Preliminary results of a prospective trial using three dimensional radiotherapy for lung cancer

Pulmonary complications following different radiotherapy techniques for breast cancer, and the association to irradiated lung volume and dose

PURPOSE

This study investigates the incidence of short-term pulmonary complications following radiotherapy (RT) for breast cancer (BC) with different treatment techniques/incidentally irradiated lung volumes and the importance of confounding factors on RT-induced pulmonary complications.

PATIENTS AND METHODS

Prospectively, 475 patients with BC were followed for pulmonary complications 1, 4 and 7 months post-RT. Mean lung dose volume histograms (MDVH) were constructed and compared for the different RT-techniques. Among a subset of the mastectomized patients treated with loco-regional (LR-) RT, who had undergone complete three-dimensional (3-D) dose planning (n = 43), MDVH for asymptomatic patients was compared with MDVH for patients experiencing both radiological and clinical pulmonary side-effects.

RESULTS

Moderate pulmonary complications, that is requiring treatment with corticosteroids, were rare following local RT (< 1%), but were diagnosed among 11% of the patients treated with LR-RT. A correlation between increasing irradiated lung volumes at the >20 Gy-level (V20), based on MDVH for the RT-techniques, and pulmonary complications was found (P < 0.001). Furthermore, increasing age and reduced pre-RT functional level were independently associated with a higher rate of pulmonary complications (P = 0.005 and P = 0.018). Among the subgroup of mastectomized patients treated with LR-RT, who had undergone complete 3-D dose planning, a difference in mean V20 was found between patients experiencing both clinical and radiological pulmonary side-effects compared to patients experiencing neither of the two side-effects (P = 0.007).

CONCLUSION

Moderate pulmonary complications following local RT for BC are rare. The incidence of short-term moderate pulmonary complications in LR-RT is, however, clinically significant and to define quality assurance guidelines for these RT-techniques, 3-D RT planning can be used.

An evaluation of two techniques for beam intensity modulation in patients irradiated for stage III non-small cell lung cancer

In locally advanced lung cancer, the use of high dose radiotherapy (RT) and/or concurrent chemo-RT is associated with significant pulmonary and esophageal toxicity. Despite a 3D conformal RT technique and the omission of elective mediastinal fields, three (of ten) patients with inoperable stage 3 NSCLC who were treated with induction chemotherapy (carboplatin-paclitaxel) followed by RT to 70 Gy, developed symptomatic radiation pneumonitis. In this planning study, the actual treatment plans of all ten patients were compared to plans derived using two beam intensity-modulated (BIM) techniques, for which similar geometrical beam setup parameters were used. In the first technique (BF-BIM), cranial and caudal boost fields were applied in order to allow field length reduction. The second technique (C-BIM) utilised 3-D missing-tissue compensators for all radiation beams. Both BIM techniques resulted in a significant sparing of critical normal tissues and the C-BIM technique was superior in all cases. When compared to the actual RT technique used for treatment, a reduction of 8.1+/-4.7% (1 S.D.) was observed in the mean lung dose for the BF-BIM plan, vs. 20.3+/-5.8% (1 S.D.) for the C-BIM plan. Similar reductions were observed in the percentage of the total lung volume exceeding 20 Gy (V(20)) for these techniques. BIM techniques appear to be a promising tool for enabling radiation dose-escalation and/or intensive concurrent chemo-RT in inoperable lung cancer.

Hyperfractionated radiation therapy and concurrent low-dose, daily carboplatin/etoposide with or without weekend carboplatin/etoposide chemotherapy in stage III non-small-cell lung cancer: a randomized trial

PURPOSE

To investigate whether the addition of weekend chemotherapy consisting of carboplatin/etoposide to hyperfractionated radiation therapy (Hfx RT) and concurrent daily carboplatin/etoposide offers an advantage over the same Hfx RT/daily carboplatin/etoposide.

METHODS AND MATERIALS

A total of 195 patients (Group I, 98; Group II, 97) were treated with either Hfx RT to a total tumor dose of 69.6 Gy via 1.2 Gy b.i.d. fractionation and daily 50 mg each of carboplatin and etoposide during the RT course (Group I) or the same Hfx RT with daily carboplatin/etoposide consisting of 30 mg each of carboplatin and etoposide and with weekend (Saturdays and Sundays) 100 mg each of carboplatin and etoposide during the RT course (Group II).

RESULTS

No difference was found regarding median survival time and 5-year survival rates (20 vs. 22 months and 20% vs. 23%; p = 0.57). Median time to local progression was 20 and 19 months, respectively, while 5-year local progression-free survival rates were 28% and 27%, respectively (p = 0.66). Also, there was no difference regarding either median time to distant metastasis and 5-year distant metastasis-free survival (21 vs. 25 months and 29% vs. 34%, p = 0.29). There was no difference in the incidence of various nonhematologic toxicities between the two treatment groups, but patients treated with the weekend CHT had significantly more high-grade (> or = 3) hematologic toxicity (p = 0.0046). Late high-grade toxicity was not different between the two treatment groups.

CONCLUSION

The addition of weekend carboplatin/etoposide did not improve results over those obtained with Hfx RT and concurrent low-dose, daily carboplatin/etoposide, but it led to a higher incidence of acute high-grade hematologic toxicity.

The role of positron emission tomography with 18F-fluoro-2-deoxy-D-glucose in respiratory oncology

In the past 5 yrs, positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (FDG) has become an important imaging modality in lung cancer patients. At this time, the indication of FDG-PET as a complimentary tool to computed tomography in the diagnosis and staging of nonsmall cell lung cancer has gradually gained more widespread acceptance and also reimbursement in many European countries. This review focuses on the data of FDG-PET in the diagnosis of lung nodules and masses, and in locoregional and extrathoracic staging of nonsmall cell lung cancer. Emphasis is put on the potential clinical implementation of the currently available FDG-PET data. The use of FDG-PET in these indications now needs further validation in large-scale multicentre randomized studies, focusing mainly on treatment outcome parameters, survival and cost-efficacy. Interesting findings with 18F-fluoro-2-deoxy-D-glucose-positron emission tomography have also been reported for the evaluation of response to radio- or chemotherapy, in radiotherapy planning, recurrence detection and assessment of prognosis. Finally, a whole new field of application of positron emission tomography in molecular biology, using new radiopharmaceuticals, is under extensive investigation.

The curative treatment by radiation therapy alone of Stage I non-small cell lung cancer in a geriatric population

This review was initiated to assess the outcome of treatment with radical radiation therapy with curative intent for elderly patients diagnosed to have Stage I non-small cell lung cancer (NSCLC). The study involved a retrospective review of 347 patients with T1 and T2N0M0 tumours treated at the Queensland Radium Institute (QRI) during the period 1985-1992. The main reasons for not proceeding to surgery included poor performance status, old age or refusal to submit to surgery. The median age for the group was 70 years with the range being 34-90 years. Patients in this group were all treated by a standard technique involving external beam radiation therapy to a dose of 50 Gray Minimum Tumour Dose in 20 fractions over 4 weeks. When the study group was divided into those patients aged < 70 years and those patients age > or = 70 years, the overall survival at 5 years was 22 and 34%, respectively (median survival 22 months for age < 70 years, and 26 months for age > or = 70 years). The same division in terms of recurrence free survival yielded 5-year survival rates of 18% for the age < 70 years group and 30% for the age > or = 70 years group with the median survival being 17 months in both sub-groups. Both the difference in overall survival and recurrence free survival between the two age groups approached, but did not reach, statistical significance at the P < 0.05 level of significance. Further sub-division into 5-year age groups failed to confirm the hypothesis that older age groups had a poorer outcome. The 75-79-year group showed better survival than other age groups with the 5-year overall survival for this group being 53%, while the 5-year recurrence free survival was 45%. We conclude from this large series of Stage I NSCLC that radical radiation therapy with curative intent may be a viable alternative to surgery in those elderly patients who either refuse surgery or are judged to be unfit for operation. In view of the fact that comparable results can be achieved in elderly lung cancer patients at the price of minimal toxicity, a nihilist approach to treatment in the elderly can no longer be justified.

Bronchoscopically-guided conformal radiation therapy for radiographically occult lung carcinoma

Radiographically occult lung carcinoma has a very good prognosis after complete surgical resection. In medically inoperable patients three-dimensional conformal radiation therapy cannot be performed, as computed tomography scan images fail to localize the disease. Presented here is an original technique of marking radiographically occult tumors by fiberoptic bronchoscopy, applied on four patients. No short-term complications were recorded. All the patients are alive, with no evidence of disease, after a mean follow-up of 15 months.

73.6 Gy and beyond: hyperfractionated, accelerated radiotherapy for non-small-cell lung cancer

PURPOSE

To assess results with twice-daily high-dose radiotherapy (RT) for non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Between 1991 and 1998, 94 patients with unresectable NSCLC were prescribed > or = 73.6 Gy via accelerated fractionation. Fifty were on a phase II protocol (P group); 44 were similarly treated off-protocol (NP group). The clinical target volume received 45 Gy at 1.25 Gy bid (6-hour interval). The gross target volume received 1.6 Gy bid to 73.6 to 80 Gy over 4.5 to 5 weeks using a concurrent boost technique. Overall survival (OS) and local progression-free survival (LPFS) were calculated by the Kaplan-Meier method. Median follow-up durations for surviving P and NP patients were 67 and 16 months, respectively.

RESULTS

Total doses received were > or = 72 Gy in 97% of patients. The median OS by stage was 34, 13, and 12 months for stages I/II, IIIa, and IIIb, respectively. LPFS was significantly longer for patients with T1 lesions (median, 43 months) versus T2-4 (median, 7 to 10 months; P =.01). Results were similar in the P and NP groups. Acute grade > or = 3 toxicity included esophagus (14 patients; 15%), lung (three patients; 3% [one grade 5]), and skin (four patients; 4%). Grade > or = 3 late toxicity in 86 assessable patients included esophagus (three patients; 3%), lung (15 patients; 17% [three grade 5]), skin (five patients; 6%), heart (two patients; 2%), and nerve (one patient; 1%).

CONCLUSION

This regimen yielded favorable survival results, particularly for T1 lesions. Acute grade > or = 3 toxicity seems greater than for conventional RT, though most patients recovered. Late grade > or = 3 pulmonary toxicity occurred in 17%. Because of continued locoregional recurrences, we are currently using doses > or = 86 Gy.

Dose escalation in non-small-cell lung cancer using three-dimensional conformal radiation therapy: update of a phase I trial

PURPOSE

High-dose radiation may improve outcomes in non-small-cell lung cancer (NSCLC). By using three-dimensional conformal radiation therapy and limiting the target volume, we hypothesized that the dose could be safely escalated.

MATERIALS AND METHODS

A standard phase I design was used. Five bins were created based on the volume of normal lung irradiated, and dose levels within bins were chosen based on the estimated risk of radiation pneumonitis. Starting doses ranged from 63 to 84 Gy given in 2.1-Gy fractions. Target volumes included the primary tumor and any nodes >or= 1 cm on computed tomography. Clinically uninvolved nodal regions were not included purposely. More recently, selected patients received neoadjuvant cisplatin and vinorelbine.

RESULTS

At the time of this writing, 104 patients had been enrolled. Twenty-four had stage I, four had stage II, 43 had stage IIIA, 26 had stage IIIB, and seven had locally recurrent disease. Twenty-five received chemotherapy, and 63 were assessable for escalation. All bins were escalated at least twice. Although grade 2 radiation pneumonitis occurred in five patients, grade 3 radiation pneumonitis occurred in only two. The maximum-tolerated dose was only established for the largest bin, at 65.1 Gy. Dose levels for the four remaining bins were 102.9, 102.9, 84 and 75.6 Gy. The majority of patients failed distantly, though a significant proportion also failed in the target volume. There were no isolated failures in clinically uninvolved nodal regions.

CONCLUSION

Dose escalation in NSCLC has been accomplished safely in most patients using three-dimensional conformal radiation therapy, limiting target volumes, and segregating patients by the volume of normal lung irradiated.

Predictive factors in radiotherapy for non-small cell lung cancer: present status

PURPOSE

To evaluate the predictive factors for radiation response in non-small cell lung cancer (NSCLC) and the role of such factors in guiding high dose radiation therapy.

METHODS

The first International Workshop on Prognostic and Predictive Factors in Lung Cancer was organized by the Hellenic Cooperative Oncology Group and held in Athens, Greece under the auspices of the International Association for the Study of Lung Cancer. Presentations at this meeting provided the outline of this report, which has also been supplemented with available data from the current literature.

RESULTS

The predictive factors for both the natural history and the therapy outcome of NSCLC are grouped as follows: (1) tumor related factors (anatomic factors); the extent of tumor (tumor stage) is one of most important prognostic factors affecting the therapy outcome. Tumor size (T stage), anatomical structures involved (T4 vs. T3 lesion), and the presence of regional lymph node metastasis have a significant impact on both prognosis and response to appropriate therapy; (2) host-related factors (clinical factors) that are important in therapy response include performance status, weight loss of more than 10% of body weight in the previous 6 months, and associated co-morbidities, i.e. pulmonary and cardiac diseases; (3) technical factors of radiation therapy which play a decisive role in successful outcome. The target volume should be defined accurately using modern imaging studies. The radiation dose fractionation schedule, in terms of the dose intensity and total dose, should be high enough to provide local tumor control in the majority of patients. Three-dimensional (3-D) conformal planning is an essential tool in dose escalation studies to determine the maximum tolerated dose of radiation; (4) biological/radiobiological/metabolic factors. Biologic markers resulting from genetic lesions in lung cancer are grouped as follows: (a) oncogene amplification and overexpression (aberrant gene expression) and mutated tumor suppressor genes -- ras gene, myc gene, HER-2/neu and survivin gene, p53 and mutated beta-tubulin gene; (b) tumor biologic/radiobiologic factors -- tumor cell proliferation kinetics, hypoxia, intrinsic cellular radiosensitivity, gamma factor, and DNA content; (c) enzymes and hormones: neuron-specific enolase, serum lactate dehydrogenase, and enhanced glucose metabolic rate supported by increased glucose transporter protein. The surviving fraction of tumor cells at 2.0 Gy of radiation (SF2) as a measure of intrinsic tumor cell radiosensitivity, potential doubling time (T(Pot)) as a measure of the rate of tumor cell proliferation and gamma factor representing the slope of the survival curve at 50% survival rate are being investigated as potential predictors for therapy response. Enhanced glucose utilization, a hallmark of malignant transformation, is being studied as a potential monitor for therapy response by using PET-FDG.

CONCLUSION

Current data indicate that there is a dose-response relationship between radiation dose and local tumor control, and also between local tumor control and survival in stage III NSCLC. Therapeutic factors, i.e. total radiation dose, fractionation schedule and dose intensity, and use of 3-D conformal radiation to secure the optimum therapeutic ratio are important for improved local tumor control and survival. Future research should be directed towards radiation dose escalation using 3-D conformal therapy to determine the maximum tolerated dose (MTD) of radiation in chemo-radiotherapy, and the use of this MTD for improved local tumor control and survival. Radiobiological, molecular, and metabolic markers may have potential for monitoring tumor response and optimizing radiation therapy.

Evaluation of microscopic tumor extension in non-small-cell lung cancer for three-dimensional conformal radiotherapy planning

PURPOSE

One of the most difficult steps of the three-dimensional conformal radiotherapy (3DCRT) is to define the clinical target volume (CTV) according to the degree of local microscopic extension (ME). In this study, we tried to quantify this ME in non-small-cell lung cancer (NSCLC).

MATERIAL AND METHODS

Seventy NSCLC surgical resection specimens for which the border between tumor and adjacent lung parenchyma were examined on routine sections. This border was identified with the naked eye, outlined with a marker pen, and the value of the local ME outside of this border was measured with an eyepiece micrometer. The pattern of histologic spread was also determined.

RESULTS

A total of 354 slides were examined, corresponding to 176 slides for adenocarcinoma (ADC) and 178 slides for squamous cell carcinoma (SCC). The mean value of ME was 2.69 mm for ADC and 1.48 mm for SCC (p = 0.01). The usual 5-mm margin covers 80% of the ME for ADC and 91% for SCC. To take into account 95% of the ME, a margin of 8 mm and 6 mm must be chosen for ADC and SCC, respectively. Aerogenous dissemination was the most frequent pattern observed for all groups, followed by lymphatic invasion for ADC and interstitial extension for SCC.

CONCLUSION

The ME was different between ADC and SCC. The usual CTV margin of 5 mm appears inadequate to cover the ME for either group, and it must be increased to 8 mm and 6 mm for ADC and SCC, respectively, to cover 95% of the ME. This approach is obviously integrated into the overall 3DCRT procedure and with other margins.

The physical parameters and molecular events associated with radiation-induced lung toxicity

Radiation therapy (RT) is frequently used to treat patients with tumors in and around the thorax. Clinical radiation pneumonitis is a common side effect, occurring in 5% to 20% of patients. Efforts to identify patients at risk for pneumonitis have focused on physical factors, such as dose and volume. Recently, the underlying molecular biological mechanisms behind RT-induced lung injury have come under study. Improved knowledge of the molecular events associated with RT-induced lung injury may translate into a better ability to individualized therapy. This review discusses our current understanding of the physical and molecular factors contributing to RT-induced pulmonary injury.

Counterpoint: better radiation treatment of non-small cell lung cancer using new techniques without elective nodal irradiation

The treatment of non-small cell lung cancer has continued to evolve with the advent of improved staging technologies, chemotherapeutic agents, and methods of radiation delivery. Treatment of clinically uninvolved, regional lymph nodes historically has been delivered in the attempt to cover unseen disease, reduce regional failure, and improve survival. None of these suppositions has been tested nor are they supported by data. With enhanced staging using modalities like positron emission tomography and esophageal ultrasonography, treatment portals can be designed to encompass known disease with greater accuracy and confidence. Data for early-stage non-small cell lung cancer is now increasing and strongly suggest that eliminating elective nodal irradiation does not result in a high incidence of nodal relapse and does not compromise survival. Three-dimensional conformal radiotherapy incorporates better targeting and beam directions to effect smaller treatment volumes that include only clinically evident disease. It provides treatment techniques that maximize tumor dose and minimize normal tissue toxicity. Using smaller fields that do not incorporate elective nodal regions may allow higher doses, and these may help improve local control and survival in a disease where current results are unacceptable.

Prospective evaluation of early lung toxicity following three-dimensional conformal radiation therapy in non-small-cell lung cancer: preliminary results

PURPOSE

Radiation pneumonitis is the restricting complication following lung cancer irradiation. The correlation between dose-volume histograms (DVHs) and pneumonitis, with a clinical, radiological, and respiratory function evaluation was assessed. Special endpoint was the evaluation of respiratory function after three-dimensional conformal radiotherapy (3D-CRT).

METHODS AND MATERIALS

Fifty-four patients with non metastatic non-small-cell lung cancer (NSCLC) were treated with a curative intent with 3D-CRT (66 Gy). Thirty-one patients were treated postoperatively (pneumonectomy in 9 patients) for residual tumor or massive nodal involvement (N2 or N3); 23 patients were treated with exclusive radiotherapy. Clinical evaluation, CT scan, and pulmonary functional tests were performed before and 6 weeks after irradiation. The DVHs were calculated applying lung density heterogeneity.

RESULTS

Twenty patients had radiation pneumonitis. Irradiation significantly decreased total lung capacity. Volume of the PTV2 (more than 200 cm(3)) was a significant prognostic factor for lung complication.

CONCLUSION

DVHs combined with initial pulmonary functional tests can predict pulmonary toxicity and could allow us to adjust volume that received total highest dose with acceptable toxicity.

The impact of three-dimensional radiation on the treatment of non-small cell lung cancer

PURPOSE

Non-small cell lung cancer (NSCLC) patients with locally advanced unresectable disease have a grim prognosis. Radiotherapeutic strategies are necessary to improve the permanent eradication of thoracic disease. The poor results achieved with conventional external beam radiation therapy reflect in part, the inadequacy of such therapy in achieving its primary objective of achieving local control. The impact of three-dimensional conformal radiation therapy (3-DCRT) on local disease eradication and its potential role in improving survival is assessed.

DESIGN

This review addresses aspects of the software and hardware technology of 3-DCRT, the clinical and technical aspects of target volume definition, the use of 3-DCRT to predict radiation pneumonitis, strategies for dose escalation in NSCLC, and analyses the clinical results to date.

RESULTS

Initially investigators compared the best treatment techniques devised with conventional planning techniques to those devised with 3-DCRT. These analyses showed that 3-DCRT had the potential to deliver high dose radiation (>70 Gy) with minimal underdosing and with a concomitant relative sparing of normal tissues. This technical demonstration of enhanced therapeutic ratio is the basis for the evolving clinical utilization of 3-DCRT for NSCLC. Software and hardware developments continue to develop and have the potential to solve evolving clinical issues. Dose-volume-histograms have been used to accurately quantify lung dose and derived parameters have the potential to predict the risk of pneumonitis for individual patients before treatment. Initial clinical results have been promising and strategies for further dose escalation are emerging.

CONCLUSION

Preliminary experience has resulted in promising survival following three-dimensional conformal radiation therapy alone for locally advanced NSCLC. More follow-up and experience will determine late toxicity, maximum dose, and efficacy of dose escalation with three-dimensional conformal radiation therapy. Strategies should be developed to integrate this modality into the combined treatment of locally advanced non-small cell lung cancer.

The impact of (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) lymph node staging on the radiation treatment volumes in patients with non-small cell lung cancer

PURPOSE

(18)F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) combined with computer tomography (PET-CT) is superior to CT alone in mediastinal lymph node (LN) staging in non-small cell lung cancer (NSCLC). We studied the potential impact of this non-invasive LN staging procedure on the radiation treatment plan of patients with NSCLC.

PATIENTS AND METHODS

The imaging and surgical pathology data from 105 patients included in two previously published prospective LN staging protocols form the basis for the present analysis. For 73 of these patients, with positive LN's on CT and/or on PET, a theoretical study was performed in which for each patient the gross tumour volume (GTV) was defined based on CT and on PET-CT data. For each GTV, the completeness of tumour coverage was assessed, using the available surgical pathology data as gold standard. A more detailed analysis was done for the first ten consecutive patients in whom the PET-CT-GTV was smaller than the CT-GTV. Theoretical radiation treatment plans were constructed based on both CT-GTV and PET-CT-GTV. Dose-volume histograms for the planning target volume (PTV), for the total lung volume and the lung volume receiving more than 20 Gy (V(lung(20))), were calculated.

RESULTS

Data from 988 assessed LN stations were available. In the subgroup of 73 patients with CT or PET positive LN's, tumour coverage improved from 75% when the CT-GTV was used to 89% with the PET-CT-GTV (P=0.005). In 45 patients (62%) the information obtained from PET would have led to a change of the treatment volumes. For the ten patients in the dosimetry study, the use of PET-CT to define the GTV, resulted in an average reduction of the PTV by 29+/-18% (+/-1 SD) (P=0.002) and of the V(lung(20)) of 27+/-18% (+/-1 SD) (P=0.001).

CONCLUSION

In patients with NSCLC considered for curative radiation treatment, assessment of locoregional LN tumour extension by PET will improve tumour coverage, and in selected patients, will reduce the volume of normal tissues irradiated, and thus toxicity. This subgroup of patients could then become candidates for treatment intensification.

Thoracic reirradiation for symptomatic relief after prior radiotherapeutic management for lung cancer

Limited information is available in the medical literature on thoracic reirradiation for patients with recurrent/persistent lung carcinoma or new primary lung tumors. Controversy exists regarding the retreatment because of concerns regarding the risk of radiation toxicity. The medical and radiotherapeutic records of more than 1,500 patients with lung cancer seen in the Department of Radiation Oncology at Thomas Jefferson University Hospital from 1982 through 1997 were searched. Twenty-three patients with history of previous thoracic radiation therapy underwent thoracic reirradiation for either biopsy-proven and/or radiographically evident tumor recurrence, metastasis, or second lung primary. Most patients were reirradiated because of progressive dyspnea, cough, thoracic pain, or hemoptysis. Each of these symptoms was evaluated separately with regard to the subjective response to reirradiation. The median follow-up time from completion of reirradiation to last correspondence with the patient and/or family was 3.2 months, with a range of 0 to 17.5 months. In six patients with hemoptysis, a decrease or resolution of this symptom was noted. Of five patients with thoracic pain attributed to carcinoma, four noted an improvement in pain after reirradiation. Of 15 patients with cough, 9 had an improvement in cough, and of 15 patients with dyspnea, 11 had an improvement. Thoracic reirradiation is an effective modality in patients with hemoptysis, thoracic pain, cough, and dyspnea attributed to a radiographically defined recurrence and/or progression of lung cancer.

Optimization of beam weights in conformal radiotherapy planning of stage III non-small cell lung cancer: effects on therapeutic ratio

PURPOSE

To evaluate the effects of beam weight optimization for 3D conformal radiotherapy plans, with or without beam intensity modulation, in Stage III non-small cell lung cancer (NSCLC).

METHODS AND MATERIALS

Ten patients with Stage III NSCLC were planned using a conventional 3D technique and a technique involving noncoplanar beam intensity modulation (BIM). Two planning target volumes (PTVs) were defined: PTV1 included macroscopic tumor volume and PTV2 included macroscopic and microscopic tumor volume. Virtual simulation defined the beam shapes and incidences as well as the wedge orientations (3D) and segment outlines (BIM). Weights of wedged beams, unwedged beams, and segments were determined by human trial and error for the 3D-plans (3D-manual), by a standard weight table (SWT) for the BIM-plans (BIM-SWT) and by optimization (3D-optimized and BIM-optimized) using an objective function with a biological and a physical component. The resulting non-optimized and optimized dose distributions were compared, using physical endpoints, after normalizing the median dose of PTV1 to 80 Gy.

RESULTS

Optimization improved dose homogeneity at the target for 3D- and BIM-plans and the minimum dose at PTV1. The minimum dose at PTV2 was decreased by optimization especially in 3D-plans. After optimization, the dose-volume histograms (DVHs) of lung and heart were shifted to lower doses for 80-90% of the organ volume. Since lung is the dose-limiting organ in Stage III NSCLC, an increased minimum dose at PTV1 together with a decreased dose at the main lung volume suggests an improved therapeutic ratio. Optimization allows 10% dose escalation for 3D-plans and 20% for BIM-plans at isotoxicity levels of lung and spinal cord. Upon dose escalation, esophagus may become the dose-limiting structure when PTV1 extends close to the esophagus.

CONCLUSIONS

Optimization using a biophysical objective function allowed an increase of the therapeutic ratio of radiotherapy planning for Stage III NSCLC.

Novel approaches to locally advanced unresectable non-small cell lung cancer

The management of advanced non-small cell lung cancer (NSCLC) is rapidly evolving. Advances in combined chemo-radiation therapy have led to improvements in patient survival which are statistically significant, but most patients still succumb to their disease. New chemotherapeutic agents, such as taxanes (paclitaxel, docetaxel), topoisomerase inhibitors (topotecan, irinotecan), and novel analogs (gemcitabine, vinorelbine), may offer the promise of improved outcome, but have not yet been tested in phase III trials. Molecular therapeutics, such as gene therapy, drugs that target specific oncogene activation (such as Ki-ras inactivation by farnesyl transferase inhibitors), and hypoxic cell toxins (such as tirapazamine), are in clinical trials. The optimum use of these agents awaits more rapid and widespread molecular diagnostics. Finally, technological advances in radiotherapy will allow higher tumor doses, while minimizing doses to dose-limiting normal structures, such as the esophagus, normal lung and heart. We describe a move towards molecular strategies, both for therapy and diagnostics, that may result in more effective treatment. While the outcome for patients with advanced non-small cell lung carcinoma is still poor, new agents are being developed rapidly and offer the hope of improved survival.

Characteristics of 49 patients who survived for 5 years following radical radiation therapy for non-small cell lung cancer: the potential for cure

PURPOSE

To investigate the long-term curative potential of radical radiation therapy (RT) for non-small cell lung cancer (NSCLC) by studying characteristics of patients from a large prospective database who survived >5 years after RT, and by analyzing survival beyond 5 years.

METHODS AND MATERIALS

Five-year survivors were identified from a database containing information on 488 patients given radical RT following presentation to the Peter MacCallum Cancer Institute with NSCLC between 1984 and 1990. Additional data were obtained from case notes of survivors. RT was computed tomography (CT)-planned, conventionally-fractionated, and given without chemotherapy.

RESULTS

Actuarial survival for 49 5-year survivors was 65% at 10 years. Five 5-year survivors had documented disease progression within the first 5 years and subsequently died. Of 44 patients free-from-progression (FFP) at 5 years, an estimated 81% remained FFP in the second 5 years. Age and histology were not significant prognostic factors, and only 22 patients (4.5%) had weight loss >10%. For 277 patients who had not undergone thoracotomy, median RT dose was 60 Gy and survival at 5 and 10 years was 7% and 3%, respectively. For 207 patients who received radical RT post-thoracotomy, median dose was 60 Gy and survival at 5 and 10 years was 24% and 18%, respectively. Five-year survivors of post-thoracotomy RT had been treated for gross residual disease (n = 10), positive-margin (n = 6), or probable microscopic residual disease (n = 17). Failure to regain ECOG performance status = 0 post-thoracotomy was associated with reduced survival (p<0.0012). FFP in the second 5 years was superior for patients who had postoperative radiotherapy (90%) compared to patients without thoracotomy (62%, p = 0.008).

CONCLUSION

Most patients FFP >5 years after radical RT for NSCLC remained FFP in the following 5 years and were apparently cured. RT alone can cure small but significant numbers of patients. Long-term results of combined chemotherapy/RT protocols, which are associated with increased median survival, are awaited for comparison.

The rationale and use of three-dimensional radiation treatment planning for lung cancer

Treatment of lung cancer with conventional radiation therapy is associated with suboptimal local tumor control and poor long-term survival. Poor local tumor control may result from inaccurate tumor targeting, failure to satisfactorily conform to dose distribution with the target volume, and/or inadequate radiation doses. Three-dimensional treatment planning is a radiotherapy technique that provides more accurate dose targeting via the direct transfer of three-dimensional anatomic information from diagnostic scans into the planning process. This technology can assist treatment planning by providing dose-volume histograms, an estimation of normal tissue complication probabilities, and facilitate dose escalation. Preliminary clinical studies suggest that this is a feasible approach worthy of additional study. The three-dimensional tools provide new opportunities to better understand radiation-induced changes in pulmonary function.

Radiotherapy: the last 25 years

Some of the major changes in radiotherapy over the last years are reviewed in this paper. Radiotherapy has played a role in the changes in oncological practice including an increase in organ-sparing treatment and achieving good local control and improving survival. About half of all breast cancer patients are now treated with breast conserving therapy. Organ preservation, usually with multimodality therapy, has also been further developed in the treatment of cancers in the head and neck, anus, bladder and soft tissue sarcomas. Developments in radiobiology have led to the development of new fractionation schedules. Hyperfractionation allows an increase in the tumour dose whilst sparing normal tissues and accelerated fractionation combats accelerated tumour proliferation during treatment. Advances in accelerator technology and computerized treatment planning have enabled the development of three-dimensional conformal radiotherapy. This gives the oportunity to spare normal tissues and escalate the dose to the tumour. Quality control and standardization of dosimetry and treatment delivery at departmental and international level has also improved treatment results.

[Conformal radiotherapy of non-small-cell lung cancer]

About one third of lung cancers initially present with a localised disease, without any curative surgery potential, because of local spread or comorbidity. Definitive radiation, alone or combined with chemotherapy, then represents the treatment of choice for these patients. The results, however, are disappointing, with a biopsy-proven local control of 10% at two years and a 5-10% five-year survival rate. These poor results may be partially explained by the difficulties in delineating the tumour volume as well as the dose limitations due to poor tolerance of surrounding normal organs. Lung parenchyma sequelae remain daily worrying events for the oncologist. The advent of 3D conformal radiation therapy (3DRT) allows progress and innovations, including the use of modern imaging techniques, sophisticated dosimetry and treatment planning, efficient immobilisation devices and on-line verification procedures. With more precise (and time-consuming) procedures, 3DRT will allow a better tumour volume delineation, an increased tumour dose and a dose limitation in normal tissues. These improvements may help increase local control and survival results. 3DRT, which has been used for several years for prostate cancer and benefits from recent imaging improvements, will now allow treatment of other locations, such as lung cancer, with conformal therapy. The few preliminary results are encouraging. This work reviews the current data and remaining questions regarding lung cancer treated with 3DRT, and presents and discusses the literature before discussing future trends in this area.

Dose escalation of chart in non-small cell lung cancer: is three-dimensional conformal radiation therapy really necessary?

PURPOSE

To evaluate, preclinically, the potential for dose escalation of continuous, hyperfractionated, accelerated radiation therapy (CHART) for non small-cell lung cancer (NSCLC), we examined the strategy of omission of elective nodal irradiation with and without the application of three-dimensional conformal radiation technology (3DCRT).

METHODS AND MATERIALS

2D, conventional therapy plans were designed according to the specifications of CHART for 18 patients with NSCLC (Stages Ib, IIb, IIIa, and IIIb). Further plans were generated with the omission of elective nodal irradiation (ENI) from the treatment portals (2D minus ENI plans [2D-ENI plans]). Both sets were inserted in the patient's planning computed tomographies (CTs). These reconstructed plans were then compared to alternative, three-dimensional treatment plans which had been generated de novo, with the omission of ENI: 3D minus elective nodal irradiation (3D-ENI plans). Dose delivery to the planning target volumes (PTVs) and to the organs at risk were compared between the 3 sets of corresponding plans. The potential for dose escalation of each patient's 2D-ENI and 3D-ENI plan beyond 54 Gy, standard to CHART, was also determined.

RESULTS

PTV coverage was suboptimal in the 2D CHART and the 2D-ENI plans. Only in the 3D-ENI plans did 100% of the PTV get > or = 95% of the dose prescribed (i.e., 51.5 Gy [51.3-52.2]). Using 3D-ENI plans significantly reduced the dose received by the spinal cord, the mean and median doses to the esophagus and the heart. It did not significantly reduce the lung dose when compared to 2D-ENI plans. Escalation of the dose (minimum > or = 1 Gy) with optimal PTV coverage was possible in 55.5% of patients using 3D-ENI, but was possible only in 16.6% when using the 2D-ENI planning strategy.

CONCLUSIONS

3DCRT is fundamental to achieving optimal PTV coverage in NSCLC. A policy of omission of elective nodal irradiation alone (and using 2D technology) will not achieve optimal PTV coverage or dose escalation. 3DCRT with omission of ENI can achieve true escalation of CHART in 55.5% of tumors, depending on their site and N-stage.

18F-deoxyglucose positron emission tomography (FDG-PET) for the planning of radiotherapy in lung cancer: high impact in patients with atelectasis

PURPOSE

18F-deoxyglucose positron emission tomography (FDG-PET) is increasingly applied in the staging of lung cancer (LC). This study analyzes the potential contribution of PET in radiotherapy planning for LC with special respect to tumor-associated atelectasis.

METHODS AND MATERIALS

Thirty-four patients with histologically confirmed LC, who had been examined by PET during pretreatment staging, were included. All were irradiated after CT-based therapy planning with anterior/posterior (AP) portals encompassing the primary tumor and the mediastinum (CT portals, CP). The result of the PET examination was unknown in treatment planning. In retrospect, a PET portal (PP) was delineated and compared with the CP.

RESULTS

In 12/34 cases, the shape and/or size of the portals were changed, primarily (n = 10) the size of the fields was reduced. The median area of CP was 182 cm2 versus 167 cm2 of PP. Seventeen of 34 patients had dys- or atelectasis caused by a central primary tumor. In these cases, differences between CP and PP were significantly more frequent than in the other patients (8/17 vs. 3/17, p = 0.03).

CONCLUSION

In this retrospective analysis, the information provided by FDG-PET would have contributed to a substantial reduction of the size of radiotherapy portals. This applies particularly for patients with tumor-associated dys- or atelectasis.

Inhomogeneous target-dose distributions: a dimension more for optimization?

PURPOSE

To evaluate if the use of inhomogeneous target-dose distributions, obtained by 3D conformal radiotherapy plans with or without beam intensity modulation, offers the possibility to decrease indices of toxicity to normal tissues and/or increase indices of tumor control stage III non-small cell lung cancer (NSCLC).

METHODS AND MATERIALS

Ten patients with stage III NSCLC were planned using a conventional 3D technique and a technique involving noncoplanar beam intensity modulation (BIM). Two planning target volumes (PTVs) were defined: PTV1 included macroscopic tumor volume and PTV2 included macroscopic and microscopic tumor volume. Virtual simulation defined the beam shapes and incidences as well as the wedge orientations (3D) and segment outlines (BIM). Weights of wedged beams, unwedged beams, and segments were determined by optimization using an objective function with a biological and a physical component. The biological component included tumor control probability (TCP) for PTV1 (TCP1), PTV2 (TCP2), and normal tissue complication probability (NTCP) for lung, spinal cord, and heart. The physical component included the maximum and minimum dose as well as the standard deviation of the dose at PTV1. The most inhomogeneous target-dose distributions were obtained by using only the biological component of the objective function (biological optimization). By enabling the physical component in addition to the biological component, PTV1 inhomogeneity was reduced (biophysical optimization). As indices for toxicity to normal tissues, NTCP-values as well as maximum doses or dose levels to relevant fractions of the organ's volume were used. As indices for tumor control, TCP-values as well as minimum doses to the PTVs were used.

RESULTS

When optimization was performed with the biophysical as compared to the biological objective function, the PTV1 inhomogeneity decreased from 13 (8-23)% to 4 (2-9)% for the 3D-(p = 0.00009) and from 44 (33-56)% to 20 (9-34)% for the BIM plans (p < 0. 00001). Minimum PTV1 doses (expressed as the lowest voxel-dose) were similar for both objective functions. The mean and maximum target doses were significantly higher with biological optimization for 3D as well as for BIM (all p values < 0.001). Tumor control probability (estimated by TCP1 x TCP2) was 4.7% (3D) and 6.2% (BIM) higher for biological optimization (p = 0.01 and p = 0.00002 respectively). NTCP(lung) as well as the percentage of lung volume exceeding 20 Gy was higher with the use of the biophysical objective function. NTCP(heart) was also higher with the use of the biophysical objective function. The percentage of heart volume exceeding 40 Gy tended to be higher but the difference was not significant. For spinal cord, the maximum dose as well as NTCP(cord) were similar for 3D plans (D(max): p = 0.04; NTCP: p = 0.2) but were significantly lower for BIM (D(max): p = 0.002; NTCP: p = 0.008) if the biophysical objective function was used.

CONCLUSIONS

When using conventional 3D techniques, inhomogeneous dose distributions offer the potential to further increase the probability of uncomplicated local control. When using techniques as BIM that would lead to large escalation of the median and maximum target doses, it seems indicated to limit target-dose inhomogeneity to avoid dose levels that are so high that the safety becomes questionable.

Radiotherapy for lung cancer: target splitting by asymmetric collimation enables reduction of radiation doses to normal tissues and dose escalation

PURPOSE

This study was performed to develop a method of reducing the radiation doses to normal thoracic tissues, increasing the target dose, especially in the primary radiotherapy of non-small cell lung cancer (NSCLC), and to evaluate acute/subacute toxicity of dose escalation.

METHODS AND MATERIALS

From December 1195 to March 1998, the technique of target splitting has been applied to 58 patients. In this period, 30 patients were treated with doses > 80 Gy (ICRU-specification, mean 85.1 Gy, range 80. 1-90.2 Gy). The target volume is split into a cranial part (e.g., upper mediastinum) and a caudal part (e.g., primary tumor and middle mediastinum). Both volumes are planned and treated independently, using conformal irradiation techniques for both parts with half-collimated fields to prevent over- or underdosage in the junction plane. After fine-adjustment of the jaws, a verification film, exposed in a polymethylmethacrylate (PMMA) phantom, demonstrates the homogeneity of dose in the entire target volume. For comparison with conventional techniques, planning to identical doses is performed for 5 patients. Dose-volume histograms (DHVs) for normal lung tissue are presented for both methods.

RESULTS

The irradiated volume of normal tissue of the ipsilateral lung can be lowered at dose levels > or = 65, > or =45 Gy, and > or = 20 Gy to values of 37% (range 25-54%), 49% (range 46-54%), and 86% (range 55-117%), respectively. Other organs at risk, such as heart or esophagus, can also be spared significantly. Only 1 patient showed a transient grade 3 toxicity (pneumonitis), and there where no grade 4 acute/subacute side-effects. Two patients with Stage III A central tumors in close proximity to the large vessels died due to a pulmonary hemorrhage 2 and 4 months after therapy, respectively. No patient developed esophagitis. Antimycotic prophylaxis for esophagitis and posttherapeutic steroid prophylaxis for pneumonitis for several weeks were routinely used.

CONCLUSION

The technique of target splitting by asymmetric collimation helps to increase conformation, and thus enhances the sparing of normal tissues. It can be used whenever there is a marked difference in the shape of the planning target volume (PTV) in a cranio-caudal direction. This technique can principally be handled with 2D-planning systems, because it is coplanar. We consider target splitting as an important tool for dose escalation in the primary radiotherapy of NSCLC, that should also be used for other lung cancer patients necessitating moderate doses only.

Beam intensity modulation for penumbra enhancement in the treatment of lung cancer

PURPOSE

A treatment planning study was performed for patients with lung cancer in order to investigate the extent to which doses to critical structures could be reduced by penumbra enhancement at the superior and inferior field edges, using beam intensity modulation (BIM) with a multileaf collimator. By applying two independent published models for the prediction of the incidence of normal tissue complications, the potential for dose escalation without increasing the incidence of pneumonitis was estimated.

METHODS AND MATERIALS

For 12 patients, the standard treatment technique was compared with the BIM technique using the Cadplan 3D planning system (Varian-Dosetek). Dose distributions in the healthy lung tissue were evaluated by considering both lungs minus the tumor as one functional unit. The following parameters were compared: (i) the average normalized total dose (NTD), (ii) the lung volume receiving an NTD of more than 20 Gy, and (iii) the calculated normal tissue complication probability (NTCP).

RESULTS

Due to the applied BIM technique, the field lengths could be reduced by 1.4 cm for all patients, while achieving a minimum dose at the superior and inferior parts of the target of 95% of the isocenter dose. Compared to the standard technique, BIM reduced the patient mean of the average NTD for the healthy lung tissue from 16.5 to 15.3 Gy. The volume of healthy lung tissue receiving an NTD of 20 Gy or more was reduced by 9.7% (range 2.2 to 23.1%). The calculated NTCP reduced from 10.7% to 7.6% on average. The length of the esophagus that received a dose of 60 Gy or more could be reduced for 5 of the 6 stage III patients in this study. Based on equal lung NTCPs for the standard technique and the BIM technique, a mean dose escalation of 5.7 Gy (range 1.1 to 16.0 Gy) was possible for the 12 patients in this study. Based on equal average NTDs for the two techniques, the patient mean of the allowed dose escalation was 6.5 Gy (range 1.1 to 18.2 Gy). All dose escalations would be possible without exceeding the spinal cord tolerance dose.

CONCLUSIONS

The BIM technique reduced the dose delivery to critical tissues. Two published methods for estimating the incidence of pneumonitis both pointed to a potential for dose escalation of 6 to 7 Gy on average with the BIM technique, without increasing the incidence of pneumonitis. For 2 of the 12 patients in this study the estimated allowed dose escalation even exceeded 15 Gy.

Predictors of subclinical nodal involvement in clinical stages I and II non-small cell lung cancer: implications in the inoperable and three-dimensional dose-escalation settings

PURPOSE

When mediastinal lymph nodes are clinically uninvolved in the setting of inoperable non-small cell lung cancer, whether conventional radiation techniques or three-dimensional dose-escalation techniques are used, the benefit of elective nodal irradiation is unclear. Inclusion of the clinically negative mediastinum in the radiation portals increases the risk of lung toxicity and limits the ability to escalate dose. This analysis represents an attempt to use clinical characteristics to estimate the risk of subclinical nodal involvement, which may help determine which patients are most likely to benefit from elective nodal irradiation.

METHODS

From 1987 to 1990, 346 patients undergoing complete resection of non-small cell lung cancer underwent a preoperative computed tomographic scan revealing no clinical evidence of N2/N3 involvement. Multivariate regression and regression tree analyses attempted to define which patients were at highest risk for subclinical mediastinal involvement (N2) and which patients were at highest risk for subclinical N1 and/or N2 involvement (N1/N2). Immunohistochemical data suggest that the conventional histopathologic techniques used during this study somewhat underestimate the true degree of lymph node involvement; therefore, a third end point was also evaluated: N1 involvement and/or N2 involvement and/or local-regional recurrence (N1/N2/LRR).

RESULTS

Regression analyses revealed that the following factors were independently associated with a high risk of more advanced disease: positive preoperative bronchoscopy (N2, p = 0.02; N1/N2, p < 0.0001; N1/N2/LRR, p < 0.001) and tumor grade 3/4 (N1/N2/LRR, p < 0.01). A regression tree analysis was then used to separate patients into risk groups with respect to N1/N2/LRR.

CONCLUSION

In inoperable non-small cell lung cancer, the patients for whom mediastinal radiation therapy may most likely be indicated are those with a positive preoperative bronchoscopy, especially with large (> 3 cm) primary tumors.

Concurrent radiochemotherapy for patients with stage III non-small-cell lung cancer (NSCLC): long-term results of a phase II study

PURPOSE

To investigate the feasibility and activity of concurrent radiochemotherapy in patients with Stage III nonsmall-cell lung cancer (NSCLC).

MATERIALS AND METHODS

Forty-one patients were treated with hyperfractionated radiation therapy (HfxRT) using 1.2 Gy bid, to a total of 69.6 Gy and concurrent low-dose daily chemotherapy (CHT) consisting of 30 mg of carboplatin (CBDCA) and 30 mg of etoposide (VP-16) given Mondays to Fridays during the RT course. On Saturdays and Sundays during the RT course, CBDCA and VP-16 were both given in a daily dose of 100 mg each.

RESULTS

Median survival time was 25 months, and 3- and 5-year survival rates were 34% and 29%, respectively. Median relapse-free survival time was 22 months, and 3- and 5-year relapse-free survival rates were 32%, and 29%, respectively. Median time to local recurrence was 24 months and 3- and 5-year local recurrence-free survival rates were 41% and 38%, respectively. Median time to distant metastasis was 28 months, and 3- and 5-year distant metastasis-free survival rates were 44% and 44%, respectively. Acute high-grade (> or = 3) toxicity was mostly hematological (30%), esophageal (15%), and bronchopulmonary (12%). Late high-grade toxicity was infrequent.

CONCLUSION

This combined radiochemotherapy regimen produced promising results and warrants further studies with more patients before testing it in a prospective randomized fashion.

Evaluation of two dose-volume histogram reduction models for the prediction of radiation pneumonitis

PURPOSE

To evaluate the similarities between the mean lung dose and two dose-volume histogram (DVH) reduction techniques of 3D dose distributions of the lung.

PATIENTS AND METHODS

DVHs of the lungs were calculated from 3D dose distributions of patients treated for malignant lymphoma (44), breast cancer (42) and lung cancer (20). With a DVH reduction technique, a DVH is summarized by the equivalent uniform dose (EUD), a quantity which is directly related to the normal tissue complication probability (NTCP). Two DVH reduction techniques were used. The first was based on an empirical model proposed by Kutcher et al. (Kutcher, G.J., Burman, C., Brewster, M.S., Goitein, M. and Mohan, R. Histogram reduction method for calculating complication probabilities for three-dimensional treatment planning evaluations. Int. J. Radiat. Oncol. Biol. Phys. 21: 137-146, 1991), which needs a volume exponent n. Several values for n were tested. The second technique was based on a radiobiological model, the parallel functional subunit model developed by Niemierko et al. (Niemierko, A. and Goitein, M. Modeling of normal tissue response to radiation: the critical volume model. Int. J. Radiat. Oncol. Biol. Phys. 25: 135-145, 1993) and Jackson et al. (Jackson, A., Kutcher, G.J. and Yorke, E.D. Probability of radiation-induced complications for normal tissues with parallel architecture subject to non-uniform irradiation. Med. Phys. 20: 613-625, 1993), for which a local dose-effect relation needed to be specified. This relation was obtained from an analysis of perfusion and ventilation SPECT data.

RESULTS

It can be shown analytically that the two DVH reduction techniques are identical, if the local dose-effect relation obeys a power-law relationship in the clinical dose range. Local dose-effect relations based on perfusion and ventilation SPECT data can indeed be fitted with a power-law relationship in the range 0-80 Gy, from which values of n = 0.8-0.9 were deduced. These correspond to the commonly used value of n = 0.87 for lung tissue and yielded EUDn=0.87 values which were almost identical to the mean lung doses. For other n values, for which no experimental data are present, differences exist between EUD and mean dose values. Six patients with malignant lymphoma (6/44) and none of the breast cancer patients (0/42) developed radiation pneumonitis. These cases occurred only at high values for the mean lung dose.

CONCLUSION

The two DVH reduction techniques are identical for lung and are very similar to mean dose calculations. The two techniques are also relatively similar for other model parameter values.

Conformal radiotherapy of Stage III non-small cell lung cancer: a class solution involving non-coplanar intensity-modulated beams

PURPOSE

We developed a semiautomatic class solution to irradiate centrally located Stage III non-small cell lung cancer (NSCLC), involving a beam intensity modulation technique and optimization using a biophysical cost function.

METHODS AND MATERIALS

Treatment for 10 patients with Stage III NSCLC was planned, using a conventional three- or four-beam three-dimensional (3D) technique and two techniques involving, respectively, seven (BIM1) and five (BIM2) noncoplanar beam incidences with intensity modulation. Two planning target volumes were defined: PTV1 included macroscopic tumor volume and PTV2 included macroscopic and microscopic disease. Beams were divided into beam parts (segments) and their outlines were defined during virtual simulation. Optimization using a biophysical cost function determined beam weights, segment weights, and wedge angles. Biological end points included tumor control probability of both target volumes (TCP1 and TCP2) and normal tissue complication probability (NTCP) of heart, lung, and spinal cord. The resulting uncomplicated local control probability (UCLP) was calculated. Physical end points included dose at PTV1 expressed as a dose minimum and dose maximum. Target-dose inhomogeneity was constrained in all plans.

RESULTS

Concerning tumor evaluation, TCP1 was 74% (range 54-89%) for the 3D plan, 78.0% (range 62-94%) for BIM1, and 86.0% (range 59-93%) for BIM2. TCP1*TCP2 was, respectively, 67.0% (range 39-81%), 73.0% (range 56-94%), and 81.0% (range 54-93%). Minimum doses to PTV1 were 85, 80, and 88 Gy with the three respective techniques, while dose maxima were 89, 101, and 100 Gy. NTCPs of lung were 45.0% (range 11-75%) for 3D, 19.5% (range 8-59%) for BIM1, and 24.5% (range 3-61%) for BIM2. NTCPs of heart and spinal cord were comparable for all techniques. ULCPs were 37.0% (range 9-73%), 52.5% (range 22-86%), and 60.0% (range 20-85%), respectively. Applying physical limits to ensure clinical safety, minimum doses at PTV1 were recalculated. These were 72, 71, and 74 Gy for 3D, BIM1, and BIM2, respectively.

CONCLUSION

The BIM2 plan is a candidate class solution for dose escalation studies in centrally located Stage III NSCLC.

Dose-effect relations for early local pulmonary injury after irradiation for malignant lymphoma and breast cancer

PURPOSE

To quantify the influence of treatment- and patient-related factors on the severity of early local pulmonary injury and to establish whether regional differences are present for local dose-effect relations for early radiation-induced pulmonary injury.

METHODS

Forty-two patients with malignant lymphoma and 40 breast cancer patients were examined prior to and 3 months after radiotherapy. The lymphoma patients were irradiated with mantle fields to an average dose of 38 Gy and the breast cancer patients were irradiated with internal mammary node fields with or without tangential breast fields to an average dose of 50 Gy. Dose-effect relations for local perfusion, ventilation and density changes were determined using correlated single photon emission computed tomography (SPECT) and CT data. A multivariate analysis was performed to study the influence of irradiated volume, chemotherapy (CMF and MOPP/ABV), smoking, age and gender. In addition, dose-effect relations for different regions in the lung were determined.

RESULTS

A similar and almost linear increase of early functional changes as a function of radiation dose was observed for perfusion and ventilation, whereas the shape of the dose-effect relation and the magnitude of early structural changes were different for density. For the three end-points studied, regional differences in radiosensitivity could not be demonstrated. For the posterior lung region compared to the anterior lung region, however, a difference was observed, which could be attributed to a gravity-related effect in the measuring procedure. Local structural changes (density) were significantly smaller for smokers (P = 0.002) and young patients (P = 0.007), whereas the CMF chemotherapy regimen given after radiotherapy (P = 0.017) significantly increased the amount of functional changes (perfusion). The magnitude of local pulmonary changes was independent of the irradiated volume, the MOPP/ABV chemotherapy regimen and gender.

CONCLUSION

The dose-effect relations for early radiation-induced local pulmonary changes were independent of the irradiated volume, MOPP/ABV, gender and lung region. CMF, smoking and age influenced the magnitude of early pulmonary changes and should be taken into account in dose-escalation protocols.

Considerations in optimizing radiation therapy for non-small cell lung cancer

Irradiation therapy for lung cancer is mostly restricted to conventional methods. To improve therapeutic ratio, we have combined a treatment planning and a gene therapy approach. Three-dimensional conformal radiotherapy is described as carried out by methods of gene therapy for radiation protection using the manganese-superoxide-dismutase transgene delivered by inhalation gene transfer. These methods may improve therapeutic outcomes in lung cancer.

Non-coplanar beam intensity modulation allows large dose escalation in stage III lung cancer

PURPOSE

To evaluate the feasibility of dose escalation in stage III non-small cell lung cancer, we compared standard coplanar (2D) with non-coplanar beam arrangements, without (3D) and with beam intensity modulation (3D-BIM).

MATERIALS AND METHODS

This study was a planning effort performed on a non-selected group of 10 patients. Starting from a serial CT scan, treatment planning was performed using Sherouse's GRATIS 3D planning system. Two target volumes were defined; gross tumor volume (GTV) defined a high-dose target volume that had to receive a dose of at least 80 Gy and GTV plus the lymph node regions with >10% probability of invasion defined an intermediate-dose target volume (GTV + N). It was our intention to irradiate GTV + N up to 56 Gy or more. If the prescribed doses on GTV and GTV + N could not be reached with either the 2D or 3D technique, a 3D-BIM plan was performed. The 3D-BIM plan was a class solution involving identical gantry angles, segment arrangements and relative segment weights for all patients. Dose volume histograms for GTV, GTV + N, lung and spinal cord were calculated. Criteria for tolerance were met if no points inside the spinal cord exceeded 50 Gy and if at least 50% of the lung volume received less than 20 Gy. Under these constraints, maximal achievable doses to GTV and GTV + N were calculated.

RESULTS

In all 2D plans, spinal cord was the limiting factor and the prescribed doses for GTV and GTV + N could not be reached in any patient. The non-coplanar 3D plan resulted in a satisfying solution in 4 out of 10 patients under the same constraints. In comparison with 2D, the minimum dose in GTV + N was increased. Six patients had to be planned with the 3D-BIM technique. The theoretical minimum dose to GTV + N ranged between 56 and 98 Gy. The delivery of 80 Gy or more to GTV was possible in all patients. For a minimal dose of 80 Gy to GTV, the maximal dose to any point of the spinal cord varied between 27 and 46 Gy. The lung volume receiving more than 20 Gy ranged from 26 to 46%.

CONCLUSION

The potential of 3D-BIM for dose escalation is explained as follows: (i) compared to other planning techniques, a larger amount of lung tissue can be spared by using beam directions that are well-aligned with the mediastinal structures. Such beam directions have narrow angles with the sagittal plane; (ii) dividing all beams into segments with well-specified geometrical restrictions in relation to the spinal cord and well-defined relative weights results in a lower dose to the spinal cord.

Women and lung cancer: waiting to exhale

Lung cancer is now the leading cause of cancer deaths among women. In the United States, 64,300 women are expected to die of lung cancer in 1996. Smoking is responsible for about 80% of lung cancer cases. Unfortunately, the prevalence of smoking among women remains unacceptably high at about 22% and is expected to surpass the rate in men by the year 2000. Smoking rates are highest among young girls and the less educated. Whether lung cancer represents a different disease in women than in men is unclear. Data are conflicting regarding the magnitude of the relative risk of developing lung cancer due to smoking between the genders. There appears to be a difference in the relative distribution of lung cancer histologic features between men and women that is not explained entirely by differences in smoking patterns. Women who smoke appear to be at higher risk of developing small cell lung cancer than squamous cell lung cancer, whereas men who smoke have a similar risk for the two histologic conditions. Furthermore, women smokers are more likely to develop adenocarcinoma of the lung, and estrogens may play a causative role in this phenomenon. Data are unclear regarding whether the outcome of lung cancer treatment differs between genders. Solutions to the lung cancer epidemic among US women include (1) prevention of the disease by reducing smoking rates, (2) improving early detection methods, and (3) exploring new therapeutic strategies.

Dose escalation for non-small cell lung cancer using conformal radiation therapy

PURPOSE

Improved local control of non-small cell lung cancer (NSCLC) may be possible with an increased dose of radiation. Three-dimensional radiation treatment planning (3D RTP) was used to design a radiation therapy (RT) dose escalation trial, where the dose was determined by (a) the effective volume of normal lung irradiated, and (b) the estimated risk of a complication. Preliminary results of this trial were reviewed.

METHODS AND MATERIALS

A graph of the iso-normal tissue complication probability (NTCP) levels associated with a dose and effective volume (V(eff)) was derived, using normal tissue parameters derived from the literature. This led to a dose escalation schema, where patients were sorted into 1 of 5 treatment bins, determined by the V(eff) of the best possible treatment plan. The starting doses ranged from 63 to 84 Gy. Each treatment bin was then escalated separately, as in Phase I dose escalation fashion, with Grade > or = 3 radiation pneumonitis defined as dose limiting. To allow for dose escalation, we required patient follow-up to be > or = 6 months for at least three patients. 3D treatment planning was used to irradiate only the radiographically abnormal areas, with 2.1 Gy (corrected for lung inhomogeneity)/day. Clinically uninvolved lymph nodes were not treated prophylactically.

RESULTS

A total of 48 NSCLC patients have been treated (Stage I/II: 18 patients; Stage III: 28 patients; mediastinal recurrence postsurgery: 2 patients). No radiation pneumonitis has been observed in the 30 patients currently evaluable beyond the 6-month time point. All treatment bins have been escalated at least once. Current doses in the five treatment bins are 69.3, 69.3, 75.6, 84, and 92.4 Gy. None of the 15 evaluable patients in any bin with > or = 30% NTCP experienced clinical radiation pneumonitis, implying that the actual risk is < 20% (beta error rate 5%). Despite the observation of the clinically negative lymph nodes at high risk, there has been no failure in the untreated mediastinum as the sole site of first failure. Three of 10 patients receiving > or = 84 Gy have had biopsy proven residual or locally recurrent disease.

CONCLUSION

Successful dose escalation in a volume-dependent organ can be performed using this technique. By incorporating the effective volume of irradiated tissue, some patients have been treated to a total dose of radiation over 50% higher than traditional doses. The literature-derived parameters appear to overestimate pneumonitis risk with higher volumes. There has been no obvious negative effect due to exclusion of elective lymph node radiation. When completed, this trial will have determined the maximum tolerable dose of RT as a single agent for NSCLC and the appropriate dose for Phase II investigation.