KIDNEY CANCER

Kidney cancer accounts for 2 to 3% of all cancers in adults and 85% of these are classified as renal cell carcinomas. The remaining 15% are transitional cell carcinomas which arise from the lining cell of the kidney and will not be further discussed. There has been some slight increase in incidence in the last decade probably due to increased use of CAT scans.

The cause of renal cell cancers is unknown but there is a positive correlation with cigarette smoking, exposure to asbestos and tanning (i.e. leather) products. Males are afflicted at double the rate of females. Patients on long term renal dialysis have a high incidence of renal cell cancers. There is a familial form of renal cancer: Von Hippell-Lindau Disease in which genetic markers have been identified.

Staging
As in almost all cancers effective treatment depends on whether or not cancer cells have spread beyond the cancerous organ. This determination is called staging. Multiple staging systems have been developed for renal cell carcinomas the most basic of which is as follows:

Stage 1 - Cancer is limited to the kidney and is one inch or less diameter.

Stage 2 - Cancer is confined to the kidney and is greater than 1 inch in diameter.

Stage 3 - Cancer has spread to the fat around the kidney or to the vein that drains blood from the kidney (renal vein) or to the large vein draining blood from the lower body (vena cava) or to the lymph nodes near the kidney.

Stage 4 - Cancer has spread to other abdominal organs or distant organs such as the lungs or bones. See diagram 1

Diagnosis
In years past most renal cell cancers were discovered because of blood in the urine, usually visible to the eye. Because of increased use of CAT scans and abdominal ultrasound, many kidney cancers are found "by accident". This is very fortunate since as we will discuss shortly many early (stage 1 and 2) cancers can be cured. High resolution CT scanning with "thin sections" and IV contrast are diagnostic for renal cell cancers in 65 to 95% of cases. Use of MRI scanning is occasionally useful in some cases where CAT scans are not diagnostic. Angiography is generally not necessary unless removing only part of the kidney is contemplated. Needle biopsy of renal lesions is rarely warranted and may be harmful.

Treatment
In stage 1 and 2 cancers, radical nephrectomy (removing the kidney with its surrounding fat and the adrenal gland) has been the standard of care. This assumes a healthy kidney on the other side. Results in stage 1 cancers reveal 60 to 90% 5-year survival rates and stage 2 lesions are only slightly lower. In cases in which small (< 1.25 inches in diameter) renal cell cancers have been found by accident there is increasing use of kidney sparing surgery. Early data suggests that results of this type of surgery are equal to radical nephrectomy but close follow-up with renal ultrasound are mandatory.

Treatment for stage 3 disease depends to some extent on why that stage was assigned. Renal vein involvement alone does not appear to adversely affect survival if the tumor is organ confined (ie without involvement of perinephric fat or lymph nodes). Radical nephrectomy with removal of the tumor thrombus will suffice. Involvement of the vena cava may go from the level of the renal vein all the way to the heart. Aggressive surgery to remove tumor from the vein, provided there is no evidence of local-regional or metastatic spread can result in 45 to 65% 5-year survival rates without regard to the extent of caval involvement. Lastly, there is the problem of nodal involvement and/or perinephric fat invasion. It appears that if the later occurs without nodal involvement, the survival rates are lower than stage 1 or 2 lesions. The issue as to whether or not complete removal of regional lymph nodes is beneficial remains controversial. It does seem obvious that node involvement markedly decreases survival.

Treatment of patients with stage 4 disease remains clouded. About one third of renal cell cancer patients present with metastatic disease. The median survival of this group of patients is less then one year. There is renewed interest in using palliative nephrectomy in conjuction with immunotherapy to increase survival rates. Interleukin-2 has been approved by the FDA in both high and low doses regimens. Toxicity of the drug remains a major problem. Multiple other regimens have been tried but unfortunately only about 10% of patients respond for any length of time. There are multiple experimental trials underway under the auspices of the National Cancer Institute (Call 1-800-4-CANCER or write National Cancer Institute, Office of Communications, Center Drive, MSC 2580 Bethesda, MD 20892-2580)