Mucosa-associated lymphoid tissue lymphoma of the stomach: long term outcome after local treatment.

BACKGROUND: Although antibiotic therapy is emerging as effective initial treatment for patients with gastric lymphoma of mucosa-associated lymphoid tissue (MALT), there is a subset of patients for whom antibiotics are ineffective or inappropriate. Surgical resection can be curative, but total gastrectomy may be required for the eradication of all disease. To identify the optimal nonantibiotic therapy for early stage gastric MALT lymphoma, the authors retrospectively evaluated the Massachusetts General Hospital experience with gastric MALT lymphoma. METHODS: Disease patterns and treatment outcomes were retrospectively analyzed in data from 21 consecutive patients with gastric MALT lymphoma who were treated between 1978 and 1995 at the Massachusetts General Hospital. RESULTS: Sixteen patients were Stage IE, and 5 were in higher stages. Treatment consisted of resection with or without radiation or chemotherapy (14 patients), radiation alone (4 patients), or radiation plus chemotherapy (2 patients). Thirteen Stage IE patients received local therapy only. The 10-year actuarial relapse free survival rate for Stage IE patients was 93%, with 1 relapse among 15 treated patients. Because the patient who relapsed was treated successfully with chemotherapy, the 10-year cancer free survival was 100%. Overall survival for Stage IE patients was 93% at 5 years and 58% at 10 years, with no deaths from lymphoma. CONCLUSIONS: These data indicate that a high probability of long term remission can be achieved with only local treatment of patients with Stage I gastric MALT lymphoma. Preliminary results suggest that radiation therapy is well tolerated and effective and may well be the optimal nonantibiotic treatment for patients with localized gastric MALT lymphoma.

TGF alpha expression in meningioma--tumor progression and therapeutic response.

Little is known of the molecular genetic mechanisms contributing to meningioma tumor progression. We evaluated a total of 26 clinical cases of meningioma: twenty three patients with meningioma treated at our institution between 1978 and 1990 and three asymptomatic cases found initially at autopsy. In addition, histologically normal meninges obtained at post-mortem examination from 5 cases were evaluated. There were 13 men and 10 women in the patient group with a median age of 48.7 years, treated by surgery and/or irradiation. Median follow-up was 46 months (range 16-152 months). Archival cases and age-matched normal meningeal tissue obtained at autopsy during the same time period were obtained for study. Patients with TGF alpha scores greater than 3.0 were more likely to fail treatment and had lower overall survival times than those with immunostaining scores of 1 or 2. Three autopsy cases where meningioma had been silent clinically had overall staining scores of 0.75, while 10 samples of normal meninges harvested from 5 cases at autopsy had staining scores of 0. Two patients each underwent 3 surgeries for recurrent tumor, serial specimens showed increased TGF alpha expression over time, though all material from these procedures was consistent with the diagnosis of histologically benign meningioma.

Echo-planar MR cerebral blood volume mapping of gliomas. Clinical utility.

Neovascularization is a common phenomenon in gliomas. MR imaging cerebral blood volume (CBV) mapping utilizes ultrasfast echo-planar imaging and simultaneous use of gadolinium-based contrast material. To determine the utility of MR CBV mapping in the clinical evaluation of gliomas, we followed 15 patients with serial studies. This technique provided functional information that was not evident with conventional CT or MR imaging. Low-grade tumors demonstrated homogeneously low CBV, while high-grade tumors often showed areas of both high and low CBV. The maximum tumor CBV/white matter ratio was compared between low- (n = 3) and high-grade gliomas (n = 5) in patients without previous treatment and with histologic verification (n = 8) and was significantly higher in high-grade gliomas (p < 0.01). High CBV foci in nonenhancing tumor areas were present in 2 cases. The distinction between radiation necrosis and active tumor could be made correctly in 3 of 4 cases. The information provided by MR CBV mapping has the potential to be an adjunct in the clinical care of glioma patients.

Prognostic significance of proliferative indices in meningiomas.

The prognostic value of tumor proliferative indices in meningiomas was assessed by mitotic counts and by immunocytochemistry using a monoclonal antibody against the proliferating cell nuclear antigen (PCNA) (clone 19A2), a 36-kd nuclear protein involved in DNA synthesis. Sixty-three intracranial meningiomas were classified as benign (26), with atypical features (24) or as malignant (13). The patients included 24 men and 39 women, mean age 54.2 +/- 1.7 (mean +/- SEM) (range 15-78) at initial presentation. Twenty-four of the 63 primary tumors recurred locally, including 23.1% (6/26) of the benign, 37.5% (9/24) of the atypical, and 69.2% (9/13) of the malignant meningiomas. Among tumors that recurred, 1/9 (11%) of the atypical and 5/9 (55.5%) of the malignant tumors had had macroscopical total excision at the initial surgery. The mean interval to recurrence was 52 +/- 11.8 months. The mean progression-free follow-up period for patients without tumor recurrence was 82 +/- 8.5 months. Analysis of variance revealed that significant differences existed between tumor grades for both PCNA indices (1.16 +/- 0.29% for benign; 14.14 +/- 2.07% for atypical and 21.37 +/- 5.47% for malignant) and mitotic indices (total counts per ten high power fields) (0.08 +/- 0.05 for benign, 4.75 +/- 0.91 for atypical and 19.00 +/- 4.07 for malignant). Multivariate regression analysis indicated that mitotic index > 6 was the single most important factor (p < 0.05) for shorter disease-free interval. Age, sex and total surgical excision were not significant factors. PCNA index was a significant factor in the univariate model, but not in the multivariate model.(ABSTRACT TRUNCATED AT 250 WORDS)

Hodgkin disease, nodular sclerosis type. Implications of histologic subclassification.

BACKGROUND: The prognostic significance of the cellular composition of the nodules of Hodgkin disease, nodular sclerosis type (HDNS), is controversial. METHODS: Tumors from 79 patients with HDNS, who had a median follow-up time of 9.3 years, were studied. RESULTS: Based on British National Lymphoma Investigation criteria, 58 cases were classified as NSI (low-grade) and 21 as NSII (high-grade). The study included 24 male and 55 female patients, aged 10-57 years (mean, 27 years), who presented with Stage I (13 patients [12A, 1B]), Stage II (45 patients [40A, 5B]), or Stage III (21 patients [16A, 5B]) disease. Fifty-three patients had no relapse, 4 died of other causes, and 49 are in complete clinical remission. Twenty-six patients had progression of disease during therapy or relapsed and 17 were successfully salvaged. Overall length of survival was significantly shorter with NSII (P = 0.0001), extensive necrosis (P = 0.0034), high stage (P = 0.0058), and B symptoms (P = 0.030). Multivariate analysis showed that grade had the strongest effect on overall survival (P = 0.0042; hazard ratio = 10.19). The 5-year survival was 100% for NSI patients and 75% for NSII patients. Only B symptoms were significantly associated with risk of relapse after initial therapy (P = 0.030). For patients who relapsed, only histologic grade predicted subsequent disease-free survival (P = 0.0023; hazard ratio = 26.5). Five-year disease-free survival after first relapse was 94% for NSI patients and 11% for NSII patients. CONCLUSIONS: Patients with NSI disease who relapse have a more successful salvage and longer period of survival than do those with NSII disease. Histologic subclassification of HDNS appears clinically relevant, and consideration of histologic subtype may be important when planning therapy.

The role of radiotherapy in the treatment of subtotally resected benign meningiomas.

Thirty-six patients with benign meningioma were treated for primary or recurrent disease by subtotal resection and external beam irradiation from 1968-1986 at Massachusetts General Hospital. Comparison is made with 79 patients treated by subtotal surgery alone from 1962-1980. Progression-free survival for 17 patients irradiated after initial incomplete surgery was 88% at 8 years compared with 48% for similar patients treated by surgery alone (p = 0.057). 16 patients incompletely resected at time of first recurrence were irradiated and 78% were progression-free at 8 years while 11% of a similar group treated by surgery alone were progression free (p = 0.001). Long term overall survival was high and similar in both control and study groups. Two patients were irradiated at second recurrence and 1 patient at third recurrence. Twenty-five patients were treated with photons alone and have a median follow-up of 57 months, 6 patients have recurred at doses 45-60 Gy. Eleven patients were treated with combined 10 MV photons and 160 MV protons utilizing 3-D treatment planning. These patients have been followed for a median of 53 months and none have failed to date. Eight of 11 received 54-60.4 Gy and 3/11 greater than 64.48 Gy. Sex, age, pathology grade and score, surgery and timing of radiation therapy were not associated with significant differences in failure patterns within the irradiated study group (p less than 0.1). Complications have been seen in 6 irradiated patients.

Pineal tumors.

From 1972-1985, 30 patients with pineal area tumor have been treated with combinations of surgery and irradiation, no patient receiving chemotherapy as a primary recommendation. Patients ranged between 3 and 69 years of age, 18 were male and 12 female. In 18 patients a tissue diagnosis was made initially, 14 patients required shunts before definitive management and in 8 of the 14 tissue diagnosis was made at the same time. Eight patients had no surgical intervention at any time. Patients who have received irradiation have had whole brain irradiation, local field irradiation, or craniospinal irradiation. Two elderly patients died rapidly of their malignant processes before definitive treatment could be given. Only one patient with a non neoplastic lesion was seen. This was a bleed from an AVM with no underlying tumor. One patient with a pineocytoma was not irradiated. Overall, two-thirds of our patients are alive 5 to 15 years after treatment. There has been no surgical mortality and minimal morbidity from biopsy. Late effects of treatment include one patient with mild hearing loss and three patients with endocrinopathies amenable to medical treatment. We believe that tissue diagnosis allows optimal field design and dose recommendations to be made by the radiotherapist in addition to defining prognosis. In our experience, endodermal sinus tumor and pineoblastoma are highly malignant, and in view of their poor prognosis with conventional management consideration of more radical treatment with a possible role for chemotherapy is suggested.

Radiation therapy in the management of early stage Hodgkin's disease presenting in later life.

This study examined the contention that although elderly patients with Hodgkin's disease have a worse prognosis overall than younger patients, a subgroup of older patients fit enough to be managed like younger patients can fare just as well. A retrospective analysis was made on 29 patients older than 60 years of age with Stage I and II Hodgkin's disease treated by radiation therapy alone. Fourteen of these patients were managed optimally, i.e., were adequately staged (defined by one or more of the following: laparotomy, computed tomography [CT] scan, and/or lymphangiogram), followed by radical radiation therapy (mantle or inverted-Y). The remaining 15 patients, because of their general medical condition, were managed suboptimally with limited staging and/or involved-field irradiation. None of the 14 patients managed optimally relapsed over a median of 4.75 years of follow-up compared with 10 of 15 patients in the suboptimal group. For the optimally managed versus suboptimally managed groups, the actuarial 5-year disease-free survival rates were 61% and 6%, respectively; the actuarial overall survival rates (death from all causes) were 61% and 19%, respectively; and the disease-specific survival rates were 100% and 39%, respectively. Only three of the patients irradiated radically had acute complications severe enough to warrant a break in treatment. In the opinion of the authors, those elderly patients able to tolerate adequate staging and radical radiation therapy can anticipate a high likelihood of cure.

Chemotherapeutic treatment of extensive optic pathway tumors in infants.

Two infants, ages 14 and 4 months, with extensive optic pathway tumors were treated with intensive chemotherapy called MADDOC: nitrogen mustard, doxorubicin, cis-platinum, dacarbazine, vincristine, and cyclophosphamide. The first child had hydrocephalus with an enhancing mass at the hypothalamus which followed the optic radiation to include the lateral geniculate body and medial temporal lobe. A v-p shunt was placed, and biopsy revealed a Grade II astrocytoma. One month later, the child developed malignant ascites. Intensive induction chemotherapy was then begun with cis-platinum 100 mg/m2 and cyclophosphamide 3 g/m2 for two initial cycles. The ascites resolved within one week, and chemotherapy was continued for 10 courses of the 6-drug MADDOC regimen. CT scans showed a gradual shrinkage of the tumor mass by approximately 70%. The enhancing areas continued to decrease in size through 20 months after completing MADDOC. The child has not received radiation and is well 4 years 7 months post diagnosis. The second infant had massive enlargement of the right optic nerve with an enhancing chiasmatic mass extending into the suprasellar space, hypothalamus, and brain stem. This infant was not biopsied; she also received induction MADDOC chemotherapy for 12 cycles. CT scans showed a definite decrease in the chiasmatic mass by the fifth cycle, with continued reduction by approximately 40% after 10 months. Twenty-three months from diagnosis there was asymptomatic evidence of tumor growth. The child is being treated with carboplatinum and remains ophthalmologically and radiographically stable 43 months from diagnosis.

Central nervous system neurocytoma and neuroblastoma in adults--report of eight cases.

The clinical features, pathologic findings and treatment courses of eight adults with central nervous system small-cell neuronal tumors were reviewed. Five patients had central neurocytomas, two patients central nervous system neuroblastomas, and one patient a neurocytoma-like spinal cord tumor. The neurocytomas were intraventricular, moderately cellular tumors with bland nuclei and perinuclear halos. Patients with neurocytoma were treated with surgery, radiation therapy, and/or chemotherapy, and have followed favorable clinical courses. The neuroblastomas were intraparenchymal, hypercellular tumors with necrosis and frequent mitoses. Patients with neuroblastomas were treated with surgery, radiation therapy and chemotherapy, with some clinical response, but overall poor survival. One of the two patients developed extracranial metastasis. The spinal cord tumor had histologic features of neurocytoma, and responded well to biopsy and radiation therapy. The cases are compared with the varieties of small-celled neuronal tumors described in the literature, and pathologic, histogenetic and treatment implications are discussed.

Conjunctival lymphoma: results and treatment with a single anterior electron field. A lens sparing approach.

Lymphoma of the conjunctiva is rare. It presents in older patients as a mass lesion and usually remains localized. Surgery is limited to biopsy, and radiation therapy is the definitive treatment of choice. The entire conjunctiva is treated. Relatively high doses (approximately 30 Gy) are required for local control, which may lead to cataract formation. Twelve patients with conjunctival lymphoma were treated at the Massachusetts General Hospital between 1979 and 1988. Ten of 12 patients presented with a unilateral lesion; 2 of 12 with bilateral lesions. Two of 12 patients were found to have systemic disease at the time of presentation. One patient developed conjunctival lymphoma 5 years after the diagnosis of generalized disease. Using electron beam, all patients were treated with a single anterior circular field to total doses ranging from 24 Gy to 30 Gy delivered in 8 to 16 fractions over 9 to 20 days. In all cases, the lens was shielded by a specially designed plastic contact lens bearing a 12 mm diameter lead shield. The lens dose was determined at varying depths beneath the shield for 6 MeV and 9 MeV electron beams and ranged from a minimum of 5% to an absolute maximum of 18% of the total dose delivered to the tumor. Local control was maintained in all patients with follow-up to 9 1/2 years. One patient relapsed distantly 3 years after treatment. One of 12 patients died of systemic disease 4 years after treatment of the ocular lesion. Two patients developed cataracts 4 and 5 years after treatment; one had bilateral cataract, although only one eye had been treated. Both patients were over 75 years old. In both cases, the cataracts were felt to be senile cataracts which are ophthalmologically and radiographically distinguishable from radiation induced lesions.

Immunohistologic features predict clinical behavior of orbital and conjunctival lymphoid infiltrates.

The natural history of lymphoid infiltrates of the orbit and conjunctiva is poorly understood. To determine if immunohistologic features could predict clinical outcome, these features were evaluated in 61 patients with orbital and conjunctival lymphoid infiltrates, including 44 patients with lesions localized to one or both orbits or conjunctivae. Using histologic criteria, 20 infiltrates were classified as malignant lymphoma (cytologically atypical), 14 cases were classified as benign (follicular hyperplasia or inflammatory pseudotumor), and 27 infiltrates (44%) were dense infiltrates of small lymphocytes without cytologic atypia, which could not be confidently classified as benign or malignant (histologically indeterminate). Based on expression of monotypic immunoglobulin, 20 of these cases were reclassified as small lymphocytic lymphoma. For all cases, monotypic immunoglobulin expression correlated with reduced survival (P less than .05) and increased likelihood of dissemination (P less than .001). Monotypic immunoglobulin expression also correlated with increased risk of dissemination for all histologically indeterminate (small lymphocytic) infiltrates (P less than .05). Separate analysis of the localized infiltrates showed that monotypic immunoglobulin expression significantly correlated with an increased likelihood of dissemination for all 44 cases (P less than .005) and for the 22 histologically indeterminate lesions (P = .06). For the localized small lymphocytic infiltrates, monotypic immunoglobulin expression conferred a 50% risk of dissemination. In contrast, no patients with polytypic small lymphocytic infiltrates have disseminated, although one lesion locally recurred 30 months later as lymphoma. Thus, monotypic immunoglobulin expression significantly correlates with reduced patient survival and increased risk of dissemination by orbital and conjunctival lymphoid infiltrates. Monotypic small lymphocytic infiltrates without cytologic atypia behave as do low grade B-cell malignant lymphomas with a significant risk of dissemination and an indolent clinical course. The relationship of polytypic small lymphocytic infiltrates to lymphoma remains to be determined.

High-dose methotrexate for non-AIDS primary central nervous system lymphoma. Report of 13 cases.

Thirteen patients with primary lymphoma of the central nervous system (CNS) were treated with high-dose intravenous methotrexate (MTX), 3.5 gm/sq m, followed by calcium leucovorin rescue, at 3-week intervals, for three cycles. Eleven patients subsequently received radiation therapy to the whole brain, 30 to 44 Gy. Before radiation therapy, eight patients responded completely and four partially; there was one non-responder. The median Karnofsky score before high-dose MTX therapy was 60 and increased to 90 after treatment. Five of the eight complete responders reached a Karnofsky rating of 100. The three longest responders (one of whom received MTX only) were without recurrence of their disease at 29+, 32, and 32+ months posttherapy. The median response period is 9+ months. The median survival time from the date of the first MTX treatment is 9+ months, and the three longest survival times are 29+, 32+, and 54+ months. All patients received corticosteroids in either unchanging or diminishing dosages during therapy. It is concluded that primary CNS lymphoma is sensitive to high-dose MTX, which provides a safe and easily administered adjuvant to radiation therapy for this neoplasm.

Mediastinal large cell lymphoma. An uncommon subset of adult lymphoma curable with combined modality therapy.

Thirty adults with large cell lymphoma predominantly localized to the mediastinum diagnosed at the Massachusetts General Hospital between 1976 and 1985 were identified. The median age of the 20 females and 10 males was 34 years. All but one presented with symptoms due to an enlarging mediastinal mass, which was localized in 22 patients (73%) and exceeded 10 cm in maximal diameter in 65%. Superior vena cava syndrome and large pleural and pericardial effusions were common. Employing CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone) and consolidation radiation therapy in most cases, 80% achieved a complete remission and 59% survive failure-free at 5 years by actuarial calculation. The size of the mediastinal mass adversely affected failure-free survival (89% vs. 40%, P less than 0.05). No other pretreatment risk factor predicted outcome, but more intense chemotherapy was associated with improved survival (P = 0.035). Large cell mediastinal lymphoma is a locally invasive, often bulky malignancy with a predilection for young women; disease of low or moderate bulk is curable with full dose CHOP chemotherapy and consolidation radiation, but bulky disease requires more aggressive treatment.

Three-dimensional volumetric assessment of response to treatment: stage I and II diffuse large cell lymphoma of the mediastinum.

From 1981 to 1986, 12 patients with Stage I and II diffuse large cell lymphoma of the mediastinum were treated with 4 or more cycles of multiagent chemotherapy and for nine patients this was followed by mediastinal irradiation. The response to treatment was assessed by three-dimensional volumetric analysis utilizing thoracic CT scans. The initial mean tumor volume of the five patients relapsing was 540 ml in contrast to an initial mean tumor volume of 360 ml for the seven patients remaining in remission. Of the eight patients in whom mediastinal lymphoma volumes could be assessed 1-2 months after chemotherapy prior to mediastinal irradiation, the three patients who have relapsed had volumes of 292, 92, and 50 ml (mean volume 145 ml) in contrast to five patients who have remained in remission with residual volume abnormalities of 4-87 ml (mean volume 32 ml). Four patients in prolonged remission with CT scans taken one year after treatment have been noted to have mediastinal tumor volumes of 0-28 ml with a mean value of 10 ml. This volumetric technique to assess the extent of mediastinal large cell lymphoma from thoracic CT scans appears to be a useful method to quantitate the amount of disease at presentation as well as objectively monitor response to treatment.

Pre-irradiation internal carotid artery BCNU in treatment of glioblastoma multiforme.

High-dose 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) infusion into the internal carotid artery following cranial irradiation in the treatment of glioblastoma multiforme is accompanied by evidence of leukoencephalopathy in a significant number of patients. In an attempt to avoid this problem, a phase I trial was performed using intracarotid BCNU infusion before irradiation. Twenty-eight patients with grade III/III astrocytoma (World Health Organization Classification, equivalent to Kernohan grade IV) received a 400-mg infusion of BCNU into the infraophthalmic carotid artery. The treatment was repeated every 4 weeks for a total of four cycles prior to cranial irradiation (5500 to 6000 cGy). The major toxic sequelae included nausea and vomiting (24%), decreased visual acuity (14%), transient cerebral ischemia (3.5%), and thrombocytopenia (3.5%). Fatal leukoencephalopathy occurred in two patients. The median survival time was 37 weeks for all evaluable patients and 56+ weeks for those completing the protocol. The tumor response to drug infusion as judged by computerized tomography (CT) was complete in 22% of patients and partial in 22%; 56% showed no CT tumor response. Pre-irradiation intracarotid artery BCNU benefits a very small group of patients with grade III/III astrocytoma. The associated severe leukoencephalopathy makes this mode of therapy unacceptable for a phase III trial.

Stage IA to IIB mediastinal Hodgkin's disease: three-dimensional volumetric assessment of response to treatment.

From 1979 to 1986, the response to treatment of 53 patients with stage IA to IIB mediastinal Hodgkin's disease was evaluated by three-dimensional volumetric analysis using thoracic computed tomographic (CT) scans. The mean initial volume of mediastinal disease in 34 patients treated with mantle and para-aortic irradiation was 166 mL, whereas for 19 patients treated with two to six cycles of multiagent chemotherapy and mantle and para-aortic irradiation the mean initial volume was 446 mL. Preliminary data suggested that patients with mediastinal volumes of less than 200 mL had a lower mediastinal relapse rate (13%) than patients with volumes greater than 200 mL (32%). For 12 patients receiving six cycles of nitrogen mustard, vincristine, procarbazine, and prednisone (MOPP), those with a greater than 85% reduction in volume 1 to 2 months after chemotherapy had a lower incidence of mediastinal relapse (zero of six, 0%) compared with patients having 85% or less reduction in volume (four of six, 67%). The primary value of this technique is that it provides a sensitive assessment of response to treatment and may aid in monitoring the effectiveness of a given treatment.

Computed tomography in the evaluation of lymphoma of the uterine cervix.

Primary involvement of the uterine cervix is a rare presentation of extranodal lymphoma. The clinical and computed tomography findings are described in four patients ranging from 23 to 74 years of age. All presented with vaginal bleeding. Computed tomography findings were similar to those of other primary pelvic neoplasms, with diffuse uterine enlargement and lobular contour alteration often mimicking fibroids. Lymphadenopathy was not observed in comparison to secondary lymphoma of the female genitalia. All patients had excisional biopsies. One patient had an initial TAH and BSO. Histology was varied with one case of large cell lymphoma, one of diffuse histiocytic, one of unclassifiable poorly differentiated lymphoma, and one of nodular poorly differentiated lymphocytic lymphoma that was finally classified as granulocytic sarcoma. Disease extent could be assessed by computed tomography and aided treatment planning. In conclusion, computed tomography was found to be useful in the evaluation of uterine lymphoma. Although the findings are not specific, the local tumor extent can be evaluated at the same time as other sites of potential involvement.

The effect of the respiratory cycle on mediastinal and lung dimensions in Hodgkin's disease. Implications for radiotherapy gated to respiration.

Changes in mediastinal and lung dimensions during respiration were studied to assess the potential of radiotherapy gated to respiration to minimize normal tissue irradiation. Twelve patients with mediastinal Hodgkin's disease were assessed using chest radiographs and thoracic computed tomography (CT) scans both during quiet breathing and at maximum inspiration in the standing, supine, and prone positions. A simple measure of the bulk of mediastinal disease, the ratio of the width of mediastinal mass to thoracic diameter, was determined from posteroanterior (PA) chest radiographs. The volumes of mediastinum, irradiated and protected lung if anteroposterior (AP) and PA mantle fields were used were determined from sequential thoracic CT scans and three-dimensional treatment planning and compared at quiet breathing and deep inspiration. The mediastinal width to thoracic diameter ratio decreased from quiet breathing to deep inspiration an average of 3%, 9%, and 11% for the standing, supine, and prone positions, respectively. Lung volumes as measured from the thoracic CT scans showed that on average, 8% more lung was protected at deep inspiration than at quiet breathing, independent of treatment position. The maximum increase in the percentage of protected lung from quiet breathing to deep inspiration was seen in patients with extensive mediastinal adenopathy suggesting that radiotherapy gated to respiration may be most advantageous in the subset of patients.