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Originally published as JCO Early Release 10.1200/JCO.2005.01.9810 on October 31 2005 © 2005 American Society of Clinical Oncology. Risk-Adapted Management for Patients With Clinical Stage I Seminoma: The Second Spanish Germ Cell Cancer Cooperative Group StudyFrom the Departments of Medical Oncology, Hospital Universitario La Fe; Hospital Universitari Doctor Peset, Valencia; Idibell-Institut Catalá d'Oncologia Duran i Reynals; Hospital de Sant Pau; Hospital Mutua de Terrassa; Hospital del Mar; Hospital Clinic i Provincial, Barcelona; Hospital General Universitario Gregorio Marañón; Hospital Universitario 12 de Octubre, Madrid; Hospital Clínico Universitario Lozano Blesa, Zaragoza; Hospital Universitari Germans Trias i Pujol, Badalona; Hospital Universitari Josep Trueta, Girona; Hospital Universitari Sant Joan, Reus; Hospital Clínico Universitario Virgen de la Victoria, Málaga; Hospital Donostia; Instituto Oncológico de Guipúzcoa, San Sebastián; Hospital Universitari Arnau de Vilanova, Lleida; Hospital Universitario Marqués de Valdecilla, Santander; and Hospital Provincial, Castellón, Spain Address reprint requests to Jorge Aparicio, MD, Servicio de Oncología Médica, Hospital Universitario La Fe, Avda Campanar 21, E-46009 Valencia, Spain; e-mail: japariciou{at}seom.org
PURPOSE: To assess the efficacy of a risk-adapted treatment policy for patients with stage I seminoma by using universally accepted risk criteria. PATIENTS AND METHODS: Between 1999 and 2003, 314 patients with clinical stage I seminoma after orchiectomy were prospectively included. One hundred patients (31.8%) presented no risk factors and were managed with surveillance. In contrast, 131 patients (41.7%) had tumors larger than 4 cm, 33 patients (10.5%) had rete testis involvement, and 50 patients (15.9%) had both risk factors. All the latter received two courses of adjuvant carboplatin. RESULTS: Chemotherapy was well tolerated, as only 17 patients (7.9%) presented grade 3 to 4 toxicity. Relapses were observed in six patients (6.0%) on surveillance and in seven patients (3.3%) treated with carboplatin (0.8% of tumors larger than 4 cm, 9.1% of those involving the rete testis, and 6.0% of patients with both risk criteria). All were located at the retroperitoneum, except for one at the spermatic cord. Median tumor size was 25 mm (range, 11 to 70 mm), and median time to relapse was 9 months (range, 4 to 28 months). All patients were rendered disease-free with chemotherapy (etoposide plus cisplatin). Median follow-up was 34 months (range, 12 to 72 months). The actuarial 5-year disease-free survival rate was 93.4% for patients on surveillance and 96.2% for patients treated with adjuvant chemotherapy. Overall 5-year survival was 100%. CONCLUSION: Adjuvant carboplatin is effective in reducing the relapse rate in patients with stage I seminoma and risk factors. A risk-adapted strategy is safe and feasible and should be considered an alternative to systematic approaches, such as irradiation, chemotherapy, or surveillance.
Stage I seminoma represents approximately 35% of all germ cell testicular cancers. In this clinical setting, definitive cure is the rule, and current therapeutic trials are aiming to maintain these favorable results while reducing treatment-related toxicity.1 Until recently, postorchiectomy irradiation to the para-aortic lymph nodes was the standard of care. Reported relapse rates have ranged from 3% to 5%, with seminoma deaths in less than 2%.2 However, a small but significant increased risk for second malignancies, cardiovascular morbidity, and peptic ulcer with this treatment approach has been confirmed. Therefore, new therapeutic options have been investigated in this patient subset. Surveillance has been shown to be a safe and effective alternative. Nonetheless, it is associated with recurrence rates of 15% to 20%3 (most of such patients can be successfully treated with salvage chemotherapy), considerable psychologic stress, and incremental costs.4 The third treatment option is adjuvant chemotherapy. A recently published randomized trial form the Medical Research Council and the European Organisation for Research and Treatment of Cancer compared one course of single-agent carboplatin with para-aortic radiotherapy (20 to 30 Gy). Three-year relapse-free survival rates were equivalent, but both the toxicity data and the incidence of second neoplasms (both testicular and extratesticular) favored adjuvant chemotherapy.5 Today no consensus exists on the optimal treatment approach. In a prior Spanish Germ Cell Cancer Group (GG) study, we demonstrated that adjuvant carboplatin may be restricted to patients with high risk of relapse. Long-term results were excellent (100% cause-specific survival), but the criteria used had not been previously validated.6 After the publication of a large pooled analysis of patients with stage I seminoma managed by surveillance, tumor size (> 4 cm) and rete testis invasion are universally accepted prognostic factors for relapse.3 This study was designed as a prospective audit of practice with the following objectives: (1) to determine whether adjuvant carboplatin is effective in reducing the relapse rate associated with large tumor size and rete testis invasion, and (2) to assess the efficacy of a risk-adapted treatment policy by using these new criteria in a nationwide multicenter setting.
Patients with histologically proven pure seminoma, clinical stage I disease, and resection margins free of tumor were included in this study after orchiectomy performed at any of the GG centers. Routine staging consisted of clinical history, physical examination, chest x-ray films, computed tomography (CT) of abdomen and pelvis, ultrasonography of the contralateral testicle, CBC, and serum chemistries including lactate dehydrogenase, alpha-fetoprotein (AFP), and beta-human chorionic gonadotropin (BHCG). Increased preoperative levels of BHCG were acceptable, but either the persistence of increased postoperative BHCG levels or any pre- or postoperative elevation of AFP were considered exclusion criteria. The American Joint Committee on Cancer (1997 edition) TNM classification was used.7 Patients with tumors larger than 4 cm or with invasion of the rete testis (considered local risk factors3) received adjuvant single-agent carboplatin (area under the curve of 7 every 21 days for two courses). Treatment was given on an outpatient basis, within 2 hours. Systematic antiemetic prophylaxis with dexamethasone and 5-hydroxytryptamine-3 antagonists was used. CBC, serum biochemistry, and toxicity assessment (WHO criteria) were performed on days 1, 22, and 43. Patients without risk factors were managed by clinical surveillance. In both groups, chest x-rays, AFP, and BHCG were scheduled at months 3, 6, 9, 12, 18, 24, 30, 36, 48, 60, and 72 months after orchiectomy, and abdominal CT scans were performed at 6, 12, 18, 24, 30, 36, 48, 60, and 72 months. Tumor relapses in both groups were treated primarily with etoposide and cisplatin chemotherapy.8
Potential prognostic factors for relapse were prospectively recorded, including patient age (
From January 1999 to December 2003, 314 patients were included in 42 centers. Median age was 32 years (range, 18 to 72 years). All patients underwent inguinal orchiectomy for testicular seminoma. Three patients (1.0%) presented a bilateral (synchronic) seminoma, whereas 161 tumors (52.4%) were right sided and 143 tumors (46.6%) were left sided. The median of maximum tumor diameter was 45 mm (range, 3 to 140 mm). Preoperative serum BHCG levels were positive (ie, > 9 U/mL) in 44 cases (14.0%; median, 32 U/mL; range, 10 to 923 U/mL). By definition, all patients were pre- and postorchiectomy AFP-negative and postorchiectomy BHCG-negative. One hundred patients (31.8%) presented with no risk factors and were managed with surveillance. In contrast, 131 patients (41.7%) had tumors greater than 4 cm in size, 33 patients (10.5%) had rete testis involvement, and 50 patients (15.9%) had both risk factors. All the latter received two courses of adjuvant carboplatin. Main patient characteristics and distribution of prognostic factors among treatment arms are summarized in Table 1.
Median time from orchiectomy to start of chemotherapy was 38 days (range, 10 to 90 days). Time interval between courses was 21 days in 155 cases (74.8%), 28 days in 49 cases (23.6%), and 35 days in three cases (1.4%). Most treatment delays (> 21 days) were due to protocol misinterpretation. No dose reductions were performed. Grade 3 to 4 adverse events consisted of uncomplicated thrombocytopenia (10 cases), afebrile neutropenia (four cases), and emesis (five cases). Chemotherapy toxicity is summarized in Table 2.
At the time of the present analysis, median follow-up time was 34 months (range, 12 to 72 months), with 212 patients (67.5%) followed up for more than 2 years, and only three cases (1%) lost to follow-up. Relapses were observed in six patients (6.0%) on surveillance and seven patients (3.3%) treated with carboplatin (0.8% of tumors larger than 4 cm, 9.1% of those involving the rete testis, and 6.0% of patients with both risk criteria). Only one patient (9.1%) relapsed with symptoms of disease, the rest being detected through routine CT scans (54.5%) or increase in serum BHCG levels (36.4%). All relapses were located at the retroperitoneum, except for one case at the spermatic cord. Median tumor size was 25 mm (range, 11 to 70 mm), and median time to relapse was 9 months (range, 4 to 28 months). All these patients were rendered disease-free with chemotherapy (etoposide plus cisplatin in 12 patients; bleomycin, etoposide, and cisplatin in one patient). Today, one patient is receiving radiotherapy for a second relapse; the rest are free of recurrence. The actuarial 5-year DFS was 93.4% (95% CI, 90.8% to 96.1%) for patients on surveillance and 96.2% (95% CI, 94.8% to 97.7%) for those treated with adjuvant chemotherapy (Fig 1). Five-year OS was 100%.
Seven patients (3.3%) suffered bilateral testicular germ cell tumors: two patients had a previous nonseminomatous germ cell testicular cancer, two had a synchronous bilateral seminoma, two had a metachronous bilateral seminoma, and one had a metachronous nonseminomatous germ cell testicular cancer. Two other patients developed a second non–germ cell neoplasm (resectable kidney carcinoma and stage 0 chronic lymphatic leukemia). All nine patients with second malignancies are living disease free. A univariate analysis of prognostic factors for DFS was performed. In the whole series, patients older than 30 years did better than younger subjects (DFS of 98.3% v 90.1%; P = .0047). For patients managed with surveillance, younger age (DFS of 97.4% v 85.0%; P = .0146) and increased serum preoperative BHCG levels (DFS of 98.2% v 86.7%; P = .0369) adversely affected outcome. Finally, in the group of patients treated with adjuvant carboplatin, the presence of rete testis invasion was the only significant adverse prognostic factor (DFS of 99.2% v 91.6%; P = .0108), whereas age was of borderline statistical significance (P = .0658). A multivariate analysis identified three independent, poor risk factors: age younger than 30 years for the whole series, increased BHCG for patients managed with surveillance, and rete testis invasion for those treated with adjuvant chemotherapy. Figure 2 shows the distribution of relapses according to the presence of tumor size greater than 4 cm, rete testis invasion, or both criteria among patients treated with carboplatin. Table 3 depicts the proportion of recurrences among prognostic categories.
Testicular cancer is an infrequent disease, accounting for 1% to 2% of all malignant neoplasms in men. However, it represents the most common malignancy in young males 15 to 34 years of age. It has become a model for curable malignancy, with an OS rate of 90% to 95% considering all stages.11 More than a half of patients are now diagnosed with pure seminoma, and approximately 75% of them present with stage I disease.1,12 Until recently, conventional management for clinical stage I seminoma consisted of adjuvant postorchiectomy irradiation. The results of this modality have been excellent, with more than 3,000 patients being reported in the literature, consistent long-term DFS rates of 96%, and OS rates of 98%.2 However, there have been recent concerns about second malignancies and cardiovascular morbidity after 10 to 15 years.2,13 Randomized studies have demonstrated that radiotherapy can be safely limited to the para-aortic field14 and the dose reduced to 20 Gy.15 Acute toxicity is reduced in this way while efficacy results are superimposable. Nevertheless, longer follow-up is needed to confirm the decrease in delayed morbidity. The success of surveillance in stage I nonseminomatous germ cell tumors, the establishment of curative chemotherapy for advanced disease, and the improvements in CT imaging have prompted to test treatment alternatives to irradiation. Surveillance studies have shown that 18% of patients experience relapse, the majority in the para-aortic lymph nodes, but almost all recurrences can be treated successfully with salvage therapy. More than 900 patients managed by this approach have already been reported, with 5-year DFS rates of 80% to 85% and OS approaching 100%.3 The main advantage of surveillance is that more than 80% of patients can be spared overtreatment. However, long follow-up is required, which is expensive and stressful (the Damocles syndrome), requiring good protocol compliance. 4,16,17 A third treatment option is adjuvant chemotherapy with single-agent carboplatin. To date, nearly 600 patients so treated have been reported.18-21 Acute toxicity is mild, and long-term side effects have not been described. Moreover, 5-year DFS is 97% to 100%, with a 100% cause-specific OS. A recently published phase III randomized study with 1,447 patients (MRC-TE19) has demonstrated that adjuvant radiotherapy and a single cycle of carboplatin are roughly equivalent.5 However, both modalities imply that all patients need to be treated in a good-prognosis disease. With cure rates reaching 100%, whichever approach is chosen, a risk-adapted management theoretically fits into the armamentarium of clinicians dealing with this disease, in a similar way than for patients with stage I nonseminomatous germ cell tumors.22-24 Furthermore, reliable prognostic factors have been established and a high-risk group can be identified,3 although these criteria require further confirmation and refinement to increase their predictive value. To our knowledge, the GG studies are the only published ones evaluating a dual policy of postorchiectomy surveillance and selective adjuvant chemotherapy for stage I seminoma. In the first study, 59% of patients were safely spared from any form of therapy with 100% 5-year cause-specific survival. However, a 16% relapse rate on surveillance (similar to that expected in unselected stage I patients) made us question the predictive value of the risk criteria used (vascular invasion and pT stage).6 This study shows an acceptable relapse rate with both individually tailored treatment approaches, thus confirming the accuracy of the new prognostic factors (tumor size and rete testis invasion). Nonetheless, the percentage of treated patients has increased to 68%. To minimize potential overtreatment, in our third study, we are planning to restrict carboplatin to patients with both risk criteria. Then approximately 80% of patients with stage I seminoma would not receive adjuvant treatment. With only two (3.3%) of 60 patients experiencing relapse in the first study and seven (3.3%) of 214 patients experiencing relapse in the second study, we confirm two courses of carboplatin as an effective adjuvant treatment even for patients with high-risk disease. Compared with the results from the pooled analysis of patients on surveillance,3 the percentage of recurrences in our study is driven from an expected 12% to 30% (depending on the number of risk criteria) to less than 10% for all patient subsets. Given these results, a less intensive follow-up (with incremental cost savings) could be safely used within this risk-adapted treatment policy. Among the prognostic factors analyzed, younger age, increased serum preoperative BHCG levels, and rete testis invasion remain as statistically significant predictors of DFS in certain subgroups, the last one even after correcting for treatment effect. Perhaps younger patients and those with elevated BHCG levels represent a subgroup with a greater likelihood of having occult nonseminomatous germ cell tumor components. Probably a multivariate model including rete testis invasion, tumor size, patient age, and serum preoperative BHCG could better predict the individual risk of tumor relapse and allow a better treatment stratification for patients with stage I seminoma. Although Oliver et al5 used one course of carboplatin in their randomized trial, there have been recent concerns that two courses are more effective19 and thus justified for high-risk cases. Again, acute toxicity was manageable. Our results also suggest that this risk-adapted treatment policy is safe and feasible in a nation-wide multicenter setting, as long-term results are equivalent to that achieved with other modalities (ie, no seminoma-related mortality was seen). The simplification of treatment according to our multicenter protocol means that there would be reduced referral of early-stage testis cancer to specialist centers to discriminate between high- and low-risk patients. However, longer follow-up is needed to rule out the occurrence of late relapses and delayed toxicity of chemotherapy in this series. Furthermore, our results should be confirmed by other groups before integrating into clinical practice. In conclusion, this dual treatment policy for patients with stage I seminoma is feasible, spares 30% of cases from adjuvant treatment without comprising long-term results, and could become a risk-adapted alternative to systematic approaches such as irradiation, surveillance, and carboplatin.
Participating members of the Spanish Germ Cell Cancer Cooperative Group are as follows: Jorge Aparicio (Hospital Universitario La Fe, Valencia), José R. Germà, Xavier García del Muro (Idibell-Institut Catalá d’Oncologia Duran i Reynals, Barcelona), Pablo Maroto (Hospital de Sant Pau, Barcelona), José A. Arranz (Hospital General Universitario Gregorio Marañón, Madrid), Alberto Sáenz (Hospital Clínico Universitario Lozano Blesa, Zaragoza), Agustín Barnadas (Hospital Universitari Germans Trias i Pujol, Badalona), Joan Dorca (Hospital Universitari Josep Trueta, Girona), Josep Gumà (Hospital Universitari de Sant Joan, Reus), David Olmos (Hospital Clínico Universitario Virgen de la Victoria, Málaga), Romá Bastús (Hospital Mutua de Terrassa, Barcelona), Joan Carles (Hospital del Mar, Barcelona), Daniel Almenar (Hospital Universitari Doctor Peset, Valencia), Miguel Sánchez (Hospital Donostia, San Sebastián), Luis Paz-Ares (Hospital Universitario 12 de Octubre, Madrid), Juan J. Satrústegui (Instituto Oncológico de Guipúzcoa, San Sebastián), Begoña Mellado (Hospital Clinic i Provincial, Barcelona), Ana Balil (Hospital Universitari Arnau de Vilanova, Lleida), Marta López-Brea (Hospital Universitario Marqués de Valdecilla, Santander), Alfredo Sánchez (Hospital Provincial, Castellón), Sergio Vázquez (Hospital Xeral-Calde, Lugo), Miguel A. Climent (Instituto Valenciano de Oncología), Francisco J. Carabantes (Hospital Carlos Haya, Málaga), Amparo Oltra (Hospital Virgen de los Lirios, Alcoy), María Lomas (Hospital Infanta Cristina, Badajoz), Alvaro Sanz (Hospital Clínico Universitario, Valladolid), María J. Méndez (Hospital Reina Sofía, Córdoba), Javier Sastre (Hospital Clínico San Carlos, Madrid), Carmen Crespo (Hospital Ramón y Cajal, Madrid), Antonio Fernández (Hospital General Universitario, Albacete), Dr Alfaro (Hospital de Terrassa, Barcelona), Eduard Batiste-Alentron (Hospital General de Vic, Barcelona), Dr Lasso de la Vega (Hospital Virgen del Rocío, Sevilla), Norberto Batista (Hospital Universitario de Canarias, Tenerife), Josefa Terrasa (Hospital Son Dureta, Mallorca), Adolfo Murias (Hospital Insular de Gran Canaria), Javier Cassinello (Hospital Universitario de Guadalajara), Juan A. Virizuela (Hospital Jerez de la Frontera, Cádiz), Enrique Barrajón (Hospital General, Elche), Sonia Del Barco (Hospital Clínico San Cecilio, Granada), Dr Montesinos (Hospital Parc Taulí, Sabadell), Nuria Laínez (Hospital de Navarra, Pamplona), and Purificación Martínez (Hospital de Basurto, Bilbao).
The authors indicated no potential conflicts of interest.
Presented in part at the 40th Annual Meeting of the American Society of Clinical Oncology, June 5-8, 2004, New Orleans, LA. See online Appendix for other Germ Cell Cancer Cooperative Group members participating in the study. Authors' disclosures of potential conflicts of interest are found at the end of this article.
1. Chang SS, Roth B: Treatment of clinical stage I germ cell tumors. Urology 59:173-179, 2002[CrossRef][Medline] 2. Zagars GK: Management of stage I seminoma: Radiotherapy, in Horwich A (ed): Testicular Cancer: Investigation and Management (ed 2). London, United Kingdom, Chapman & Hall, 1996, pp 99-121
3. Warde P, Specht L, Horwich A, et al: Prognostic factors for relapse in stage I seminoma managed by surveillance: A pooled analysis. J Clin Oncol 20:4448-4452, 2002 4. Sternberg CN: The management of stage I testis cancer. Urol Clin North Am 25:435-449, 1998[CrossRef][Medline] 5. Oliver RT, Mason M, Von der Masse H, et al: A randomised comparison of single agent carboplatin with radiotherapy in the adjuvant treatment of stage I seminoma of the testis, following orchidectomy: MRC TE 19/EORTC 30982. Proc Am Soc Clin Oncol 23:385, 2004 (abstr 4517)
6. Aparicio J, García del Muro X, Maroto P, et al: Multicenter study evaluating a dual policy of postorchiectomy surveillance and selective adjuvant single-agent carboplatin for patients with clinical stage I seminoma. Ann Oncol 14:867-872, 2003 7. Hermanek P, Sobin LH: UICC: TNM Classification of Malignant Tumours (ed 5). Berlin, Germany, Springer, 1997
8. Arranz JA, García del Muro X, Gumà J, et al: E400P in advanced seminoma of good prognosis according to the International Germ Cell Cancer Collaborative Group (IGCCCG) classification: The Spanish Germ Cell Cancer Group experience. Ann Oncol 12:487-491, 2001 9. Kaplan E, Meier P: Nonparametric estimation from incomplete observations. J Am Stat Assoc 53:457-481, 1958[CrossRef] 10. Mantel N: Evaluation of survival data and two new rank order statistics arising in its consideration. Cancer Chemother Rep 50:163-170, 1966[Medline] 11. Einhorn LH: Treatment of testicular cancer: A new and improved model. J Clin Oncol 8:1777-1781, 1990[Abstract] 12. Germà-Lluch JR, García del Muro X, Maroto P, et al: Clinical pattern and therapeutic results achieved in 1490 patients with germ-cell tumours of the testis: The experience of the Spanish Germ-Cell Cancer Group (GG). Eur Urol 42:553-563, 2002[CrossRef][Medline]
13. Zagars GK, Ballo MT, Lee AK, et al: Mortality after cure of testicular seminoma. J Clin Oncol 22:640-647, 2004
14. Fossa 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
15. Jones WG, Fossa 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 Organization for the Research and Treatment of Cancer trial 30942 (ISRCTN18525328). J Clin Oncol 23:1200-1208, 2005 16. Sharda NN, Kinsella TJ, Ritter MA: Adjuvant radiation versus observation: A cost analysis of alternate management schemes in early-stage testicular seminoma. J Clin Oncol 14:2933-2939, 1996[Abstract] 17. Fossa SD, Moynihan C, Serbouti S: Patients' and doctors' perception of long-term morbidity in patients with testicular cancer clinical stage I: A descriptive pilot study. Support Care Cancer 4:118-128, 1996[CrossRef][Medline] 18. Oliver RTD, Edmonds PM, Ong YJH, et al: Pilot studies of 2 and 1 course carboplatin as adjuvant for stage I seminoma: Should it be tested in a randomized trial against radiotherapy? Int J Radiat Oncol Biol Phys 29:3-8, 1994[Medline] 19. Dieckmann KP, Brüggeboes B, Pichlmeier U, et al: Adjuvant treatment of clinical stage I seminoma: Is a single course of carboplatin sufficient? Urology 55:102-106, 2000[CrossRef][Medline]
20. Reiter WJ, Brodowicz T, Alavi S, et al: Twelve-year experience with two courses of adjuvant single-agent carboplatin therapy for clinical stage I seminoma. J Clin Oncol 19:101-104, 2001 21. Steiner H, Höltl L, Wirtenberger W, et al: Long-term experience with carboplatin monotherapy for clinical stage I seminoma: A retrospective single-center study. Urology 60:324-328, 2002[CrossRef][Medline]
22. Cullen MH, Stenning SP, Parkinson ME, et al: Short-course adjuvant chemotherapy in high-risk stage I nonseminomatous germ cell tumors of the testis: A Medical Research Council report. J Clin Oncol 14:1106-1113, 1996
23. Pont J, Albrecht W, Postner G, et al: Adjuvant chemotherapy for high-risk clinical stage I nonseminomatous testicular germ cell cancer: Long-term results of a prospective trial. J Clin Oncol 14:441-448, 1996 24. Böhlen D, Borner M, Sonntag RW, et al: Long-term results following adjuvant chemotherapy in patients with clinical stage I nonseminomatous malignant germ cell tumors with high risk factors. J Urol 161:1148-1152, 1999[CrossRef][Medline] Submitted March 11, 2005; accepted June 1, 2005.
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Copyright © 2005 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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ABSTRACT
INTRODUCTION
30 years v > 30 years), tumor diameter (
2 test was used to compare proportions between groups. Overall survival (OS) and disease-free survival (DFS) were estimated from the date of orchiectomy with the Kaplan-Meier method.
