutrons and 45.0% after photons. Salvage surgery was performed on 18 patients in each treatment group for residual or recurrent cancer. Acute radiation reactions of the mucous membranes were significantly more severe after photons. The number of patients with serious late reactions was greater after neutron therapy but the difference was not statistically significant. There were six deaths related to late morbidity after neutron therapy but none after photon therapy. Survival was better after photon therapy but the difference compared with the neutron group failed to reach statistical significance. When intercurrent deaths are excluded, the difference is less marked. Photon therapy was clearly better in terms of disease-free survival giving a 2-year local disease-free rate of 41.3% (s.e. 5.5%) compared with 29.4% (s.e. 4.9%) after neutrons.

An analysis of the radiation related morbidity observed in a randomized trial of neutron therapy for bladder cancer

This report is an analysis of the morbidity in the bladder and bowel observed in a randomized trial of d(15)+Be neutrons versus megavoltage photons in the treatment of bladder cancer. Acute reactions in the bladder and bowel were significantly worse after photon therapy. Of the patients treated with photons 45.7% had severe reactions in the bladder compared with 10.6% after neutron therapy (p less than 0.001). Severe acute bowel reactions were observed in 8.5% of the patients after photon therapy compared with 3.8% after neutron therapy (p less than 0.05). Late reactions were significantly worse after neutrons. Severe late reactions in the bladder were seen in 58.5% of patients after neutron therapy and in 40.5% after photon therapy (p less than 0.05). In the bowel they were observed in 53.3% of patients after neutron therapy compared with 8% after photon therapy (p less than 0.0001). The disparity in the degree of early and late complications makes assessment of RBE values difficult. It is estimated that for bladder morbidity the RBE value, for photon dose fractions of 2.75 Gy, is less than 3.3 for early reactions and equal to 3.4 for late effects. The respective RBE values for early and late effects in the bowel are less than 3.4 and 3.8.

Late effects of radiation treatment of tongue and floor-of-mouth cancer on the dentition, saliva secretion, mucous membranes and the lower jaw

The purpose of this study was to determine retrospectively any changes in the dentition, saliva secretion, mucous membranes and the lower jaw resulting from the radiation treatment given to patients with cancer of the tongue or floor of the mouth. The study covers 29 patients treated at the Department of Radiotherapy and Oncology of Helsinki University Central Hospital between 1972 and 1981. 23 of the patients were treated for cancer of the tongue and the remaining 6 for cancer of the floor of the mouth. The radiation doses ranged from 5300 to 6700 rad. Clinical examination revealed that the number of carious teeth doubled as a result of radiotherapy, while the incidence of cervical lesions increased by a factor of 10, both compared with the controls. About 70% of the patients studied were found to have either moderate or extensive fungal growth. Stimulated saliva secretion had fallen to about 20% and resting saliva secretion to about 30% of the values for the control group. Radiography revealed pathological changes in the mandible in 34% of the patients. Clinically, 2 patients were found to have extra-oral fistulae. In 1 of these, the spontaneously fractured end of the mandible was visible for several cms. 3 of the patients had undergone hemimandibulectomy because of osteoradionecrosis.

Therapeutic dosimetry for Cf-252 neutron brachytherapy of pelvic cancer

252Cf (Cf) was used to treat tumors of the cervix and uterus with neutron brachytherapy (NT) in an ongoing clinical trial. Tandem and ovoids insertions were used and combinations of single and multiple applications along with high dose whole pelvic irradiation. Dosimetric analysis of treated cases for patterns of tissue dose were carried out. Tissue dose for Cf-NT was, in general, high for neutron components in the central pelvis only, and fell off rapidly with distance from the applicators. The majority and balance of therapeutic dose was contributed by low linear energy transfer (LET) high energy photon beam radiation to the whole pelvis. Comparison with fast neutron beam therapy (NBT) isodose curves showed that much more homogeneous neutron dose was delivered to the pelvic tumor and organs by NBT. Complication frequency has been reported to be higher for neutron beam therapy than for Cf-NT. It appears that the higher integral neutron biological dose to normal tissues for NBT compared to intracavitary Cf-NT probably contributed to the frequency of side effects.

Californium-252 interstitial implants in carcinoma of the tongue

A clinical study using 252Cf sources in brachytherapy of tumors began in the Research Institute of Medical Radiology of the Academy of Medical Sciences of the USSR in 1973. 252Cf afterloading cells were utilized by the method of simple afterloading. Dosimetry and radiation protection of medical personnel were developed. To substantiate optimal therapeutic doses of 252Cf neutrons, a correlation of dose, time, and treatment volume factors with clinical results of 252Cf interstitial implants in carcinoma of the tongue for 47 patients with a minimum follow-up period of 1 year was studied. Forty-nine interstitial implants have been performed. Seventeen patients received 252Cf implants alone (Group I), 17 other patients received 252Cf implants in combination with external radiation (Group II), and 15 patients were treated with interstitial implants for recurrent or residual tumors (Group III). Complete regression of carcinoma of the tongue was obtained in 48 patients (98%). Recurrences occurred in 1 patient (6%) in Group I, 6 patients (35%) in Group II, and 5 patients (33%) in Group III. Thirteen patients (27%) developed radiation necrosis. The therapeutic dose of neutron radiation from 252Cf sources in interstitial radiotherapy of primary tongue carcinomas (Group I) was found to be 7 to 9 Gy. Optimal therapeutic neutron dose in combined interstitial and external radiotherapy of primary tumors (Group II) was 5 to 6 Gy with an external radiation dose of 40 Gy. For recurrent and residual tumors (Group III), favorable results were obtained with tumor doses of 6.5 to 7 Gy.

RBE values and repair characteristics for colo-rectal injury after caesium 137 gamma-ray and neutron irradiation. II. Fractionation up to ten doses

Early and late colo-rectal damage in mice have been assessed after 137Cs gamma irradiation and 3 MeV neutrons given as 1,2,5 or 10 fractions. Damage was measured by early changes in body weight, the late production of short faecal pellets and the pattern of lethality after irradiation. The data have been analysed in terms of the time course of expression of damage, fractionation effects and the RBE for neutrons over a wide range of doses per fraction (0.5-12.5 Gy neutrons, 3.5-33.5 Gy gamma rays). An initial epithelial denudation led to an early loss of weight, maximal at 11-17 days after irradiation. A dose-dependent weight reduction persisted over the animals' life-time. Deaths after localised pelvic gamma irradiation were progressive with no sharp demarcation between early or late phases of injury. The time course for lethality was qualitatively similar after neutrons. Beyond six months the rectum became constricted by fibrosis and a higher proportion of small faecal pellets was observed. At 6-15 months relatively shallow dose-response curves were obtained for this change. The sparing effect of fractionation was marked for the gamma-irradiated mice and almost absent after neutrons. A very high repair increment (11 Gy) was seen with two gamma-ray fractions of 20 Gy. At lower doses per fraction the proportion of each gamma-ray fraction recovered was 50-69% for all assays, i.e., similar to that for other normal tissues. There was a slight enhancement in the sparing effect for the late compared with the early assays over the lower dose range. The RBE was strongly dependent on dose per fraction because of the lack of reparable damage after neutrons. The RBE for both early and late effects was 5.0 at a neutron dose per fraction of 1 Gy. Extrapolation of the RBE data to lower doses, using the linear quadratic model, predicts a higher RBE for late (7.4-12.7) than for early damage (5.7-8.5) if gamma-ray doses below 5 Gy are used.

Late effects of 50 MeV d leads to Be neutron and cobalt-60 irradiation of rhesus monkey cervical spinal cord

The cervical spinal cords of 30 rhesus monkeys were irradiated with 50 MeV d leads to Be neutrons or 60Co gamma rays to evaluate the dose-response relationships for radiation myelopathy. Three groups were treated with 50 MeV d leads to Be neutrons using dosage schedules of 1300 rad n gamma (Group I), 1425 rad n gamma (Group II), or 1550 rad n gamma (Group III) in nine fractions over 29 days. Three groups were irradiated with 60Co gamma rays using dosage schedules of 4620 rad (Group IV), 5390 rad (Group V), or 5940 rad (Group VI) in 22 fractions over 29 days. A significant dose-response relationship was observed for the groups treated with neutrons. Whereas none of the monkeys in Group I showed clinical evidence of neurologic dysfunction, all five animals in Group III became paralyzed. One animal in Group II developed transient neck stiffness and mild unilateral leg paresis. No definitive signs of neurologic injury were seen in any of the animals irradiated with 60Co. The histopathologic changes correlated well with the clinical observations. All of the animals in Group III exhibited moderate to severe malacia and demyelination of the white matter of the cervical spinal cord. The histologic data indicated that the RBE for five times weekly fractionation (approximately 270 rad 60Co fractions) was in the range of 4.2 to 4.6, since the malacia and demyelination in the spinal cords irradiated with 5940 rad of 60Co gamma-rays were greater than that observed in the spinal cords irradiated with 1300 rad n gamma of neutrons but less than the changes in those irradiated with 1425 rad n gamma of neutrons.

50-MEVd leads to Be neutrons: a comparison of normal tissue tolerance in animals with clinical observations in patients

The acute and late effects of 50 MeV neutrons were investigated by irradiating a variety of organ systems in large animals using dosage schedules similar to those that have been employed clinically. The RBEs for acute effects in pig skin and rhesus monkey oral mucosa were significantly less than the RBEs for late effects. This observation has also been noticed clinically. The RBEs for late effects in pig skin, rhesus monkey oral mucosa, and rhesus monkey kidney were consistent with values of 3.1 to 3.4 relative to approximately 200 rad 60Co fractions and approximately 2.2 to 2.6 relative to approximately 400 rad 60Co fractions. The RBE for radiation myelitis was significantly greater (4.2 to 4.6 relative to approximately 270 rad 60Co fractions). The tolerance doses for 50 MeVd leads to Be neutrons in large animals were approximately 2200 radn gamma/61/2 weeks for skin contraction, approximately 2100 radn gamma/61/2 weeks for oromucosal necrosis, approximately 1300 radn gamma/41/2 weeks for radiation myelitis, and approximately 960 radn gamma/4 weeks for radiation nephritis. These values correlate well with clinical observations at TAMVEC, since the majority of soft tissue complications in patients occurred following tissue doses in excess of 2100 radn gamma.