MORTALITY AND REOPERATION FOLLOWING

PROSTATECTOMY: OUTCOMES IN A

MEDICARE POPULATION*

ZACHARY TAYLOR, M.D. , M.S. HENRY KRAKAUER, M.D. , PH.D.

From the Agency for Heal th Care Policy and Research, Heal th Care Financing Administrat ion, and University of Maryland , Balt imore, Mary land

ABSTRACT--Data from a series of pilot projects undertaken by the Health Care Financing Administration and seven peer review organizations were used to evaluate the outcomes of prostatectomy. Outcomes in both the original ran- dom sample of 3,641 patients and subsample of 2,617 patients that had a diagnosis of benign prostatic hyperplasia and did not have a diagnosis of pros- tatic carcinoma were examined. Patients undergoing a transurethral resection had increased probabilities oil reoperation and mortality. However, the in- creased risk associated with having a transurethral resection was not statisti- cally significant after controlling for other variables associated with mortality.

in spite of the recent proliferation in therapeutic al- ternatives for the treatment of benign prostatic hy- p~rplasia, prostatectomy remains an important tr6atment option. In 1968, Lytton, Emery, and Har- Vard I reported that a forty-year-old man had a 10 percent chance of undergoing a prostatectomy in his iiietime. In 1985, the probability of a forty-year-old marl having a prostatectomy had increased to 29

percent as estimated from results of the Normative :A~ng Study. 2 Prostatectomy is considered a safe :operation with low postoperative mortality, with tra~surethral resection of the prostate having lower

reported postoperative mortality than open prosta- !ee~0my.3-5 However, recent population-based stud- !~:6sing administrative databases have found hi~her :m6rtality rates than previously reported in ~,ese :ease series and have not confirmed the reported IOW~r postoperative mortality following transure- • fal resection of the prostate compared with open prostatectomy. 6-9

This study utilizes clinical data abstracted from :the medical record of the hospitalization for initial

ork not supported by a grant or financial aid, and is not a report of a government agency.

i

SUPPLEMENT TO UROLOGY /

prostatectomy combined with Medicare administra- tive data to follow patients for up to two years after prostateetomy. The objective of the study was to look at the long-term rates of mortality and reopera- tion following prostatectomy and to determine which clinical factors are associated with mortality.

Material and Methods

In 1985 and 1986 the Health Care Financing Ad- ministration undertook a series of pilot projects with seven peer review organizations in Alabama, Ar- izona, Indiana, New York, Pennsylvania, Utah, and Wisconsin to study outcomes of selected medical and surgical procedures. A random sample of 3,641 Medicare enrollees who underwent prostatectomy in 1985 was selected as part of this pilot project. There were 283 open prostatectomies and 3,330 transure- thral resections in this sample, with transurethral re- sections accounting for 92 percent of the prostatecto- roles. The records from the hospitalizations were abstracted and abnormalities covering admission symptoms, history, and the results of preadmission tests were encoded if documented in the medical record, physical examinations, and laboratory or

JULY 1991 / VOLUME XXXVIII, NUMBER 1 27

P E R C E N T R E O P E R A T I O N 5 , 0 % ...........................................................................................................................................................................................................................

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D A Y S F O L L O W I N G S U R G E R Y

FICU~E 1. Reopera t ion fo l lowing pros ta tec tomy: T U R P vs open prosta- t ec tomy (A = subsample N = 2,617; B = original sample N = 3,641). - * - T U R P (A); -[E- O P E N (A); - x - T U R P (B); -(>- O P E N (B).

diagnostic tests. Also included were up to 30 ICD-9 diagnostic and up to 30 ICD-9 procedure codes. These data were then linked to Medicare enrollment and Part A files for 1985 and 1986. These files con- tain the dates of admission and discharge for hospi- talizations, up to five diagnostic and five procedure codes, charges, and if necessary, the date of death as determined by the Social Security Administration.

Of the original 3,641 patients in the sample, 2,617 were identified as having a diagnosis of benign pros- tatic hyperplasia and not having a diagnosis of pros- tatic carcinoma. There were 168 open prostatecto- mies and 2,449 transurethral resections in this sample, with transurethral resections accounting for 93.6 percent of the prostateetomies. The analyses re- ported in this study were conducted using both the original sample of 3,641 patients and the subsample of 2,617 patients.

Survival analysis employing a life-table method 1° was used to estimate the differences between the two surgical approaches (transurethral resection vs open) in reoperation and postoperative mortality rates for both the original sample (n = 3,641) and the subsample (n = 2,617), Cox proportional haz- ards linear regression analysis was used to assess the relationship between the type of surgery and postop- erative mortality in the subsample of patients that had a diagnosis of benign prostatic hyperplasia and did not have a diagnosis of prostatic carcinoma. H

A three-step process was used in the selection of the control variables utilized in the final model. Those variables found in 30 or more patients were selected, with variables of doubtful reliability elimi- nated. First, chi-square tests were used to determine

which variables were associated with the outcomes of interest. Second, the variables were grouped in related clusters 12 and those variables which were sig- nificantly related to the outcome were identified in each duster. Lastly, backward stepwise regression was used to identify those variables which best pre L dicted mortality after surgery, retaining only those[ variables with a regression coefficient that was l statistically significant (p < 0.01). The type of sur; gery was then inserted into the model to estimate tM relative risk of postoperative mortality.

Results

Survival analysis o f reoperation and "mortality

The cumulative probablhty of reoperation for th~l two types of procedures in both samples is illustrate~l~ in Figure 1. The difference between the two types 0~!i procedures in the original sample was statisticali~i ~ significant (p < 0.05), with the cumulative proba~ bility of having a repeat prostateetomy after tW years being 4.44 percent following a transurethI resection and 1.48 percent following an open prost teetomy.

For the subsample of the patients with benigl prostatic hyperplasia, the two-year cumulatt probability of having a repeat prostateetomy w 2.72 percent following a transurethral resection ai 1.84 percent following an open prostatectomy. Tt difference was not statistically significant. In bo! samples, the probability of reoperation demo strates an increased linearity with time in the p tients who underwent a transurethral resection.

28 SUPPLEMENT TO UROLOGY / JULY 1991 / VOLUME XXXVIII, NUMBEI!~

~ The cumulative probability of mortali ty for the ~two types of procedures in both samples is illustrated ~in Figure 2. The differences between the two types

if procedures were statistically significant in both a~ples (p < 0.05). After two years, the cumulative ir6bability of mortali ty following transurethral re- ection was 17.42 percent in the.original sample and

14.31 percent in the subsample. In comparison, the ~tW0:year cumulative probability of mortali ty fol- ~lowing an open procedure was 7.5 percent in the ~0riginal sample and 7.09 percent in the subsample. ~!irhe difference between the probabilities of death ~j fbli0wing a transurethral resection in the two sam- ~pl~ increased with time, whereas they were almost

5entieal for patients having an open procedure. T h e differences in mortali ty were apparent at hlrty days in both samples with the probability of [eath in the original sample being 1.1 percent for

patients having a transurethral resection and 0.71 percent in patients having an open procedure. In the

~gubsample of patients with benign prostatic hyper- ~plasia, the probability of death at thirty days was ~0.94 percent for patients having a transurethral ren

seetion and 0.60 percent for patients having an ope

~ pr0eedure.

~Cox Proportional Hazards L inear ~ltegression Model

Twelve variables were included in the final regres- !~ ion model predicting mortali ty in the subsample of ~2,617 patients that had a diagnosis of benign pros-

~ tlc hyperplasia. The incidence of these variables I~ I etween the two procedures is shown in Table I. ~None of the differ nc b t een e o r u as ~} e es e w th tw g o p s w

~UPPLEMENTTO UROLOGY / JULY1991 / VOLUME

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14% .......................................................................................................................................................................................................... ;~::::[ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12%

10 % .......................................................................................................................................................................... :::::2": ............................................................................

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0% I I I I

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D A Y S F O L L O W I N G S U R G E R Y

FIGURE 2. Cumula t i ve mortal i ty f o l l ow ing pros tatec tomy: T U R P vs open pros ta tec tomy (A = subsample N = 2,617; B = original sample N = 3,641). - • - T U R P (A); - D - O P E N (A); - x - T U R P (B); -~)- O P E N (B).

TABLE I. Distr ibut ion of variables b e t w e e n T U R P and open pros ta tec tomy

Open Variable TURP (%) Prost. ( % )

Age (yrs.) 65-69 617 (25) 39 (23) 70-74 765 (31) 60 (36) 75-79 538 (22) 44 (26) 80-84 297 (12) 15 (9) _>85 136 (5) 7 (4)

Physical and laboratory findings Atrial fibrillation 73 (3) 4 (2) Taehyeardia 54 (2) 9 (5) Albumin <3.0 27 (1) 3 (2) Elevated BUN 186 (8) 10 (6) Lung infiltrate 36 (1.4) 5 (3)

Comorbidities (listed as additional ICD-9 Codes) Congestive heart failure 37 (1.5) 1 (0.6) Obstructive pulmonary

disease 213 (9) 13 (8) Cancer 97 (4) 1 (0.6)

Significant medical history Diabetes 259 (11) 17 (10) Metastasis 11 (0.5) 0 Chronic obstructive

pulmonary disease 242 (10) 13 (8)

statistically significant except for the percent having a eomorbidity of cancer listed as a diagnosis. In the group of patients undergoing a transurethral resec- tion, 4 percent had a diagnosis of cancer whereas only 0.6 percent of patients undergoing an open pro- eedure had a diagnosis of cancer.

The relative risk of mortali ty following prostatee- tomy was 1.68 (95% CI 0.89, 3.17) for patients un- dergoing a transurethral resection (Table II). Similar

XXXVIII, NUMBER 1 29

TABLE II. Predictors o f m o r t a l i t y ]o l lowing p r o s t a t e c t o m y

Relative Variable Risk 95 % CI

TURP 1.68 0.89-3.17 History of metastasis 5.74 2.84-11.57 Congestive heart failure 3.56 2.09-6.09 Cancer 3.15 2.16-4.60 Elevated BUN 2.75 2.03-3.73 Albumin <3 2.69 1.45-4.99 Atrial fibrillation 2.33 1.46-3.71 Lung infiltrate 2.22 1.25-3.95 Obstructive pulmonary disease 2.17 1.49-3.15 History of diabetes 2.04 1.50-2.78 Taehycardia 1.88 1.12-3.15 History of COPD 1.56 1.09-2.22 Age* 1.13 1.10-1.15

*Age squared. ~95 % confidence interval.

to ease studies, increasing age, elevated blood urea nitrogen value, history of diabetes, and indicators of poor cardiorespiratory health were all associated with mortality following prostateetomy. Another in- dication of poor health, having an albumin less than 3.0, was strongly associated with mortali ty with a relative risk of 2.69 (95% CI 1.45, 4.99). Finally, having both a eomorbidity of cancer and a history of metastasis were strongly associated with subsequent mortality.

Comment

The results of this study are similar to other popu- lation-based studies using administrative data in finding higher postoperative mortality rates than re- ported in ease series. Roos and associates 9 reported ninety-day mortality rates of 2.47 percent in Den- mark, 1.73 percent in Manitoba, and 4.39 percent in Oxford, U.K., following transurethral resection of the prostate in one study. In a separate study, Roos and Ramsey 7 found a postoperative mortali ty rate of 1.6 percent after forty-two days. This study found a thirty-day probability of mortali ty of 1.1 percent and a ninety-day probability of mortali ty of 3.25 percent for patients undergoing a transurethral re- section in the original sample. In the subsample of patients, the probabilities of mortali ty at thir ty and ninety days for patients undergoing a transurethral resection were 0.94 percent and 2.57 percent, re- spectively. This compares with a 0.23 percent thirty- day mortality following transurethral resection re- p o r t e d in a r ecen t ease series i n v o l v i n g 13 participating institutions. 5 Differences in postopera- tive mortality between ease series and population- based studies may be due to ascertainment of death and in how postoperative mortali ty is defined as il-

lustrated by a 1985 study of the outcomes of surgery among the Medicare aged that established only 4 I percent of the deaths within forty-five days after surgery took place in the hospital.~3

This study was also similar to other population- based studies using administrative data in finding increased probabilities of mortality and reoperation for patients having a transurethral resection com- pared with open prostateetomy. However, after e°n- trolling for other variables associated with mortal- ity, the risk of mortality a t t r ibutable to having a transurethral resection, although higher, was not statistically significant. Roos and colleagues 9 also found that the elevated risk of mortality associated with transurethral resection in a healthy subgroup of patients was not statistically significant and Wennberg et al. 6 reported no difference in mortality~ between transurethral resection and open prostatee~ tomy in teaching hospitals. This may indicate t h a t there is not an increased risk of mortality attribut~:~ able to the type of procedure, but that surgeons mayi~ select a transurethral resection in patients whose! health would preclude an open prostateetomy.

This type of study cannot provide the level of evi-:i ~ denee that well-designed prospective studies or clini~:~ eal trials can. The limitations of administrative data~i are well known, ~3 and clinical data abstraction from '*: medical records earinot match the thoroughness of data collection methods employed in prospectiv, studies. The results of this and previous studies usin~ administrative data do indicate that the very lo~ postoperative mortality observed following tran. urethral resection in ease series may not be repri sentative and may indicate the need for prospeetiv! clinical studies to evaluate the two procedures to bl undertaken.

Agency for Toxic Substances and' D1V1 1 Disease Regis[r~

Heal" 's'on of Health Studi~ th Investigations BranCi

Mailstop E-3 1600 Clifton Road, N] Atlanta, Georgia 303~

(DR. TAYLOt

References

1. Lytton B, Emery JM, and Harvard BM: The incidence ~ benign prostatic obstruction, J Urol 99:639 (1968).

2. Glynn RJ, et ah The development of benign prostatic hyper!~ Atoll plasia among volunteers in The Normative Aging Study, i~

Epldemlol 121:78 (1985). 3. Holtgrewe HL, and Valk WL: Factors influencing the rn0~!

tality and morbidity of transurethral prostatectomy: a study ~ 2,015 cases, J Urol 87:450 (1962).

4. Melchior J, et ah Transurethral prostatectomy: compate,r~ ized analysis of 2,223 consecutive cases, J Urol 112:634 (1974)~

5. Mebust WK, et al: Transurethral prostatectomy: immedia!~ :a~ and postoperative complications. A cooperative study of 13 par~

30 SUPPLEMENT TO UROLOGY / JULY 1991 / VOLUME XXXVIII, NUMBEtt~

i i l c i p a t i t t g institutions evaluating 3,885 patients, J Urol 141:243

(1989). nber¢ rE, ah Use of claims data systems to evatuate G W e n ~ j et health Care outcomes: mortality and reoperation following pros- taieetorny, JAMA 257:933 (1987).

ROOS NP, and Ramsey EW: A population-based study of .... "atectomy: outcomes associated with differing surgical ap- Pr°aStehes I Urol 137:1184 (1987). Pr~9 Wennberg JE, et ah An assessment of prostateetomy for b6~gn urinary tract obstruction: geographic variations and the ev~uation of medical care outcomes, JAMA 259:3027 (1988). ;i 91 l~oos NP, et ah Mortality and reoperation after open and traiasurethral resection of the prostate for benign prostatic hyper-

plasia, N Engl J Med 320:1120 (1989). 10. SAS Institute Inc.: The Lifetest Procedure, in SAS User's

Guide: Statistics, Version 5 edition, Cary, NC, SAS Institute !ng., 1985, p 529.

11. Harrell FE: ThePHGLM Procedure, in SAS Institute Inc. : SUGI Supplemental Library User's Guide, Version 5 edition, Cary, NC, SAS Institute Inc., 1986, p 437.

12. SAS Institute Inc.: The CLUSTER Procedure, in SAS User's Guide: Statistics, Version 5 edition, Gary, NC, SAS Institute Inc., 1985, p 255.

13. Lubitz J, Riley G, and Newton M: Outcomes of surgery among the Medieare aged: mortality after surgery, Health Care Financing Rev 6:103 (1985).

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