Clinical Investigation
Total Gross Tumor Volume Is an Independent Prognostic Factor in Patients Treated With Selective Nodal Irradiation for Stage I to III Small Cell Lung Cancer

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Purpose

In non-small cell lung cancer, gross tumor volume (GTV) influences survival more than other risk factors. This could also apply to small cell lung cancer.

Methods and Materials

Analysis of our prospective database with stage I to III SCLC patients referred for concurrent chemo radiation therapy. Standard treatment was 45 Gy in 1.5-Gy fractions twice daily concurrently with carboplatin-etoposide, followed by prophylactic cranial irradiation (PCI) in case of non-progression. Only fluorodeoxyglucose (FDG)-positron emission tomography (PET)-positive or pathologically proven nodal sites were included in the target volume. Total GTV consisted of post chemotherapy tumor volume and pre chemotherapy nodal volume. Survival was calculated from diagnosis (Kaplan-Meier ).

Results

A total of 119 patients were included between May 2004 and June 2009. Median total GTV was 93 ± 152 cc (7.5-895 cc). Isolated elective nodal failure occurred in 2 patients (1.7%). Median follow-up was 38 months, median overall survival 20 months (95% confidence interval = 17.8-22.1 months), and 2-year survival 38.4%. In multivariate analysis, only total GTV (P=.026) and performance status (P=.016) significantly influenced survival.

Conclusions

In this series of stage I to III small cell lung cancer patients treated with FDG-PET-based selective nodal irradiation total GTV is an independent risk factor for survival.

Introduction

Classic prognostic factors for survival in small cell lung cancer (SCLC) include stage, age, level of lactate dehydrogenase (LDH), time between start of any treatment to the end of radiation therapy (SER), male sex, N3 nodal status, and WHO performance score (WHO-PS) (1).

Clinicians intuitively accept that larger tumors are less likely to remain controlled. Gross tumor volume (GTV) is a fairly recent concept, which could not be investigated in the pre-computed tomography (CT) era. Indeed, in the International Union Against Cancer (UICC) TNM classification, only the T-stage may include the 2-dimensional (2D) diameter of the primary tumor, but size of nodes or total GTV are not present (2).

In prognostic models concerning non-small cell lung cancer (NSCLC), GTV, together with the number of nodal stations, outweigh TNM stage 3, 4 Therefore we investigated the value of total GTV, defined as the volume of the primary tumor and the involved lymph nodes on a planning positron emission tomography (PET)-CT as a potential stratification factor in SCLC. Furthermore, we updated our results of selective nodal irradiation (SNI) based on PET-CT (5).

Section snippets

Patient population

Since 2003, patients treated at Maastro Clinic are collected in a prospective database.

We analyzed all patients with stage I to III SCLC referred for concurrent chemoradiation therapy from May 2004 until June 2009.

Patients had pathologically proven SCLC stage I to III according to UICC TNM classification version 6, excluding T4 disease due to malignant pleural or pericardial effusion (6). WHO-PS of 0 to 2 and adequate pulmonary function (forced expiratory volume at 1 second [FEV1], carbonic

Patient characteristics

From April 2004 until June 2009, 119 patients with stage I to III SCLC were referred to Maastro Clinic for concurrent chemoradiation therapy.

Patient characteristics are summarized in Table 1.

Patients were 41 to 85 years of age, with a median age of 66 ± 8.8 years. All but 2 patients received carboplatin-etoposide. Both of these patients received carboplatin-paclitaxel instead: 1 patient because of synchronous ovarian cancer, and the other because of intolerance to etoposide.

Two patients (1.6%)

Discussion

In the past years, the interest of researchers in selective nodal irradiation in SCLC has grown. Already starting from the late 1980s, smaller radiation ports were used in trials to decrease the acute toxicity of emerging combined modality treatments (10). However, omission of elective nodal irradiation was pioneered by De Ruysscher et al, whose first attempt of CT-based SNI yielded an elective nodal failure rate of 11%, probably due to the low sensitivity and specificity of CT in mediastinal

References (18)

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Conflict of interest: none.

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