Influence of the Interval Between Primary Tumor Removal and Chemotherapy on Kinetics and Growth of MÃ©Tastases1

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[CANCER RESEARCH 43, 1488-1492, April 1983] 0008-5472/83/0043-OOOOS02.00 Influence of the Interval between Primary Tumor Removal and Chemotherapy on Kinetics and Growth of MÃ©tastases1

Bernard Fisher,2 Nurten Gunduz, and Elizabeth A. Saffer

Departmentof Surgery, Universityof Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania15261

ABSTRACT occurring in a residual tumor focus following removal of a transplantable C3H mammary tumor. The increased cellular prolifer In many animal models, primary tumor removal produces ation occurring in mÃ©tastases,noted in all of the investigations, increased proliferation of cells in metastatic foci. The present has received little attention, despite the potential importance of investigations using a murine mammary tumor were carried out the observation. This kinetic perturbation, because of its poten to determine how a variation in the time interval between primary tially harmful effect through acceleration of metastatic growth, tumor removal and administration of a single dose of cyclophos- requires consideration as to how it may be either abrogated or phamide (CY) affected labeling indices of residual tumor cells, exploited for therapeutic benefit. To our knowledge, no studies their growth, and animal survival. The CY (240 mg/kg) had a have been specifically directed toward that end. Such an effort more favorable effect when given on the day of tumor removal could produce information which might provide a more precise than 3 days after, a time when the labeling index (LI) of mÃ©tas biological rationale for the use of perioperative adjuvant chemo tases was at a peak. It was least effective if given at 7 days therapy. following primary tumor excision, when the LI had returned to The present report provides information concerning the effect the preoperative level. The greatest effect occurred when the of the time interval between primary tumor removal and CY3 CY was given prior to operation. It completely prevented the therapy on the LI of metastatic or residual tumor cells. It corre increase in LI resulting from tumor removal, more effectively lates those findings with the tumor growth and survival of ani suppressed the growth of residual tumor, and prolonged survival mals. to a greater extent than was noted under any other circum stance. The interval between tumor removal and administration MATERIALS AND METHODS of a relatively small amount of CY (60 mg/kg) was critical. When given on the day of tumor removal, an increase in LI of the Animals. Eight- to 12-week-oldfemale C3HeB/FeJ mice from The residual focus occurred which was greater than that occurring Jackson Laboratory (Bar Harbor, Maine) were used. All animals were as a result of tumor removal. When given 3 days after tumor housed in separate cages and fed standard laboratory chow and water removal, the smaller dose was almost as effective in suppressing ad libitum. LI as was the larger. From a kinetic standpoint, there was no Tumors. The spontaneousmammaryadenocarcinomaoriginatingin advantage in reducing the tumor burden prior to the use of a female C3H/HeJ mouse was maintained by transplant in C3HeB/FeJ mice.Tumor cellsuspensionswere preparedby mincingtumor fragments chemotherapy. The tumor response in this model suggests that, with scissors on an 80 mesh nylon screen and washing the cells through for the most effective control of mÃ©tastases,the largest tolerable the screen with Medium 199. The cells were counted using trypan blue dose of chemotherapy would best be used at the time of or exclusionas a test of viability.Viabletumor cells(2 x 105)wereinoculated before primary tumor removal. The results provide a biological s.c. in the left hind leg proximal to the popliteal node to induce tumors rationale for the use of perioperative adjuvant chemotherapy. arbitrarilydesignatedas "primary," and 3 x 104tumor cells were injected into the right hind leg at the same location to induce tumors designated as being "metastatic" or "residual tumor focus." Primary tumors were INTRODUCTION removed by amputation of the left tumor-bearingleg. Investigations over the years have indicated in many animal TumorGrowth.Tumorgrowthwas followedbycalipermeasurement models that the presence of a primary tumor inhibited (1, 2, 6, of 2 perpendicular diameters. Tumor volumes were calculated, and 7,10-12, 20, 22) and its removal accelerated (9-12,15,17, 21) curves of mean volume versus time were plotted on semilog paper. CY. CY was dissolved in distilled water, and 60, 120, or 240 mg/kg metastatic tumor growth. Those studies exclusively used gross were injected i.p. at times indicated. tumor growth as the index of effect. More recently, information In VitroLI. Animalsweresacrificedbycervicaldislocation,andtumors has accumulated regarding the kinetic characteristics of both were removed immediately. A single-cell suspension was prepared by primary and metastatic tumors, but few investigations have mincingthe tumor in McCoy's medium with 20% fetal calf serum (Grand determined the effect of removal or manipulation of a primary Island Biological Co., Grand Island, N. Y.) at room temperature and tumor on the kinetics of tumor cells in mÃ©tastases. Simpson- filtered through a nylon screen. The single-cellsuspension (3 to 5 x 107 cells/ml) was incubated for 1 hr at 37Â°infresh medium with 2.5 Â¿Â¿Ciof Herren ef al. (18, 19) described the consequences of excision of [3H]thymidineper ml (14 to 17 Ci per mmol).Labelingwas terminated by a Lewis lung tumor on the kinetics of lung mÃ©tastases, and inserting tubes containingcells into ice. The cells were washed with cold Schiffer ef a/. (16) briefly noted the alteration in kinetics of one Ca2+-Mg2+-freeEagle'sminimalessential medium (Grand Island Biologi tumor after complete or partial removal of a second of the same cal Co.). After the cells were washed, they were digested in 0.25% type. Our own studies (8) described in detail the kinetic changes Bacto-trypsin (Difco Laboratories, Inc., Detroit, Mich.) plus DNase (0.1 1Supported by USPHSGrant CA-14972 and by funds contributed by Mr. and mg/ml; Sigma ChemicalCo., St. Louis, Mo.) and incubated for 10 min at Mrs. Franco Torresy. 2To whom requests for reprints should be addressed. ReceivedJuly 19, 1982; accepted December 10, 1982. 3The abbreviations used are: CY, cyclophosphamide;LI, labelingindex.

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37Â°.They were centrifugea at 500 x g for 3 to 5 min and resuspended 1,000 in fresh medium, and viability tests were made by trypan blue exclusion. Cell viability was in excess of 90% (100% viability was not infrequent). The cells were centrifuged at 500 x g for 3 to 5 min, resuspended in cold 0.1 M citric acid for 2 min, and centrifuged again at 500 x g for 3 to 5 min. They were resuspended in Carnoy's fixative for 5 min at 4Â°,and "drop" preparations were made. Autoradiography and Counting Procedure. Autoradiography was carried out as described in detail previously (3). To intensify the latent â€¢H image, slides were incubated in KAuCU for 20 min at 15Â°and rinsed in distilled water just prior to development. The slides were then developed Ill in Kodak Amidol developer for 15 min at 15Â°,fixed, washed, air dried, l 100 and stained with hematoxylin. Gold activation reduces the exposure time ÃœJ to 1 day. With this method, background labeling was approximately 4 grains/cell, while the grains over labeled cells were usually too dense to count. To determine LI, 700 to 1500 cells were counted for each tumor sample. Slides were counted by either 2 or 3 observers and the results, O which were in good agreement, were pooled to obtain a mean value. LI is the percentage of labeled cells in the sample. Experimental Design. In these experiments, groups of animals bear PRIMARY. ing 14-day-old tumors were subjected to primary tumor removal or CY â€¢PRESENT administration. Those having their tumors removed on this day received OREMOVED either CY at the same time, CY 3 days or 7 days later, or no chemother DAYS'0 apy. When CY was the initial treatment, tumor removal was performed IO 5 or 7 days later. â€¢ 12 12 7 Â«MICE O 12 12 II

RESULTS Chart 2. Effect of primary tumor removal on growth of a distant focus. Bars, S.E. Effect of Tumor Removal. Mice bearing both a large primary and a small secondary tumor focus were subjected to removal of the larger tumor. The LI of the residual focus was found to 40 increase (Chart 1). By 1 day following tumor removal, there was a mean increase of 32% in LI; by the third day, it was 55% greater than that found at time of tumor removal. By 7 days, the 30 average LI had returned to the control level. At each time, there was considerable variation in the LI of tumors. Amputation of a normal leg in mice with a single tumor of a size equivalent to the - 20 residual focus in animals with 2 tumors resulted in no increase H in tumor LI. Removal of the primary tumor was followed by accelerating growth (p = 0.02) of the distant focus (Chart 2) in 10 keeping with the observed changes in LI. Influence of the Interval between Primary Tumor Removal and CY. CY was administered on the day of tumor removal. The effect on the LI of the residual focus was related to the amount 02468 of drug used (Chart 3). When 60 mg/kg were used, the LI of DAYS FOLLOWING TUMOR REMOVAL Chart 3. Effect of CY the day of tumor removal on LI of a residual tumor focus. Dose of CY: Â»,60 mg/kg; O, 120 mg/kg; x, 240 mg/kg; A, none. Bars, S.E. 40 -

tumors after 24 hr was greater than that observed in concomitant 30 controls which received no chemotherapy following tumor re moval. At the third and fourth days, however, Lis were consid erably lower than those in untreated tumor-removed controls but 20 were little different from those observed prior to treatment. At 7 days, the LI in both untreated and treated mice were at the level observed at the time of tumor removal. When CY (120 or 240 IO mg/kg) was administered, no increase in LI was observed at any â€”â€¢PRIMARY TUMOR REMOVED â€”Â«LEG WITHOUT TUMOR REMOVED time subsequent to tumor removal; in fact, a marked depression was noted which was sustained for at least 7 days when the larger dose was used. When tumor growth curves were exam I 3 4 7 10 DAYS FOLLOWING TUMOR REMOVAL ined, they reflected the kinetic changes (Chart 4). The growth of Chart 1. Effect of tumor removal on labeling index (LI) ot a residual tumor tumors in animals receiving the small dose of CY (60 mg/kg) at focus. the time of amputation was uninhibited. When 240 mg/kg were

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Downloaded from cancerres.aacrjournals.org on September 30, 2021. © 1983 American Association for Cancer Research. B. Fisher et al. used, the greatest tumor growth retardation was observed. almost returned to that in non-CY-treated tumors. The nadir of If CY was given 3 days following tumor removal at the peak the LI was similar when CY (240 mg/kg) was given at the time of the increase in LI, the depression of LI noted on the first 3 of, 3 or 7 days following, or 5 days prior to tumor removal. days following chemotherapy was similar when CY (60, 120, or When compared with animals having primary tumors removed 240 mg/kg) was used (Chart 5). When the 60- or 120-mg/kg and no chemotherapy (Group A), those receiving CY (240 mg/ dose was used, the peak depression occurred 3 days after drug kg) either at the time of tumor removal (Group B) or 3 (Group C) administration, with a return to control levels by the seventh day or 7 (Group D) days later all demonstrated retardation of the after therapy. A greater depression occurred at the fourth day growth of a residual tumor focus (Chart 7). When CY was given following 240 mg/kg, and by 7 days the LI had not yet returned 5 or 7 days prior to tumor removal (Group E), a similar effect to control levels. The effect on tumor growth when CY was given was noted. Because of the concordance in growth, the findings 3 days after amputation was, as when therapy was given at the were combined. In each circumstance, a different growth pattern time of amputation, dose related. emerged. For the first 10 to 12 days, the most effective suppres Administration of CY (240 mg/kg) 7 days following tumor sion of growth occurred in the animals (Group E) receiving CY removal resulted in a reduction in LI during the next 7 days followed by tumor removal 5 or 7 days later. Progressively (Chart 6). Removal of a primary tumor 5 days following CY delaying the onset of chemotherapy following amputation sup administration, at the nadir of the LI resulting from the chemo pressed the growth of successively larger tumors. In all groups therapy, failed to produce an increase in LI greater than that receiving CY, the length of the initial retardation was variable, as which occurs during recovery from chemotherapy (Chart 6). By was the subsequent growth rate. By =3 weeks, the size of tumor 12 days (7 days following tumor removal), the level of the LI had in the various treated groups was similar. Survival of animals was evaluated relative to the interval 10,000 between primary tumor removal and CY administration (Chart 8). Mortality during the first 4 weeks following the initiation of treatment was considerably lower when the CY was adminis tered prior to or at the time of primary tumor removal. Survival during that time decreased with a prolongation of the interval between tumor removal and CY administration, but even when given 7 days later, there was a notable benefit. Subsequently,

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4 6 8 IO 14 TREATMENT DAY Chart 6. Effect of the interval between tumor removal and CY on the LI of a 100 residual tumor focus. CY (240 mg/kg): A (â€¢):tumorremoval, Day 0; CY, none; B (x): tumor removal, Day 0; CY, Day 0; C (O);tumor removal, Day 0; CY, Day 3; D t (â€¢):tumorremoval, Day 0; CY, Day 7; E (A); CY, Days 0 and 5. CY 40 0 7 14 2l 28 1000 - DAYS AFTER TUMOR REMOVAL Chart 4. Effect of CY at time of tumor removal on growth of a residual tumor. Bars, S.E.

30 100 -

10 30 0 5 10 15 20 25 DAYS 2468 10 Chart 7. Relationof the interval between primary tumor removal and CY admin DAYS FOLLOWING TUMOR REMOVAL istration on the growth of a residual tumor focus. CY (240 mg/kg): A (â€¢):tumor removal, Day 0; CY, none; B (x): tumor removal. Day 0; CY, Day 0; C (O): tumor Chart 5. Effect of CY 3 days following tumor removal on LI of a residual tumor removal. Day 0; CY, Day 3; D (â€¢):tumorremoval. Day 0; CY, Day 7; E (A): CY, focus. â€¢,60mg/kg; O, 120 mg/kg; x, 240 mg/kg; A, none. Bars, S.E. Day 0; tumor removal. Days 5 and 7. Â£12mice/group.

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Downloaded from cancerres.aacrjournals.org on September 30, 2021. © 1983 American Association for Cancer Research. Timing of Chemotherapy and Tumor Removal the mortality rate was more rapid in those who received CY at by us previously (8) indicating that a transient increase in the LI the time of tumor removal than in those receiving the drug prior of a residual tumor focus occurs during the first 3 to 4 days to operation; median survival was 28 days in the former and 34 following primary tumor removal but not following amputation of days in the latter. a normal leg. The observed kinetic changes are associated with Influence of CY in the Presence or Absence of a Primary more rapid growth of mÃ©tastases.These studies demonstrated Tumor. When CY was administered to a group of animals on the that tumor removal was not associated with shortening of cell day of their tumor removal and to a second group whose tumors cycle or DMA synthesis times. Thus, the increase in LI was due were left intact, no significant difference in the LI of metastatic to noncycling cells becoming proliferative and therefore more tumors in the 2 groups was observed (Chart 9). Both the de vulnerable to cytostatic agents. The rapidity of the onset of the crease and subsequent increase of LI were similar in the groups. kinetic changes and their relatively short duration provide a These findings occurred whether CY (120 mg/kg) or CY (240 rationale for the use of adjuvant chemotherapy as soon as mg/kg) was used. When the administration of CY was delayed possible following primary tumor removal. for 3 days, although the LI in the group with the tumor removed The present investigations tested this hypothesis. They indi was higher at the time of CY administration, the subsequent cate the importance, in this model, of the interval between tumor depression and recovery of LI were similar in the 2 groups. removal and the initiation of adjuvant chemotherapy. The shorter Growth curves were in keeping with findings relative to LI. No the time after operation that therapy is begun, the more complete significant difference was observed in the growth of mÃ©tastases is the abrogation of the kinetic changes in distant tumor foci. between those having a primary tumor removed and those Consequently, the more effective becomes the suppression of having a primary tumor left intact. residual tumor burden and the more prolonged is the survival. A single large dose of CY was more effective when given the day DISCUSSION of operation than when given after an interval of 3 days, a time when the LI of the metastasis was at a peak. This benefit may The current findings provide additional support to those noted be attributed to the effect of CY on tumor cells in the G0-Gi compartment which are about to go into S phase and which are stimulated to do so by tumor removal. The therapy was least too effective if the interval was 7 days when the LI had already returned to the preoperative level and an additional increment of 80 tumor growth had occurred. Administration of CY and delay of operation until the LI was at the nadir completely prevented an increase in LI following tumor removal and was associated with a more effective suppression of residual tumor burden and prolongation of survival than occurred under any other circum 40 stance. The findings provide a biological rationale for the administration 20 of perioperative adjuvant chemotherapy which is different from that which provided the basis for such therapy in the late 1950's and early 1960's (4, 5, 13, 14). At that time, it was used for the 14 21 28 35 42 purpose of destroying those tumor cells which were dissemi DAYS nated at the time of operation and which were considered to be Chart 8. Relation of interval between primary tumor removal and CY adminis tration on survival. CY (240 mg/kg): A (â€¢):tumorremoval, Day 0; CY, none; B (x): responsible for the development of metastatic tumor. The mod tumor removal, Day 0; CY, Day 0; C (O): tumor removal, Day 0; CY, Day 3; D (â€¢): est effect of the therapy in those early studies may well have tumor removal, Day 0; CY, Day 7; E (A): CY, Day 0; tumor removal, Days 5 and 7. been due, at least in part, to the destruction of cells in existent e12 mice/group. metastatic foci which had been stimulated by the removal of the

-I20mg/hg- â€¢â€”â€¢ -240mg/kg- tumor rather than by the elimination of circulating tumor cells. Of interest is the observation that when CY (240 mg/kg) was B used at different times in relation to tumor removal, i.e., before, at the time of, or at various times after, the nadir of the LI was essentially the same, despite the variation in the proportion of labeled cells existing at the time of drug administration. That finding indicates that the effectiveness of the drug in suppressing cell division was related to the proportion of cells undergoing DMA synthesis at the time of its administration. The findings also indicate that, when a relatively small dose of 20 CY (60 mg/kg) was used, the interval between its administration and tumor removal was critical. Its effectiveness was related to the proliferative activity of the mÃ©tastases. When given to an animal whose metastatic focus contained more cells in S phase

6 8 IO O 2 because of primary tumor removal, i.e., at 3 days, it was almost TREATMENT DAY as effective in suppressing LI as was the larger dose of the same Chart 9. Influence of CY on the LI of a metastatic tumor focus in the presence drug. Recovery of cell proliferation was, however, more rapid or absence of a primary tumor. following the lower dose. When the smaller amount was admin-

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istered at the time of primary tumor removal, an increase in LI Cancer Res., 32: 374-379, 1972. resulted which was greater than that occurring as a consequence 3. Fisher, B., and Gunduz, N. Further observations on the inhibition of tumor growth by Corynebacterium parvum with cyclophosphamide. X. Effect of of the tumor removal. That increase is difficult to explain, since treatment on tumor cell kinetics in mice. J. Nati. Cancer Inst. 62: 1545-1551, the administration of the same dose of drug to animals with a 1979. 4. Fisher, B., Ravdin, R. G., Ausman, R. K., Slack, N. H., Moore, G. E., Noer, R. single intact tumor was earlier found to result in a depression of J. and Cooperating Investigators. Surgical adjuvant chemotherapy in cancer the LI (3). The tumor response in this model suggests that, for of the breast: results of a decade of cooperative investigation. Ann. Surg., chemotherapy to be most effective for controlling micrometas- 768:337-356,1968. 5. Fisher, B., Slack, N., Katrych, D., and Wolmark. N. Ten year follow-up results tases, it should be given using the largest tolerable dose at the of patients with carcinoma of the breast in a co-operative clinical trial evaluating time of or before primary tumor removal. surgical adjuvant chemotherapy. Surg. Gynecol. Obstet., 740: 528-534,1975. It is generally assumed that chemotherapy is apt to be more 6. Goldie, H., Walker, M., Kelley, L, and Gaines, J. Free tumor cell growth in the peritoneal cavity (ascites tumor) of mice bearing subcutaneous tumors. Cancer effective when there is a lower total tumor burden in a host. The Res., 76:553-558, 1956. present finding that the reduction in LI of mÃ©tastasesfollowing 7. Goodman, G. J. Effects of one tumor upon the growth of another. Proc. Am. Assoc. Cancer Res., 2: 207, 1957. CY administration was similar whether the primary tumor had or 8. Gunduz, N., Fisher, B., and Saffer, E. A. Effect of surgical removal on the had not been removed does not support that thesis. It suggests growth and kinetics of residual tumor. Cancer Res., 39: 3861-3865,1979. that from a kinetic standpoint there is neither an advantage nor 9. Kaplan, H. S., and Murph, E. D. The effect of local roentgen irradiation on the biological behavior of a transplantable mouse carcinoma. I. Increased fre a disadvantage when surgical efforts are used to reduce tumor quency of pulmonary metastasis. J. Nati. Cancer Inst., 9: 407-413, 1948. burden ("debulking") prior to the use of chemotherapy. 10. Ketcham, A. S., Kinsey, D. L., Wexler, H., and Mantel, N. The development of spontaneous mÃ©tastasesafter the removal of a primary tumor. II. Standardiza It is not to be inferred from these studies that a delay in tion protocol of five animal tumors. Cancer (Phila.), 14: 875-882, 1961. administration of chemotherapy beyond the time when the kinetic 11. Ketcham, A. S., Wexler, H., and Mantel, N. The effect of removal of a "primary" perturbation in a distant tumor focus after primary tumor removal tumor on the development of spontaneous mÃ©tastases. I. Development of a standardized experimental technique. Cancer Res., 79: 940-944, 1959. had disappeared will negate all benefit from such therapy. In 12. Milas, L., Hunter, N., Mason, K., and Withers, H. R. Immunological resistance these studies, prolongation of survival was observed no matter to pulmonary mÃ©tastasesin C3Hf/Bu mice bearing syngeneic fibrosarcoma of different sizes. Cancer Res., 34: 61-71,1974. when the therapy was instituted. The advantage of earlier ther 13. Nissen-Meyer, R., Kjellgren, K., Malmin, K., Mansson, B., and Norin, T. Surgical apy is that it eliminates the transient acceleration of growth adjuvant chemotherapy: results with one short course of cyclophosphamide resulting from removal of the primary tumor. By delaying the after mastectomy for breast cancer. Cancer (Phila.), 41: 2088-2098,1978. 14. Nissen-Meyer, R., Kjellgren, K., and Mansson, B. Preliminary report from the onset of therapy, it will be directed toward a larger tumor burden Scandinavian adjuvant chemotherapy study group. Cancer Chemother. Rep., having a different sensitivity to the drug. Although there is no 55:561-566,1971. information relative to whether, and if so when, primary tumor 15. Schatten, W. E. An experimental study of postoperative tumor metastasis. I. Growth of pulmonary mÃ©tastases following total removal of a primary leg removal in the human affects the kinetics of residual tumor tumor. Cancer (Phila.), 11: 455-459,1958. microfoci, it would seen worthwhile to use adjuvant therapy at 16. Schiffer, L. M., Braunschweiger, P. G., and Stragand, J. J. Tumor cell popu lation kinetics following noncurative treatment. Antibiot. Chemother. (Basel), the time of and/or prior to tumor removal in order to test the 23:148-156,1978. thesis that by eliminating a kinetic response to tumor removal 17. Sheldon, P. W., and Fowler, J. F. The effect of irradiating a transplanted murine there will result an improvement in patient outcome. lymphosarcoma on the subsequent development of mÃ©tastases.Br. J. Cancer, 28:508-514, 1973. 18. Simpson-Herren, L., Sanford, A. H., and Holmquist, J. P. Effects of surgery on the cell kinetics of residual tumor. Cancer Treat. Rep., 60:1749-1760,1976. ACKNOWLEDGMENTS 19. Simpson-Herren, L., Springer, T. A., Sanford, A. H., and Holmquist, J. P. Kinetics and mÃ©tastasesin experimental tumors. In: S. B. Day, W. P. L. Myers, We acknowledge the technical aid of Barbara Breidenbach, Judy Benson, and P. Stanley, S. Garattini, and M. G. Lewis (eds.), Cancer Invasion and Metas Morton Levine. tasis: Biologic Mechanisms and Therapy, pp. 117-133. New York: Raven Press. 1977. 20. Tyzzer, E. E. Factors in the production and growth of tumor mÃ©tastases.J. REFERENCES Med. Res., 28: 309-332, 1913. 21. van den Brenk, H. A. S., and Sharpington, C. Effect of local x-irradiation of a 1. Chesshire, P. J. The effect of multiple tumors on mammary tumor growth rates primary sarcoma in the rat on dissemination and growth of mÃ©tastases:dose- in the C3H mouse. Br. J. Cancer, 24: 542-547, 1970. response characteristics. Br. J. Cancer, 25: 812-830,1971. 2. DeWys, W. D. Studies correlating the growth rate of a tumor and its mÃ©tastases 22. Yuhas, J. M., and Pazmino, N. H. Inhibition of subcutaneously growing Line 1 and providing evidence for tumor-related systemic growth-retarding factors. carcinomas due to metastatic spread. Cancer Res., 34: 2005-2010, 1974.

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Downloaded from cancerres.aacrjournals.org on September 30, 2021. © 1983 American Association for Cancer Research. Influence of the Interval between Primary Tumor Removal and Chemotherapy on Kinetics and Growth of Metastases

Bernard Fisher, Nurten Gunduz and Elizabeth A. Saffer

Cancer Res 1983;43:1488-1492.

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