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Biomedical subjects

L Krishnan

Publications and source records attributed to L Krishnan.

At least 55 records · Page 3Linked to original sources
PubMed1991

A review of the role of radiation therapy in the treatment of patients with breast cancer.

Irradiation has been used to treat cancer of the breast since 1895. Over the period between 1895 to the present, the therapeutic use of irradiation has evolved from a cauterizing agent to a sophisticated use of theory and practice to cause tumor cell death while at the same time producing maximum normal tissue sparing. The use of radiation has made it possible for the surgeon to use conservative breast sparing surgery to obtain excellent cosmetic results, while at the same time producing a local control equal to that of mastectomy. For the patient, conservative surgery becomes a better option than mastectomy because it not only produces local control equal to that of mastectomy, but gives the wonderful added benefit of a more superior and pleasing cosmetic result.

Antineoplastic Agents↗
PubMed1990

Radiobiological advantages of an immediate interstitial boost dose in conservative treatment of breast cancer.

Minimum surgery with irradiation is emerging as one of the main modalities of therapy for operable early breast cancer. Between June 1982 and June 1986, 110 breasts with Tis, T1 to T3 lesions have been treated at our institution with lumpectomy and interstitial irradiation to the tumor bed with Iridium-192 perioperatively followed by external beam irradiation. There have been two local recurrences at or near the vicinity of the primary, at a median follow-up of 60 months. To analyze the parameters that might have contributed to the local control, we have examined the treatment volumes, prescribed dose to the tumor bed, dose at the core of the tumor bed, and dose to the surrounding normal tissue. Immediate interstitial implant has the radiobiological advantage of delivering continuous low dose irradiation, immediately upon removal of gross tumor to residual foci. Implantation of the afterloading catheters intraoperatively facilitates accurate dose delivery and avoidance of geographical misses. By precise treatment of any residual foci, immediately upon removal of the gross mass, perioperative interstitial irradiation improves local control and by facilitating less radical surgical excision, leads to better cosmetic results.

Brachytherapy↗
PubMed1990

Dosimetric analysis in brachytherapy of carcinoma of the cervix.

Brachytherapy plays an essential role in the definitive radiation treatment of cervical carcinoma. The dosimetry of intracavitary irradiation is complex in that the optimum doses that can be delivered are dictated not only by the volume and extent of tumor but also by the close vicinity of dose-limiting structures, such as the small and large intestines, rectum, and bladder. To facilitate understanding of the relationships between the various dosimetric parameters involved, a retrospective analysis of 50 randomly chosen intracavitary insertions with Cesium-137 in 41 patients performed at our institution between 1975 and 1985 was carried out. All 50 cases utilized Fletcher-Suit-Delcos applicators and only the insertions using three sources in the tandem and one in each of the ovoids were included in this analysis. Using the AP and lateral radiographs and the lymphatic trapezoid, the reference points were obtained and transferred digitally to the treatment planning computer, and computerized dosimetry performed. In addition to the specified reference points, points were added and modified to obtain more complete information. The doses at the specified points were normalized to the average dose at AT, a reference point 2 cm superior to external os and 2 cm lateral to the tandem, and expressed as a percentage. It was noted that the average dose at the closest bladder point was 103 +/- 41% of the dose at AT, the maximum rectal dose 77 +/- 29% of the dose at AT and the maximum small bowel dose 65 +/- 16% of that at AT. The analysis of percent contribution of various sources to different reference points revealed that the dose to point AT was equally contributed to by all sources; bladder and rectal doses were mainly contributed to by the lowermost uterine and ovoid sources. Our analysis may provide a model for optimizing brachytherapy in cervical carcinoma.

Brachytherapy↗
PubMed1990

Testicular neoplasms: seminoma.

From 1969 to 1984, 58 patients with a diagnosis of testicular seminoma were seen and treated at the University of Kansas Medical Center. The median age was 34 years (range of 20 to 62 years). The American Joint Committee on Cancer Staging System was followed: stage I (34 patients); stage II (6); stage III (8); and stage IV (10). Forty-two patients had typical seminoma, and 16 had anaplastic histology. Nine patients had elevated B subunit of human chorionic gonadotropin, and nine had a history of cryptorchidism. Fifty-six patients received radiation treatment, and seven received chemotherapy with or without radiation. The median follow-up was 7 years (range 3 to 16 years). The overall disease-free (absolute) survival according to stage was: stage I, 91% (100%); stage II, 66% (80%); stage III, 75% (85%); and stage IV, 50% (50%). There were no late complications. The survival for patients with anaplastic histology or with elevated B subunit of human chorionic gonadotropin was not significantly different from that of typical seminoma.

Adult↗
PubMed1989

Treatment options in early breast cancer.

Conservative management of early breast cancer with limited surgical excision and radiotherapy is now being accepted as a viable alternative to mutilating surgical procedures. In this paper, the major steps in the historical development of conservative management are traced, and the results of the current randomized trials are summarized. An innovative method used at the University of Kansas Medical Center delivers a "boost" dose to the tumor bed with interstitial Ir-192 immediately following resection of the primary tumor mass. The results obtained in terms of local control and cosmesis with this technique are presented, and the current state of the art is discussed.

Adult↗
PubMed1988

Immediate effect of irradiation on microvasculature.

The immediate effects of irradiation on microvasculature in muscle in an animal model are described in this paper. By using triple isotopes of 125I, 131I, and 22Na, the transcapillary transfer of albumin from the vascular bed to the extravascular space is determined in terms of mg/g of tissue, after single doses of 2 to 14 Gy. These results reveal an increase in the extravascular albumin immediately after irradiation and suggest an instantaneous compromise in vascular permeability even after 2 Gy. This effect was apparently dose related.

Animals↗
PubMed1988

Cosmetic results in early breast cancer treated with lumpectomy, peri-operative interstitial irradiation, and external beam radiation.

Patients with operable breast cancer were treated at the University of Kansas Medical Center with lumpectomy, peri-operative interstitial Iridium, and external beam radiotherapy, and concomitant adjuvant chemotherapy in a majority of node positive cases. Examination of the cosmetic results in 85 breasts followed for at least 2 years, at a median of 41 months revealed 20% to be excellent, 44% to be very good, 24% good, 9% fair, and 4% to have poor results. In this paper cosmesis is analyzed with reference to the size of the primary, its location, age of the patient, whether the patient received adjuvant chemotherapy, and whether the regional nodes were treated. In this group of patients, the size and the site of the primary, patient's age, and whether adjuvant chemotherapy was administered or not, did not adversely affect the aesthetic outcome. Treatment of the regional nodes gave a worse mean cosmetic score compared to the group in whom only the breast was treated (37.51 vs. 58.98 respectively, p less than 0.001). Among the 11 patients with fair/poor cosmesis, all had regional nodal treatment, 7/11 had inner quadrant lesions, and 7/11 had lesions greater than T1. Further follow-up and accrual would be needed to confirm our results and affirm if other factors would change.

Adult↗
PubMed1987

Intraoperative implantation radiation therapy plus lumpectomy for carcinoma of the breast.

The preponderance of evidence indicates that lumpectomy plus radiation therapy produces the same survival as modified radical mastectomy in patients with early breast cancer and further suggests that the local failure rate may be lower in the patients who undergo irradiation. In this series, patients were treated with immediate implantation of the tumor bed with iridium Ir 192. There have been two recurrences in the breast from 110 breast cancers (44% had a clinical stage greater than T1, and 41% had axillary-node involvement) in 107 patients followed up for four to 52 months (25.8 +/- 13.3 months [mean +/- SD]). These preliminary data suggest that local treatment failure can be minimized by aggressive, immediate intraoperative implantation of the tumor bed with iridium Ir 192.

Adult↗
PubMed1987

Perioperative interstitial irradiation in the conservative management of early breast cancer.

Conservation of the breast in early breast cancer with limited resection and radiation is proving to be as effective as modified radical mastectomy in survival and in loco-regional control. Management at the University of Kansas Medical Center consists of an interstitial implant at the time of lumpectomy to facilitate perioperative irradiation with Iridium-192 to the tumor bed. An axillary node dissection is also performed at that time. Two to 3 weeks later external beam irradiation is delivered to the entire breast. One hundred and twenty-three breasts in 120 patients have been treated between June 1982 and June 1986. There were 49 pathological Stage I, 63 Stage II, 8 Stage III carcinomas, and 3 carcinomas in situ, consisting of 72 T1, 43 T2, 5 T3, and 3 TIS lesions. Patients have been followed for a median of 30 months. One patient had a "true" recurrence in the breast. Another patient developed recurrence in a different quadrant. Ninety percent of the patients had good to excellent cosmetic results, 7% were considered fair, and 3% had poor results. Seven patients developed mild arm edema, 4 were found to have moderate edema, and 1 had severe arm edema. Our preliminary results indicate that interstitial irradiation immediately after excision results in excellent local control, with very satisfactory cosmesis and no morbidity due to the simultaneous excision and irradiation.

Adult↗
PubMed1987

Breast conservation treatment with perioperative interstitial irradiation.

Limited resection of the breast combined with radiation has proved to be as effective as more radical surgery in treating early breast cancer. At the University of Kansas Medical Center, the radiotherapy consists of an interstitial implant at the time of lumpectomy to deliver an interstitial boost dose to the tumor bed with iridium-192 immediately following the surgical procedure. An axillary node dissection is also performed at the time of lumpectomy. A dose of 2,000 cGy is delivered to the tumor bed between 40 and 60 h. Two to three weeks later, 4,500-5,000 cGy is delivered to the entire breast with external beam radiation over 5-5.5 weeks. One hundred breasts in 98 patients were so treated between June 1982 and February 1986, with 2 carcinomas in situ, 40 stage I, 51 stage II, and 7 stage III cancers, consisting of 2 TIS, 54 T1, 39 T2, and 5 T3 lesions. Locoregional control with a median follow-up of 31 months was 98%. One recurrence was in a different quadrant, and the other revealed predominantly the in situ component. Immediate implant did not compromise wound healing or cosmesis. The cosmetic result was graded as good to excellent in 88% of the breasts. Our preliminary results appear to suggest a better local control with immediate interstitial irradiation.

Adult↗
PubMed1987

Dose-dependent radiation effect on microvasculature and repair.

It has been postulated that the damage to microvasculature may be a major factor in the manifestation of late radiation damage to organized tissue. In this study, the radiation damage to microvasculature was investigated in a rabbit model during the early phases of irradiation with the use of vascular permeability as a marker. By means of a triple isotopic technique, the vascular, extravascular, and intracellular spaces could be defined. A forelimb and hindlimb of New Zealand White rabbits were irradiated with single doses of 2-30 Gy. 125I- and 131I-labeled bioscreened albumin were used to determine the changes in vascular permeability due to irradiation. The rabbits were sacrificed at various intervals post irradiation. Vascular and extravascular spaces and the respective albumin concentrations in tissue samples from irradiated limbs were compared with control values from the unirradiated contralateral limbs in each animal. The results indicated a definite increase in the vascular permeability of albumin secondary to irradiation. The increase in vascular permeability was apparent instantaneously with irradiation, even at 2 Gy. The microvascular compromise appear to be dose related. When examined at 16-24 hours post irradiation, the excess extravasation of albumin was significant at and beyond 8 Gy. At 10-30 days post irradiation, injury was not apparent up to 15 Gy. Thus there appeared to be an instantaneous injury at the capillary level due to irradiation, which appeared to be dose related. A repair process became evident as early as 16-24 hours and appeared to be dose related as well as related to elapsed time post irradiation.

Animals↗
PubMed1987

Effect of irradiation on microvasculature: a quantitative study.

In clinical radiation therapy, normal tissues and organs are unavoidably irradiated during the course of treatment of neoplastic diseases. Rubin and Cassaret [Clinical radiation pathology. Philadelphia: W.B. Saunders, 1968; Vols 1, 2] have postulated that microvascular damage may be the major contributing factor to late manifestation of radiation damage. It has been theorized that vascular leakage of the protein-rich fluid leads to fibrosis caused by the accumulation of fibroblasts and macrophages. Vascular changes after irradiation have been demonstrated qualitatively. To quantitate the alteration in permeability characteristics at different doses and time-dose fractionations, we have developed an isotopic technique using 125I, 22Na, and 3H2O that allows us to define vascular, interstitial, and intracellular water spaces. Using these values it is possible to quantitate the vascular changes and membrane integrity. Results show that the permeability of the vascular bed is altered by irradiation.

Animals↗
PubMed1986

Electron beam irradiation after reconstruction with silicone gel implant in breast cancer.

Irradiation for breast cancer in the presence of a silicone gel breast prosthesis is sometimes necessary. There is a concern among radiation and other oncologists as to whether the presence of the prosthetic implant would interfere with delivery of the needed irradiation doses. Electron beams, with their finite penetration and rapid fall-off, offer a mode of adequately treating the recurrence and minimizing the radiation to the underlying normal structures, such as the lung and the heart. The dose distribution using 9-20 MeV electrons in the presence of a breast prosthesis is compared to the dose distribution without the implant in a tissue equivalent water phantom. The results reveal no significant difference in the dose delivered due to the presence of the prosthesis. Clinical verification of the dosimetry in the presence of the prosthesis confirmed that the presence of the silicone gel implant does not compromise treatment by irradiation in the management of breast cancer.

Breast Neoplasms↗
PubMed1986

Tumor size: effect on monoclonal antibody uptake in tumor models.

Studies were performed to determine the effect of tumor size on the incorporation of radiolabeled monoclonal antitumor antibodies (MoAbs) into human tumors growing in nude mice. The colon tumors ranged in size from 0.03-1.6 g, the melanoma from 0.1 to 6.7 g, and the lymphoma from 0.06 to 10.2 g. Indium-111 was primarily used as the radiolabel, however, both 125I and 111In were used as tracers for the MoAb in one experiment. The per g radiopharmaceutical uptake by tumors was inversely proportional to tumor size when tumor specific MoAb was administered. This finding was independent of the radiolabel and was demonstrable when the mice bore two tumors of differing size. When the MoAb was not specific for the tumor, the data were less well defined and a statistically significant correlation with size did not occur. These data are strong evidence for a decrease in per g uptake of labeled tumor specific antibodies as tumors increase in size.

Animals↗
PubMed1985

In vivo kinetics of radiolabeled monoclonal anti-CEA antibodies in animal models.

Studies were performed to determine the effect of the radiolabel and circulating carcinoembryonic antigen (CEA) on the pharmacodynamics of monoclonal anti-CEA antibodies (MoAbs). The studies were performed in normal BALB/c mice and in nude mice bearing human colon tumors. Three different tumors were used, each of which produced CEA levels characteristic of that particular tumor's secretory rate. The CEJ-326 MoAb labeled with either 111In or 125I was used in all studies. Circulating CEA induced the removal of 125I and 111In MoAbs from the vascular compartment. Liver concentrations of 111In increased and 125I levels decreased as the CEA secretory rate of the tumor rose. This indicates that circulating CEA complexes form in the vascular compartment which, in an animal model, are removed by the liver and spleen. This results in decreased tumor uptake of the labeled MoAb. The iodinated MoAb complexes are dehalogenated while the 111In is retained by the liver. This dehalogenation may account for the relatively low liver activity observed in radioimmunoimaging with intact radioiodinated anti-CEA MoAbs, provided the CEA complexes are similarly removed from the vascular compartment by the human liver.

Animals↗
PubMed1984

Perceived time: its relationship with locus of control, filled versus unfilled time intervals, and perceiver's sex.

The present study examined the role of locus of control and the perceiver 's sex in the estimation of filled and unfilled time intervals. One hundred male and 100 female undergraduates, ranging in age between 16 and 21 years, were administered Collins' I-E Scale followed by a time-estimation task. The latter involved judging 10 time intervals which were either "filled" with a tapping sound presented by the E, or were "unfilled." Results indicate that (a) high internals, compared to low internals, were less likely to overestimate filled intervals, but were more likely to overestimate unfilled intervals, possibly because high internals are more time-conscious; (b) the extent of absolute error in estimation is jointly affected by internality, filled/unfilled intervals, and the perceiver 's sex, but the last-mentioned variable had the most prominent independent effect. In general, males made less error in time estimation than females. It is suggested that the observed sex differences in the present study was probably due to socially learned differences in time consciousness.

Adolescent↗