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Letters To The Editor |
Department of Radiology, New York Presbyterian Hospital, Weill Medical College, New York, New York, USA
Correspondence: Claudia I. Henschke, Ph.D., M.D., Department of Radiology, New York Presbyterian Hospital-Weill Medical College, 525 East 68th Street, New York, New York 10065, USA. Telephone: 212-746-2529; Fax: 212-746-2811; e-mail: chensch{at}med.cornell.edu
Received March 20, 2008; accepted for publication April 16, 2008.
We appreciate the opportunity to respond to Dr. Bach's letter and have addressed the questions he posed in the order presented.
1. Bach questioned whether survival data were used by Mountain as a basis for developing the staging system for lung cancer. Mountain states, in the paper referenced in our article, that, "Stage grouping involves the concept of combining subsets of patients classified according to TNM descriptors into categories or stages, each having generally similar treatment options and survival expectations." In another paper [1], he states "survival data support the revised categories and confirm the significant relationship between the extent of the disease and prognosis for patients with this disease."
2 and 3. Bach states that the terms "curability rate" and "cure rate" are not "concept(s) found in conventional epidemiology." To the contrary, Professor O. S. Miettinen [2, 3], considered one of the founders of modern epidemiology, defines curability rate as the proportion of genuine cases of cancer that are curable by optimal treatment. In Figure 1 in our article, the number of new cases and deaths from several types of cancer were provided from the 2006 Cancer Facts and Figures from the American Cancer Society (ACS) [4]. Using these, we estimated cure rates and also provided them in Figure 1. By way of clarification and correction, our estimates are not included in the ACS publication.
4 and 5. Bach questions the distinction between baseline and repeat rounds of screening, because only a single round is described in the article by Morrison [5]. Morrison states in his introduction that "the presentation is based on a one-time screening programme, but .... readily extended to a programme of repeated screening examinations." Surely, there is no question that a distinction exists between cancers found in the baseline (also called "prevalence") round and repeat (also called "incidence") rounds of screening. We provided Morrison's paper as an early reference for various biases. We did not say length bias is only seen in the baseline round, but that the baseline round is different from the repeat rounds in this regard, and that repeat rounds are similar to each other and thus can be pooled.
6. We did not specifically state that the prostate cancers were screen detected in the Bill-Axelson et al. [6] study; however, in the context it was written, that could be implied. The participants in that study had newly diagnosed, early, localized prostate cancer. The essential point here is that, under certain conditions, even with cancer, it may be possible to perform randomized trials that include watchful waiting versus treatment.
7 and 8. Bach is correct that the references we cited to support the statement that the median length of follow-up for the National Lung Screening Trial (NLST) is 4 years do not directly provide this information. The follow-up time for the NLST is 4–6 years, as was recently confirmed by the principal investigator of the NLST [7], not the 5–7 years as stated by Bach. We estimated that the median follow-up time would be further shortened and closer to 4 years, because the NLST protocol [8] calls for information regarding cause of death to be obtained from the National Death Index, which is usually not available until one and a half years after the death has occurred.
9. We erred in stating that the Bach et al. [8] study had shown a decrease in cumulative mortality rates in years 5 and 6. We had intended to refer to the data that were published in Bach's correction [9] to his original article [8].
10. Bach questions whether various biases affect randomized controlled trials (RCTs), focusing mainly on whether we used the proper references; there were five references, not four, as cited by Bach. It is understood that biases affect RCTs (see section in the NLST protocol titled "Limitation of the RCT") [10]. In randomized trials, it is important to focus on the appropriate time interval when the mortality reduction should become apparent, and as shown by Miettinen et al. [11] and Hanley [12], annual rates can demonstrate the benefit of screening without dilution of the effect that is seen in cumulative rates. Our references describe various aspects associated with these biases.
11. The cause of death of the eight patients with untreated stage I lung cancer was inadvertently omitted in the final version of the article [13]. All died of lung cancer, as we stated in response to a letter to the editor [14]. Since then, five new patients with stage I lung cancer who were untreated have died of lung cancer and that information was included in Figure 11 in The Oncologist. The accumulating experience, that is, death from untreated stage I lung cancer, continues to provide useful information about the natural course of screen-detected lung cancer. Regarding Bach's final question, there is no censoring of the data for the untreated patients because all died of their lung cancer.
We fully agree with Dr. Bach that "the evaluation of cancer screening approaches is complex..." and we share his appreciation of "subtle epidemiologic concepts..." These points, among others, have prompted the International Early Lung Cancer Action Project investigators to repeatedly call for serious, open, academic debate of the merits of alternative approaches to the randomized trial for the evaluation of computed tomography screening for lung cancer.
Disclosure: Dr. Henschke has the following relationships with General Electric and the National Cancer Institute (NCI).
General Electric: Dr. Henschke is a coinventor on a patent and other pending patents owned by Cornell Research Foundation (CRF) that are nonexclusively licensed and related to General Electric for technology involving computer-aided diagnostic methods, including measurement of nodules. She receives royalties from CRF pursuant to Cornell policy, which in turn is consistent with the Bayh-Dole Act. None of the General Electric products were required for any of the research reported in this article.
NCI: Dr. Henschke is compensated for serving as a study section member for NCI.
Dr. Henschke also receives research support in the form of grants and contracts from the American Legacy Foundation, Flight Attendants' Medical Research Institute, NCI, AstraZeneca, Inc., Carestream Health, Inc., and Foundation for Lung Cancer: Early Detection, Prevention, and Treatment (primary source of funding was an unrestricted gift by the Vector group, the parent company of Liggett Tobacco).
The following is a listing of the patent and patent applications in which Claudia Henschke is listed as a coinventor.
1) U.S. Patent No. 7,274,810 "System and Method for Three-Dimensional Image Rendering and Analysis" (patent issued to CRF September 25, 2007); CRF has two pending divisional applications related to this patent.
2) CRF has two pending patent applications for "System, Method and Apparatus for Small Pulmonary Nodule Computer Aided Diagnosis from Computed Tomography Scans."
3) CRF has a pending patent application for "System and Method for Providing Remote Analysis of Medical Data."
4) CRF has a pending patent application for "System and Method for Analyzing Medical Data to Determine Diagnosis and Treatment."
5) CRF has a pending patent application for "System and Method for Conducting a Clinical Trial Study."
6) CRF has a pending PCT application for "Medical Imaging Visibility Index System and Method for Cancer Lesions."
7) CRF has a pending patent application (and foreign pending patent applications) for "Method for Expanding the Domain of Imaging Software in a Diagnostic Workup."
8) CRF has a pending patent application for "System and Method for Position Matching of a Patient for Medical Imaging."
9) Dr. Henschke is an inventor on a pending patent application for "Medical Imaging System for Accurate Measurement Evaluation of Changes in a Target Lesion" (foreign patent applications also pending).
Dr. Yankelevitz Financial and Research Disclosures:
Dr. Yankelevitz has the following relationships with PneumRx, Inc. and with General Electric.
PneumRx, Inc.: Dr. Yankelevitz is an inventor on a pending patent related to biopsy needles assigned to PneumRX, Inc., a paid medical advisor, and holds stock in the company.
General Electric: Dr. Yankelevitz is a coinventor on a patent and other pending patents owned by CRF that are nonexclusively licensed and related to technology involving computer-aided diagnostic methods, including measurement of nodules. He receives royalties from CRF pursuant to Cornell policy, which in turn is consistent with the Bayh-Dole Act.
Dr. Yankelevitz receives research support in the form of grants and contracts from the American Legacy Foundation, Flight Attendants' Medical Research Institute, NCI, AstraZeneca, Inc., OSI Pharmaceutical, GlaxoSmithKline, Visiongate, Carestream Health, Inc., and Foundation for Lung Cancer: Early Detection, Prevention, and Treatment (primary source of funding was an unrestricted gift by the Vector group, the parent company of Liggett Tobacco).
The following is a listing of the patent and patent applications in which David Yankelevitz is listed as a coinventor.
1) U.S. Patent No. 7,274,810 "System and Method for Three-Dimensional Image Rendering and Analysis" (patent issued to CRF September 25, 2007); CRF has two pending divisional applications related to this patent.
2) CRF has two pending patent applications for "System, Method and Apparatus for Small Pulmonary Nodule Computer Aided Diagnosis from Computed Tomography Scans."
3) CRF has a pending patent application for "System and Method for Providing Remote Analysis of Medical Data."
4) CRF has a pending patent application for "System and Method for Analyzing Medical Data to Determine Diagnosis and Treatment."
5) CRF has a pending patent application for "System and Method for Conducting a Clinical Trial Study."
6) CRF has a pending PCT application for "Medical Imaging Visibility Index System and Method for Cancer Lesions."
7) CRF has a pending patent application (and foreign pending patent applications) for "Method for Expanding the Domain of Imaging Software in a Diagnostic Workup."
8) CRF has a pending patent application for "System and Method for Position Matching of a Patient for Medical Imaging."
9) Dr. Yankelevitz is an inventor on a pending patent application for "Medical Imaging System for Accurate Measurement Evaluation of Changes in a Target Lesion" (foreign patent applications also pending).
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  P. B. Bach Untreated Patients in "CT Screening for Lung Cancer: Update 2007" Oncologist, September 1, 2008; 13(9): 1030 - 1032. [Full Text] [PDF]
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