Interstitial pneumonitis after hyperfractionated total body irradiation in HLA-matched T-depleted bone marrow transplantation

Improving total body irradiation with a dedicated couch and 3D-printed patient-specific lung blocks: A feasibility study

Introduction

Total body irradiation (TBI) is an important component of the conditioning regimen in patients undergoing hematopoietic stem cell transplants. TBI is used in very few patients and therefore it is generally delivered with standard linear accelerators (LINACs) and not with dedicated devices. Severe pulmonary toxicity is the most common adverse effect after TBI, and patient-specific lead blocks are used to reduce mean lung dose. In this context, online treatment setup is crucial to achieve precise positioning of the lung blocks. Therefore, in this study we aim to report our experience at generating 3D-printed patient-specific lung blocks and coupling a dedicated couch (with an integrated onboard image device) with a modern LINAC for TBI treatment.

Material and methods

TBI was planned and delivered (2Gy/fraction given twice a day, over 3 days) to 15 patients. Online images, to be compared with planned digitally reconstructed radiographies, were acquired with the couch-dedicated Electronic Portal Imaging Device (EPID) panel and imported in the iView software using a homemade Graphical User Interface (GUI). In vivo dosimetry, using Metal-Oxide Field-Effect Transistors (MOSFETs), was used to assess the setup reproducibility in both supine and prone positions.

Results

3D printing of lung blocks was feasible for all planned patients using a stereolithography 3D printer with a build volume of 14.5×14.5×17.5 cm³. The number of required pre-TBI EPID-images generally decreases after the first fraction. In patient-specific quality assurance, the difference between measured and calculated dose was generally<2%. The MOSFET measurements reproducibility along each treatment and patient was 2.7%, in average.

Conclusion

The TBI technique was successfully implemented, demonstrating that our approach is feasible, flexible, and cost-effective. The use of 3D-printed patient-specific lung blocks have the potential to personalize TBI treatment and to refine the shape of the blocks before delivery, making them extremely versatile.

The Burden of Survivorship on Hematological Patients-Long-Term Analysis of Toxicities after Total Body Irradiation and Allogeneic Stem Cell Transplantation

Simple Summary

Total body irradiation is an essential large-field technique enabling myeloablation before allogeneic stem cell transplantation. With its field encompassing all organs, a diverse spectrum of toxicities may arise. This work analyzes long-term pulmonary, cardiac, ocular, neurological and renal toxicities in a monocentric patient cohort and identifies possible risk factors. Both the number of patients and the duration of the follow-up period exceed those of many comparable studies in the literature.

Abstract

Total body irradiation is an effective conditioning modality before autologous or allogeneic stem cell transplantation. With the whole body being the radiation target volume, a diverse spectrum of toxicities has been reported. This fact prompted us to investigate the long-term sequelae of this treatment concept in a large patient cohort. Overall, 322 patients with acute leukemia or myelodysplastic syndrome with a minimum follow-up of one year were included (the median follow-up in this study was 68 months). Pulmonary, cardiac, ocular, neurological and renal toxicities were observed in 23.9%, 14.0%, 23.6%, 23.9% and 20.2% of all patients, respectively. The majority of these side effects were grades 1 and 2 (64.9–89.2% of all toxicities in the respective categories). The use of 12 Gray total body irradiation resulted in a significant increase in ocular toxicities (p = 0.013) and severe mucositis (p < 0.001). Renal toxicities were influenced by the age at transplantation (relative risk: 1.06, p < 0.001) and disease entity. In summary, total body irradiation triggers a multifaceted, but manageable, toxicity profile. Except for ocular toxicities and mucositis, a 12 Gray regimen did not lead to an increase in long-term side effects.

Pulmonary Toxicity after Total Body Irradiation-An Underrated Complication? Estimation of Risk via Normal Tissue Complication Probability Calculations and Correlation with Clinical Data

Simple Summary

Total body irradiation is an integral part of many conditioning regimens prior to allogeneic stem cell transplantation. It is a large-field technique affecting all organs at risk, of which the lungs are critical for patient survival. However, the precise rates of long-term pulmonary toxicities are unknown. This analysis provides a large patient cohort with long-term follow-up investigating TBI sequelae. Additionally, we present normal tissue complication probability calculations for acute and chronic lung toxicities to enable comparison between biophysical and real-world data. To our knowledge, this is the first adaption of this model to a total-body irradiation patient cohort, which will help to evaluate the feasibility and appropriateness of this approach.

Abstract

Total body irradiation (TBI) is an essential part of various conditioning regimens prior to allogeneic stem cell transplantation, but is accompanied by relevant (long-term) toxicities. In the lungs, a complex mechanism induces initial inflammation (pneumonitis) followed by chronic fibrosis. The hereby presented analysis investigates the occurrence of pulmonary toxicity in a large patient collective and correlates it with data derived from normal tissue complication probability (NTCP) calculations. The clinical data of 335 hemato-oncological patients undergoing TBI were analyzed with a follow-up of 85 months. Overall, 24.8% of all patients displayed lung toxicities, predominantly pneumonia and pulmonary obstructions (13.4% and 6.0%, respectively). NTCP calculations estimated median risks to be 20.3%, 0.6% and 20.4% for overall pneumonitis (both radiological and clinical), symptomatic pneumonitis and lung fibrosis, respectively. These numbers are consistent with real-world data from the literature and further specify radiological and clinical apparent toxicity rates. Overall, the estimated risk for clinical apparent pneumonitis is very low, corresponding to the probability of non-infectious acute respiratory distress syndrome, although the underlying pathophysiology is not identical. Radiological pneumonitis and lung fibrosis are expected to be more common but require a more precise documentation by the transplantation team, radiologists and radiation oncologists.

Late toxicity of a novel allogeneic stem cell transplant using single fraction total body irradiation for hematologic malignancies in children

Single fraction total body irradiation (SFTBI) as part of a myeloablative preparative regimen in allogeneic hematopoietic stem cell transplantation (HSCT) for hematopoietic malignancies was shown to have similar survival compared with fractionated total body irradiation (FTBI)-containing regimens, with less acute toxicity. The objective of this study was to determine long-term toxicity >2 years following SFTBI-based HSCT. Twenty-one patients were evaluated at a median follow-up of 6.8 years. Thyroid dysfunction was found in 21% of patients, 1 of whom (5.2%) was symptomatic; 23% had gonadal failure; 50% of patients with growth potential had linear growth disturbance; 27% had mild to moderate pulmonary disease; and 25% had cataracts. Intelligence quotient was stable. cGVHD was present in 28%, and 4 patients (19%) were on immune suppression 2 years posttransplant. Overall survival subsequent to 2 years posttransplant was 76% in this cohort of patients. No secondary malignancies were observed. In conclusion, the toxicities of SFTBI occurred at similar or reduced frequency compared with FTBI. SFTBI should be considered for patients who may benefit from a radiation-containing HSCT preparative regimen.

Pretransplant pulmonary function tests predict risk of mortality following fractionated total body irradiation and allogeneic peripheral blood stem cell transplant

PURPOSE

To determine the value of pulmonary function tests (PFTs) done before peripheral blood stem cell transplant (PBSCT) in predicting mortality after total body irradiation (TBI) performed with or without dose reduction to the lung.

METHODS AND MATERIALS

From 1997 to 2004, 146 consecutive patients with hematologic malignancies received fractionated TBI before PBSCT. With regimen A (n=85), patients were treated without lung dose reduction to 13.6 gray (Gy). In regimen B (n=35), total body dose was decreased to 12 Gy (1.5 Gy twice per day for 4 days) and lung dose was limited to 9 Gy by use of lung shielding. In regimen C (n=26), lung dose was reduced to 6 Gy. All patients received PFTs before treatment, 90 days after treatment, and annually.

RESULTS

Median follow-up was 44 months (range, 12-90 months). Sixty-one patients had combined ventilation/diffusion capacity deficits defined as both a forced expiratory volume in the first second (FEV1) and a diffusion capacity of carbon dioxide (DLCO)<100% predicted. In this group, there was a 20% improvement in one-year overall survival with lung dose reduction (70 vs. 50%, log-rank test p=0.042).

CONCLUSION

Among those with combined ventilation/diffusion capacity deficits, lung dose reduction during TBI significantly improved survival.

Dose response and factors related to interstitial pneumonitis after bone marrow transplant

PURPOSE

Total body irradiation (TBI) and chemotherapy are common components of conditioning regimens for bone marrow transplantation. Interstitial pneumonitis (IP) is a known regimen-related complication. Using published data of IP in a multivariate logistic regression, this study sought to identify the parameters in the bone marrow transplantation conditioning regimen that were significantly associated with IP and to establish a radiation dose-response function.

METHODS AND MATERIALS

A retrospective review was conducted of articles that reported IP incidence along with lung dose, fractionation, dose rate, and chemotherapy regimen. In the final analysis, 20 articles (n = 1090 patients), consisting of 26 distinct TBI/chemotherapy regimens, were included in the analysis. Multivariate logistic regression was performed to determine dosimetric and chemotherapeutic factors that influenced the incidence of IP.

RESULTS

A logistic model was generated from patients receiving daily fractions of radiation. In this model, lung dose, cyclophosphamide dose, and the addition of busulfan were significantly associated with IP. An incidence of 3%-4% with chemotherapy-only conditioning regimens is estimated from the models. The alpha/beta value of the linear-quadratic model was estimated to be 2.8 Gy. The dose eliciting a 50% incidence, D50, for IP after 120 mg/kg of cyclophosphamide was 8.8 Gy; in the absence of chemotherapy, the estimated D50 is 10.6 Gy. No dose rate effect was observed. The use of busulfan as a substitute for radiation is equivalent to treating with 14.8 Gy in 4 fractions with 50% transmission blocks shielding the lung. The logistic regression failed to find a model that adequately fit the multiple-fraction-per-day data.

CONCLUSIONS

Dose responses for both lung radiation dose and cyclophosphamide dose were identified. A conditioning regimen of 12 Gy TBI in 6 daily fractions induces an IP incidence of about 11% in the absence of lung shielding. Shielding the lung to receive 50% of this dose lowers the estimated incidence to about 2.3%. Because the lungs can be adequately shielded, we recommend against using busulfan as a substitute for fractionated TBI with cyclophosphamide.

Total body irradiation and pneumonitis risk: a review of outcomes

A review was undertaken of all patients treated at Royal Adelaide Hospital, South Australia with total body irradiation (TBI) for the purpose of assessing the incidence of interstitial pneumonitis (IP) and possible prognostic factors for its development. The aim was also to assess the impact of IP and other prognostic factors on long-term survival outcome following bone marrow transplantation. A total of 84 patients received TBI, with 12 Gy in six fractions delivered using two different instantaneous dose rates of 7.5 and 15 cGy min⁻¹. This series included 26 cases of acute lymphoblastic leukaemia, 26 of multiple myeloma and 15 of acute myelogenous leukaemia. On multivariate analysis, a higher dose rate was independently significant for an increased risk of IP.

Cataracts in patients receiving stem cell transplantation after conditioning with total body irradiation

One hundred and ninety-three patients with hematological malignancies and a follow-up > or =1 year, treated with stem cell transplantation (45 autologous, 99 allogeneic T cell-depleted matched, 49 allogeneic T cell-depleted mismatched) from July 1985 to May 1998, were considered evaluable for the development of cataracts. Total body irradiation (TBI), administered either according to a hyperfractionated scheme (HTBI) or in a single dose (STBI), was employed in the conditioning regimens. HTBI was prescribed in 94% of patients undergoing allogeneic matched transplant, while STBI was used in 71% of patients receiving allogeneic mismatched and in all patients undergoing autologous transplant. The median follow-up was 7.56 years in the HTBI and 3.02 years in the STBI group. Among the different risk factors analyzed by univariate analysis only the TBI scheme and type of transplant reached statistical significance (P < 0.0001 and P < 0.001, respectively). By multivariate analysis only the TBI scheme was an independent factor for cataract development (STBI vs HTBI RR 7.2; P < 0.01). Our results showed that STBI is more cataractogenic than HTBI. The incidence of cataract we observed was among the lowest described in the literature. T cell depletion, because it prevents graft-versus-host disease and reduces the protracted use of post-transplant steroids, explains the results we obtained.

Radiobiological modelling of the treatment of leukaemia by total body irradiation

PURPOSE

Total body irradiation (TBI) has been used as part of the conditioning regimen before bone marrow transplantation or stem cell re-infusion for more than 30 years. A wide variety of regimens have been used, and no single one has emerged as the best. Experimental evidence suggests a diversity of radiosensitivities of leukaemia cells in culture, which may correlate with a significant variation of leukaemic cell radiosensitivities between patients. The purpose of this project was to compute leukaemic cell killing by different schedules and determine whether a "best treatment" could be devised for individual patients.

METHODS

We have developed a mathematical model for leukaemic cell killing by alternative TBI schedules, applied to a patient population with diverse leukaemic radiosensitivities. We considered 13 schedules in clinical use, and 14 theoretical schedules calculated (by the linear-quadratic model) to be iso-effective for risk of radiation pneumonitis. When each schedule of treatment is applied to the patient population, a distribution of leukaemic cell kills (log cell kill values) can be obtained for that schedule. The leukaemic kill distribution was also computed for optimized individual scheduling, each individual being treated by the schedule that was most effective for that patient. Using available data on the clinically observed dose response relationship for acute myeloid leukaemia, the model was extended to provide leukaemia cure probabilities for each of the schedules and for the individualized strategy.

RESULTS

The computer simulations show that each schedule, applied to the treatment of a radiobiologically diverse patient population, results in a broad distribution of leukaemic log kill values, with a mean of 3-5 for most schedules (i.e. 10(-3)-10(-5) surviving fraction of leukaemic cells), and a broad variation (1-10 log kill) amongst patients. The distributions generated by the various schedules were found to be overlapping, implying that many of the schedules would be difficult to distinguish reliably in clinical trials. Individualized optimum treatment is possible if radiobiological parameters are known for each patient and would improve the leukaemic log kill distribution by about 1 log on average, corresponding to an increase of leukaemia cure probability of several percent overall. For some individual patients, however, optimal scheduling could make a large difference to treatment outcome.

CONCLUSIONS

The use of many different clinical treatment schedules may be continuing because outcomes are similar when these diverse schedules are applied to unselected patient populations. The measurement of individual leukaemic cell radiosensitivity would allow individualized scheduling, which could result in modest increases in overall curability, but substantial improvements in survival or duration of remission for individual patients.

Decreased pulmonary radiation resistance of manganese superoxide dismutase (MnSOD)-deficient mice is corrected by human manganese superoxide dismutase-Plasmid/Liposome (SOD2-PL) intratracheal gene therapy

The pulmonary ionizing radiation sensitivity of C57BL/6 Sod2(+/-) mice heterozygous for MnSOD deficiency was compared to that Sod2(+/+) control littermates. Embryo fibroblast cell lines from Sod2(-/-) (neonatal lethal) or Sod2(+/-) mice produced less biochemically active MnSOD and demonstrated a significantly greater in vitro radiosensitivity. No G(2)/M-phase cell cycle arrest after 5 Gy was observed in Sod2(-/-) cells compared to the Sod2(+/-) or Sod2(+/+) lines. Subclonal Sod2(-/-) or Sod2(+/-) embryo fibroblast lines expressing the human SOD2 transgene showed increased biochemical activity of MnSOD and radioresistance. Sod2(+/-) mice receiving 18 Gy whole-lung irradiation died sooner and had an increased percentage of lung with organizing alveolitis between 100 and 160 days compared to Sod2(+/+) wild-type littermates. Both Sod2(+/-) and Sod2(+/+) littermates injected intratracheally with human manganese superoxide dismutase-plasmid/liposome (SOD2-PL) complex 24 h prior to whole-lung irradiation showed decreased DNA strand breaks and improved survival with decreased organizing alveolitis. Thus underexpression of MnSOD in the lungs of heterozygous Sod2(+/-) knockout mice is associated with increased pulmonary radiation sensitivity and parallels increased radiation sensitivity of embryo fibroblast cell lines in vitro. The restoration of cellular radioresistance in vitro and in lungs in vivo by SOD2-PL transgene expression supports a potential role for SOD2-PL gene therapy in organ-specific radioprotection.

Intratracheal injection of manganese superoxide dismutase (MnSOD) plasmid/liposomes protects normal lung but not orthotopic tumors from irradiation

To determine whether intratracheal (IT) lung protective manganese superoxide-plasmid/liposomes (MnSOD-PL) complex provided 'bystander' protection of thoracic tumors, mice with orthotopic Lewis lung carcinoma-bacterial beta-galactosidase gene (3LL-LacZ) were studied. There was no significant difference in irradiation survival of 3LL-LacZ cells irradiated, then cocultured with MnSOD-PL-treated compared with control lung cells (D0 2.022 and 2.153, respectively), or when irradiation was delivered 24 h after coculture (D0 0.934 and 0.907, respectively). Tumor-bearing control mice showed 50% survival at 18 days and 10% survival at 21 days. Mice receiving liposomes with no insert or LacZ-PL complex plus 18 Gy had 50% survival at 22 days, and a 20% and 30% survival at day 50, respectively. Mice receiving MnSOD-PL complex followed by 18 Gy showed prolonged survival of 45% at 50 days after irradiation (P < 0.001). Nested RT-PCR assay for the human MnSOD transgene demonstrated expression at 24 h in normal lung, but not in orthotopic tumors. Decreased irradiation induction of TGF-beta1, TGF-beta2, TGF-beta3, MIF, TNF-alpha, and IL-1 at 24 h was detected in lungs, but not orthotopic tumors from MnSOD-PL-injected mice (P < 0.001). Thus, pulmonary radioprotective MnSOD-PL therapy does not provide detectable 'bystander' protection to thoracic tumors.

Fractionated total body irradiation in allogeneic bone marrow transplantation in leukemia patients: analysis of prognostic factors and results in 136 patients

BACKGROUND AND PURPOSE

The results of a single-institution series of patients with chronic and acute leukemias are analyzed with regard to literature-reported predictor variables.

MATERIALS AND METHODS

Between 1985 and 1994, 136 patients, 82 patients with chronic myeloid leukemia (CML) and 54 with acute leukemia (AL), received a uniform preparatory regimen of fractionated total body irradiation (TBI; 12 Gy in 3 days) plus different chemotherapy regimens before bone marrow transplantation. Eighty-six patients were considered to be in early phase of disease (CML in chronic phase or AL in first complete remission) and 50 in advanced phase (all those beyond first remission or first chronic phase). Ninety-five patients received unmanipulated allogeneic BM, and 41 T-lymphocyte-depleted BM.

RESULTS

The 5-year overall survival (OS) and disease-free survival (DFS) of the whole series were 43% and 31%, and median survival was 43 and 10 months, respectively. A Cox proportional hazard model identified variables related to overall and disease-free survival. For OS, graft versus host disease (GVHD) was the first independent variable (P < 0.0001), followed by age (P < 0.001), T-depletion (P < 0.01), disease status (P < 0.05) and type of leukemia (P < 0.05). With regard to DFS, only T-depletion (P < 0.0001), disease status (P < 0.01) and GVHD (P < 0.01) resulted predictor factors. Early complications after BMT were reported in 59 patients, TBI-induced delayed toxicity in 9 patients, and 16 patients suffered late complications.

CONCLUSIONS

Our results confirm the curability of early phase leukemias with standard fractionated TBI-induced Allogeneic bone marrow transplantation (ABMT). With an homogeneous fractionated TBI schedule as employed in our series, T-cell depletion negatively affected the outcome.

Interstitial pneumonitis in acute leukemia patients submitted to T-depleted matched and mismatched bone marrow transplantation

PURPOSE

To identify factors that could contribute to interstitial pneumonitis (IP), which remains one of the major causes of morbidity and mortality after both matched and mismatched bone marrow transplantation (BMT).

METHODS AND PATIENTS

Ninety acute leukemia patients received an allogeneic T-depleted matched (n = 54) or mismatched (n = 36) BMT. They were preconditioned with total body irradiation (TBI), thiotepa, rabbit anti-thymocyte globulin, and cyclophosphamide. The TBI scheme was hyperfractionated in matched, and a single dose in mismatched patients. The dose to the lungs was reduced in both groups.

RESULTS

Five of the 54 matched patients developed IP. All cases were fatal. There were 16 cases of IP, 13 fatal, in the mismatched group. The probability of developing IP was 11.3 +/- 4.9% and 48.6 +/- 9.0%, respectively. The between-group difference was statistically significant (p < 0.0001). The type of transplant and the TBI scheme were the most important parameters for IP development in univariate analysis, whereas acute graft-versus-host disease, disease stage and sex were nonsignificant. Median follow-up was 342 days (range 17-2900).

CONCLUSIONS

The low incidence of IP in matched patients and the lack of idiopathic cases are evidence for the validity of the TBI schedule. In contrast, the incidence in mismatched patients remains too high; therefore, new strategies should be studied in an attempt to lower it.

Repair capacity of mouse lung after total body irradiation alone or combined with cyclophosphamide

PURPOSE

Cyclophosphamide (CTX) combined with fractionated total body irradiation (TBI) is frequently used in the conditioning of patients prior to bone marrow transplantation (BMT). This study was performed to investigate the effect of CTX on the repair capacity of lung tissue after TBI in a mouse model for BMT.

MATERIALS AND METHODS

TBI was given as a single fraction, 3 fractions in 3 days (Fx 3) or 9 fractions in 3 days (Fx 9) either alone or 24 h after a single dose of CTX. The single fraction TBI was given at either high dose rate (HDR) of 0.71 Gy/min or low dose rate (LDR) of 0.08 Gy/min. All mice were transplanted 4-6 h after the last TBI fraction. Lung damage was assessed using ventilation rate (VR) and lethality between 28 and 180 days. The repair capacity of lung tissue was estimated using the direct analysis method with the probability of reaching the end point described by a logistic formulation of the linear quadratic model.

RESULTS

The VR data confirmed the high repair capacity of lung tissue with an alpha/beta ratio of 4.4 Gy though with a wide 95% confidence interval (CI = 0.03-10.5). Giving CTX before fractionated TBI markedly reduced the doses needed to cause response in 50% of the animals. The sparing effect of using fractionated TBI was still evident in the combined CTX-TBI schedules. The estimated alpha/beta ratio was 1.6 Gy (CI = 0.01-4.7) which is within the range of values reported after thoracic radiation only. On the other hand, the sparing effect seen in going from single fraction HDR to LDR was completely abolished when CTX was given 24 h before TBI. The same pattern was repeated when lethality between 28-180 days was used. Yet, the use of lethality to estimate lung damage in a TBI model, markedly underestimated the repair capacity.

CONCLUSIONS

These results confirm the high repair capacity of lung tissue after TBI and emphasize the value of using a specific end point in testing lung damage after TBI. It also shows that there can be a negative effect of CTX on the repair capacity of lung damage which is more pronounced when CTX is followed (24 h later) by single fraction TBI at LDR than by a fractionated TBI course over a few days.

Pulmonary function changes in long-term survivors of bone marrow transplantation

PURPOSE

This study was undertaken to evaluate long-term pulmonary function changes in patients undergoing bone marrow transplantation (BMT), to assess their clinical significance, and to identify factors influencing these changes.

METHODS AND MATERIALS

Pulmonary function tests (PFT) were evaluated before and after BMT in 111 adult patients undergoing BMT between 1985 and 1991. Forced expiratory volume at 1 s (FEV1), forced vital capacity (FVC), diffusing capacity (DLCO), and total lung capacity (TLC) were evaluated. One hundred and three patients (92.8%) received total body irradiation (TBI) to a total dose of 14 Gy in nine equal fractions. The lung dose was restricted to < 6.5 Gy in 95% of patients with partial transmission lung shielding. Seventy-eight percent of patients had acute graft-versus-host disease (aGVHD), 69% chronic graft-vs.-host disease (cGVHD), and 63% posttransplant pulmonary infection. Effects of GVHD, TBI, radiation dose to the lungs, dose rate of TBI, posttransplant pulmonary infection, Busulfan use for conditioning, age, and history of smoking were evaluated for their influence on pulmonary function.

RESULTS

Posttransplant FEV1, FVC, and TLC were lower than pretransplant values (p < 0.05) at 6 months and 1 year posttransplant with subsequent recovery. DLCO was significantly lower at all posttransplant intervals. FEV1 did not fall significantly in patients without acute or chronic GVHD and recovered earlier than in patients without posttransplant pulmonary infection. Recovery of FVC, TLC, and DLCO was also delayed in patients with acute and chronic GVHD and posttransplant pulmonary infection. Multiple regression analysis revealed an association between a higher radiation dose to the lungs, and decreased FVC at 2 years (p = 0.01). Progressive obstructive pulmonary disease was not observed.

CONCLUSION

An initial decline in PFTs with subsequent recovery was observed. Factors associated with delayed recovery and incomplete recovery of PFTs were GVHD, posttransplant pulmonary infection, and higher radiation dose to the lungs. The conditioning regimen used at Medical College of Wisconsin, including relatively high TBI doses with partial transmission pulmonary shielding, appears to be well tolerated by the lungs in long-term survivors. No progressive decline in PFTs or symptomatic decline in pulmonary function was observed during the time interval studied.

Oxidative stress in radiation-induced interstitial pneumonitis in the rat

The involvement of free radical metabolism in the pathogenesis of interstitial pneumonitis was investigated in an animal model. Male Wistar rats were irradiated at the thoracic region by gamma-rays from a 60Co source. Histopathological examination confirmed that 50% of the rats developed pneumonitis between 2 and 8 weeks following a single dose of 14 Gy. Parallel biochemical studies in the lung of these rats showed that mitochondria and microsomes had higher levels of lipid peroxidation. In the cytoplasmic fraction of the lung the activities of superoxide dismutase and catalase were markedly reduced in the pneumonitic rat. In lung mitochondria, however, the levels of these two enzymes were not significantly altered. On the contrary, lipid peroxidation and superoxide dismutase, as well as catalase activities in lung tissue in the non-pneumonitic group of the irradiated rat were comparable with that of control animals. The results indicate that free radical-induced oxidative stress following thoracic irradiation may be one of the causative factors in the development of interstitial pneumonitis.

Single dose versus fractionated total body irradiation before bone marrow transplantation: radiobiological and clinical considerations

PURPOSE

This present review is intended to evaluate the specific influence of fractionation of total body irradiation on the outcome of a subsequent bone marrow transplantation.

METHODS AND MATERIALS

Available experimental and clinical data on the influence of fractionation on leukemia cell killing, immunosuppression, and sparing of normal tissues were analyzed.

RESULTS

Review of available data shows: (a) The role of fractionation on leukemia cell killing may vary with the leukemia type. For acute nonlymphoblastic leukemia, a few experimental and several clinical studies show no or little fractionation effect; a 12-13 Gy fractionated scheme could, therefore, be more efficient than a conventional 10 Gy single dose total body irradiation. For chronic myelogenous leukemia, some sensitivity to fractionation is suggested, so that an increase in total or fractional dose may be necessary in fractionated schemes to equate the efficacy of a 10 Gy single dose. For acute lymphoblastic leukemia, a high fractionation sensitivity was observed for some leukemic cell lines in vitro, without undisputable clinical confirmation for the moment. (b) Numerous experimental studies have demonstrated that the immunosuppressive effect of total body irradiation, a major determinant of engraftment, is highly fractionation sensitive. In humans, high rates of graft failures have been reported when T-cell depletion of the graft was associated to fractionated total body irradiation schedules. (c) A large amount of radiobiological and clinical data have demonstrated that late radiation-induced injuries to normal tissues and organs are highly fractionation sensitive. However, in a context of total body irradiation for bone marrow transplantation, the number of other determinants of normal tissue damage makes it difficult to demonstrate a clear-cut advantage of fractionated over single dose scheme, with a possible exception for children.

CONCLUSIONS

In 1994, available data suggest that very cautious attempts could be made to adapt total body irradiation schedules to the potential normal tissue toxicity, T-cell depletion, and to the type of leukemia.

Verification of lung attenuator positioning before total body irradiation using an electronic portal imaging device

PURPOSE

We report the first clinical experience with an electronic portal imaging device for lung attenuator positioning before delivery of total body irradiation. We demonstrate a technique for lung attenuator placement which reduces the dose to the patient during setup, reduces the patient setup time, and increases the accuracy of lung attenuator positioning.

METHODS AND MATERIALS

Patients are treated with total body irradiation using a dedicated dual source irradiation facility prior to receiving bone marrow transplantation. The dose rate to the patient's midline is limited to 0.10 Gy/min, and partial transmission lung blocks are used to minimize radiation induced pneumonitis while delivering adequate dose to the regions under the blocks. Lung blocks are placed on the patient's back and chest wall, and portal images are used to verify proper block placement before the remaining treatment dose is delivered.

RESULTS

We report the use of a liquid ionization chamber matrix electronic portal imaging device for imaging total body irradiation patient setups.

CONCLUSION

The dose to the patient using the EPID for portal imaging is a factor of 7.5 lower than that needed for film. Image quality is superior to that of film due to digital processing. Since less time and dose are needed for imaging, it is demonstrated that better and more efficient final placement of the lung blocks can be achieved.