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In Reply:

Medical Research Council Clinical Trials Unit–Cancer Division, London, United Kingdom; Cookridge Hospital, Leeds, United Kingdom; and Norwegian Radium Hospital, Oslo, Norway

We would like to thank Dr Chan for his comments on our trial, and hope that we can address his concerns.

First, with regard to the role of radiation field, a higher pelvic relapse rate with para-aortic strip only irradiation (PAS) was anticipated, based on the results of our previous randomized trial, Medical Research Council (MRC) Trial TE10,¹ which compared 30 Gy in 15 fractions given to either the dogleg (DL) or PAS field. However, data from MRC TE10 suggested that radiation field affected the location of relapse, but not the overall relapse rate, with nine relapses in each group.

We would agree with Dr Chan's caution over dissecting out small numbers of relapses, but an alternative view of the data from the current trial, MRC TE18,² may provide reassurance on the efficacy of 20 Gy PAS. In each of the 20 Gy and 30 Gy groups, 274 patients received PAS only. The number of patients who relapsed in the 20-Gy group was slightly smaller than the number of patients who relapsed in the 30-Gy group (7 v 9, respectively), but the number of nonpelvic relapses was identical in each group (four relapses). Thus applying Dr Chan's logic, one might deduce that adding effective pelvic irradiation to both groups would still result in an identical relapse rate.

The question of whether 30 Gy DL irradiation may be more effective in terms of relapse rate than 20 Gy PAS irradiation can only be addressed indirectly by these sequential trials. We should point out that the two trials are not directly comparable, as MRC TE18—unlike MRC TE10—did not exclude patients with previous ipsilateral inguinal surgery (for whom dogleg field irradiation was recommended). Making these indirect comparisons does, though, provide further reassurance with crude relapse rates of nine (3.7%) of 242 after 30 Gy DL in MRC TE10, compared with seven (2.6%) of 274 after 20 Gy PAS in MRC TE18, with median follow-up duration of 4.5 and 5 years, respectively. It is important to note that both trials were motivated by the desire to reduce the sequelae of irradiation without an unacceptable impact on efficacy. Consequently, the noninferiority bounds were chosen to balance probable benefits for all in terms of acute and late adverse effects against possible detriments for some patients in terms of relapse risk, bearing in mind the potential for successful salvage.

Authors' Disclosures of Potential Conflicts of Interest

The authors indicated no potential conflicts of interest.

REFERENCE

1. Fosså SD, Horwich A, Russell JM, et al: Optimal planning target volume for stage I testicular seminoma: A Medical Research Council Randomized Trial. J Clin Oncol 17:1146-1154, 1999[Abstract/Free Full Text]

2. Jones WG, Fosså SD, Mead GM, et al: Randomized trial of 30 versus 20 Gy in the adjuvant treatment of stage I testicular seminoma: A report on Medical Research Council Trial TE18, European Organisation for Research and Treatment of Cancer Trial 30942 (ISRCTN18525328). J Clin Oncol 23:1200-1208, 2005[Abstract/Free Full Text]

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Related Correspondence

• Randomized Trial of 30 Versus 20 Gy in the Adjuvant Treatment of Stage I Testicular Seminoma: A Report on Medical Research Council Trial TE18, European Organisation for Research and Treatment of Cancer Trial 30942 (ISRCTN18525328)
  Roscoe Chan
  JCO 2005 23: 6806 [Full Text]

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