Renal Cell Carcinoma - Metastasis to Bone

These images are from a 75 year old man with a large painful scapular mass, which proved to be a renal cell cancer metastasis.  He had complete resection of this mass and now has a chance for long term survival, a prospect not enjoyed by most patients with metastatic adenocarcinomas.

Although renal cell cancers rank as the approximately sixth most common site of origin of metastatic deposits in the skeleton, this tumor has several unique features that increase its significance.
First, the metastatic deposits may occur many years after the primary tumor has been treated.  This means a patient who seems to be cures after a RCCA is removed from the kidney needs to be monitored for up to ten years for possible bone metastasis.

Second, RCCA metastases may occur as a solitary focus of disease, and as such an
en bloc surgical resection of a solitary metastasis may render the patient free of cancer and offer hope for a cure.  These patients have been shown to enjoy significantly better survival if aggressive treatment is used.  Palliative surgery for these solitary metastatic deposits is not indicated and may lead to spreading the cancer.  Instead, the lesion should be evaluated by an experienced orthopaedic oncologist for possible curative resection.

Although the number of cases of this cancer is proportionally small, the tumor has a high avidity for bone and thus creates relatively large number of bone lesions. Patients are usually over 40, and the average age is around 55. Patients may have no other manifestation of cancer other than their painful bone lesion. Because the primary tumor can grow fairly large without creating local symptoms such as flank pain or a mass in the abdomen, kidney cancer often presents only when a metastasis develops.  Hematuria is also a  common sign, but small amounts of blood in the urine cannot be detected without a urinalysis  When a patient has a metastasis and no site of origin can be found  (a metastasis of unknown origin) the most likely site is the lung or kidney.

Pain is the most common presenting symptom.  Pathological fracture rarely occurs without a history of a few weeks or months of increasingly severe pain.  In some cases the patient has tried to ignore or deny the symptoms.  Sometimes a painful bone lesion is thought to be a "muscle pull" or a "sprain" and strong pain medicines are prescribed, allowing the patient to continue to tolerate very severe pain before the true nature of the problem is discovered. Systemic symptoms may also occur, such as hypercalcemia.  An occasional patient may have hypertesion from the tumor affecting the renin-angiotensin pathway.

Kidney cancer metastasis most commonly affects the spine, ribs, pelvis, and proximal long bones. Kidney cancer may metastasize extremely late after the treatment of the primary lesion, up to ten years or more.  Why the tumor seems to lay dormant for so long and then suddenly pop up in the bone is not known. Another unusual feature of this lesion is its extremely aggressive appearance and behavior in some cases.  Lesions may be large and appear as a "blowout" of the particular bone involved.  Kidney cancers are more likely to become "hideously large" than other lesions, due to their propensity to extend massively in the soft tissues surrounding the bone. Since the kidney is comprised of mostly blood vessels, kidney cancer metastases may also have a rich blood supply, and may bleed extensively (even audibly) after a simple biopsy.  When you see a patient over age 40 with hematuria and a large blow-out bone lesion, think kidney cancer.

Kidney cancer with metastasis to bone can be a very aggressive tumor and patients with multiple bone lesions at presentation have an unfavorable prognosis.  Radiation is not very effective in palliating this lesion, and no conventional chemotherapy is available.  Advanced cancer centers, like the University of Massachusetts and others have ongoing research and clinical trials ongoing.  I believe all patients should be started and maintained on bisphosphonates as soon as a diagnosis of metastasis to bone is confirmed.  The average survival after the diagnosis of metastasis to bone is about 12 - 18 months. 

A few selected cases have been associated with prolonged survival with appropriate treatment.  Patients who present with a SINGLE bone metastasis, whose primary tumor can be resected with negative margins, may be treated with curative intent.  This means these patients have a chance for a cure, and "palliative" care is not appropriate in these special cases.  The prognosis is even more favorable if there has been a prolonged period between the treatment of the primary tumor and the discovery of the metastasis.  Kidney cancer is one of the few types of metastatic adenocarcinoma that may be cured by surgery.  Physicians unfamiliar with these recent developments in the treatment of this disease should consider referring the patient to a regional or national cancer center.  When there are several sites of bone metastasis, treatment follows general principles.  Orthopedic stabilization of weakened bones should be done promptly, before fractures can occur.  Patients should receive complete treatment according to their wishes and the extent of the disease.  Orthopaedic stabilization of actual or impending pathological fractures should not be withheld unless the patient cannot tolerate anaesthesia or would definitely not be benefited by surgery. The pain relief that is expectedfrom stabilization of damaged bones is a good enough reason for surgery, even if the patient cannot enjoy a functional benefit, such as increased walking ability.





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