Transplantation of human renal cell carcinoma into NMRI nu/nu mice. III. Effect of irradiation on tumor acceptance and tumor growth

Radiotherapy and Renal Cell Carcinoma: A Continuing Saga

Renal cell carcinoma (RCC) is one of the most aggressive malignancies of the genito-urinary tract, having a poor prognosis especially in patients with metastasis. Surgical resection remains the gold standard for localized renal cancer disease, with radiotherapy (RT) receiving much skepticism during the last decades. However, many studies have evaluated the role of RT, and although renal cancer is traditionally considered radio-resistant, technological advances in the RT field with regards to modern linear accelerators, as well as advanced RT techniques have resulted in breakthrough therapeutic outcomes. Additionally, the combination of RT with immune checkpoint inhibitors and targeted agents may maximize the clinical benefit. This review article focuses on the role of RT in the therapeutic management of renal cell carcinoma.

Role of radiation therapy for renal tumors

Renal cell carcinoma (RCC) is an aggressive malignancy that carries a poor prognosis, especially in patients presenting with advanced stage. Primary treatment for localized RCC is surgical resection however, a significant number of patients still develop locoregional and distant metastasis after curative resection. In metastatic disease, radiation therapy (RT) has been used for palliation routinely for brain and other extracranial lesions with respectable response rates. However, RT for primary RCC has questionable benefit. In this article, the authors discuss the evidence with regards to the role of RT in primary RCC either as a primary treatment, adjuvant treatment, or preoperatively to improve resection outcomes. In addition, novel RT techniques such as stereotactic body radiation therapy and its use in RCC management are also addressed. Finally, the authors discuss the techniques and doses of RT for primary RCC.

[Standards, options, and recommendations for radiotherapy of kidney cancer]

CONTEXT

The "Standards, Options and Recommendations" (SOR), initiated in 1993, is a collaborative project between the Federation of the French Cancer Centres (FNCLCC), the 20 French Cancer Centres and specialists from French Public Universities, General Hospitals and Private Clinics. The main objective is the development of clinical practice guidelines to improve the quality of health care and outcome for cancer patients. The methodology is based on literature review and critical appraisal by a multidisciplinary expert group, with feedback from specialists in cancer care delivery.

OBJECTIVES

To develop clinical practice guidelines for the diagnosis, management and treatment of patients with renal cancer. This review is part of previously published complete guidelines and focuses on the place of radiotherapy in this disease.

METHODS

The data was identified by literature search using Medline (up to June 1999) and personal reference lists. The main endpoints considered were survival, risk factors for late effects of radiotherapy, safety and quality of life.

RESULTS

The key recommendations are: 1) In localised renal cancer, adjuvant radiotherapy has a limited role: it is not indicated for T1 and T2 tumours and there is no proof of a survival benefit for T3 N1-N2 tumours. Postoperative radiotherapy can be considered in young patients without risk factors for the development of post-radiotherapy complications and without loco-regional invasion (renal capsule, renal pelvis, vena cava, regional lymph nodes); 2) For metastatic tumours, the multidisciplinary team must decide whether palliative radiotherapy is appropriate after consideration of the prognostic factors. An isolated metastasis can be treated by radiosurgery and stereotaxic radiosurgery may be of benefit in the case of one or two cerebral metastasis. The optimal dose for palliative treatment is not known. Radiotherapy followed by immunotherapy can also be considered if the patient has no contraindication to such treatments.

The role of interleukin-6 in the induction of hypercalcemia in renal cell carcinoma transplanted into nude mice

Hypercalcemia is a well known complication of renal cell carcinoma (RCC). As RCCs can produce IL-6, and IL-6 may stimulate bone resorption and cause mild hypercalcemia, we examined whether IL-6 is involved in renal cancer-associated hypercalcemia in vivo. Three human renal cell carcinoma tumor lines (RC-8, RC-9, and NC-65) growing in nude mice were studied. Tumors were implanted s.c., and parameters of bone metabolism and serum human IL-6 levels were determined in relation to tumor volume (TV). All three tumor lines secreted human IL-6, although in different quantities. The maximum level of IL-6 in RC-8 was 434 pg/ml (TV, 200 mm3), that in RC-9 was 81 pg/ml (TV, 1800 mm3), and that in NC-65 was 2368 pg/ml (TV, 1800 mm3). Hypercalcemia developed in RC-8 and RC-9 tumor-bearing animals, but not in NC-65-bearing animals. The hypercalcemia in both RC-8 and RC-9 tumor lines was associated with elevated levels of PTH-related peptide (PTHrP) and loss of trabecular bone volume. Serum calcium and phosphate concentrations showed an almost linear relationship with plasma PTHrP independently of the tumor line and serum IL-6 levels. No hypercalcemia occurred in the NC-65 animals, which had the highest levels of IL-6, but no detectable plasma PTHrP and PTHrP messenger RNA expression in the tumor. Administration of neutralizing antibodies to IL-6 to RC-8 animals normalized serum calcium concentrations and PTHrP values and induced a significant inhibition of tumor growth. No such effect on tumor growth of anti-IL-6 was seen in the other two tumor lines. The normalization of serum calcium in RC-8 mice is most likely attributed to the growth-inhibiting effect of anti-IL-6 on RC-8 tumor. We conclude that IL-6 secreted by RCC does not contribute directly to hypercalcemia, but may enhance hypercalcemia by stimulating the tumor growth of a subpopulation of PTHrP-secreting carcinomas.

Monoclonal antibody-targeted radiotherapy of renal cell carcinoma using a nude mouse model

Radiation dosimetry and monoclonal antibody (MAB)-targeted radiotherapy studies were performed to evaluate the feasibility of using tumor-preferential MAB as targeting agents for internal radiotherapy of renal cell carcinoma (RCC). Two human RCC xenograft lines, TK-177G and TK-82, were established in nude mice and studied using MAB A6H as a targeting agent. This MAB has previously demonstrated excellent in vivo localization to RCC xenografts. Two doses of A6H (13 to 19 micrograms) labeled with iodine 131 (110 to 130 microCi) caused the tumor to regress or arrested the tumor growth in both xenografts. Similar doses (18 to 43 micrograms; 120 microCi) of 131I-labeled control MAB AFP-22 or of unlabeled A6H did not inhibit tumor growth. While most mice in the control groups had tumors greater than 250 mg in weight by day 43, none of the tumors in mice treated with 131I-labeled A6H grew to that size during the 3-month observation period. Sequential computerized scintigraphy was used to calculate the amount of radioisotope localized in tumor versus normal mouse tissue. Therapeutic doses of 131I-labeled A6H delivered a median calculated radiation dose of 38 cGy/microCi (range, 28 to 57) injected dose to RCC xenografts, and a median of 0.9 cGy/microCi to normal mouse tissues. These findings suggest that A6H is able to target radioisotopes highly specifically to RCC and achieve a therapeutic effect in the experimental setting.

Chemotherapy and human bladder carcinoma transplanted into NMRI nu/nu mice

Transitional and squamous-cell carcinomas of the bladder that were transplanted and successfully retransplanted in further passages to NMRI nu/nu mice were used to test the efficacy of chemotherapy. Mitomycin and bleomycin consistently retarded tumor growth; results with platinex and methotrexate were variable. Combination therapy was not much better than single-drug therapy. Substances that proved effective in the mouse model produced some response in the corresponding patients in a series of patients on specific chemotherapy. In a previous study we have shown that tumor growth of transplanted human bladder carcinoma accelerates, unlike transplanted renal cell carcinoma when successfully subpassaged, resulting in a uniformly fast growing rate similar in all transplanted tumors including those which initially started with slow growing rates. Most importantly, however, tests in a given tumor conducted on a slow-growing early passage and on a fast-growing late passage produced different results. We concluded that this finding might explain the clinical observation that tumor remission due to chemotherapy in patients with metastatic bladder carcinoma does not last very long and seldom prolongs survival. It is assumed--it is not proved--that substances that proved effective in fast growing passages are probably likely to yield greater prolongation of life than those effective in slow-growing passages.