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

Radiation Therapy for Thoracic Malignancies

Radiotherapy is the most commonly used nonsurgical modality in treatment of lung cancers, non-small cell lung cancer (NSCLC) in particular. Radiation therapy has been increasingly used as definitive radical treatment, either alone or in combination with concurrent chemoradiation for locally advanced disease. More recently with the advent of novel radiation techniques and modalities such as stereotactic radiotherapy and proton therapy, radiotherapy can now be used as sole radical treatment of small solitary tumors. This article reviews the current indications and future directions of radiotherapy in lung cancer management.

Chemoradiotherapy of locally-advanced non-small cell lung cancer: Analysis of radiation dose-response, chemotherapy and survival-limiting toxicity effects indicates a low α/β ratio

PURPOSE

To analyse changes in 2-year overall survival (OS_2yr) with radiotherapy (RT) dose, dose-per-fraction, treatment duration and chemotherapy use, in data compiled from prospective trials of RT and chemo-RT (CRT) for locally-advanced non-small cell lung cancer (LA-NSCLC).

MATERIAL AND METHODS

OS_2yr data was analysed for 6957 patients treated on 68 trial arms (21 RT-only, 27 sequential CRT, 20 concurrent CRT) delivering doses-per-fraction ≤4.0 Gy. An initial model considering dose, dose-per-fraction and RT duration was fitted using maximum-likelihood techniques. Model extensions describing chemotherapy effects and survival-limiting toxicity at high doses were assessed using likelihood-ratio testing, the Akaike Information Criterion (AIC) and cross-validation.

RESULTS

A model including chemotherapy effects and survival-limiting toxicity described the data significantly better than simpler models (p < 10^-14), and had better AIC and cross-validation scores. The fitted α/β ratio for LA-NSCLC was 4.0 Gy (95%CI: 2.8-6.0 Gy), repopulation negated 0.38 (95%CI: 0.31-0.47) Gy EQD2/day beyond day 12 of RT, and concurrent CRT increased the effective tumour EQD2 by 23% (95%CI: 16-31%). For schedules delivered in 2 Gy fractions over 40 days, maximum modelled OS_2yr for RT was 52% and 38% for stages IIIA and IIIB NSCLC respectively, rising to 59% and 42% for CRT. These survival rates required 80 and 87 Gy (RT or sequential CRT) and 67 and 73 Gy (concurrent CRT). Modelled OS_2yr rates fell at higher doses.

CONCLUSIONS

Fitted dose-response curves indicate that gains of ~10% in OS_2yr can be made by escalating RT and sequential CRT beyond 64 Gy, with smaller gains for concurrent CRT. Schedule acceleration achieved via hypofractionation potentially offers an additional 5-10% improvement in OS_2yr. Further 10-20% OS_2yr gains might be made, according to the model fit, if critical normal structures in which survival-limiting toxicities arise can be identified and selectively spared.

The SABRTooth feasibility trial protocol: a study to determine the feasibility and acceptability of conducting a phase III randomised controlled trial comparing stereotactic ablative radiotherapy (SABR) with surgery in patients with peripheral stage I non-small cell lung cancer (NSCLC) considered to be at higher risk of complications from surgical resection

Background

Stage I non-small cell lung cancer (NSCLC) is potentially curable, and surgery is considered to be the standard of care for patients with good performance status and minimal co-morbidity. However, a significant proportion of patients with stage I NSCLC have a poorer performance status and significant medical co-morbidity that make them at higher risk of morbidity and mortality from surgery.

Stereotactic ablative radiotherapy (SABR), which uses modern radiotherapeutic techniques to deliver large doses of radiation, has shown superiority over conventional radiotherapy in terms of local control and toxicity and is a standard of care for patients with stage I NSCLC who are at too high risk for surgery. However, it is not known whether surgery or SABR is the most effective in patients with stage I NSCLC who are suitable for surgery but are less fit and at higher risk surgical complications. Previous randomised studies have failed to recruit in this setting, and therefore, a feasibility study is required to see whether a full randomised control trial would be possible.

Methods/design

SABRTooth is a UK-based, multi-centre, open-label, two-group individually (1:1) randomised controlled feasibility study in patients with peripheral stage I NSCLC considered to be at higher risk from surgical resection. The study will assess the feasibility of conducting a definitive large-scale phase III trial. The primary objective is to assess recruitment rates to provide evidence that, when scaled up, recruitment to a large phase III trial would be possible; the target recruitment being 54 patients in total, over a 21-month period. There are multiple secondary and exploratory objectives designed to explore the optimum recruitment and data collection strategies to help optimise the design of a future phase III trial.

Discussion

To know whether SABR is a better, equivalent or inferior alternative to surgery for higher risk patients is a key question in lung cancer. Other studies comparing SABR to surgery have closed early due to poor recruitment, and therefore, the SABRTooth feasibility study has been designed around the UK National Health Service (NHS) cancer pathway incorporating many design features in order to maximise recruitment for a future definitive phase III trial.

Trial registration

controlled-trials.com ISRCTN13029788

DART-bid: dose-differentiated accelerated radiation therapy, 1.8 Gy twice daily: high local control in early stage (I/II) non-small-cell lung cancer

BACKGROUND

While surgery is considered standard of care for early stage (I/II), non-small-cell lung cancer (NSCLC), radiotherapy is a widely accepted alternative for medically unfit patients or those who refuse surgery. International guidelines recommend several treatment options, comprising stereotactic body radiation therapy (SBRT) for small tumors, conventional radiotherapy ≥ 60 Gy for larger sized especially centrally located lesions or continuous hyperfractionated accelerated RT (CHART). This study presents clinical outcome and toxicity for patients treated with a dose-differentiated accelerated schedule using 1.8 Gy bid (DART-bid).

PATIENTS AND METHODS

Between April 2002 and December 2010, 54 patients (median age 71 years, median Karnofsky performance score 70%) were treated for early stage NSCLC. Total doses were applied according to tumor diameter: 73.8 Gy for <  2.5 cm, 79.2 Gy for 2.5-4.5 cm, 84.6 Gy for 4.5-6 cm, 90 Gy for > 6 cm.

RESULTS

The median follow-up was 28.5 months (range 2-108 months); actuarial local control (LC) at 2 and 3 years was 88%, while regional control was 100%. There were 10 patients (19%) who died of the tumor, and 18 patients (33%) died due to cardiovascular or pulmonary causes. A total of 11 patients (20%) died intercurrently without evidence of progression or treatment-related toxicity at the last follow-up, while 15 patients (28%) are alive. Acute esophagitis ≤ grade 2 occurred in 7 cases, 2 patients developed grade 2 chronic pulmonary fibrosis.

CONCLUSION

DART-bid yields high LC without significant toxicity. For centrally located and/or large (> 5 cm) early stage tumors, where SBRT is not feasible, this method might serve as radiotherapeutic alternative to present treatment recommendations, with the need of confirmation in larger cohorts.

Biological considerations when comparing proton therapy with photon therapy

Owing to the limited availability of data on the outcome of proton therapy, treatments are generally optimized based on broadly available data on photon-based treatments. However, the microscopic pattern of energy deposition of protons differs from that of photons, leading to a different biological effect. Consequently, proton therapy needs a correction factor (relative biological effectiveness) to relate proton doses to photon doses, and currently, a generic value is used. Moreover, the macroscopic distribution of dose in proton therapy differs compared with photon treatments. Although this may offer new opportunities to reduce dose to normal tissues, it raises the question whether data obtained from photon-based treatments offer sufficient information on dose-volume effects to optimally use unique features of protons. In addition, there are potential differences in late effects due to low doses of secondary radiation outside the volume irradiated by the primary beam. This article discusses the controversies associated with these 3 issues when comparing proton and photon therapy.

Analysis of single nucleotide polymorphisms and radiation sensitivity of the lung assessed with an objective radiologic endpoin

BACKGROUND

The primary objective of this study was to evaluate the association between radiation sensitivity of the lungs and candidate single nucleotide polymorphisms (SNP) in genes implicated in radiation-induced toxicity.

METHODS

Patients with lung cancer who received radiation therapy (RT) had pre-RT and serial post-RT single photon emission computed tomography (SPECT) lung perfusion scans. RT-induced changes in regional perfusion were related to regional dose, which generated patient-specific dose-response curves (DRC). The slope of the DRC is independent of total dose and the irradiated volume, and is taken as a reflection of the patient's inherent sensitivity to RT. DNA was extracted from blood samples obtained at baseline. SNPs were determined by using a combination of high-resolution melting, TaqMan assays, and direct sequencing. Genotypes from 33 SNPs in 22 genes were compared against the slope of the DRC by using the Kruskal-Wallis test for ordered alternatives.

RESULTS

Thirty-nine self-reported Caucasian patients with pre-RT and ≥6 month post-RT SPECTs, and blood samples were identified. An association between genotype and increasing slope of the DRC was noted in G(1301) A in XRCC1 (rs25487) (P = .01) and G(3748) A in BRCA1 (rs16942) (P = .03).

CONCLUSIONS

By using an objective radiologic assessment, polymorphisms within genes involved in repair of DNA damage (XRCC1 and BRCA1) were associated with radiation sensitivity of the lungs.

Correlation of conventional and conformal plan parameters for predicting radiation pneumonitis in patients treated with breast cancer

Purpose

The purpose of this study is to evaluate the correlation between the conventional plan parameters and dosimetric parameters obtained from conformal radiotherapy (RT) planning, and between these parameters and radiation pneumontitis (RP) incidence.

Methods

Clinical and dosimetric data of 122 patients that were treated with mastectomy and adjuvant 3D conformal RT (39% received 2-field RT [2-FRT], and in addition, 61% received 4-field RT [4-FRT]) were retrospectively analyzed. Central lung depth (CLD), maximum lung depth (MLD), and lung length were measured by the conventional plan. Lung dose-volume histograms (DVH) were created with conformal planning, and the lung volumes receiving 5 to 50 Gy (V_5Gy to V_50Gy) were calculated. Minimum (D_min), maximum (D_max), and mean doses (D_mean) for the ipsilateral lung and bilateral lungs were measured by DVH. Correlations between 3D dosimetric data and 2D radiographic parameters were analyzed.

Results

The conventional plan parameters did not significantly differ between 2-FRT and 4-FRT. The conformal plan D_min, D_max, and D_mean values were higher in 4-FRT versus 2-FRT. CLD and MLD were correlated with DVH parameter V_5Gy to V_45Gy values for ipsilateral, as well as bilateral lungs for 2-FRT. MLD and ipsilateral D_mean via 2-FRT planning had the strongest positive correlation (r=0.76, p<0.01). Moderate correlations existed between CLD and ipsilateral and bilateral lung V_5Gy-45Gy, and between MLD and bilateral lung V_5Gy-45Gy values in 2-FRT. Only four patients developed symptomatic RP, 4 with 4-FRT and one with 2-FRT.

Conclusion

The conformal plan parameters were strongly correlated with dose-volume parameters for breast 2-FRT. With only 4 cases of Grade 3 RP observed, our study is limited in its ability to provide definitive guidance, however assuming that CLD is an indicator for RP, V_20Gy could be used as a predictor for RP and for 2-FRT. A well-defined parameters are still required to predict RP in 4-FRT.

Mature results of a phase II trial on individualised accelerated radiotherapy based on normal tissue constraints in concurrent chemo-radiation for stage III non-small cell lung cancer

BACKGROUND

Sequential chemotherapy and individualised accelerated radiotherapy (INDAR) has been shown to be effective in non-small cell lung cancer (NSCLC), allowing delivering of high biological doses. We therefore performed a phase II trial (clinicaltrials.gov; NCT00572325) investigating the same strategy in concurrent chemo-radiation in stage III NSCLC.

METHODS

137 stage III patients fit for concurrent chemo-radiation (PS 0-2; FEV(1) and DLCO ≥ 30%) were included from April 2006 till December 2009. An individualised prescribed dose based on normal tissue dose constraints was applied: mean lung dose (MLD) 19 Gy, spinal cord 54 Gy, brachial plexus 66 Gy, central structures 74 Gy. A total dose between 51 and 69 Gy was delivered in 1.5 Gy BID up to 45 Gy, followed by 2 Gy QD. Radiotherapy was started at the 2nd or 3rd course of chemotherapy. Primary end-point was overall survival (OS) and secondary end-point toxicity common terminology criteria for adverse events v3.0 (CTCAEv3.0).

FINDINGS

The median tumour volume was 76.4 ± 94.1 cc; 49.6% of patients had N2 and 32.1% N3 disease. The median dose was 65.0 ± 6.0 Gy delivered in 35 ± 5.7 days. Six patients (4.4%) did not complete radiotherapy. With a median follow-up of 30.9 months, the median OS was 25.0 months (2-year OS 52.4%). Severe acute toxicity (≥ G3, 35.8%) consisted mainly of G3 dysphagia during radiotherapy (25.5%). Severe late toxicity (≥ G3) was observed in 10 patients (7.3%).

INTERPRETATION

INDAR in concurrent chemo-radiation based on normal tissue constraints is feasible, even in patients with large tumour volumes and multi-level N2-3 disease, with acceptable severe late toxicity and promising 2-year survival.

Results of proton beam therapy without concurrent chemotherapy for patients with unresectable stage III non-small cell lung cancer

INTRODUCTION

This study was performed retrospectively to evaluate the outcome of patients with stage III non-small cell lung cancer (NSCLC) after proton beam therapy (PBT) alone.

METHODS

The subjects were 57 patients with histologically confirmed NSCLC (stage IIIA/IIIB: 24/33) who received PBT without concurrent chemotherapy. The cohort included 32 cases of squamous cell carcinoma, 18 adenocarcinoma, and 7 non-small cell carcinoma. Lymph node metastases were N0 7, N1 5, N2 30, and N3 15. Planned total doses ranged from 50 to 84.5 GyE (median, 74 GyE).

RESULTS

Planned treatment was completed in 51 patients (89%). At the time of analysis, 20 patients were alive, and the median follow-up periods were 16.2 months for all patients and 22.2 months for survivors. The median overall survival period was 21.3 months (95% confidence interval: 14.2-28.4 months), and the 1- and 2-year overall survival rates were 65.5% (52.9-78.0%) and 39.4% (25.3-53.5%), respectively. Disease progression occurred in 38 patients, and the 1- and 2-year progression-free survival rates were 36.2% (23.1-49.4%) and 24.9% (12.7-37.2%), respectively. Local recurrence was observed in 13 patients, and the 1- and 2-year local control rates were 79.1% (66.8-91.3%) and 64.1% (47.5-80.7%), respectively. Grade ≥ 3 lung toxicity was seen in six patients, esophageal toxicity occurred at grade ≤ 2, and there was no cardiac toxicity.

CONCLUSION

The prognosis of patients with unresectable stage III NSCLC is poor without chemotherapy. Our data suggest that high-dose PBT is beneficial and tolerable for these patients.

High-dose conformal radiotherapy for patients with stage III non-small-cell lung carcinoma

PURPOSE

To determine the effectiveness of high-dose conformal radiotherapy to the involved field for patients with Stage III non-small-cell lung cancer (NSCLC).

METHODS AND MATERIALS

Between May 1999 and April 2006, a total of 100 consecutive patients with inoperable Stage IIIA or IIIB NSCLC with a performance score of 0 to 2 and treatment by radical radiotherapy combined with chemotherapy were included. Up to August 2002, 33 patients underwent conventional radiotherapy of 56 Gy to 66 Gy using anteroposterior opposite ports to the primary tumor and elective lymph nodes (conventional group). After September 2002, the remaining 67 patients underwent high-dose radiotherapy of 66 Gy to 84 Gy to the involved volume with three-dimensional (3-D) conformal radiotherapy (conformal group).

RESULTS

The median survival was 13.2 months (95% confidence interval [CI], 7.5-18.5 months) in the conventional group and 17.3 months (95% CI, 10.7- 24.0 months) in the conformal group. The overall survival at 3 years were 9.1% (95% CI, -0.7-18.9%) in the conventional group and 31.0% (95% CI, 18.9-43.1%) in the conformal group; the conformal group had a significantly better overall survival (p < 0.05). The radiotherapy method (hazard ratio = 0.55, p < 0.05) and performance status (hazard ratio = 1.48, p < 0.05) were shown to be statistically significant independent prognostic factors.

CONCLUSIONS

Based on the practical experience reported here, 3-D conformal radiotherapy allowed dose escalation without excessive toxicity, and may improve overall survival rates for patients with Stage III NSCLC.

21 years of biologically effective dose

In 1989 the British Journal of Radiology published a review proposing the term biologically effective dose (BED), based on linear quadratic cell survival in radiobiology. It aimed to indicate quantitatively the biological effect of any radiotherapy treatment, taking account of changes in dose-per-fraction or dose rate, total dose and (the new factor) overall time. How has it done so far? Acceptable clinical results have been generally reported using BED, and it is in increasing use, although sometimes mistaken for "biologically equivalent dose", from which it differs by large factors, as explained here. The continuously bending nature of the linear quadratic curve has been questioned but BED has worked well for comparing treatments in many modalities, including some with large fractions. Two important improvements occurred in the BED formula. First, in 1999, high linear energy transfer (LET) radiation was included; second, in 2003, when time parameters for acute mucosal tolerance were proposed, optimum overall times could then be "triangulated" to optimise tumour BED and cell kill. This occurs only when both early and late BEDs meet their full constraints simultaneously. New methods of dose delivery (intensity modulated radiation therapy, stereotactic body radiation therapy, protons, tomotherapy, rapid arc and cyberknife) use a few large fractions and obviously oppose well-known fractionation schedules. Careful biological modelling is required to balance the differing trends of fraction size and local dose gradient, as explained in the discussion "How Fractionation Really Works". BED is now used for dose escalation studies, radiochemotherapy, brachytherapy, high-LET particle beams, radionuclide-targeted therapy, and for quantifying any treatments using ionising radiation.

Mature results of an individualized radiation dose prescription study based on normal tissue constraints in stages I to III non-small-cell lung cancer

PURPOSE

We previously showed that individualized radiation dose escalation based on normal tissue constraints would allow safe administration of high radiation doses with low complication rate. Here, we report the mature results of a prospective, single-arm study that used this individualized tolerable dose approach.

PATIENTS AND METHODS

In total, 166 patients with stage III or medically inoperable stage I to II non-small-cell lung cancer, WHO performance status 0 to 2, a forced expiratory volume at 1 second and diffusing capacity of lungs for carbon monoxide >or= 30% were included. Patients were irradiated using an individualized prescribed total tumor dose (TTD) based on normal tissue dose constraints (mean lung dose, 19 Gy; maximal spinal cord dose, 54 Gy) up to a maximal TTD of 79.2 Gy in 1.8 Gy fractions twice daily. Only sequential chemoradiation was administered. The primary end point was overall survival (OS), and the secondary end point was toxicity according to Common Terminology Criteria of Adverse Events (CTCAE) v3.0.

RESULTS

The median prescribed TTD was 64.8 Gy (standard deviation, +/- 11.4 Gy) delivered in 25 +/- 5.8 days. With a median follow-up of 31.6 months, the median OS was 21.0 months with a 1-year OS of 68.7% and a 2-year OS of 45.0%. Multivariable analysis showed that only a large gross tumor volume significantly decreased OS (P < .001). Both acute (grade 3, 21.1%; grade 4, 2.4%) and late toxicity (grade 3, 4.2%; grade 4, 1.8%) were acceptable.

CONCLUSION

Individualized prescribed radical radiotherapy based on normal tissue constraints with sequential chemoradiation shows survival rates that come close to results of concurrent chemoradiation schedules, with acceptable acute and late toxicity. A prospective randomized study is warranted to further investigate its efficacy.

Nonresected non-small-cell lung cancer in Stages I through IIIB: accelerated, twice-daily, high-dose radiotherapy--a prospective Phase I/II trial with long-term follow-up

PURPOSE

Our purpose was to investigate the tolerability of accelerated, twice-daily, high-dose radiotherapy. The secondary endpoints were survival and locoregional tumor control.

METHODS AND MATERIALS

Thirty consecutive patients with histologically/cytologically proven non-small-cell lung cancer were enrolled. Tumor Stage I, II, IIIA, and IIIB was found in 7, 3, 12, and 8 patients, respectively. We applied a median of 84.6 Gy (range, 75.6-90.0 Gy) to the primary tumors, 63.0 Gy (range, 59.4-72.0 Gy) to lymph nodes, and 45 Gy to nodes electively (within a region of about 6 cm cranial to macroscopically involved sites). Fractional doses of 1.8 Gy twice daily, with an interval of 11 hours, were given, resulting in a median treatment time of 35 days. In the majority of patients the conformal target-splitting technique was used. In 19 patients (63%) two cycles of induction chemotherapy were given. The median follow-up time of survivors is 72 months (range, 62-74 months).

RESULTS

We found Grade 1, 2 and 3 acute esophageal toxicity in 11 patients (37%), 2 patients (7%), and 2 patients (7%), respectively. Grade 2 acute pneumonitis was seen in 2 patients (7%). No late toxicity greater than Grade 1 was observed. The actual overall survival rates at 2 and 5 years are 63% and 23%, respectively; the median overall survival, 27.7 months. In 9 patients a local failure occurred, 7 of them presenting initially with an atelectasis without availability of 18-fluorodeoxyglucose-positron emission tomography staging at that time. In 4 patients recurrence occurred regionally.

CONCLUSIONS

This Phase I/II trial with long-term follow-up shows low toxicity with promising results for survival and locoregional tumor control.

Late complications of high-dose (>/=66 Gy) thoracic conformal radiation therapy in combined modality trials in unresectable stage III non-small cell lung cancer

BACKGROUND

Combined modality treatment is the standard of care for patients (pts) with unresectable stage III non-small cell lung cancer. Dose escalation of radiotherapy is one strategy used to improve locoregional control and survival, but it increases the risk of both early and late treatment related toxicities.

METHODS

From May 1996 to August 2004, a total of 112 stage III non-small cell lung cancer pts were treated on 4 phase I/II or phase II trials to assess the safety and feasibility of high-dose (60-90 Gy) thoracic conformal radiotherapy. Patients who received >/=66 Gy (n = 88) were included in an analysis of late complications. Late complications were defined as complications that developed or persisted >/=90 days postradiotherapy. The classic lung toxicities of radiation pneumonitis and fibrosis were not included in this analysis.

RESULTS

Of the 88 patients included in this analysis of late complications, 21 patients (24%) developed a late complication and a total of 28 late complications were observed. The late complications were: pulmonary (n = 5; bronchial stenosis [n = 3] and fatal pulmonary hemoptysis [n = 2]), esophageal (n = 6), cardiac (n = 9), osseous (n = 6), and second primary tumor (n = 2). The median survival for all patients enrolled on the 4 trials (with 95% confidence interval [CI]) was 24.7 months (18.1-30.4 months), and the 5-year overall survival (with 95% CI) was 24% (16-32%). Data to assess for radiographic evidence of local progression were available for 99 patients, and the rate of local progression was 43% (95% CI 34-53%).

CONCLUSIONS

High-dose thoracic conformal radiotherapy is feasible and results in promising survival outcomes. Late complications occur in a minority of patients.

Systematic review of dose-volume parameters in the prediction of esophagitis in thoracic radiotherapy

PURPOSE

With dose escalation and increasing use of concurrent chemoradiotherapy, radiation esophagitis (RE) remains a common treatment-limiting acute side effect in the treatment of thoracic malignancies. The advent of 3DCT planning has enabled investigators to study esophageal dose-volume histogram (DVH) parameters as predictors of RE. The purpose of this study was to assess published dosimetric parameters and toxicity data systematically in order to define reproducible predictors of RE, both for potential clinical use, and to provide recommendations for future research in the field.

MATERIALS AND METHODS

We performed a systematic literature review of published studies addressing RE in the treatment of lung cancer and thymoma. Our search strategy included a variety of electronic medical databases, textbooks and bibliographies. Both prospective and retrospective clinical studies were included. Information relating to the relationship among measured dosimetric parameters, patient demographics, tumor characteristics, chemotherapy and RE was extracted and analyzed.

RESULTS

Eighteen published studies were suitable for analysis. Eleven of these assessed acute RE, while the remainder assessed both acute and chronic RE together. Heterogeneity of esophageal contouring practices, individual differences in information reporting and variability of RE outcome definitions were assessed. Well-described clinical and logistic modeling directly related V(35Gy), V(60Gy) and SA(55Gy) to clinically significant RE.

CONCLUSIONS

Several reproducible dosimetric parameters exist in the literature, and these may be potentially relevant in the prediction of RE in the radiotherapy of thoracic malignancies. Further clarification of the predictive relationship between such standardized dosimetric parameters and observed RE outcomes is essential to develop efficient radiation treatment planning in locally advanced NSCLC in the modern concurrent chemotherapy and image-guided IMRT era.

Individualized radical radiotherapy of non-small-cell lung cancer based on normal tissue dose constraints: a feasibility study

PURPOSE

Local recurrence is a major problem after (chemo-)radiation for non-small-cell lung cancer. We hypothesized that for each individual patient, the highest therapeutic ratio could be achieved by increasing total tumor dose (TTD) to the limits of normal tissues, delivered within 5 weeks. We report first results of a prospective feasibility trial.

METHODS AND MATERIALS

Twenty-eight patients with medically inoperable or locally advanced non-small-cell lung cancer, World Health Organization performance score of 0-1, and reasonable lung function (forced expiratory volume in 1 second > 50%) were analyzed. All patients underwent irradiation using an individualized prescribed TTD based on normal tissue dose constraints (mean lung dose, 19 Gy; maximal spinal cord dose, 54 Gy) up to a maximal TTD of 79.2 Gy in 1.8-Gy fractions twice daily. No concurrent chemoradiation was administered. Toxicity was scored using the Common Terminology Criteria for Adverse Events criteria. An (18)F-fluoro-2-deoxy-glucose-positron emission tomography-computed tomography scan was performed to evaluate (metabolic) response 3 months after treatment.

RESULTS

Mean delivered dose was 63.0 +/- 9.8 Gy. The TTD was most often limited by the mean lung dose (32.1%) or spinal cord (28.6%). Acute toxicity generally was mild; only 1 patient experienced Grade 3 cough and 1 patient experienced Grade 3 dysphagia. One patient (3.6%) died of pneumonitis. For late toxicity, 2 patients (7.7%) had Grade 3 cough or dyspnea; none had severe dysphagia. Complete metabolic response was obtained in 44% (11 of 26 patients). With a median follow-up of 13 months, median overall survival was 19.6 months, with a 1-year survival rate of 57.1%.

CONCLUSIONS

Individualized maximal tolerable dose irradiation based on normal tissue dose constraints is feasible, and initial results are promising.

[Stage IIIA and IIIB non-small cell lung cancer: results of chemotherapy combined with radiation therapy and analysis of prognostic factors]

OBJECTIVE

Most patients with stage III non-small cell lung cancer (NSCLC) are not candidates for surgery but can benefit from chemotherapy combined with radiation therapy. The objective of the present study was to analyze the results of sequential chemotherapy and radiation therapy and the prognostic value of initial clinical and laboratory variables.

PATIENTS AND METHODS

We carried out a retrospective study of 92 patients with stage III NSCLC treated with a sequential regimen of chemotherapy (carboplatin-etoposide, carboplatin-gemcitabine, and carboplatin-paclitaxel), and radiation therapy (6000 cGy in daily doses of 200 cGy, 5 d/wk). Response to therapy, overall survival, and the prognostic value of epidemiological, clinical, and laboratory variables were evaluated using univariate and multivariate analyses.

RESULTS

Median survival time was 14 months, with a 3-year survival rate of 16.1%. Poor performance status (score of 2 on the Eastern Cooperative Oncologic Group [ECOG] scale), anemia, and elevated serum concentrations of carcinoembryonic antigen were predictive of poorer survival in the multivariate analysis. In the univariate analysis, weight loss and diagnosis before the year 2000 were also associated with poorer prognosis (P<.01). TNM stage was not significantly correlated (P=.08). Toxicity was low, with 1 death and few cases of grade 3 or 4 toxicity according to World Health Organization criteria.

CONCLUSIONS

The use of chemotherapy combined with radiation therapy should be considered contraindicated in cases of poor performance status (ECOG scale score of 2). Weight loss, an elevated serum concentration of carcinoembryonic antigen, and a hemoglobin concentration of 12 g/dL or less carry a poor prognosis.

A neural network model to predict lung radiation-induced pneumonitis

A feed-forward neural network was investigated to predict the occurrence of lung radiation-induced Grade 2+ pneumonitis. The database consisted of 235 patients with lung cancer treated using radiotherapy, of whom 34 were diagnosed with Grade 2+ pneumonitis at follow-up. The network was constructed using an algorithm that alternately grew and pruned it, starting from the smallest possible network, until a satisfactory solution was found. The weights and biases of the network were computed using the error back-propagation approach. Momentum and variable leaning techniques were used to speed convergence. Using the growing/pruning approach, the network selected features from 66 dose and 27 non-dose variables. During network training, the 235 patients were randomly split into ten groups of approximately equal size. Eight groups were used to train the network, one group was used for early stopping training to prevent overfitting, and the remaining group was used as a test to measure the generalization capability of the network (cross-validation). Using this methodology, each of the ten groups was considered, in turn, as the test group (ten-fold cross-validation). For the optimized network constructed with input features selected from dose and non-dose variables, the area under the receiver operating characteristics (ROC) curve for cross-validated testing was 0.76 (sensitivity: 0.68, specificity: 0.69). For the optimized network constructed with input features selected only from dose variables, the area under the ROC curve for cross-validation was 0.67 (sensitivity: 0.53, specificity: 0.69). The difference between these two areas was statistically significant (p = 0.020), indicating that the addition of non-dose features can significantly improve the generalization capability of the network. A network for prospective testing was constructed with input features selected from dose and non-dose variables (all data were used for training). The optimized network architecture consisted of six input nodes (features), four hidden nodes, and one output node. The six input features were: lung volume receiving > 16 Gy (V16), generalized equivalent uniform dose (gEUD) for the exponent a = 1 (mean lung dose), gEUD for the exponent a = 3.5, free expiratory volume in 1 s (FEV1), diffusion capacity of carbon monoxide (DLCO%), and whether or not the patient underwent chemotherapy prior to radiotherapy. The significance of each input feature was individually evaluated by omitting it during network training and gauging its impact by the consequent deterioration in cross-validated ROC area. With the exception of FEV1 and whether or not the patient underwent chemotherapy prior to radiotherapy, all input features were found to be individually significant (p < 0.05). The network for prospective testing is publicly available via internet access.

Predicting lung radiotherapy-induced pneumonitis using a model combining parametric Lyman probit with nonparametric decision trees

PURPOSE

To develop and test a model to predict for lung radiation-induced Grade 2+ pneumonitis.

METHODS AND MATERIALS

The model was built from a database of 234 lung cancer patients treated with radiotherapy (RT), of whom 43 were diagnosed with pneumonitis. The model augmented the predictive capability of the parametric dose-based Lyman normal tissue complication probability (LNTCP) metric by combining it with weighted nonparametric decision trees that use dose and nondose inputs. The decision trees were sequentially added to the model using a "boosting" process that enhances the accuracy of prediction. The model's predictive capability was estimated by 10-fold cross-validation. To facilitate dissemination, the cross-validation result was used to extract a simplified approximation to the complicated model architecture created by boosting. Application of the simplified model is demonstrated in two example cases.

RESULTS

The area under the model receiver operating characteristics curve for cross-validation was 0.72, a significant improvement over the LNTCP area of 0.63 (p = 0.005). The simplified model used the following variables to output a measure of injury: LNTCP, gender, histologic type, chemotherapy schedule, and treatment schedule. For a given patient RT plan, injury prediction was highest for the combination of pre-RT chemotherapy, once-daily treatment, female gender and lowest for the combination of no pre-RT chemotherapy and nonsquamous cell histologic type. Application of the simplified model to the example cases revealed that injury prediction for a given treatment plan can range from very low to very high, depending on the settings of the nondose variables.

CONCLUSIONS

Radiation pneumonitis prediction was significantly enhanced by decision trees that added the influence of nondose factors to the LNTCP formulation.

Therapeutic advances in local-regional therapy for stage III non-small-cell lung cancer: evolving role of dose-escalated conformal (3-dimensional) radiation therapy

Lung cancer is the leading cause of cancer-related death among men and women in the United States. Approximately 80%-85% of lung cancer cases are non-small-cell lung cancer, and approximately 30%-40% of these patients have unresectable stage IIIA/B disease at diagnosis. The standard of care for locally advanced disease in patients with a good performance status consists of combined modality therapy, chemotherapy and radiation therapy (RT). Despite improved survival with combined modality therapy, local-regional recurrences and the development of distant metastases are still problematic. The radiation dose of 60 Gy for inoperable stage III non-small-cell lung cancer, established by Radiation Therapy Oncology Group trials 7301 and 7302, has remained the standard until the present time. More recently, trials suggest that local-regional control can be improved with RT dose escalation, improved tumor targeting (eg, 3-dimensional planning and intensity-modulated RT), and altered RT fractionation. Improvements in local-regional control could translate into an overall survival benefit. This article reviews the rationale for aggressive therapy and techniques to improve local disease control. It also provides an overview of trials that utilize such techniques, with a focus on efficacy, toxicity, and overall survival. Further well-designed clinical trials that examine RT dose escalation, improved tumor targeting, altered fractionation, and incorporation of biologic agents are crucial for progress in this disease.

The impact of induction chemotherapy and the associated tumor response on subsequent radiation-related changes in lung function and tumor response

PURPOSE

To assess the impact of induction chemotherapy, and associated tumor shrinkage, on the subsequent radiation-related changes in pulmonary function and tumor response.

METHODS AND MATERIALS

As part of a prospective institutional review board-approved study, 91 evaluable patients treated definitively with thoracic radiation therapy (RT) for unresectable lung cancer were analyzed. The rates of RT-associated pulmonary toxicity and tumor response were compared in the patients with and without pre-RT chemotherapy. In the patients receiving induction chemotherapy, the rates of RT-associated pulmonary toxicity and tumor response were compared in the patients with and without a response (modified Response Evaluation Criteria in Solid Tumor criteria) to the pre-RT chemotherapy. Comparisons of the rates of improvements in pulmonary function tests (PFTs) post-RT, dyspnea requiring steroids, and percent declines in PFTs post-RT were compared in patient subgroups using Fisher's exact test, analysis of variance, and linear or logistic regression.

RESULTS

The use of pre-RT chemotherapy appears to increase the rate of radiation-induced pneumonitis (p = 0.009-0.07), but has no consistent impact on changes in PFTs. The degree of induction chemotherapy-associated tumor shrinkage is not associated with the rate of subsequent RT-associated pulmonary toxicity. The degree of tumor response to chemotherapy is not related to the degree of tumor response to RT.

CONCLUSIONS

Additional study is needed to better clarify the impact of chemotherapy on radiation-associated disfunction.

Combined modality therapy for stage III non-small cell lung cancer

Lung cancer remains the leading cause of cancer death in the U.S. among both men and women. Approximately 45% of patients present with stage III disease. A proportion of these patients is amenable to surgical resection; however, the majority are "unresectable." For patients with unresectable stage IIIA/B disease, thoracic radiation therapy (TRT) was considered the standard of care until the late 1980s despite a very poor 5-year survival rate. Several clinical trials demonstrated that the combination of chemotherapy and TRT was superior to TRT alone. Based on these data, combined modality therapy became the standard of care for patients with good performance status. Recent trials have shown that concurrent chemoradiotherapy offers a significant survival advantage over sequential chemoradiotherapy. Despite a substantial number of clinical trials, important questions on the optimal treatment paradigm remain. The most effective chemotherapy combination, the use of induction or consolidation chemotherapy in addition to the concurrent portion of therapy, and the optimal dose of chemotherapy with concurrent TRT have yet to be determined. The optimal total dose, fractionation, acceleration, treatment volume, and tumor targeting remain questions related to the TRT portion of therapy. Although significant progress has been made, the majority of patients experience locoregional or distant progression of their disease and die within 5 years of diagnosis. Thus, continued development and participation in clinical trials is crucial to further improvements in the treatment of patients with stage III disease.

The Role of Radiation Therapy in Thoracic Tumors

Radiation plays an important role in the treatment of thoracic tumors. During the last 10 years there have been several major advances in thoracic RT including the incorporation of concurrent chemotherapy and the application of con-formal radiation-delivery techniques (eg, stereotactic RT, three-dimensional conformal RT, and intensity-modulated RT) that allow radiation dose escalation. Radiation as a local measure remains the definitive treatment of medically inoperable or surgically unresectable disease in NSCLC and part of a multimodality regimen for locally advanced NSCLC, limited stage SCLC, esophageal cancer, thymoma, and mesothelioma.

Radiation-induced narrowing of the tracheobronchial tree: An in-depth analysis

PURPOSE

Symptomatic narrowing of the tracheobronchial tree is not a common clinical problem after conventional-dose external beam radiation therapy but has been described when higher doses are utilized. This in-depth study quantifies changes in the caliber of the trachea and mainstem bronchi after high-dose external beam radiation therapy (EBRT).

METHODS AND MATERIALS

As part of an IRB-approved prospective clinical trial to assess for radiation-induced lung injury, patients with thoracic malignancies had pre- and serial post-RT CT scans in the radiation oncology department. This report focuses on 18 enrolled patients who received high-dose (> or = 73.6 Gy) EBRT for NSCLC. The caliber of the trachea, right mainstem bronchus, and left mainstem bronchus were measured utilizing three-dimensional coordinates in axial and coronal planes such that multiple measurements were made of each structure. The decrease in airway caliber was tested for significance using a one-sided Wilcoxon matched-pairs signed-ranks test. The correlation between airway caliber changes, dose, and follow-up interval was tested using the Spearman rank correlation coefficient and the effect of chemotherapy on airway narrowing was evaluated with a one-sided exact Wilcoxon rank sum test.

RESULTS

There was no significant narrowing of the trachea for all dose and time points. There were significant decreases in the caliber of both mainstem bronchi on axial measurements (p = 0.07 and 0.005 for right and left mainstem bronchi, respectively). Decrease in airway caliber ranged from 6 to 57% and appeared to be dose dependent (p = 0.08), progressed with increasing time post-RT (p = 0.04), and was worse in patients who also received chemotherapy (p = 0.04).

CONCLUSION

High-dose EBRT (> or = 73.6 Gy) appears to cause narrowing of the mainstem bronchi as early as 3 months post radiation therapy. Additional study is needed to assess the impact of such narrowing on RT-induced pulmonary symptoms.

Response to combined modality therapy correlates with survival in locally advanced non–small-cell lung cancer

PURPOSE

Although concurrent chemoradiotherapy can now achieve demonstrated long-term survival in patients with locally advanced non-small-cell lung cancer (LANSCLC), it is difficult to predict which patients will benefit most from this therapeutic approach. Studies have suggested that local control, and the response to therapy, may be linked to improved survival; however, detailed analysis of the impact of tumor response to chemoradiotherapy on survival has not been thoroughly reported. Therefore, we sought to determine the impact of the response rate on survival for patients who were treated with combined modality therapy for LANSCLC.

METHODS AND MATERIALS

We reviewed the data from 116 patients enrolled between 1994 and 1997 in three trials investigating paclitaxel-based concurrent chemoradiotherapy for LANSCLC. Tumor size measurements were assessed immediately before and 2 months after completion of combined modality therapy to determine the response and to calculate the percentage of decrease in tumor size.

RESULTS

Patients with a response (complete or partial) had an improved 4-year overall survival rate compared with patients with no response (stable or progressive disease; 21.1% vs. 3.3%, p <0.0001) in the 109 assessable patients. Progression-free survival also improved significantly with response. An analysis of the percentage of decrease in tumor size vs. survival was performed (n = 74) using Cox proportion model analysis. After combined modality therapy, a 20%, 40%, 60%, 80%, and 100% decrease in tumor size conferred a 39%, 63%, 78%, 86%, and 92% reduction in risk of death compared with a 0% decrease in tumor size (p <0.0001).

CONCLUSION

The response by conventional response criteria correlated strongly with improved overall survival and progression-free survival and an increasing percentage of decrease in tumor size resulted in a reduction in the risk of death. Additional investigation of the degree of response as a factor predictive of improved therapeutic efficacy, translating into improved survival, is warranted.

Dose-Intensive Thoracic Radiation Therapy for Patients at High Risk with Early-Stage Non–Small-Cell Lung Cancer

Recent studies suggest that radiation therapy (RT) dose escalation in early-stage non-small-cell lung cancer (NSCLC) is feasible when 3-dimensional therapy is used. However, the accompanying prolongation of the treatment course when standard fractionation is used could be suboptimal from a practical and biologic standpoint. We report results of a compressed course of RT for patients with pathologically documented clinical stage 1 NSCLC who were unsuitable for curative surgery because of pulmonary dysfunction or other medical comorbidities. Thirty-one lesions were treated with dose-intensive RT (eg, fraction>or=2.25 Gy and nominal total dose>or=60 Gy) and have been followed up for >or=6 months from the completion of treatment. All patients completed therapy without interruption. Three patients developed grade 3 pulmonary toxicity 1-3 months after therapy. The overall tumor response rate was 88% (35% complete response and 53% partial response), whereas in-field tumor progression was documented for 5 of 31 lesions. Actuarial median survival was 38 months and 3-year overall survival was 60%, and most deaths were secondary to intercurrent disease. Moderately accelerated single daily fractionated RT is feasible for high-risk patients with early-stage NSCLC and merits further investigation.

Phase III study of the Eastern Cooperative Oncology Group (ECOG 2597): induction chemotherapy followed by either standard thoracic radiotherapy or hyperfractionated accelerated radiotherapy for patients with unresectable stage IIIA and B non-small-cell lung cancer

PURPOSE

To compare once-daily radiation therapy (qdRT) with hyperfractionated accelerated radiation therapy (HART) after two cycles of induction chemotherapy.

PATIENTS AND METHODS

Eligible patients were treatment naive, and had stage IIIA and B unresectable non-small-cell lung cancer, Eastern Cooperative Oncology Group performance status 0/1, and normal organ function. Induction chemotherapy consisted of two cycles of carboplatin area under time-concentration curve 6 mg/mL . min plus paclitaxel 225 mg/m2 on day 1. RT consisted of arm 1 (qdRT), 64 Gy (2 Gy/d), versus arm 2 (HART), 57.6 Gy (1.5 Gy tid for 2.5 weeks). A total of 388 patients were needed to detect a 50% increase in median survival from 14 months of qdRT to 21 months of HART; accrual was not achieved and the study closed prematurely.

RESULTS

Of 141 patients enrolled, 83% were randomly assigned after chemotherapy to qdRT (n = 59) or HART (n = 60). Median survival was 20.3 and 14.9 months for HART and qdRT, respectively (P = .28). Overall response was 25% and 22% for HART and qdRT, respectively (P = .69). Two- and 3-year survival was 44% and 34% for HART, and 24% and 14% for qdRT, respectively. Grade > or = 3 toxicities included esophagitis in 14 v nine patients, and pneumonitis in 0 v 6 patients for HART and qdRT, respectively. Any subsequent trials of the HART regimen must address the issues that led to early closure, including slow accrual, logistics of HART, mucosal toxicity, and the fact that concurrent chemoradiotherapy now seems more effective than sequential treatment.

CONCLUSION

After two cycles of induction chemotherapy with carboplatin-paclitaxel, HART is feasible with an acceptable toxicity profile. Although statistical significance was not achieved and the study closed early, there was a positive statistical trend suggesting a survival advantage with the HART regimen.

Dosimetric and clinical predictors for radiation-induced esophageal injury

PURPOSE

To evaluate the clinical and three-dimensional dosimetric parameters associated with esophageal injury after radiotherapy (RT) for non-small-cell lung cancer.

METHODS AND MATERIALS

The records of 254 patients treated for non-small-cell lung cancer between 1992 and 2001 were reviewed. A variety of metrics describing the esophageal dose were extracted. The Radiation Therapy Oncology Group toxicity criteria for grading of esophageal injury were used. The median follow-up time for all patients was 43 months (range, 0.5-120 months). Logistic regression analysis, contingency table analyses, and Fisher's exact tests were used for statistical analysis.

RESULTS

Acute toxicity occurred in 199 (78%) of 254 patients. For acute toxicity of Grade 2 or worse, twice-daily RT, age, nodal stage of N2 or worse, and most dosimetric parameters were predictive. Late toxicity occurred in 17 (7%) of 238 patients. The median and maximal time to the onset of late toxicity was 5 and 40 months after RT, respectively. Late toxicity occurred in 2%, 3%, 17%, 26%, and 100% of patients with acute Grade 0, 1, 2, 3, and 4 toxicity, respectively. For late toxicity, the severity of acute toxicity was most predictive.

CONCLUSION

A variety of dosimetric parameters are predictive of acute and late esophageal injury. A strong correlation between the dosimetric parameters prevented a comparison between the predictive abilities of these metrics. The presence of acute injury was the most predictive factor for the development of late injury. Additional studies to define better the predictors of RT-induced esophageal injury are needed.

Can the use of amifostine improve cure rates for patients with advanced non-small cell lung cancer?

Concurrent chemoradiation, probably plus systemic chemotherapy, currently offers the best treatment strategy in stage IIIA/IIIB non-small cell lung cancer. However, such approaches do not control local disease well, perhaps because of inadequate radiation dose. While few studies have explored higher than standard radiation doses (ie, 60 Gy), the major fear is that higher doses increase patient morbidity without improving cure rates. A University of North Carolina (Chapel Hill, NC) phase I/II trial suggests that at least 74 Gy can be given safely to patients with cytotoxic drugs, with a suggestion of improved survival. Moreover, other trial data have suggested that the cytoprotective and radioprotective agent amifostine can be used to reduce esophagitis and possibly pneumonitis in patients treated with conventional radiation doses. We describe herein a proposed clinical trial designed to test: (1) the hypothesis that higher radiation doses can lead to a survival advantage in patients with non-small cell lung cancer, and (2) the value of amifostine as a cytoprotective agent in the high-radiation dose range.

Bronchial stenosis: An underreported complication of high-dose external beam radiotherapy for lung cancer?

PURPOSE

To assess the incidence of clinically significant bronchial stenosis in patients treated with high doses (i.e., >70 Gy) of twice-daily external beam radiation therapy (RT).

METHODS AND MATERIALS

The outcomes of 103 patients with unresectable non-small-cell lung cancer, treated twice daily to doses ranging from 7080 to 8640 cGy between 1992 and 2001, were analyzed. Most were treated on prospective clinical trials. For the dose-effect comparison, the patients were divided on the basis of the total dose: 67 received 74 Gy (range, 70.8-74.5 Gy; median, 73.6 Gy), 20 received 80 Gy, and 16 received 86 Gy (range, 85.2-86.4 Gy; median, 86.4 Gy). Sixty-six patients received sequential chemotherapy before RT. RT-induced bronchial stenosis was defined as symptomatic airway narrowing diagnosed by bronchoscopy or computed tomography scan without evidence of recurrent tumor in that region.

RESULTS

Eight patients developed RT-induced, clinically significant, bronchial stenosis 2-48 months (median, 6 months) after RT. The 1-year and 4-year actuarial rate of stenosis was 7% and 38%, respectively. The median overall survival was 2.5 years (5 of 8 were alive at the writing of this report). A suggestion was also found of a dose-response effect with external beam radiotherapy-induced stenosis, with a rate of 4% and 25% at a dose of approximately 74 Gy and 86 Gy, respectively.

CONCLUSION

Radiation therapy-induced bronchial stenosis is a significant clinical complication of dose escalation for lung cancer. This complication has been previously mentioned in the literature, but ours is the largest report to date, and the findings suggest that the risk rises with increasing dose. It is likely that this process would manifest in more patients if their disease were controlled well enough for more prolonged survival.

How can we further improve radiotherapy for stage-III non-small-cell lung cancer?

Combined modality treatment in advanced NSCLC has produced some gain in treatment outcome. Local control as addressed by radiotherapy is still a significant site of failure. Doses higher than achieved by conventional conformal radiotherapy are shown to result in better control rates. Volume restriction seems to be the most important issue in dose escalation. Integration of PET imaging into target definition, omission of clinically uninvolved lymph-node areas and measures to decrease set-up and movement uncertainties are explored. Introduction of risk estimation based on dose-volume analysis for dose prescription may further optimise individual treatment.

Induction and concurrent chemotherapy with high-dose thoracic conformal radiation therapy in unresectable stage IIIA and IIIB non-small-cell lung cancer: a dose-escalation phase I trial

PURPOSE

Local control rates at conventional radiotherapy doses (60 to 66 Gy) are poor in stage III non-small-cell lung cancer (NSCLC). Dose escalation using three-dimensional thoracic conformal radiation therapy (TCRT) is one strategy to improve local control and perhaps survival.

PATIENTS AND METHODS

Stage III NSCLC patients with a good performance status (PS) were treated with induction chemotherapy (carboplatin area under the curve [AUC] 5, irinotecan 100 mg/m(2), and paclitaxel 175 mg/m(2) days 1 and 22) followed by concurrent chemotherapy (carboplatin AUC 2 and paclitaxel 45 mg/m(2) weekly for 7 to 8 weeks) beginning on day 43. Pre- and postchemotherapy computed tomography scans defined the initial clinical target volume (CTV(I)) and boost clinical target volume (CTV(B)), respectively. The CTV(I) received 40 to 50 Gy; the CTV(B) received escalating doses of TCRT from 78 Gy to 82, 86, and 90 Gy. The primary objective was to escalate the TCRT dose from 78 to 90 Gy or to the maximum-tolerated dose.

RESULTS

Twenty-nine patients were enrolled (25 assessable patients; median age, 59 years; 62% male; 45% stage IIIA; 38% PS 0; and 38% > or = 5% weight loss). Induction CIP was well tolerated (with filgrastim support) and active (partial response rate, 46.2%; stable disease, 53.8%; and early progression, 0%). The TCRT dose was escalated from 78 to 90 Gy without dose-limiting toxicity. The primary acute toxicity was esophagitis (16%, all grade 3). Late toxicity consisted of grade 2 esophageal stricture (n = 3), bronchial stenosis (n = 2), and fatal hemoptysis (n = 2). The overall response rate was 60%, with a median survival time and 1-year survival probability of 24 months and 0.73 (95% CI, 0.55 to 0.89), respectively. CONCLUSION Escalation of the TCRT dose from 78 to 90 Gy in the context of induction and concurrent chemotherapy was accomplished safely in stage III NSCLC patients.

A challenge to traditional radiation oncology

PURPOSE

To investigate and compare the biologically effective doses, equivalent doses in 2-Gy fractions, log tumor cells killed, and late effects that can be estimated for the large fractions in short overall times that are now being delivered in various clinically used schedules in several countries for the treatment of cancer in human lungs, liver, and kidney.

METHODS AND MATERIALS

Linear quadratic (LQ) modeling is employed with only the standard assumptions that tumor alpha/beta ratio is 10 Gy, pneumonitis and late complication alpha/beta ratios are 3 Gy, that intrinsic radiosensitivity of tumor cells is 0.35 ln/Gy, that no tumor repopulation occurs within 2 weeks, and that LQ modeling is valid up to 23 Gy per fraction. As well as the planning target volume (PTV), we propose a practical term called the prescription isodose volume (PIV) to be used in this discussion. In the ideal case of 100% conformity, PIV equals PTV, but usually PIV is larger than the PTV. Biologically effective doses (BED) in Gy(10) for tumors or Gy(3) for normal lung are calculated and converted to equivalent doses in 2 Gy fractions (= normalized total doses [NTD]), and to estimated log cell kill. How such large biologic doses might be delivered to tissues is discussed.

RESULTS

Tumor cell kill varies between 16 and 27 logs to base 10 for schedules from 4F x 12 Gy to 3F x 23 Gy. The rationale for the high end of this scale is the possible presence of hypoxic or otherwise extraordinarily resistant cells, but how many tumors and which ones require such doses is not known. How can such large doses be tolerated? In "parallel type organs," it is shown to be theoretically possible, provided that suitably small volumes are irradiated, with rapid fall-off of dose outside the PTV, and a mean dose (excluding PTV and allowing for local fraction size) to both lungs of less than 19 Gy NTD. If suitably small PTVs were used, local late BEDs have been given which were as large as 600 Gy(3), equivalent to 2 Gy x 180F = 360 Gy in 2-Gy fractions, with remarkably few complications reported clinically. Questions of concurrent chemotherapy and microscopic extension of lung tumor cells are discussed briefly.

CONCLUSIONS

Such large doses can apparently be given, with suitable precautions and experience. Ongoing clinical trials from an increasing number of centers will be reporting the results of tumor control and complications from this new modality of biologically higher doses.

Vinorelbine plus low-dose cisplatinum with concomitant radiotherapy for the treatment of locally advanced or inoperable non-metastasized non-small-cell lung cancer (stage I–IIIB): a phase II study

In a phase II study, we assessed the toxicity and efficacy of daily low-dose cisplatin (6 mg/m2) and weekly vinorelbine (15 mg/m2) with concurrent thoracic irradiation (60 Gy) for locally advanced non-metastasized non-small-cell lung cancer. The overall response rate was 65%, complete response 12% and the median overall survival was 64 weeks.

Carboplatin/Paclitaxel or Carboplatin/Vinorelbine Followed by Accelerated Hyperfractionated Conformal Radiation Therapy: Report of a Prospective Phase I Dose Escalation Trial From the Carolina Conformal Therapy Consortium

Purpose

To prospectively determine the maximum-tolerated dose of accelerated hyperfractionated conformal radiotherapy (RT; 1.6 Gy bid) for unresectable locally advanced lung cancer (IIB to IIIA/B) following induction carboplatin/paclitaxel (C/T) or carboplatin/vinorelbine (C/N).

Methods

Induction chemotherapy, C/T or C/N, was followed by escalating doses of conformally-planned RT (73.6 to 86.4 Gy in 6.4-Gy increments). Concurrent boost methods delivered 1.6 and 1.25 Gy bid to the gross and clinical target volumes, respectively.

Results

Between November 1997 and February 2002, 44 patients were enrolled (median age, 59 years; 59% male; stage III, 98%; median tumor size, 4 cm). Thirty-nine patients completed induction chemotherapy: 19 had a partial response, seven progressed, 15 had no response, and three were not assessable. Chemotherapy-associated toxicities were similar in the two chemotherapy groups. The incidence of grade ≥ 3 RT-induced toxicity was 1/13, 2/14, and 4/12 at 73.6, 80, and 86.4 Gy, respectively, thus defining the maximum tolerated dose at ≈80 Gy. Toxicities were in both lung and esophagus and were similar in the two chemotherapy arms. With a median followup of 34 months in the survivors, the actuarial 2-year survival was 47%, the median survival was 18 months. Fifteen patients had tumor relapse: 5 local failures in the high-dose volume, 2 regional failures outside of the high-dose volume, and 8 distant metastases.

Conclusion

High-dose conformal twice-daily radiation therapy to approximately 80 Gy appears tolerable in well-selected patients with unresectable lung cancer following either C/T or C/N. Dose-limiting toxicities are mainly pulmonary and esophageal.

Treatment planning for dose escalation in non-small cell lung cancer (NSCLC)

This study was performed to examine potential field arrangements for irradiating non-small cell lung cancer (NSCLC) on a dose escalation study. An example patient was chosen and 7 coplanar treatment plans were created to treat a NSCLC. Two plans included prophylactic nodal irradiation (PNRT) and 5 did not. Four plans used 4 fields, 2 plans used 5 fields, and 1 plan included dynamic conformal 360 degrees rotational therapy. All plans delivered 80 Gy to the isocenter with 10-MV x-rays. Each plan was initially created without dose inhomogeneity corrections and then was recalculated with these corrections, maintaining the same weighting and number of monitor units. Avoiding PNRT spared a considerable volume of normal tissue from radiation. Plans with 5 fields generally spared normal tissues better than 4-field plans. There was no benefit to the dynamic conformal 360 degrees rotational plan. Inhomogeneity corrections revealed that higher doses were delivered to both the tumor and normal structures. Seven beam arrangements for the treatment of NSCLC were compared to develop potential beam arrangements that would be applicable to treating NSCLC on a multi-institutional dose escalation study. We favor the use of at least 5 beams in most situations. It is possible that the use of more fields would further improve plans up to a point of diminishing returns, as exemplified by the lack of benefit seen with the dynamic conformal 360 degrees rotational plan. It is possible that the use of noncoplanar fields or intensity-modulated radiation therapy (IMRT) may further improve the therapeutic ratio.

Normal-tissue toxicities of thoracic radiation therapy: esophagus, lung, and spinal cord as organs at risk

The evolution of therapeutic approaches for lung cancer illustrates the trend for treatment intensification, with hopes that dose-intense chemotherapy regimens, higher radiation therapy (RT) doses, or novel fractionation schemes will result in prolongation of survival. Current chemotherapy- and RT-intense regimens may not be intensified further without addressing dose-limiting toxicities such as esophagitis. It is important to understand factors pre-disposing to esophagitis so that strategies to minimize its severity can be investigated. Pulmonary complications such as pneumonitis and fibrosis from RT (with or without chemotherapy) are dose and volume dependent. Methods to better identify the target tissues and improved RT-delivery systems may facilitate increasing target doses or reducing doses to adjacent normal tissues. Biologic predictors may allow clinicians in the future to individualize RT treatment based on a patient's toxicity risk profile. Radiation myelopathy is still the most feared radiation complication of lung cancer treatment. The authors address the known parameters that influence the incidence of thoracic radiation myelopathy and the putative factors that could be considered when a clinician may be required to push the spinal cord dose in favor of tumor control.

Digital fluoroscopy to quantify lung tumor motion: potential for patient-specific planning target volumes

PURPOSE

To apply digital fluoroscopy integrated with CT simulation to measure lung tumor motion and aid in the quantification of individualized planning target volumes.

METHODS AND MATERIALS

A flat panel digital fluoroscopy unit was modified and integrated with a CT simulator. The stored fluoroscopy images were overlaid with digitally reconstructed radiographs, allowing measurement of the observed lung tumor motion in relation to the corresponding contours on the static digitally reconstructed radiographs. CT simulation and digital fluoroscopy was performed on 10 patients with non-small-cell lung cancer. Actual tumor motion was measured in three dimensions using the overlaid images.

RESULTS

Combining the dynamic data with digitally reconstructed radiographs allowed the tumor shadow from the fluoroscopy to be tracked in relation to the CT lung tumor contour. For all patients, the extent of tumor motion in three dimensions was unique. The motion was greatest in the superoinferior direction and minimal in the AP and lateral directions.

CONCLUSION

We have developed a tool that allows CT simulation to be combined with digital fluoroscopy. Quantitative evaluation of the tumor motion in relation to the CT plan allows for customization of the planning target volume. The variability observed clearly demonstrates the need to generate patient-specific internal motion margins.

Risk of long-term complications after TFG-beta1-guided very-high-dose thoracic radiotherapy

PURPOSE

To report the incidence of late complications in long-term survivors of very-high-dose thoracic radiotherapy (RT) treated on a prospective clinical trial.

METHODS AND MATERIALS

Patients with locally advanced or medically inoperable non-small-cell lung cancer received three-dimensional conformal RT to the primary tumor and radiographically involved lymph nodes to a dose of 73.6 Gy at 1.6 Gy twice daily. If the plasma transforming growth factor-beta1 (TGF-beta1) level was normal after 73.6 Gy, additional twice-daily RT was delivered to successively higher total doses until the maximal tolerated dose was reached. Patients within a given dose level were followed for 6 months before escalation to the next dose level was permitted. Late complications were defined according to Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria.

RESULTS

Thirty-eight patients were enrolled between 1996 and 1999. Twenty-four patients were not eligible for radiation dose escalation beyond 73.6 Gy because of persistently abnormal TGF-beta1 levels. Fourteen patients received dose escalation (80 Gy in 8; 86.4 Gy in 6). Grade 3 or greater late complications occurred in 4 of 24, 1 of 8, and 2 of 6 patients treated to 73.6, 80, and 86.4 Gy, respectively. The corresponding patient numbers with late Grade 4-5 toxicity were 3 of 24, 0 of 6, and 0 of 8. Overall, 7 (18%) of the 38 patients developed Grade 3-5 late toxicity. Nonpulmonary complications predominated (4 of 7). Five (71%) of seven serious complications developed within 11 months after RT; however, the remaining two complications (29%) occurred very late (at 43 and 62 months). The 5-year actuarial risk of late Grade 3-5 complications was 33%.

CONCLUSION

Long-term survivors of very-high-dose RT for non-small-cell lung cancer have a significant risk of severe treatment-related complications. At these high dose levels, the predominant toxicity may no longer be pulmonary. All Grade 4-5 complications occurred in patients whose dose was limited to 73.6 Gy because of a persistently elevated TGF-beta1. Thus, persistently elevated plasma TGF-beta1 levels toward the end of RT may identify patients at greatest risk of severe complications.

Accelerated superfractionated radiotherapy with concomitant boost for invasive bladder cancer

PURPOSE

To determine the toxicity and clinical effectiveness of accelerated superfractionated radiotherapy with delayed concomitant boost (ASCBRT) in locally invasive carcinoma of the bladder.

METHODS AND MATERIALS

Between July 1997 and December 2001, 87 patients (unsuitable or refusing cystectomy) with invasive bladder cancer underwent ASCBRT. The mean patient age was 66 years (range 40-90). The stage distribution was as follows: 2 T1, 51 T2, 13 T3, and 21 T4. Initially, the whole pelvis was treated by 1.8-Gy conventional daily fractions up to a total dose of 45 Gy. A small field boost covering gross disease was added as a second daily fraction (1.5 Gy) during the last 3 weeks of the 5-week schedule up to a total dose of 67.5 Gy. The interfraction interval was a minimum of 6 h. The patients were evaluated in follow-up for toxicity, local control, and survival.

RESULTS

All but 2 patients completed the study protocol. Grade 3 acute urinary toxicity was observed in 2 patients. Grade 2 and 3 late bladder toxicity was observed in 12 patients and 1 patient, respectively. Grade 2 and 3 late bowel toxicity was observed in 5 and 3 patients, respectively. The 3-year actuarial local control, distant disease control, cause-specific survival, and overall survival rate was 64%, 78%, 58%, and 46%, respectively. Multivariate analysis revealed T stage as independent predictor of complete response. For Stage T2 and T3, the 3-year local control rate was 77% and 48%, respectively. At the last follow-up, 53 patients (61%) were still alive with a survival time between 6 and 62 months.

CONCLUSION

ASCBRT is feasible with acceptable tolerance even in relatively old patients with Stage T3 or greater tumor. The encouraging locoregional control and survival results of this institutional experience, favorable compared with conventional radical and other accelerated fractionated (with or without a concomitant boost) RT series, make ASCBRT worthy of further study in a Phase III trial.

Tolerance of organs at risk in small-volume, hypofractionated, image-guided radiotherapy for primary and metastatic lung cancers

PURPOSE

To determine the organ at risk and the maximum tolerated dose (MTD) of radiation that could be delivered to lung cancer using small-volume, image-guided radiotherapy (IGRT) using hypofractionated, coplanar, and noncoplanar multiple fields.

MATERIALS AND METHODS

Patients with measurable lung cancer (except small-cell lung cancer) 6 cm or less in diameter for whom surgery was not indicated were eligible for this study. Internal target volume was determined using averaged CT under normal breathing, and for patients with large respiratory motion, using two additional CT scans with breath-holding at the expiratory and inspiratory phases in the same table position. Patients were localized at the isocenter after three-dimensional treatment planning. Their setup was corrected by comparing two linacographies that were orthogonal at the isocenter with corresponding digitally reconstructed images. Megavoltage X-rays using noncoplanar multiple static ports or arcs were used to cover the parenchymal tumor mass. Prophylactic nodal irradiation was not performed. The radiation dose was started at 60 Gy in 8 fractions over 2 weeks (60 Gy/8 Fr/2 weeks) for peripheral lesions 3.0 cm or less, and at 48 Gy/8 Fr/2 weeks at the isocenter for central lesions or tumors more than 3.0 cm at their greatest dimension.

RESULTS

Fifty-seven lesions in 45 patients were treated. Tumor size ranged from 0.6 to 6.0 cm, with a median of 2.6 cm. Using the starting dose, 1 patient with a central lesion died of a radiation-induced ulcer in the esophagus after receiving 48 Gy/8 Fr at isocenter. Although the contour of esophagus received 80% or less of the prescribed dose in the planning, recontouring of esophagus in retrospective review revealed that 1 cc of esophagus might have received 42.5 Gy, with the maximum dose of 50.5 Gy. One patient with a peripheral lesion experienced Grade 2 pain at the internal chest wall or visceral pleura after receiving 54 Gy/8 Fr. No adverse respiratory reaction was noted in the symptoms or respiratory function tests. The 3-year local control rate was 80.4% +/- 7.1% (a standard error) with a median follow-up period of 17 months for survivors. Because of the Grade 5 toxicity, we have halted this Phase I/II study and are planning to rearrange the protocol setting accordingly. The 3-year local control rate was 69.6 +/- 10.6% for patients who received 48 Gy and 100% for patients who received 60 Gy (p = 0.0442).

CONCLUSIONS

Small-volume IGRT using 60 Gy in eight fractions is highly effective for the local control of lung tumors, but MTD has not been determined in this study. The organs at risk are extrapleural organs such as the esophagus and internal chest wall/visceral pleura rather than the pulmonary parenchyma in the present protocol setting. Consideration of the uncertainty in the contouring of normal structures is critically important, as is uncertainty in setup of patients and internal organ in the high-dose hypofractionated IGRT.

Lung cancer 5: state of the art radiotherapy for lung cancer

Radiotherapy has a key role in curative and palliative treatments of patients with lung cancer. Important advances are described in the technique of treatment delivery and its integration with chemotherapy.