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Journal of Clinical Oncology, Vol 26, No 28 (October 1), 2008: pp. 4610-4616 © 2008 American Society of Clinical Oncology. DOI: 10.1200/JCO.2008.16.9383 Computed Tomography Response, But Not Positron Emission Tomography Scan Response, Predicts Survival After Neoadjuvant Chemotherapy for Resectable Non–Small-Cell Lung Cancer
From the Division of Thoracic Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL Corresponding author: Tawee Tanvetyanon, MD, 12902 Magnolia Dr, Tampa, FL 33612; e-mail: tanvett{at}moffitt.org
Purpose Tumor response is considered a surrogate marker of survival. We investigated whether tumor response based on computed tomography (CT) scan or whole-body [18F]fluorodeoxyglucose positron emission tomography (PET) scan after neoadjuvant chemotherapy for resectable non–small-cell lung cancer (NSCLC) is prognostic of survival. Patients and Methods Two consecutive phase II clinical trials were jointly analyzed. Patients underwent CT and PET scans before and after completion of neoadjuvant chemotherapy, followed by surgery. Results Eighty-nine patients were included. Patients with a partial or complete response based on Response Evaluation Criteria in Solid Tumors categories (n = 33) had a better overall survival than those with stable or progressive disease (n = 56; median survival time, not reached v 36 months, respectively; P = .04). Of all patients, those with response in the highest quartile had 1- and 2-year survival rates of 100% and 81%, respectively, compared with 77% and 61%, respectively, among patients in the lowest quartile. However, on the basis of visual analysis of PET scan, patients with a metabolic response (n = 28) had no significant difference in survival compared with patients without response (n = 61; median survival time, 35.6 months v not reached, respectively; P = .94). In addition, on the basis of a semiquantitative analysis of PET scan, using at least 30% reduction in tumor metabolism as a response (n = 59), we also found no significant difference in survival among those with or without response. Conclusion Among patients with resectable NSCLC treated with neoadjuvant chemotherapy, we found no evidence that tumor response by PET scan after chemotherapy is prognostic of survival; however, response by CT scan was associated with better survival.
Tumor response after chemotherapy is a surrogate marker of survival. Response, as manifested by shrinkage of lesions seen by a computed tomography (CT) scan, reflects a reduction of tumor load and generally translates into a survival benefit.1 Previous studies conducted in patients with advanced or metastatic non–small-cell lung cancer (NSCLC) have shown that response to chemotherapy as determined by CT scan after 8 weeks of treatment is a strong predictor of subsequent survival.2 In addition, for patients with nonmetastatic cancer, response early in the course of disease often facilitates subsequent effective treatments, resulting in favorable overall survival as well.3 Besides the response as seen by CT scan, recent data suggest that a response by [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) after chemotherapy may have a significant correlation with survival in NSCLC.4 Among patients with unresectable (but nonmetastatic) NSCLC receiving definitive radiation or chemoradiotherapy, it has been reported that tumor response from PET scan is a better survival predictor than tumor response from CT scan.5 Among those with advanced or metastatic disease, tumor response by PET scan—defined as 20% reduction of tumor metabolic activity after the first cycle of chemotherapy—is also associated with an improved survival.6 Although tumor response by both CT scan and PET scan seems to have prognostic significance among patients with advanced NSCLC, this association is less clear among patients who have earlier stages of disease and undergo neoadjuvant chemotherapy. Most available data are derived from patients with stage III NSCLC. For example, in patients with stage III NSCLC who underwent neoadjuvant chemotherapy followed by surgery, the median overall survival was almost four times longer among patients with no significant residual glucose metabolism detected than those with residual glucose hypermetabolism.7 In patients with stage III NSCLC, a greater than 50% decrease in the metabolic activity of the tumor by PET scan after three cycles of induction chemotherapy was associated with an improved survival.8 To date, however, limited data are available on patients who have early, resectable stages of NSCLC (ie, stages IB and II and resectable stage III). One study has suggested that tumor response by CT scan after neoadjuvant chemotherapy is prognostic of survival,9 but limited information is currently available with regard to the prognostic value of a response by PET scan. In this article, we investigated the prognostic value of tumor response, assessed by CT scan and PET scan, after neoadjuvant chemotherapy for patients with resectable NSCLC.
Patients and Treatments Patients were included from two prospective clinical trials of neoadjuvant chemotherapy followed by surgical resection. Both clinical trials enrolled patients with histologically confirmed NSCLC who had resectable disease, including stages IB, II, IIIA, or IIIB (T4 with two lesions in one lobe).10,11 Patients with N2 disease were eligible if surgically resectable without multistation or bulky mediastinal lymph node involvement. Staging procedures included mediastinoscopy in all patients. Preoperative chemotherapy consisted of gemcitabine 1,000 mg/m2 and vinorelbine 25 mg/m2 administered on days 1, 8, 22, and 29 or gemcitabine 1,500 mg/m2 and pemetrexed 500 mg/m2 administered on days 1, 15, 29, and 43. Patients had thoracotomy between days 50 and 70 in the first study and between days 64 and 77 in the second study.
Imaging Studies
Response
Statistical Considerations
Patient Characteristics and Treatments There were 114 patients; 62 were from the gemcitabine plus vinorelbine study, and 52 were from the gemcitabine plus pemetrexed study. Of these, 89 patients (78%) completed both pre- and postchemotherapy CT and PET scans (Table 1). All CT scans were performed with the use of intravenous nonionic contrast. The median thickness of CT slice was 5 mm in both pre- and postchemotherapy scans (range, 4 to 8 mm and 5 to 8 mm, respectively). For PET scanning, the median administered dosages of FDG were 12.7 and 12.0 µCi in pre- and postchemotherapy scans, respectively (range, 7 to 30 µCi and 8.7 to 14.9 µCi, respectively). The median serum glucose levels in these patients, immediately before pre- and postchemotherapy PET scans, were 116 and 107 mg/dL, respectively (range, 85 to 208 mg/dL and 79 to 214 mg/dL, respectively). Chemotherapy was well tolerated, and the toxicity profile has been previously reported.10,11 All but eight patients underwent a surgical resection of lung cancer. Of the patients who underwent resection, 71 of 81 patients had a complete resection. To date, 34 patients have died. The median survival time of the entire cohort has not been reached. The 1-year and 2-year survival rates are 85% (95% CI, 76% to 91%) and 71% (95% CI, 60% to 79%), respectively.
Survival Based on Tumor Response by CT Scan The median change in the sum of unidimensional tumor size was a decrease of 18% (ranging from 100% decrease to 95% increase). A waterfall plot demonstrating responses of 89 patients is shown in Figure 1A. On the basis of RECIST categories, complete response occurred in one patient (1%), partial response occurred in 32 patients (36%), stable disease occurred in 50 patients (56%), and progressive disease occurred in six patients (7%). Patients with a partial or complete response by CT scan (n = 33) had a better survival than patients without response (n = 56; median survival time, not reached v 36 months, respectively; P = .04; Fig 2). The estimated probabilities of survival at 1 and 2 years among patients with and without response were 100% v 77% and 80% v 65%, respectively. In addition, greater degrees of CT response seemed to be associated with better survival. Patients in the top quartile of CT response had 1- and 2-year survival rates of 100% and 81%, respectively; whereas patients in the lowest quartile had 1- and 2-year survival rates of 77% and 61%, respectively.
Survival Based on Tumor Response by PET Scan We first examined the prognostic value of PET response based on visual analysis. By visual analysis, PET response occurred in 28 patients (31%). Comparing patients with and without PET responses, there was no significant difference in the overall survival between the two groups (median survival time, 35.6 months v not reached, respectively; P = .93; Fig 3A).
Second, we examined the prognostic value of PET response based on a semiquantitative analysis. There were 59 patients with complete pre- and postchemotherapy data sets. All but 23 prechemotherapy PET scans were performed at our institution. The median interval between pre- and post-treatment PET scans was 70 days (range, 48 to 115 days). The patient and treatment characteristics were comparable to the entire cohort (Table 1). A plot demonstrating PET responses of individual patients, in the same order as presented in Figure 1A, is shown in Figure 1B. The median change in the SUVmax before and after neoadjuvant chemotherapy was a decrease of 20.5% (ranging from 86% decrease to 117% increase). To parallel the radiographic criteria, we first considered a 30% or greater reduction in the SUVmax as a response. We found no significant difference in survival between patients who achieved (n = 24) and who did not achieve response (n = 35; median survival time, not reached in both groups; P = .70; Fig 3B). We then explored the use of a 50% or greater reduction in the SUVmax as a metabolic response. Again, we found no significant difference in the survival between patients who responded (n = 10) and patients who did not (n = 49; median survival time, 26.9 months v not reached, respectively; P = .57).
Impact of Clinical Stage, Tumor Size, and Completeness of Surgical Resection on Survival In the first analytic model, we took stage, tumor size, completeness of surgical resection, and response by RECIST into consideration. After adjusting for stage and completeness of surgical resection, the response by CT scan remained a significant survival predictor (hazard ratio = 0.25; 95% CI, 0.07 to 0.94; P = .04). In this model, stage was also a significant survival predictor (P = .05). Tumor size was of borderline significance (P = .07). However, the completeness of resection was not a significant survival predictor (P = .14). We also found that the effect of CT scan response on survival was clearest among patients with stage III disease; CT responders (n = 11) had a median survival time of 35.6 months compared with 15.5 months in nonresponders (n = 25; P = .02; Fig 4C). However, the prognostic value of CT scan response was unclear among patients with stage I and II disease. In these patients, median survival times were not reached in both the responder groups and the nonresponder groups. Overall, we found no significance differences among responders versus nonresponders who had stage I or II disease (P = .74 and P = .27, respectively; Figs 4A and 4B).
In the second analytic model, we took stage, tumor size, completeness of surgical resection, and PET response by semiquantitative reading into consideration. In this model, we found that stage and completeness of resection were significant predictors of survival (hazard ratio = 4.58; 95% CI, 1.24 to 16.73; P = .02 and hazard ratio = 3.76; 95% CI, 1.29 to 10.92; P = .02, respectively). Tumor size was of borderline significance (P = .07). However, the PET response by semiquantitative reading was still not prognostic of survival (P = .38).
Correlation Between PET and CT Responses Second, we examined the correlation between PET response by semiquantitative reading and the CT response in 59 patients. Again, PET response showed a weak but significant correlation with CT response; Spearman's correlation coefficient was –0.34 (P = .008). Finally, we investigated whether the use of SUVmax after neoadjuvant chemotherapy alone would be predictive of survival. Using a Cox regression model adjusting for stage and completeness of resection, the postchemotherapy SUVmax by itself was not predictive of survival (P = .44).
On the basis of data from our two prospective trials of neoadjuvant chemotherapy followed by surgery in resectable NSCLC, we found that the tumor response by CT scan correlated with survival, especially for patients with stage III disease. However, the tumor response by PET scan was not predictive of survival. These findings remained true after adjusting for completeness of subsequent surgical resection, tumor size, and stage. Because neoadjuvant chemotherapy followed by surgery has now been shown to provide a survival benefit over surgery alone14 and because CT scan and PET scan are recommended tests before surgery, clinicians may become more likely to face the daunting task of interpreting a response from PET scans and CT scans in this clinical setting.15 The observation that patients with a tumor response from CT scan had a superior survival is not surprising; a reduction in tumor size might have facilitated a complete surgical resection, resulting in a favorable survival. However, the observation that patients with a tumor response from PET scan did not have an improved survival is quite unexpected. What could have accounted for this finding? First, it may help to interpret this in the context of existing literature on PET response and survival among patients with nonmetastatic NSCLC. Our search of the MEDLINE database identified nine pertinent studies—three from induction chemotherapy trials, four from chemoradiotherapy trials, and two from mixed approaches (Table 2). Among the trials of induction chemotherapy, the observed response rate by PET scan was high, ranging from approximately 50% to 60%. In two of these trials in which a 50% or greater reduction in SUVmax was considered as a response, the response by PET scan was found to be a significant predictor of survival. In our trial, if considering 50% or greater reduction in SUVmax as response, the response rate was 17%, which is relatively low. It seemed that our chemotherapy regimens were less active. It is possible that this has masked any potential prognostic value of a response by PET scan.
Second, our study included a large number of patients with stage I and II disease, as opposed to the two previous trials of neoadjuvant chemotherapy that reported on prognostic significance of PET response, in which only patients with stage III disease were included.7,8 Patients with stage I or II NSCLC in general have a longer survival time than patients with stage III disease. For a cohort of patients with prolonged survival, several factors may influence the long-term outcome. Although, in our study, we have adjusted for stage, other confounders such as comorbidity and subsequent treatment can still influence a subsequent survival. In addition, for a group of patients with prolonged survival, a long-term follow-up may be necessary, although our duration of follow-up seems to be adequate to see the prognostic value of a response by CT scan. Third, the lack of prognostic value of the PET scan may stem from the determination of PET scan response based on visual analysis that was used in our study. Although response based on visual analysis has been used in previous studies and is perhaps the most widely used criteria in clinical practice, this approach is subjected to an interpretation by radiologists, who may vary in the stringency of interpretation.23 In addition, out of a research setting, this problem can be further exacerbated by scans performed at different facilities. Interfacility technical variability, including time from injection of radioactive glucose until scan is performed, can further limit its prognostic accuracy.24 Our study has a number of limitations. First, the patient sample size may be too small to detect subtle differences between groups, although our report constitutes one of the largest numbers of patients with early-stage NSCLC receiving neoadjuvant chemotherapy (Table 2). Second, data on PET scan by semiquantitative analysis were not available in all patients, although the group of patients with available data seemed to be representative of the entire cohort, and it seems unlikely that a major prognostic value of a response by PET scan exists based on current data. Finally, it is possible that the results from visual analysis of PET scan in our study may not be generalizable, although the PET scan reports in our studies emanated from various radiologic facilities in diverse locations, and we believe that these are representative of what clinicians are facing in current practice. In summary, for patients with resectable NSCLC undergoing neoadjuvant chemotherapy, the tumor response based on CT scan seems to have a prognostic value on survival, but the tumor response by PET scan, either by visual analysis or semiquantitative reading, does not necessarily portend a good prognosis. Clinicians should use caution in interpreting a tumor response by PET scan in this clinical setting.
The author(s) indicated no potential conflicts of interest.
Conception and design: Tawee Tanvetyanon, Edward A. Eikman, Gerold Bepler Financial support: Gerold Bepler Administrative support: Gerold Bepler Provision of study materials or patients: Tawee Tanvetyanon, Edward A. Eikman, Eric Sommers, Lary Robinson, Gerold Bepler Collection and assembly of data: Tawee Tanvetyanon, Edward A. Eikman, Gerold Bepler Data analysis and interpretation: Tawee Tanvetyanon, Edward A. Eikman, Lary Robinson, David Boulware, Gerold Bepler Manuscript writing: Tawee Tanvetyanon, Edward A. Eikman, Lary Robinson, David Boulware, Gerold Bepler Final approval of manuscript: Tawee Tanvetyanon, Edward A. Eikman, Eric Sommers, Lary Robinson, David Boulware, Gerold Bepler
Authors disclosures of potential conflicts of interest and author contributions are found at the end of this article.
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Copyright © 2008 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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