Effect of irradiation on healing of newly made colonic anastomoses in the rat.

PURPOSE: Short-term effects of radiotherapy on the healing process of newly made colonic anastomoses are investigated by measuring the anastomotic strength in a rat model. METHODS AND MATERIALS: Four groups of Wistar rats were used. In all groups, rats underwent a 1 cm sigmoid resection with end-to-end anastomosis. Group I served as a control group. In group II the anastomosis was irradiated after closure of the abdominal wall with a single dose of 20 Gy of 250 kV x rays. Group III was irradiated with a single dose of 20 Gy while the abdominal wall was not closed, and the surrounding tissues were carefully covered by a lead plate, simulating intra-operative radiotherapy. Group IV was treated as group III, but a larger dose of 25 Gy was applied. Animals were sacrificed 3 or 7 days after the operation. General condition of the rats was determined by observation, weight loss, serum protein and albumin at sacrifice. Anastomotic healing was evaluated by inspection, bursting pressure, hydroxyproline and protein contents of the anastomotic segment. RESULTS: Direct postoperative externally irradiated rats (group II) showed a marked weight loss, hypoproteinaemia and hypo-albuminaemia because of involvement of small bowel in the irradiated volume. With respect to anastomotic healing there were no significant differences between control and irradiated groups. CONCLUSION: These data suggest that the application of a single dose of irradiation (20 and 25 Gy) on colonic anastomoses given in a direct postoperative or intraoperative model has no measurable side effect on the early healing of newly made colonic anastomoses. Direct postoperative external irradiation results in unwanted side effects in the adjacent bowel.

Total lymphoid irradiation in the Wistar rat: technique and dosimetry.

The technical and dosimetric aspects of total lymphoid irradiation (TLI) in the Wistar rat were evaluated as part of a set-up to develop a new model for tumor xenotransplantation. Information obtained from anatomical dissections, radionuclide imaging of the spleen, lymphography and chromolymphography was used to standardize the localization of lymph nodes, thymus and spleen. A practical advantage was found in the simultaneous irradiation through two portals cut out in a lead plate. The two portals encompassed the lymphoid tissue above and below the diaphragm. A specially designed masonite phantom was used to measure the dose distribution in the simulated target volumes. Ionization chamber dosimetry, thermoluminescence dosimetry and film densitometry were used for measuring exposure and absorbed dose. Irradiation was performed with 250 kV X rays (HVL 3.1 mm Cu). The dose rate was regulated by adjusting the treatment distance. The dose inhomogeneity measured in the target volumes varied between 80-100%. The side scatter dose to non target tissues under the shielded area between the two portals ranged between 20-30%. The technique and dosimetry of total lymphoid irradiation in Wistar rats are now standardized and validated and pave the way for tumor xenotransplantation experiments.

Surgery and radiation therapy in the management of craniopharyngiomas.

Twenty-nine patients with histologically confirmed craniopharyngioma were treated from 1960 to 1978, inclusive. Twelve patients were below the age of 15 years, the remaining were adults. Seventy-five percent (9/12) of the patients below the age of 15 showed increased intracranial pressure at presentation and 58% (7/12) showed visual disturbances. In the adult group, 47% (8/17) presented with increased intracranial pressure and 88% (15/17) with visual disturbances. Hormonal, mental and behavior changes were almost equally distributed in both age groups. All patients underwent craniotomy, with subtotal resection of the tumor. Three adults died of postoperative complications (10%), of whom two died of pulmonary emboli and one of cerebral hemorrhage. Of the remaining 26 patients, 13 received immediate postoperative radiotherapy to a total dose of 50.0 to 56.0 Gy, in a target volume including the sellar and parasellar region during an overall treatment period of five to six weeks. All patients were evaluable with a minimum follow-up of four years since they finished their treatment or until death. The five-year recurrence-rate in the group that did not receive postoperative radiation therapy was 45% (5/11 patients) and the five-year rate of death of disease in this group was 27% (3/11 patients). For the group that received immediate postoperative radiation therapy the five-year recurrence-rate was 11% (1/9 patients) and no death of disease was observed in this group. This difference between the two groups was not significant. The corresponding 10-year rates were 71% (5/7 patients) for recurrence and 57% (4/7 patients) for death of disease in the group without, and in the group with immediate postoperative radiation therapy the rate was 25% (2/8 patients) for recurrence and 0 for death of disease. This difference turns out to be significant. Critical analysis of the morbidity in patients surviving after treatment showed no adverse effect on the visual or endocrine status of the group that received postoperative irradiation. It is concluded that in the management of patients with craniopharyngiomas, postoperative irradiation after subtotal resection improves the prognosis of the patient and does not add to visual or endocrine morbidity.

Effectiveness in inhibition of recovery of cell survival by cisplatin and carboplatin: influence of treatment sequence.

Clinical protocols have been designed to combine platinum-based drugs and radiation in the treatment of cancer. The rationale for this approach has been developed from preclinical studies demonstrating that platinum compounds can potentiate the cytotoxic effects of radiation toward cells. In the present study multicellular spheroids derived from squamous cell carcinoma cell line HN-1 have been used to study the effects of both cisplatin and carboplatin when administered prior to, concurrently, and after irradiation treatment. To study the influence of platinum compounds on sublethal damage repair, single and split doses of radiation were applied. Growth delay and proportion cured spheroids served as endpoints. Both cisplatin and carboplatin had no potentiating effect when administered 24 hr prior to irradiation. When administered 3 hr after completion of irradiation procedures, growth delay after single and split doses were enhanced to the same extent. The drug enhancement ratio for cisplatin was larger (1.5) than for carboplatin (1.2). Both single and split doses were enhanced by the same factor, which was interpreted as no effect on sublethal damage repair. When platinum compounds were present in the target cells at the time of irradiation, especially the split dose radiation response was strongly enhanced: the drug enhancement ratio was 3.9 for cisplatin and 3.2 for carboplatin. Recovery from sublethal damage was totally repressed. This study shows that platinum compounds can potentiate radiation and that for maximum effect the sequence of the two treatment modalities is of utmost importance. Moreover, these results may in part explain the heterogeneous outcomes of trials combining platinum compounds and radiation.

Late effects of intraoperative radiation therapy in anastomotic rat colon.

PURPOSE: to determine whether intraoperative radiotherapy causes long-term negative effects on the healing of colonic anastomoses in the rat. METHODS AND MATERIALS: 175 rats were divided into seven equal groups. One group served as sham-irradiated control group. In the others, following a colonic resection, 1 or 2 cm of the distal bowel limb was irradiated with a single dose of 10, 15, or 20 Gy (groups 10/1, 15/1, 20/1, 10/2, 15/2, and 20/2, respectively). Subsequently, an anastomosis was constructed. The animals were killed after 6 (n = 10 in each group) or 12 (n = 15) months. The abdomen was inspected for abnormalities and the colonic diameter was measured. The anastomotic segment was analyzed biochemically (hydroxyproline) and histologically. RESULTS: During the experimental period, 1 rat (group 15/1) died because of anastomotic leakage and 3 others died from unknown causes. There was no difference in colonic diameter between groups. Altogether 17 rats developed an adenocarcinoma in the irradiated area: 11 of these had received a dose of 20 Gy. Histological observation indicated that fibrosis was present only in a limited number of animals, mostly after irradiation with a dose of 15 or 20 Gy. All anastomoses were functional and showed normal histology. The hydroxyproline content of the anastomotic segment was increased--with respect to the control group--only in the 20/2 group after 6 months. After 12 months, the hydroxyproline concentration in the (irradiated) segment distal to the anastomosis proper was higher in the 10/1 and 15/1 groups than in the control group. Otherwise, there were no differences between groups. CONCLUSION: Intraoperative irradiation with a single dose of 10-20 Gy, delivered to the distal limb used for anastomotic construction, does not appear to constitute a threat to anastomotic integrity. Dose-related changes included formation of adenocarcinomas and fibrosis, but function and histology of the anastomosis proper remained unaffected.

Radiosensitivity of different human tumor cells lines grown as multicellular spheroids determined from growth curves and survival data.

Five human tumor cell lines were grown as multicellular tumor spheroids (MTS) to determine whether multicellular tumor spheroids derived from different types of tumors would show tumor-type dependent differences in response to single-dose irradiation, and whether these differences paralleled clinical behavior. Multicellular tumor spheroids of two neuroblastoma, one lung adenocarcinoma, one melanoma, and a squamous cell carcinoma of the oral tongue, were studied in terms of growth delay, calculated cell survival, and spheroid control dose50 (SCD50). Growth delay and cell survival analysis for the tumor cell lines showed sensitivities that correlated well with clinical behavior of the tumor types of origin. Similar to other studies on melanoma multicellular tumor spheroids our spheroid control dose50 results for the melanoma cell line deviated from the general pattern of sensitivity. This might be due to the location of surviving cells, which prohibits proliferation of surviving cells and hence growth of melanoma multicellular tumor spheroids. This study demonstrates that radiosensitivity of human tumor cell lines can be evaluated in terms of growth delay, calculated cell survival, and spheroid control dose50 when grown as multicellular tumor spheroids. The sensitivity established from these evaluations parallels clinical behavior, thus offering a unique tool for the in vitro analysis of human tumor radiosensitivity.

Radiosensitivity of human melanoma spheroids influenced by growth rate.

The radiosensitivity of human melanoma cell line BRO was investigated using the multicellular tumor spheroid system. By adding different concentrations of bovine serum to the tissue culture medium, two different growth rates could be obtained. Spheroids (200-250 microns) were irradiated with graded single doses of X rays (2-8 Gy). The radiation response was quantified using specific growth delay, clonogenic cell survival, and spheroid cure. All three assays showed a growth rate dependent radiation response. At both growth rates the spheroid growth fraction and critical cell number were of comparable magnitude. There was a strong correlation between the radiation response of spheroid regenerating units and clonogenic cells from dispersed spheroids. Cell survival curves indicated a decreased ability to accumulate sublethal damage in fast growing multicellular tumor spheroids. From this study it appears that the intrinsic radiosensitivity of human melanoma cell line BRO cells in multicellular spheroids is modulated by intratumoral conditions.

Repair of sublethal damage in two human tumor cell lines grown as multicellular spheroids.

Multicellular tumor spheroids (MTS) provide a suitable in vitro model to study radiation sensitivity of tumor cells. Two cell lines of human origin, obtained from a neuroblastoma (NB-100) and a squamous cell carcinoma (HN-1), were exposed to graded doses (4-9 Gy) of radiation with 18 MV photons. Radiation was applied either as a single or as a split dose with an interval of 6 hr to determine the extent of sublethal damage repair. Treated spheroids regrew at approximately the same growth rate as control multicellular tumor spheroids, preceded by a static or regression phase. Radiation response was quantified in terms of regrowth delay, expressed as the time needed for treated spheroids to obtain an 8-fold increase of the initial volume at the time of irradiation. Data obtained from regrowth delay analysis were used to calculate the extent of sublethal damage repair, showing for the squamous cell carcinoma line a fractionally higher capacity to repair sublethal damage than the neuroblastoma line. Repair increased with larger dose fractions in both cell lines. Our results show that multicellular tumor spheroids from the two cell lines used in this study are best applicable at relatively high total radiation doses. This makes multicellular tumor spheroids a suitable model for the in vitro evaluation of clinical treatment rationales such as hyperfractionation.

Growth pattern of tumor xenografts in Wistar rats after treatment with cyclophosphamide, total lymphoid irradiation and/or cyclosporin A.

Wistar rats treated with cyclophosphamide, total lymphoid irradiation (TLI), and/or cyclosporin A (CSA) develop a state of immune suppression permitting the growth of tumor xenografts. Experiments were carried out on this newly developed model to investigate the growth patterns of a mouse osteosarcoma and a human colon adenocarcinoma. The combination of cyclophosphamide and CSA permitted a limited period of growth of the mouse osteosarcoma with a tumor take rate of 66%. No takes were observed with the human adenocarcinoma. The combination of cyclophosphamide and TLI resulted in a period of immunosuppression followed by recovery of the immune status. During the period of immunosuppression, tumor xenografts showed a 100% take rate. The most efficient immunosuppression was achieved by a combination of cyclophosphamide, TLI and CSA administered on alternate days. Wistar rats subjected to this treatment showed prolonged tolerance to mouse osteosarcoma and human adenocarcinoma xenografts. There was no alteration in the tumor doubling time or histological morphology of the xenografts in the adapted host as compared with those in the donor tumors. The tumor growth curve showed a pattern of initial growth, a period of stagnation, followed by a steady but slower growth phase. The significance of the results and the advantages of the rat model described in this paper for human tumor xenotransplantation are discussed.

Combined preoperative irradiation and direct postoperative 5-fluorouracil without negative effects on early anastomotic healing in the rat colon.

BACKGROUND AND PURPOSE: Preoperative irradiation with direct postoperative chemotherapy could benefit patients undergoing surgery for colorectal cancer. This study was designed to examine, in an experimental model, if such treatment is feasible without detrimental effects on early anastomotic healing. MATERIAL AND METHODS: A colonic segment was irradiated (25 Gy) in 3 groups (n = 10 each) of male Wistar rats. After 5 days, a colonic resection was performed with anastomotic construction; only the distal limb consisted of irradiated bowel. Postoperatively, animals received daily intraperitoneal 5-fluorouracil (5-FU, group I/CH: 17.5 mg/kg; group I/CL: 12.5 mg/kg) or saline (group I). Three additional groups were treated similarly, but with sham-irradiation: CH, CL and C, respectively. All rats were killed 7 days postoperatively. Parameters measured were: weight, serum albumin and protein, and anastomotic bursting pressure, breaking strength and hydroxyproline content. RESULTS: Body weight was diminished significantly in rats receiving chemotherapy. Serum albumin and protein was significantly lower in irradiated groups. At sacrifice, 40% of I/CH rats had functional rectal stenosis. The average bursting pressure (P = 0.0005) and the average breaking strength (P = 0.012) were only reduced significantly in the CH group. The anastomotic hydroxyproline content was significantly higher in the I/CH and I/CL groups vs. the control group. CONCLUSION: High-dose direct postoperative 5-FU leads to reduced anastomotic strength. Although the combination of preoperative irradiation (25 Gy) and direct postoperative high-dose 5-FU does not reduce early anastomotic strength, some stenosis may occur. The combination of preoperative irradiation and low-dose 5-FU has no such effect.

Clinical and physical aspects of total body irradiation for bone marrow transplantation in Nijmegen.

Eighty-nine patients were transplanted with allogeneic bone marrow after a standard conditioning regimen consisting of cyclophosphamide and fractionated total body irradiation (2 x 4.5 Gy) with average dose rates of 4.1 and 12.3 cGy/min, respectively. The average rectum and lung dose was 9.2 +/- 0.45 and 7.5 +/- 0.78 Gy. In vivo dosimetry was performed in 71 patients irradiated with 18 MV X-rays from left and right lateral. Forty-three patients (48%) died. After increasing the dose rate the incidence of interstitial pneumonitis increased, but the number of relapses decreased.

The effect of a single fraction compared to multiple fractions on painful bone metastases: a global analysis of the Dutch Bone Metastasis Study.

PURPOSE: To answer the question whether a single fraction of radiotherapy that is considered more convenient to the patient is as effective as a dose of multiple fractions for palliation of painful bone metastases. PATIENTS: 1171 patients were randomised to receive either 8 Gy x 1 (n = 585) or 4 Gy x 6 (n = 586). The primary tumour was in the breast in 39% of the patients, in the prostate in 23%, in the lung in 25% and in other locations in 13%. Bone metastases were located in the spine (30%), pelvis (36%), femur (10%), ribs (8%), humerus (6%) and other sites (10%). METHOD: Questionnaires were mailed to collect information on pain, analgesics consumption, quality of life and side effects during treatment. The main endpoint was pain measured on a pain scale from 0 (no pain at all) to 10 (worst imaginable pain). Costs per treatment schedule were estimated. RESULTS: On average, patients participated in the study for 4 months. Median survival was 7 months. Response was defined as a decrease of at least two points as compared to the initial pain score. The difference in response between the two treatment groups proved not significant and stayed well within the margin of 10%. Overall, 71% experienced a response at some time during the first year. An analysis of repeated measures confirmed that the two treatment schedules were equivalent in terms of palliation. With regard to pain medication, quality of life and side effects no differences between the two treatment groups were found. The total number of retreatments was 188 (16%). This number was 147 (25%) in the 8 Gy x 1 irradiation group and 41 (7%) in the 4 Gy x 6 group. It was shown that the level of pain was an important reason to retreat. There were also indications that doctors were more willing to retreat patients in the single fraction group because time to retreatment was substantially shorter in this group and the preceding pain score was lower. Unexpectedly, more pathological fractures were observed in the single fraction group, but the absolute percentage was low. In a cost-analysis, the costs of the 4 Gy x 6 and the 8 Gy x 1 treatment schedules were calculated at 2305 and 1734 Euro respectively. Including the costs of retreatment reduced this 25% cost difference to only 8%. The saving of radiotherapy capacity, however, was considered the major economic advantage of the single dose schedule. CONCLUSION: The global analysis of the Dutch study indicates the equality of a single fraction as compared to a 6 fraction treatment in patients with painful bone metastases provided that 4 times more retreatments are accepted in the single dose group. This equality is also shown in long term survivors. A more detailed analysis of the study is in progress.

Radiosensitization by cytotoxic drugs. The EORTC experience by the Radiotherapy and Lung Cancer Cooperative Groups.

UNLABELLED: A three-arm randomized trial was performed to assess the acute and late toxicity and the impact on survival of the combination high-dose, split-course radiotherapy with 30 mg/m2 cisplatin (cDDP) weekly, with 6 mg/m2 cisplatin daily compared to radiotherapy alone in patients with non-small cell lung cancer (NSCLC). The study started in May 1984 and was closed in May 1989 after 331 patients were randomised. The analysis was performed after a minimum follow-up period of 22 months. Radiotherapy (RT) consisted of 30 Gy, 10 fractions, five fractions a week; then a 3-week split followed by 25 Gy in 10 fractions. Nausea and vomiting were increased for a majority of the patients in the combined treatment arms during treatment. There was no addition of bone marrow suppression, renal dysfunction or esophagitis. Increase of late radiation damage was not observed. Local control (= absence of local progression) was improved for patients treated according to the daily cisplatin arm. This has lead to an improvement in overall survival. There was no effect in time to distant metastasis due to the combined modality. The treatment influence was confirmed in the multivariate analysis. CONCLUSION: local control and survival can be improved by combining radiotherapy with daily low-dose cisplatin in patients with inoperable NSCLC.

High-dose preoperative irradiation without detrimental effect on early repair of anastomoses in the colon of the rat.

Preoperative radiotherapy as an adjunct to surgery for rectal carcinoma is generally thought to impair the healing of colorectal anastomoses. To delineate the presumed hazards of preoperative irradiation, we investigated this effect in a new model where, in contrast to experiments reported so far, anastomoses were constructed using normal tissue for the proximal limb and irradiated tissue for the distal limb. A group of 120 male Wistar rats, divided randomly into 12 groups of 10 each, were used. In 60 animals, a colonic segment of 2.2 cm was irradiated with a single dose of 25 Gy X rays administered 28 or 5 days or 3 or 1 day(s) before colonic resection. For each experimental group, a control group was included which was sham-irradiated on the same preoperative day. The animals were sacrificed on the third or the seventh postoperative day, and healing of the anastomosis was evaluated by measurement of bursting pressure, breaking strength and hydroxyproline concentration and content. Comparison between each experimental group and its control group showed that preoperative irradiation did not reduce the strength of the anastomoses. Also, the concentration and content of hydroxyproline in the tissue of the anastomoses were unchanged. These data indicate that construction of a colonic anastomosis consisting of one irradiated bowel end in rats is not by definition detrimental to the development of early wound strength.

Intra-operative irradiation prolongs the presence of matrix metalloproteinase activity in large bowel anastomoses of the rat.

There exists a growing interest in intra-operative radiation therapy as a treatment modality for large bowel cancer. In a previous experimental study we showed that high-dose intra-operative irradiation delays the healing of colonic anastomoses. However, the contribution of proteases is unknown. In the present study, the gelatinolytic and collagenolytic activity in the healing anastomoses is investigated. After a resection of a 1-cm length of colon (uninjured colon), the rats were irradiated with a single dose of 25 Gy, either to the proximal limb, referred to as the proximal group, or to both proximal and distal limbs of the bowel, referred to as the combined group, before anastomotic construction. Both groups were compared to a control group with anastomoses which were sham-irradiated. The animals were killed 1, 3 or 7 days after operation. The gelatinolytic activity in uninjured and anastomotic tissue was quantified by gelatin zymography and the collagenolytic activity by an assay using a fibrillar rat collagen substrate. Compared with resected uninjured colon, most of the gelatinolytic activities were markedly increased in anastomotic tissue of all groups during the first postoperative week, and new additional activities were detected. The additional metalloproteinases (the 95-kDa family) of both irradiated groups were significantly elevated compared to the anastomoses of the sham-irradiated control group at 7 days after operation. In anastomotic tissue of all groups, the collagenolytic activity of the tissue was also significantly increased at 1 and 3 days after construction with respect to the resected, uninjured colon. After 7 days this effect had disappeared for the sham-irradiated anastomoses, but the activity in the anastomoses in both the proximal and combined groups remained significantly elevated. The findings provide evidence that intra-operative irradiation prolongs the presence of elevated gelatinolytic and collagenolytic activities in colon anastomoses. It may contribute to a reduced or delayed accumulation of collagen and other matrix proteins that supply anastomotic strength.

Moderate doses of intraoperative radiation severely suppress early strength of anastomoses in the rat colon.

Intraoperative irradiation appears to be a valuable addition to the modalities available to treat patients with large bowel cancer. However, its potential effect on healing of anastomoses has not been investigated extensively. For this purpose, male Wistar rats underwent colonic resection. Subsequently, 1 cm of each bowel end was irradiated with doses of 10, 15, 20 or 25 Gy and intestinal continuity was restored. After 3 or 7 days, animals were killed and the anastomoses were analyzed for bursting pressure (intraluminal force), breaking strength (longitudinal force) and hydroxyproline content. Intraoperative irradiation led to a massive (40-70%) and significant (P < 0.025) reduction in bursting pressure 3 days after operation compared to the control group for every dose used. After 7 days, the bursting site was outside the area of the anastomosis in all groups. The breaking strength at day 3 was also reduced, even after 10 Gy. At day 7, when tearing still occurred in the wound area, the breaking strength was still significantly lower in the 15- and 25-Gy groups than in the control group. The hydroxyproline content of the anastomoses was significantly reduced only after irradiation with the higher doses. Thus intraoperative irradiation constitutes a threat to early strength of anastomoses in the rat colon, and even at moderate doses it may threaten the integrity of the anastomosis.

A semiquantitative histological analysis of repair of anastomoses in the rat colon after combined preoperative irradiation and local hyperthermia.

Hyperthermia is a promising method for increasing the efficacy of radiation therapy of colorectal cancer. To study the histological aspects of healing of an anastomosis in the colon, after combined preoperative (sham) irradiation and (sham) hyperthermia treatment, 48 male Wistar rats were divided randomly into four groups. In each animal, a segment of the colon was treated successively by (sham) irradiation (single dose of 25 Gy X rays) and/or (sham) hyperthermia (44 degrees C, 30 min). After 5 days, a resection of the colon was performed by construction of an anastomosis: The distal limb consisted of (sham-) irradiated and/or (sham-) hyperthermia-treated bowel. Rats were killed 3 or 7 days after the surgical procedure. Evaluation of healing of the anastomosis was made by: (1) histological analysis of sections stained with hematoxylin and eosin, (2) semiquantitative measurement of collagen in the area of the anastomosis and (3) semiquantitative analysis of the number of macrophages by immunocytochemistry. Healing of the anastomoses in animals receiving irradiation or hyperthermia alone and in control animals was relatively uneventful. There were no differences between groups in formation of collagen or infiltration by macrophages in the area of the anastomosis. Animals treated with both radiation and hyperthermia showed marked necrosis, infiltration by polymorphonuclear leukocytes and rupture of the anastomosis. It is concluded that preoperative irradiation with a single dose of 25 Gy in combination with local hyperthermia at 44 degrees C for 30 min leads to disturbed repair of anastomoses.

Combined preoperative irradiation and local hyperthermia delays early healing of experimental colonic anastomoses.

OBJECTIVE: To determine if a combination of preoperative irradiation and local hyperthermia of a colonic segment is detrimental to subsequent early anastomotic healing. DESIGN: A prospective randomized experimental trial. SETTING: An animal research laboratory. INTERVENTIONS: Eighty male Wistar rats were randomly divided into 4 groups. In each animal, a segment of the colon was treated successively by (sham) irradiation and (sham) hyperthermia. After 5 days, a colonic resection was performed and an anastomosis was constructed; the distal limb consisted of (sham) irradiated, (sham) hyperthermia-treated bowel. The rats were killed 3 or 7 days after surgery. MAIN OUTCOME MEASURES: Body weight, serum albumin and protein levels, anastomotic bursting pressure, breaking strength, and hydroxyproline content. RESULTS: All animals tolerated (sham) treatment well. Weight was diminished, though not notably, in treated animals vs the control group. After combined preoperative irradiation and hyperthermia, the frequency of local anastomotic complications increased: 4 of 20 animals had a covered perforation when they were killed. In this group, the bursting pressure was lower 3 days after the operation (P = .008). The breaking strength was also lower but not notably. The serum albumin level was significantly lower in this group vs the control group (P = .006); the serum protein level was not decreased. After 7 days, no differences existed between the groups. The hydroxyproline content of the anastomotic tissue was notably higher in rats treated with radiation plus hyperthermia vs control rats (in both the 3- and 7-day groups). The anastomotic hydroxyproline concentration did not differ between the groups. CONCLUSIONS: The combination of preoperative irradiation and hyperthermia results in increased local anastomotic complications. Anastomotic strength is at risk in the first days after the anastomotic reconstruction. Preoperative irradiation or hyperthermia alone does not lead to impaired anastomotic healing in the early phase.

The influence of pre-irradiation on the survival of two head and neck squamous cell carcinoma lines.

Induction of radioresistant tumor cells by previous irradiations may be a problem because the chance to treat a patient presenting with a recurrence with radiotherapy may be lost if a resistant subpopulation was induced by the initial treatment. We here report on experiments with two squamous carcinoma cell lines where cultures were initially irradiated with graded single doses (2-6 Gy) and were re-irradiated after 4 days with single and split doses (2-6 Gy). Both cell lines showed no alteration in radiosensitivity. Also, the split-dose recovery was not changed by the previous irradiations. Flow cytometric analysis showed no significant differences in cell cycle distribution, so that a possible influence of cell cycle redistribution could be excluded. Although preliminary, the results from this study give no indication that previously irradiated cells become more resistant to radiation. In view of the clinical importance of radioresistant clones in tumours, it seems important to perform similar experiments to those reported upon in this study with several radiation fractions as pre-irradiation treatment, to impose a stronger selection pressure on the surviving cells.

The influence of once or twice daily irradiation regimens on growth of squamous cell carcinoma spheroids of different diameters.

Large tumours are in general more difficult to cure by radiation treatment than small tumours. Several factors may be responsible for this phenomenon which evolves during tumour growth. In an earlier study using squamous cell carcinoma cell line HN-1, we have shown in split-dose recovery experiments that the amount of sublethal damage repair is equal in spheroids of different diameters. To elucidate this repair capacity further, we have employed other radiation regimens, calculated with the LQ-equation to be iso-effective, in spheroids of different sessions. Using specific growth delay to quantify radiation response after two to five fractions, it was shown that repair capacity was equal in spheroids of different sizes. For small spheroids the specific growth delay was smaller in once daily fractionation regimens than when radiation was administered in twice daily sessions. In large spheroids this advantage of accelerated fractionation was not observed. If spheroids from this squamous cell carcinoma cell line may be regarded as a relevant model system for their in vivo counterparts, then the results from the present study may indicate that accelerated fractionation of treatment is advantageous for small lesions, but not for larger tumours.